Biosensors and Nanotheranostics

1. Introduction

Nanotechnology refers to the science, engineering, and application of structures and materials that are deliberately manipulated at the atomic, molecular, and macromolecular scale, typically between 1 and 100 nanometres (Durgam & Oroszi, 2025; European Group on Ethics, 2007; Ma et al., 2024). It is widely regarded as one of the defining technological paradigms of the twenty-first century. What makes the nanoscale distinctive is not size alone. Below roughly 100 nm, materials no longer behave purely according to classical physics; they display quantum confinement effects, a markedly higher surface area-to-mass ratio, heightened chemical reactivity, and optical, magnetic, and electronic characteristics that can differ sharply from those of the same substance in bulk form (Hannah, 2008; Ma et al., 2024). When these properties are harnessed for health care, a field now broadly termed nanomedicine, they allow engineered structures to interact with biological systems at the cellular, subcellular, and molecular levels at which disease itself unfolds (European Group on Ethics, 2007; Ma et al., 2024).

The clinical appeal of this proposition is considerable. Nanostructures promise sub-cellular precision in diagnosis, targeted therapeutic intervention, regeneration of damaged tissue, and real-time monitoring of treatment response (Allon et al., 2016; Durgam & Oroszi, 2025; Ma et al., 2024). Some of this promise has already been realised: liposomal and albumin-bound chemotherapeutics have been in clinical use for years, and lipid nanoparticles proved decisive in the rapid deployment of mRNA vaccines during the COVID-19 pandemic (Durgam & Oroszi, 2025; Wilson & Geetha, 2022). At the same time, nanocarriers are being designed to overcome the biological barriers that have long frustrated conventional pharmacology, including the blood-brain barrier, opening therapeutic possibilities for neurodegenerative disorders such as Alzheimer's and Parkinson's diseases (Blanco et al., 2015; Gao et al., 2025).

There is, however, an uncomfortable symmetry in this story. The very attributes that confer clinical efficacy on engineered nanomaterials (ENMs), including their hyper-reactivity, high surface mobility, and capacity to cross intact biological membranes, are also the source of their potential hazards (Maynard, 2006; Resnik & Tinkle, 2007). Nanoparticles can evade primary anatomical defences, accumulate in organs, and provoke oxidative and inflammatory injury whose long-term consequences are not yet well understood (Hannah, 2008; Ma et al., 2024). Their life cycle, from industrial synthesis to clinical use and eventual disposal, also exposes workers and ecosystems to materials whose environmental fate remains incompletely characterised (IEEE, 2009; Schulte & Salamanca-Buentello, 2007). Beyond biology, nanomedicine raises a complex set of ethical, legal, and societal implications (ELSI): how to obtain meaningful informed consent when risks cannot be quantified, how to protect the personal data generated by ultrasensitive diagnostics, where to draw the line between therapy and enhancement, and how to prevent costly innovations from deepening global health inequities (Allon et al., 2016; Mehlich & Thiele, 2014; Resnik & Tinkle, 2007).

These challenges are compounded by the pace of development. Scientific progress in nanomedicine has outstripped the ethical frameworks and statutory regulations designed to govern it (Allon et al., 2016; Baran, 2016; Resnik & Tinkle, 2007). Regulators continue to debate how nanomaterials should be defined and whether a given nano-product should be classified as a drug, a device, or a biological agent (Hogle, 2009; Ma et al., 2024), while conventional toxicological assays, which were never designed for particulate materials, may yield misleading results (Mehlich & Thiele, 2014; Ok & Benneyan, 2009). Moving nanomedicine from proof-of-concept laboratory research into safe, equitable, and routine clinical practice therefore requires that its therapeutic capabilities be weighed against a rigorous assessment of its risks (Ma et al., 2024; Maynard, 2006).

Although a substantial literature addresses individual sub-fields, it remains fragmented. Clinical reviews tend to emphasise efficacy, toxicological studies focus on mechanisms of injury, and ethical and policy analyses often proceed with limited reference to either. What appears to be missing is an integrative, cross-disciplinary synthesis that examines the clinical promise of nanomedicine alongside its toxicological hazards and socio-ethical complexities within a single analytical frame (Allon et al., 2016; Durgam & Oroszi, 2025; Ma et al., 2024). The present review seeks to address this gap. Its specific objectives are (i) to analyse the principal applications of nanotechnology in health care, including targeted drug and gene delivery, molecular diagnostics, bioimaging, theranostics, tissue engineering, and nanovaccines (Durgam & Oroszi, 2025; Ma et al., 2024); (ii) to evaluate the toxicological mechanisms and in vivo fate of engineered nanomaterials, including intracellular transport, reactive oxygen species (ROS) generation, cytotoxicity, organ accumulation, and translocation across tissue barriers (Allon et al., 2016; Ma et al., 2024); (iii) to examine occupational and environmental life-cycle risks, including persistence, bioaccumulation, and ecological impact (IEEE, 2009; Ma et al., 2024); (iv) to critically appraise the ethical, legal, and social implications of nanomedicine, including informed consent, data privacy, human enhancement, and global health equity (Allon et al., 2016; Kermisch, 2012; Resnik & Tinkle, 2007); and (v) to review current regulatory landscapes, testing methodologies, and barriers to clinical translation in order to inform responsible innovation (Durgam & Oroszi, 2025; Ma et al., 2024; Mehlich & Thiele, 2014).

2. Nanomedicine Applications, Nanotoxicity, and Ethical and Regulatory Governance for Safe Clinical Translation

2.1 Conceptual Foundations and Classification of Biomedical Nanomaterials

2.1.1 Defining Nanomedicine

Nanotechnology can be defined as the intentional design, synthesis, characterisation, and application of structures, devices, and systems by controlling shape and size at the nanometre scale (Durgam & Oroszi, 2025; Ma et al., 2024). At this scale, materials exhibit quantum confinement, elevated surface area-to-mass ratios, heightened reactivity, and distinctive optical, magnetic, and electronic behaviour (Hannah, 2008; Maynard, 2006). Nanomedicine, the application of these properties to health care, is therefore distinguished less by any single product than by a shared capacity: engineered nanomaterials operate at the same spatial dimension as proteins and nucleic acids, allowing them to cross restrictive biological barriers and interact directly with subcellular structures (European Group on Ethics, 2007; Ma et al., 2024). Ethical commentators have noted that this capacity is precisely what makes nanomedicine both promising and contentious (Ebbesen et al., 2006; Resnik & Tinkle, 2007). The overall relationship between these defining properties, their clinical benefits, their hazards, and the governance responses they demand is summarised in a conceptual framework (Figure 1).

2.1.2 Classes of Biomedical Nanomaterials

By chemical composition and spatial dimensionality, biomedical nanomaterials fall into four broad groups (Figure 1). Organic constructs include liposomes, polymeric nanoparticles, solid lipid carriers, dendrimers, and extracellular vesicles; inorganic platforms include gold, iron oxide, mesoporous silica, and quantum dots; carbon-based nanostructures include single- and multi-walled carbon nanotubes, fullerenes, and graphene; and hybrid nanocomposites combine elements of these classes (Durgam & Oroszi, 2025; Ma et al., 2024; Mitchell et al., 2021). The European Group on Ethics (2007) characterised nanomedicine across analytical tools, nanoimaging, novel therapeutics and drug delivery systems, nanomaterials and nanodevices, and clinical, regulatory, and toxicological assessment. While these platforms offer unprecedented clinical precision, their rapid integration into health care has exposed significant gaps in nanotoxicological knowledge, regulatory oversight, and socio-ethical governance (Maynard, 2006; Mehlich & Thiele, 2014).

2.2 Clinical Applications of Nanomedicine

Nanomedicine spans a broad range of clinical modalities that can be grouped into targeted drug and gene delivery, diagnostic imaging and biosensing, theranostics, regenerative tissue engineering, and nanovaccines for infectious disease control (Durgam & Oroszi, 2025; Ma et al., 2024). These domains, their representative platforms, and their translational status are mapped in Figure 2 and detailed in Table 1.

2.2.1 Targeted Drug Delivery and Precision Pharmacotherapy

Systemic administration of conventional small-molecule therapeutics is routinely limited by poor aqueous solubility, non-specific distribution, rapid clearance, and off-target toxicity (Durgam & Oroszi, 2025; Ma et al., 2024). Engineered nanocarriers mitigate these limitations by encapsulating hydrophobic or labile agents within biocompatible matrices, protecting them from enzymatic degradation, prolonging their circulation half-life, and enhancing local bioavailability (Blanco et al., 2015; Mitchell et al., 2021). In oncology, passive targeting relies on the enhanced permeability and retention (EPR) effect, a phenomenon driven by leaky tumour vasculature and impaired lymphatic drainage, which allows nanoformulations to accumulate preferentially in malignant tissue (Chaturvedi et al., 2019; Durgam & Oroszi, 2025). Active targeting refines this localisation by functionalising nanoparticle surfaces with ligands such as antibodies, peptides, or aptamers that bind receptors overexpressed on diseased cells (Mitchell et al., 2021).

Translational success is exemplified by liposomal doxorubicin (Doxil®) and nanoparticle albumin-bound paclitaxel (Abraxane®), which increase intratumoural drug concentration while reducing systemic toxicity (Durgam & Oroszi, 2025; Ma et al., 2024). Nano-delivery systems have also shown capacity to surmount formidable physiological barriers. Functionalised metallic, polymeric, and lipid-based nanoparticles loaded with

Table 1. Mainstream clinical applications of biomedical nanotechnology: platforms, mechanisms, benefits, and translational status. The table summarises the five principal domains in which engineered nanomaterials (ENMs) are applied in health care. For each domain it lists the representative nanomaterial platforms, the physiological mechanisms and delivery routes through which they act, and the main clinical advantages over conventional approaches. The translational column distinguishes products already approved by regulators from those in clinical trials or preclinical development, illustrating the uneven maturity of the field. Abbreviations: BBB, blood-brain barrier; CT, computed tomography; ECM, extracellular matrix; EPR, enhanced permeability and retention; LNP, lipid nanoparticle; MHC, major histocompatibility complex; MIP, molecularly imprinted polymer; MOF, metal-organic framework; MRI, magnetic resonance imaging; NIR, near-infrared; NP, nanoparticle; PDT, photodynamic therapy; PET, positron emission tomography; SPION, superparamagnetic iron oxide nanoparticle; VLP, virus-like particle.

Table 2. Biological mechanisms of nanotoxicity, in vivo hazards, occupational exposure, and ecotoxicology. The table organises the reported hazards of engineered nanomaterials by level of biological organisation, from subcellular injury through organ-system accumulation to occupational and environmental exposure. For each level it identifies the nanomaterial classes most often implicated, the molecular and cellular mechanisms of injury, and the resulting pathological outcomes. The fifth column highlights the physicochemical variables that modify toxicity and the mitigation strategies proposed in the literature, underlining that much of the hazard is design-dependent. Abbreviations: Ag, silver; CNS, central nervous system; CuO, copper oxide; HEPA, high-efficiency particulate air; LCA, life-cycle assessment; LMP, lysosomal membrane permeabilisation; MWCNT/SWCNT, multi-/single-walled carbon nanotube; NLRP3, NOD-like receptor protein 3; PPE, personal protective equipment; RES, reticuloendothelial system; ROS, reactive oxygen species; TiO2, titanium dioxide; ZnO, zinc oxide.

neurotherapeutic agents can cross the blood-brain barrier (BBB), offering non-invasive strategies for central nervous system malignancies and neurodegenerative disorders such as Alzheimer's and Parkinson's diseases (Blanco et al., 2015; Gao et al., 2025). Comparable approaches are being explored for sustained ocular delivery in medical and surgical glaucoma therapy (Occhiutto et al., 2020).

2.2.2 Diagnostic Imaging and Biosensing

Beyond therapeutics, nanotechnology has substantially improved medical diagnostics by enhancing contrast resolution, signal stability, and biomarker sensitivity (European Group on Ethics, 2007; Ma et al., 2024). Superparamagnetic iron oxide nanoparticles (SPIONs) act as contrast agents in magnetic resonance imaging (MRI), improving visualisation of soft-tissue lesions, liver pathology, and inflammatory sites (Butt & Bach, 2024; Naseri et al., 2018). Gold nanoparticles (AuNPs) and quantum dots (QDs) serve as optical and computed tomography (CT) contrast probes; AuNPs functionalised with the collagen-binding adhesion protein CNA35, for example, permit prolonged CT visualisation of myocardial scar tissue after infarction (Butt & Bach, 2024; Naseri et al., 2018). Metal-organic frameworks have further been explored to enhance resolution in CT and positron emission tomography (PET) (Ma et al., 2024). At the point of care, nanostructured arrays, including nanowires, carbon nanotubes, and molecularly imprinted polymers (MIPs), incorporated into electrochemical and optical biosensors can lower detection thresholds by several orders of magnitude, enabling single-molecule detection of circulating tumour cells, microRNAs, cardiac biomarkers, and viral pathogens in blood or urine (European Group on Ethics, 2007; Ma et al., 2024).

2.2.3 Theranostics and Stimuli-Responsive Platforms

Diagnostic precision converges with therapeutic delivery in theranostics, in which a single multifunctional platform enables simultaneous diagnosis, targeted payload delivery, and real-time treatment tracking (Durgam & Oroszi, 2025; Ma et al., 2024). Theranostic nanocarriers release their cargo in response to internal triggers, such as acidic tumour pH, hypoxia, or elevated enzyme levels, or to external stimuli including near-infrared (NIR) light, magnetic fields, and ultrasound (Jia et al., 2023; Ma et al., 2024). Nanotechnology-enabled photodynamic and photothermal therapies, increasingly combined with immunotherapy, illustrate how such platforms might create a feedback loop that allows clinicians to adjust treatment to individual patient profiles (Jia et al., 2023; Mehlich & Thiele, 2014).

2.2.4 Regenerative Medicine and Tissue Engineering

In tissue engineering, biomimetic nanostructured scaffolds replicate the nanoscale architecture of the native extracellular matrix (ECM), providing mechanical support and guiding cell behaviour (Durgam & Oroszi, 2025; Ma et al., 2024). Nanofibrous hydrogels, nanocomposites, and surface-modified carbon nanotube scaffolds promote stem cell adhesion, proliferation, and lineage-specific differentiation (Patel et al., 2016). These strategies have produced encouraging advances in neural, dental, skin, cardiovascular, and bone regeneration, with nanocomposite orthopaedic implants and nanocoated vascular stents now under clinical investigation (Ruan et al., 2024).

2.2.5 Nanovaccines and Infectious Disease Control

Nanotechnology has also reshaped vaccinology. Nanovaccines use lipid nanoparticles (LNPs), virus-like particles (VLPs), or polymeric constructs to encapsulate fragile genetic cargo such as mRNA, protecting it from extracellular ribonucleases and delivering it efficiently to antigen-presenting cells (Durgam & Oroszi, 2025; Wilson & Geetha, 2022). The global deployment of mRNA-LNP COVID-19 vaccines demonstrated the clinical viability of this approach (Wilson & Geetha, 2022). Nanoparticle platforms can enhance antigen stability, facilitate dual MHC class I and class II antigen presentation, promote dendritic cell maturation, and prolong lymph node retention, thereby inducing durable humoral and cellular immunity (Chaturvedi et al., 2019; Durgam & Oroszi, 2025).

2.3 Biological Mechanisms of Nanotoxicity

Despite these advances, wider clinical implementation is constrained by biological and toxicological challenges (Durgam & Oroszi, 2025; Ma et al., 2024; Maynard, 2006). The principal pathways of injury are illustrated in Figure 3 and summarised in Table 2.

2.3.1 Cellular Entry and Oxidative Stress

Because of their minute scale, inhaled, ingested, or injected nanoparticles can bypass primary anatomical defences and cross cell membranes by endocytosis or direct penetration, reaching intracellular compartments

Figure 1. Conceptual framework linking the nanoscale properties of biomedical nanomaterials to their clinical promise, potential hazards, and governance needs. Organic, inorganic, carbon-based, and hybrid nanomaterials (left) share defining nanoscale properties (centre), including a size of 1-100 nm, a high surface area-to-mass ratio, quantum confinement, heightened reactivity, and the capacity to cross biological barriers. These same properties give rise both to clinical benefits (upper right) and to toxicological, environmental, and socio-ethical pitfalls (lower right). Both outcomes converge on a common set of governance responses (bottom). The figure synthesises Sections 2.1-2.6 and underpins the cross-domain analysis presented in the Discussion. Abbreviations: EVs, extracellular vesicles; LNP, lipid nanoparticle; MWCNT/SWCNT, multi-/single-walled carbon nanotube; NPs, nanoparticles; RES, reticuloendothelial system; ROS, reactive oxygen species; SLNs, solid lipid nanoparticles; SPIONs, superparamagnetic iron oxide nanoparticles.

Figure 2. Principal clinical applications of nanomedicine across five therapeutic and diagnostic domains. Each column represents one application domain, with its key mechanisms, representative platforms, and clinical examples. Targeted delivery exploits passive (EPR) and active (ligand-receptor) targeting, exemplified by Doxil® and Abraxane®, and enables passage across the blood-brain barrier; imaging and diagnostics rely on SPIONs, gold nanoparticles, quantum dots, and nanostructured biosensors; theranostic platforms couple imaging with stimulus-triggered release; regenerative scaffolds mimic the extracellular matrix; and nanovaccines, led by mRNA-LNP COVID-19 vaccines, enhance antigen delivery and presentation. Translational status for each domain is detailed in Table 1. Abbreviations: AD, Alzheimer's disease; BBB, blood-brain barrier; CNT, carbon nanotube; CTC, circulating tumour cell; ECM, extracellular matrix; MIP, molecularly imprinted polymer; NIR, near-infrared; PD, Parkinson's disease; PDT, photodynamic therapy; QD, quantum dot; VLP, virus-like particle.

such as mitochondria, lysosomes, and the nucleus (IEEE, 2009; Resnik & Tinkle, 2007). A unifying paradigm in nanotoxicology is oxidative stress driven by overproduction of reactive oxygen species, including hydroxyl radicals, superoxide anions, and hydrogen peroxide (Hannah, 2008; Ma et al., 2024). Excess ROS overwhelms endogenous antioxidant defences, causing lipid peroxidation, membrane degradation, mitochondrial depolarisation, and DNA strand breakage (Ma et al., 2024; Wu et al., 2020). Secondary genotoxicity may follow when nanoparticle-induced inflammation activates macrophages and neutrophils, whose oxidative burst inflicts sustained genomic damage on surrounding tissue (Allon et al., 2016; Ma et al., 2024). Toxicity generally increases as particle size decreases, whereas surface coatings such as polyethylene glycol (PEG) can attenuate ROS generation (Maynard, 2006; Setyawati et al., 2014).

2.3.2 Autophagic Dysfunction and Lysosomal Failure

A second major pathway involves autophagy dysfunction and lysosomal failure (Mao et al., 2016; Wu et al., 2020). When internalised nanoparticles overwhelm autophagosomes or accumulate in lysosomes, they can induce lysosomal membrane permeabilisation (LMP), leakage of hydrolytic enzymes into the cytosol, blockade of autophagic flux, and activation of the NLRP3 inflammasome (Mao et al., 2016; Setyawati et al., 2014; Wu et al., 2020). The consequences include apoptotic or necrotic cell death and tissue-level injury; titanium dioxide nanoparticles, for instance, have been shown to induce autophagy in primary human keratinocytes, linking this pathway to dermal toxicity (Zhao et al., 2013).

2.3.3 Organ Accumulation and Fibre Pathogenicity

Structural factors strongly influence toxicological severity. High-aspect-ratio nanomaterials such as single-walled carbon nanotubes (SWCNTs) share structural features with asbestos fibres; when inhaled or systemically distributed, rigid SWCNTs can provoke frustrated phagocytosis in macrophages, persistent pulmonary inflammation, interstitial fibrosis, granuloma formation, and pleural mesothelioma (Ebbesen et al., 2006; IEEE, 2009; Lam et al., 2006; Schulte & Salamanca-Buentello, 2007). Non-biodegradable inorganic nanoparticles, including silver, titanium dioxide, and silica, may persist within the reticuloendothelial system (RES), concentrating in the liver, spleen, bone marrow, and lymph nodes, which raises concern about chronic organ toxicity and immune dysfunction (Ebbesen et al., 2006; Ma et al., 2024; Resnik & Tinkle, 2007).

2.4 Occupational Hazards and Environmental Life-Cycle Risks

2.4.1 Occupational Exposure

Toxicological risks extend beyond patients to manufacturing plants, research laboratories, and waste-processing facilities, where workers may be exposed through inhalation, dermal contact, or accidental ingestion (Maynard & Kuempel, 2005; Schulte & Salamanca-Buentello, 2007). Airborne nanoparticles can penetrate deep into the pulmonary alveoli, translocate into the bloodstream, and migrate along the olfactory nerve into the central nervous system (Maynard & Kuempel, 2005). Dermal contact with metallic nanoparticles, such as the copper oxide and zinc oxide used in antimicrobial textiles and cosmetics, may breach compromised epidermal barriers, causing keratinocyte apoptosis, sensitisation, and systemic absorption (Ma et al., 2024; Zhao et al., 2013). Existing occupational oversight frameworks were not designed with nanomaterials in mind, and their adequacy has been questioned (Choi & Ramachandran, 2009). The full life cycle of medical nanomaterials and its exposure points are depicted in Figure 4.

2.4.2 Environmental Fate and Ecotoxicity

At the ecosystem level, free nanoparticles released through industrial effluents or medical waste undergo environmental "aging", interacting with organic matter, undergoing sulfidation, and altering their surface charge and aggregation state (Hannah, 2008; Ma et al., 2024). Released nanoscale silver, titanium dioxide, and fullerenes (C60) show acute toxicity towards algae, Daphnia, filter-feeders, and fish, disrupting membrane integrity, inhibiting photosynthesis, and accumulating along food webs (IEEE, 2009; Ma et al., 2024). In agriculture, carbon-based nanomaterials can penetrate plant root cell walls, increasing vulnerability to chemical pollutants and reducing yields of staple crops such as rice and wheat (Purohit et al., 2017). Life-cycle analyses further suggest that producing high-purity carbon nanofibres may carry an environmental toxicity and global warming footprint up to 100 times greater per unit mass than conventional materials such as steel or aluminium (Ma et al., 2024; Purohit et al., 2017). The literature on non-toxicological nano-environmental, health, and safety (EHS) risk analysis remains comparatively thin

Figure 3. In vivo toxicological pathways of engineered nanomaterials, from routes of exposure to pathological outcomes. Nanomaterials entering by inhalation, ingestion, injection, or dermal contact cross biological barriers and are taken up by cells through endocytosis or direct membrane penetration. Injury then proceeds along two intracellular routes, oxidative stress and autophagic-lysosomal failure, and two organ-level routes, reticuloendothelial accumulation and fibre-like pulmonary toxicity of high-aspect-ratio carbon nanotubes. Physicochemical modifiers (upper right), including size, surface chemistry, aspect ratio, and biopersistence, shape the severity of each pathway. The convergent pathological outcomes (bottom) are summarised with supporting sources in Table 2. Abbreviations: LMP, lysosomal membrane permeabilisation; NLRP3, NOD-like receptor protein 3; PEG, polyethylene glycol; ROS, reactive oxygen species; SWCNT, single-walled carbon nanotube.

Figure 4. Life cycle of medical nanomaterials, showing occupational, clinical, and environmental exposure points. Nanomaterials move from synthesis and manufacture through clinical use to disposal as medical waste and industrial effluent, after which they undergo environmental aging. Workers may be exposed during production through inhalation and dermal contact, and exposure may reach the central nervous system via the olfactory nerve. Once released, particles are transformed by sulfidation, organic-matter coronas, and aggregation, affecting algae, Daphnia, fish, and staple crops such as rice and wheat. The life-cycle footprint panel notes that carbon nanofibre production carries an environmental burden far exceeding that of conventional materials. Abbreviations: C60, fullerene; CNS, central nervous system; CuO, copper oxide; HEPA, high-efficiency particulate air; LCA, life-cycle assessment; NMs, nanomaterials; PPE, personal protective equipment; TiO2, titanium dioxide; ZnO, zinc oxide.

(Ok & Benneyan, 2009).

2.5 Ethical, Legal, and Societal Implications (ELSI)

The integration of nanotechnology into clinical medicine challenges classical bioethical frameworks grounded in autonomy, beneficence, nonmaleficence, and justice (Ebbesen et al., 2006; Resnik & Tinkle, 2007). Whether these challenges are genuinely new or simply more acute versions of familiar problems is itself debated (Allon et al., 2016; Kermisch, 2012). The main domains are mapped in Figure 5 and summarised in Table 3.

2.5.1 Informed Consent and Autonomy

Because nanomedicines have complex, non-linear biological mechanisms and long-term risks that cannot yet be quantified, clinicians struggle to communicate potential hazards, and patients find the novel risks difficult to grasp (Kermisch, 2012; Ma et al., 2024). The problem is most acute in early-phase clinical trials, where participants may be exposed to experimental nanomaterials before their biopersistence, metabolic fate, or teratogenic potential is understood (Resnik & Tinkle, 2007).

2.5.2 Privacy, Data Ownership, and Bio-Surveillance

Highly sensitive nano-diagnostics, point-of-care lab-on-a-chip platforms, and indwelling nanosensors can generate continuous streams of personal physiological and genetic data (Allon et al., 2016; Kermisch, 2012). Unauthorised access to, or commercial exploitation of, such data by insurers, employers, or state bodies could lead to genetic discrimination, stigmatisation, and erosion of privacy (Baran, 2016; Kato, 2009).

2.5.3 The Right to Know and the Right Not to Know

Sub-symptomatic screening creates a moral tension between the "right to know" and the "right not to know", particularly when ultra-early detection identifies conditions for which no effective treatment yet exists (Allon et al., 2016; Desai, 2012; Kato, 2009).

2.5.4 Therapy Versus Enhancement

Ethical debate also concerns a possible shift from therapy, which restores normal function, to human physical and cognitive enhancement, which alters baseline capacities (Allon et al., 2016; Durgam & Oroszi, 2025; Ebbesen et al., 2006). Implantable neural interface nanodevices, nano-enabled muscle augmentation, and memory-enhancing nanotherapeutics would blur this boundary (Gordijn, 2006). Critics argue that non-therapeutic enhancement could threaten human dignity, unsettle prevailing notions of "normality", and divide enhanced from non-enhanced individuals (Ebbesen et al., 2006; Resnik & Tinkle, 2007).

2.5.5 Distributive Justice and the "Nano-Divide"

High research and development expenditure and complex manufacturing raise the cost of nanomedicines (Ma et al., 2024). Access may consequently be confined to affluent individuals and nations, widening global health disparities, a phenomenon described as the "nano-divide" (Allon et al., 2016; Baran, 2016; Kermisch, 2012). Developing nations bear a heavy burden of infectious and neglected diseases that low-cost nano-diagnostics or vaccines could mitigate, yet commercial investment remains concentrated in lucrative markets in industrialised countries (Choi, 2005; Sahoo et al., 2010; Uskokovic, 2021).

2.5.6 Public Engagement and Responsible Innovation

Several authors have warned that public backlash, comparable to that seen with genetically modified foods, could follow if social concerns are ignored or if benefits are overstated (Mills & Fleddermann, 2005; Tegart, 2008). Proposals to address this include structured approaches to ethical analysis during research and development (van de Poel, 2008), early and transparent public dialogue (Mills & Fleddermann, 2005), and Responsible Research and Innovation (RRI) frameworks that assign explicit responsibilities to researchers and institutions (Oftedal, 2014).

2.6 Regulatory Landscapes and Alternative Testing Strategies

2.6.1 Statutory Oversight

Regulating nanomedicine presents statutory and operational challenges (Baran, 2016; Durgam & Oroszi, 2025). Because nanoscale products frequently combine mechanical, chemical, optical, and biological modes of action, whether a hybrid product should be regulated as a drug, a biological agent, or a medical device often remains ambiguous (Hogle, 2009; Ma et al., 2024). The US Food and Drug Administration (FDA) regulates nanotechnology under existing statutory authorities on a case-by-case, product-based basis, without categorical nano-specific definitions (Resnik & Tinkle, 2007; Yeagle, 2007). The European Union, by contrast, has adopted a formal definition of nanomaterial (European Commission, 2011), integrated nano-specific provisions into legislation on cosmetics, biocides, and food, and relies on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) framework, which incorporates quantitative structure-activity relationships (QSARs) to evaluate hazard (Baran, 2016; Mehlich & Thiele, 2014). At a more conceptual level, risk governance scholars have distinguished passive nanostructures from active, integrated nanosystems, arguing that each warrants a different governance frame (Renn & Roco, 2006). The governance landscape is summarised in Figure 6 and Table 4.

2.6.2 Methodological Gaps in Safety Assessment

A key bottleneck is the lack of standardised toxicological testing protocols tailored to nanomaterials (Mehlich & Thiele, 2014; Ok & Benneyan, 2009; Resnik & Tinkle, 2007). Conventional cytotoxicity assays may produce false-positive or false-negative results because nanoparticles physically interfere with assay reagents (Mehlich & Thiele, 2014; Vinken & Blaauboer, 2017). Long-term human safety data spanning 10-20 years are unavailable for most novel formulations (Ma et al., 2024). Moreover, evaluating the enormous diversity of manufactured nanomaterials with traditional vertebrate models is economically and ethically problematic; such an undertaking has been estimated to cost over US$1 billion, take more than 50 years, and require millions of animals (Wu et al., 2020).

2.6.3 Alternative Testing Strategies and the 3Rs

To address these obstacles, regulatory science is moving towards alternative testing strategies (ATS) aligned with the 3Rs principle of reduction, refinement, and replacement, building on the vision of twenty-first-century toxicity testing (Krewski et al., 2010; National Research Council, 2007). These strategies combine mechanism-based high-throughput screening in human cell lines, focusing on early markers such as ROS generation, autophagic flux disruption, and LMP, with adverse outcome pathway (AOP) reasoning and validated non-mammalian whole-organism models (Vinken & Blaauboer, 2017; Wu et al., 2020). Drosophila melanogaster, Caenorhabditis elegans, and zebrafish (Danio rerio) embryos offer ethically acceptable, cost-effective, high-throughput in vivo test beds (Ecovoiu et al., 2016; Johnston et al., 2018). Direct microtransfer of nanomaterials into Drosophila embryos, together with somatic mutation and comet assays, permits rapid evaluation of tissue-specific toxicity, genotoxicity, and developmental delay, bridging the gap between cell assays and rodent studies (Ecovoiu et al., 2016; Vega-Alvarez et al., 2014). Ultimately, harmonised international characterisation standards, transparent risk communication, safety-by-design engineering, and proactive public engagement, modelled on the ELSI programme of the Human Genome Project, will be needed if nanomedicine is to fulfil its potential safely, ethically, and equitably (Mills & Fleddermann, 2005; Renn & Roco, 2006).

3. Methods

3.1 Review Design

This study was conducted as an integrative narrative review, a design chosen because the research questions span heterogeneous forms of evidence, namely experimental and clinical studies, toxicological reviews, normative ethical analyses, and regulatory documents, that cannot be pooled statistically. The review protocol, including research questions, information sources, search strings, eligibility criteria, and the data-charting template, was defined before searching began. Four a priori review questions guided the work: (RQ1) Which nanotechnology applications have reached clinical use, and which remain investigational? (RQ2) What are the principal mechanisms and determinants of nanomaterial toxicity in humans and the environment? (RQ3) What ethical, legal, and societal issues does nanomedicine raise? (RQ4) How is nanomedicine currently regulated, and which testing strategies are proposed to support safety assessment? Because the study used only published, publicly available material and involved no human participants or animals, ethical approval was not required.

3.2 Information Sources

Four bibliographic databases were searched: PubMed/MEDLINE (National Library of Medicine), Scopus (Elsevier), Web of Science Core Collection (Clarivate), and IEEE Xplore, the last being included because a substantial part of the nanoethics and nano-EHS literature appears in engineering proceedings and journals (IEEE, 2009; Mills & Fleddermann, 2005; Ok & Benneyan, 2009). Google Scholar was used as a supplementary source, with the first 200 results per search string screened. Grey and regulatory literature was identified through targeted searches of the Official Journal of the European Union, US FDA guidance repositories, and National Academies Press publications, which yielded key regulatory and methodological sources (European Commission, 2011; National Research Council, 2007). Backward citation tracking (screening the reference lists of included sources) and forward citation tracking (identifying later works citing them) were applied to all included reviews, in particular to recent comprehensive reviews (Durgam & Oroszi, 2025; Ma et al., 2024; Wu et al., 2020).

3.3 Search Strategy

Search strings combined controlled vocabulary with free-text terms. In PubMed, Medical Subject Headings (MeSH) included "Nanomedicine"[MeSH], "Nanotechnology"[MeSH], "Nanoparticles"[MeSH], "Nanostructures"[MeSH], "Drug Delivery Systems"[MeSH], "Theranostic Nanomedicine"[MeSH], "Toxicity Tests"[MeSH], "Ecotoxicology"[MeSH], "Occupational Exposure"[MeSH], "Ethics, Medical"[MeSH], "Informed Consent"[MeSH], and "Government Regulation"[MeSH]. Four concept blocks were combined with the Boolean operator AND, with synonyms within each block combined using OR:

• Block A (technology): nanotechnolog OR nanomedicine OR nanoparticle OR nanomaterial OR nanocarrier OR liposom OR "lipid nanoparticle" OR "carbon nanotube" OR "quantum dot"

• Block B (applications, RQ1): "drug delivery" OR "gene delivery" OR theranostic OR "contrast agent" OR biosensor OR "tissue engineering" OR scaffold OR vaccine* OR "blood-brain barrier"

• Block C (hazard, RQ2): toxicit OR nanotoxicolog OR "oxidative stress" OR "reactive oxygen species" OR autophag OR lysosom OR biopersist OR ecotoxic OR "life cycle" OR occupational

• Block D (ethics and governance, RQ3-RQ4): ethic OR nanoethic OR ELSI OR "informed consent" OR privacy OR enhancement OR justice OR equit OR regulat OR governance OR "risk assessment" OR "alternative testing" OR 3Rs OR REACH OR FDA

Because the four review questions are distinct, Block A was combined separately with Blocks B, C, and D, yielding three domain-specific searches that were run in each database. Syntax was adapted to each platform (for example, TITLE-ABS-KEY fields in Scopus and TS= fields in Web of Science). Searches covered January 2004 to June 2026, a window chosen to capture the period in which nanoethics and nanotoxicology emerged as recognised fields (Ebbesen et al., 2006; Maynard, 2006) through to the most recent clinical syntheses (Durgam & Oroszi, 2025; Gao et al., 2025).

3.4 Eligibility Criteria

Sources were eligible if they (a) were peer-reviewed journal articles, systematic or narrative reviews, peer-reviewed conference papers, scholarly book chapters, or official regulatory and policy documents; (b) addressed engineered nanomaterials (approximately 1-100 nm) used in, or directly relevant to, human health care; (c) reported data or substantive analysis on at least one of the four review domains (clinical application, toxicology and environmental risk, ethics and society, or regulation and testing); and (d) were published in English. Sources were excluded if they (a) concerned purely industrial or consumer nanotechnology with no stated health-care or health-risk relevance; (b) were editorials, news items, or conference abstracts without full text; (c) reported only physicochemical synthesis without biological, clinical, ethical, or regulatory analysis; or (d) duplicated findings already captured by a more recent or more comprehensive source from the same research group.

3.5 Study Selection

All records were exported to a reference management program and de-duplicated automatically, followed by manual verification. Selection then proceeded in two stages. In the first stage, two reviewers independently screened titles and abstracts against the eligibility criteria. In the second stage, the full texts of potentially relevant records were retrieved and assessed independently by the same two reviewers. Disagreements at either stage were resolved through discussion and, when consensus could not be reached, by a third reviewer. Reasons for exclusion at the full-text stage were recorded. The final evidence base comprises the 55 sources cited in this manuscript.

3.6 Data Charting

A standardised data-charting form was developed in a spreadsheet and piloted on five sources, after which it was refined. For each included source the following items were extracted: bibliographic details; study type; review domain(s); nanomaterial class (organic, inorganic, carbon-based, or hybrid); application or exposure setting; biological or societal mechanism described; reported outcomes; translational or regulatory status; affected stakeholders; and proposed mitigation or governance measures. One reviewer charted the data and a second verified all entries against the source documents. These fields correspond directly to the column structure of Tables 1-4.

3.7 Analytical Frameworks

Pre-specified frameworks were used to code charted data consistently. Clinical applications were coded into five domains (targeted delivery, imaging and diagnostics, theranostics, regenerative medicine, and nanovaccines) following recent comprehensive reviews (Durgam & Oroszi, 2025; Ma et al., 2024), and translational status was coded as approved, in clinical trials, or preclinical. Toxicological findings were coded by level of biological organisation (subcellular, cellular, organ, occupational, and environmental) and by mechanism, following the mechanism-based and adverse outcome pathway approaches to toxicity testing (National Research Council, 2007; Vinken & Blaauboer, 2017; Wu et al., 2020). Ethical issues were coded against the four principles of biomedical ethics (autonomy, beneficence, nonmaleficence, and justice), supplemented by stage-sensitive approaches to nanoethics that ask whether issues are novel or intensified at each stage of technological development (Kermisch, 2012; van de Poel, 2008). Regulatory material was coded by jurisdiction, regulatory instrument, and risk governance frame (Renn & Roco, 2006).

3.8 Appraisal of Sources

Because the evidence base combined empirical, review, normative, and regulatory sources, no single critical appraisal instrument was applicable. Each source was instead appraised for transparency of methods or argument, currency, relevance to the review questions, and the standing of the publication venue. Sources were not excluded on appraisal grounds; rather, appraisal informed the weight given to findings during synthesis, with priority given to recent comprehensive reviews and primary mechanistic studies when sources conflicted.

3.9 Synthesis

Charted data were synthesised using thematic synthesis in three steps: (1) line-by-line coding of extracted findings; (2) grouping of codes into descriptive themes within each domain; and (3) development of analytical themes across domains, with particular attention to points where clinical benefit and hazard arise from the same physicochemical property. Owing to the heterogeneity of study designs and outcomes, no meta-analysis was attempted. Findings are presented narratively (Section 4), in structured evidence tables (Tables 1-4), and in schematic figures (Figures 1-6). The search strings, data-charting form, and coded dataset are available as supplementary material to allow independent replication.

4. Synthesis of Evidence on Clinical Applications, Nanotoxicology, Socio-Ethical Implications, and Governance of Nanomedicine

4.1 Profile of the Evidence Base

The final evidence base comprised 55 sources published between 2004 and 2026 It was, perhaps unsurprisingly, uneven. Clinical and pharmaceutical sources were dominated by recent reviews (Durgam & Oroszi, 2025; Ma et al., 2024; Mitchell et al., 2021), whereas much of the ethical and governance literature dates from the mid-2000s to early 2010s, when nanoethics first took shape as a field (Ebbesen et al., 2006; Kermisch, 2012; Renn & Roco, 2006). Toxicological evidence came mainly from mechanistic in vitro and animal studies rather than from human cohorts (Mao et al., 2016; Wu et al., 2020). This temporal and methodological spread matters for interpretation, and we return to it in the Discussion.

4.2 Clinical Translation of Healthcare Nanotechnologies

4.2.1 Targeted Delivery as the Most Mature Domain

Taken together, the literature suggests that nanomedicine has moved, at least in some areas, from concept to clinical reality, though its maturity varies considerably across therapeutic domains (Table 1; Figure 2). Targeted drug delivery is clearly the most advanced. Some estimates place it at over three-quarters of nanomedicine market value and patent activity (Ma et al., 2024; Resnik & Tinkle, 2007), although such figures should probably be read as indicative rather than precise. Organic nanocarriers, chiefly liposomes, polymeric nanoparticles, and solid lipid nanoparticles, account for most approved formulations, with liposomal doxorubicin and albumin-bound paclitaxel as the canonical examples (Durgam & Oroszi, 2025; Ma et al., 2024). These products appear to work largely by combining EPR-based accumulation with ligand-receptor targeting, raising intratumoural drug levels while limiting off-target toxicity (Durgam & Oroszi, 2025; Mitchell et al., 2021).

4.2.2 Lipid Nanoparticles and Nanovaccines

If one development shifted perceptions decisively, it was the COVID-19 pandemic. LNP vectors protected and delivered mRNA constructs at global scale, and in doing so established a platform that is now being extended to other vaccines and to immuno-oncology (Durgam & Oroszi, 2025; Wilson & Geetha, 2022). It is worth noting, though, that this success concerns one carrier class and one cargo type; it does not by itself validate the wider portfolio of nanovaccine designs still under investigation (Chaturvedi et al., 2019).

4.2.3 Imaging, Diagnostics, and Theranostics

In diagnostics, SPIONs and functionalised gold nanoparticles have shown fairly consistent value as MRI and CT contrast agents, particularly for soft-tissue lesions, vascular inflammation, and myocardial scarring (Butt & Bach, 2024; Ma et al., 2024; Naseri et al., 2018). Stimuli-responsive systems that couple imaging with pH- or light-triggered release are expanding theranostic options in oncology (Durgam & Oroszi, 2025; Jia et al., 2023), but most remain in Phase I/II trials or earlier (Table 1).

4.2.4 Regenerative and Neurological Applications

Regenerative scaffolds, neural repair, brain-targeted delivery, and nanorobotics are, by contrast, still largely preclinical (Gao et al., 2025; Patel et al., 2016; Ruan et al., 2024). The obstacles reported most often are batch-to-batch reproducibility, uncertain long-term biocompatibility, and the difficulty of scaling up complex manufacturing (Durgam & Oroszi, 2025; Ma et al., 2024). In short, the clinical record so far is strong in a few well-defined niches and considerably thinner elsewhere.

4.3 Toxicological Profiles, Biological Fate, and Environmental Risk

4.3.1 Physicochemical Determinants of Toxicity

Across the toxicological literature, one pattern recurs: the same properties that make nanomaterials useful (sub-100 nm dimensions, high surface area-to-mass ratios, and surface charge) seem to govern their reactivity and toxicokinetics (Hannah, 2008; Ma et al., 2024; Maynard, 2006). Size, surface chemistry, aspect ratio, and biopersistence emerged as the main modifiers of harm (Table 2; Figure 3).

4.3.2 Oxidative Stress and Autophagic Dysfunction

Excessive intracellular ROS generation appears to be the most commonly reported mechanism across metallic and inorganic particles, including silver, copper oxide, titanium dioxide, and quantum dots (Hannah, 2008; Ma et al., 2024; Wu et al., 2020). Uncontrolled ROS production leads, in turn, to mitochondrial depolarisation, lipid peroxidation, DNA strand breakage, and eventually apoptotic or necrotic death (Ma et al., 2024; Wu et al., 2020). A second, partly overlapping mechanism, autophagic dysfunction and lysosomal impairment, has attracted growing attention (Mao et al., 2016; Wu et al., 2020). Endocytic uptake concentrates non-biodegradable particles in the endo-lysosomal system, where LMP, enzyme leakage, and blocked autophagic flux follow (Mao et al., 2016; Setyawati et al., 2014). The resulting failure to clear damaged organelles may accelerate inflammation through NLRP3 inflammasome activation (Wu et al., 2020), although the relative contribution of this route in vivo is not yet well quantified.

4.3.3 Biopersistence and Organ-Level Effects

At the organ level, high-aspect-ratio carbon nanotubes stand out. Inhaled or systemically distributed SWCNTs display fibre-like pathogenicity reminiscent of asbestos: frustrated phagocytosis by alveolar macrophages, chronic interstitial fibrosis, and, in some studies, pleural mesothelioma (Ebbesen et al., 2006; IEEE, 2009; Lam et al., 2006; Schulte & Salamanca-Buentello, 2007). Non-biodegradable metallic particles, meanwhile, appear to translocate across biological barriers and persist in the RES, particularly the liver, spleen, and bone marrow (Ebbesen et al., 2006; Ma et al., 2024). Whether such accumulation translates into clinically meaningful chronic toxicity in humans is, frankly, still unclear, given the absence of long-term follow-up data (Ma et al., 2024).

4.3.4 Occupational and Ecological Exposure

Exposure does not stop with patients. Workers in production and research settings may inhale airborne nanofibres or absorb metal oxides through skin, and the existing occupational control framework, built around conventional particulates, may not be well suited to these hazards (Choi & Ramachandran, 2009; Maynard & Kuempel, 2005; Schulte & Salamanca-Buentello, 2007). In the environment, released particles undergo aging processes such as sulfidation and organic corona formation and can accumulate in filter-feeders, algae, and crops (Hannah, 2008; Ma et al., 2024; Purohit et al., 2017). Carbon nanomaterials have been reported to pierce plant root cell walls, reducing yields and increasing pollutant uptake in rice and wheat (Purohit et al., 2017) (Figure 4).

4.4 Socio-Ethical Patterns: Autonomy, Privacy, and Health Equity

4.4.1 Consent Under Uncertainty

The ethical literature suggests that nanomedicine intensifies existing bioethical dilemmas more often than it creates wholly new ones, though its scale and predictive power do introduce some novel uncertainties (Allon et al., 2016; Kermisch, 2012; Resnik & Tinkle, 2007) (Table 3; Figure 5). Informed consent in clinical trials is the most frequently discussed issue. When biological behaviour is non-linear and long-term risks are unknown, communicating risk becomes difficult, and participants may not fully appreciate what they are agreeing to (Kermisch, 2012; Ma et al., 2024; Resnik & Tinkle, 2007).

4.4.2 Privacy and Diagnostic Knowledge

Ultra-sensitive nanosensors and lab-on-a-chip devices capture granular physiological and genetic information, raising concerns about bio-surveillance and commercial exploitation by insurers and employers (Allon et al., 2016; Baran, 2016; Kato, 2009). Related to this, sub-symptomatic screening sharpens the tension between a right to know and a right not to know, especially when detection precedes any effective therapy (Allon et al., 2016; Desai, 2012; Kato, 2009).

4.4.3 Enhancement and the Nano-Divide

Discussions of enhancement, involving neural nanodevices or nano-augmented muscle, centre on the blurred line between restoring and upgrading human function, and on its implications for dignity and fairness (Allon et al., 2016; Durgam & Oroszi, 2025; Ebbesen et al., 2006; Gordijn, 2006). Perhaps the most consistently voiced concern, however, is distributive. High development costs and restrictive patent landscapes threaten to confine access to affluent populations, widening what several authors call the "nano-divide" between developed and developing nations (Choi, 2005; Kermisch, 2012; Sahoo et al., 2010; Uskokovic, 2021).

4.5 Comparative Governance and Alternative Testing Paradigms

4.5.1 Divergent Regulatory Models

Regulatory agencies were consistently reported to struggle with fitting nanomaterials into conventional legal categories (Baran, 2016; Hogle, 2009; Ma et al., 2024) (Table 4; Figure 6). Two broad models emerge. The US FDA regulates nano-products case by case under existing authorities, without formal nano-specific definitions (Hogle, 2009; Resnik & Tinkle, 2007; Yeagle, 2007). The European Union has instead written nano-provisions into cosmetics, food, and chemical legislation, adopted a formal definition, and relies on REACH, QSARs, and the precautionary principle (Baran, 2016; European Commission, 2011; Mehlich & Thiele, 2014). Neither model, it seems, has yet resolved the absence of 10-20-year human safety data (Ma et al., 2024; Maynard, 2006).

4.5.2 Tiered Alternative Testing

A recurring finding is that relying solely on mammalian models to test the vast and growing range of nanomaterials is neither financially nor ethically feasible (Ma et al., 2024; Wu et al., 2020). The literature therefore points towards ATS guided by the 3Rs (Wu et al., 2020). In the tiered scheme most often proposed, high-throughput in vitro screening in human cells, targeting basal cytotoxicity, ROS generation, and autophagic dysfunction (Tiers I-II), is followed by validated non-mammalian whole-organism models (Tier III) (Krewski et al., 2010; Vinken & Blaauboer, 2017; Wu et al., 2020). Drosophila, C. elegans, and zebrafish embryos appear well suited to assessing developmental toxicity, genotoxicity, and tissue-specific fate, and may help bridge cell-based assays and rodent studies (Ecovoiu et al., 2016; Johnston et al., 2018; Vega-Alvarez et al., 2014). How well these models predict human outcomes, however, has not yet been firmly established.

5. Reconciling Therapeutic Promise with Biological, Environmental, and Societal Risk

5.1 Principal Findings

This review set out to read the clinical, toxicological, ethical, and regulatory literatures on nanomedicine together rather than apart. Doing so brings one theme into focus that is easy to miss when each literature is read alone: benefit and hazard in nanomedicine are, to a large extent, two expressions of the same physicochemical properties (Figure 1). The small size that lets a carrier cross the BBB (Gao et al., 2025) is also what lets an

Figure 5. Ethical, legal, and societal implications (ELSI) of nanomedicine organised around the four core principles of biomedical ethics. Five ethical domains surround the core principles of autonomy, beneficence, nonmaleficence, and justice: informed consent under conditions of uncertain long-term risk; privacy and bio-surveillance arising from continuous nano-diagnostic data; the right to know or not to know when detection precedes treatment; the boundary between therapy and human enhancement; and distributive justice, captured by the concept of the nano-divide. The bottom panel lists the principal governance responses proposed in the literature. Each domain is described in detail, with stakeholders and sources, in Table 3. Abbreviations: ELSI, ethical, legal, and societal implications; IP, intellectual property; R&D, research and development; RRI, Responsible Research and Innovation.

Figure 6. Regulatory governance of nanomedicine and the tiered alternative testing strategy for nanomaterial safety assessment. The left panel contrasts the product-based, case-by-case approach of the US Food and Drug Administration with the definitional and precautionary approach of the European Union, and with the International Risk Governance Council's distinction between passive (Frame 1) and active (Frame 2) nanostructures. The right panel shows the tiered alternative testing strategy aligned with the 3Rs principle, progressing from high-throughput basal cytotoxicity screening (Tier I) and mechanistic assays (Tier II) to non-mammalian whole-organism models (Tier III), with targeted rodent studies reserved for confirmation. Biological complexity and cost increase from top to bottom. Supporting details appear in Table 4. Abbreviations: AOPs, adverse outcome pathways; EC, European Commission; EMA, European Medicines Agency; IRGC, International Risk Governance Council; LMP, lysosomal membrane permeabilisation; QSARs, quantitative structure-activity relationships; REACH, Registration, Evaluation, Authorisation and Restriction of Chemicals; ROS, reactive oxygen species.

airborne particle travel along the olfactory nerve (Maynard & Kuempel, 2005). The large reactive surface that enables ligand functionalisation (Mitchell et al., 2021) also drives ROS generation (Wu et al., 2020). If this reading is correct, then safety cannot reasonably be treated as a downstream check applied to finished products; it has to be designed in from the beginning.

5.2 The Translational Gap

The uneven clinical maturity documented in Table 1 deserves some reflection. That liposomal chemotherapeutics, iron-oxide contrast agents, and mRNA-LNP vaccines have succeeded while most theranostic and regenerative platforms have not is probably no accident. The successful products tend to be compositionally simple, biodegradable or well characterised, and built on decades of lipid and polymer chemistry (Durgam & Oroszi, 2025; Wilson & Geetha, 2022). Multifunctional platforms, by contrast, layer imaging agents, targeting ligands, and stimulus-responsive chemistry onto a single particle, and each added function seems to add manufacturing variability and uncertainty about biological fate (Jia et al., 2023; Ma et al., 2024). There is also reason for some caution about the EPR effect on which much of the oncology literature depends; heterogeneous tumour vasculature and the biological barriers described by Blanco et al. (2015) suggest that passive accumulation in patients may be less dependable than in animal models. None of this argues against complex platforms, but it does suggest that claims of imminent clinical transformation should be tempered (Chaturvedi et al., 2019; Mehlich & Thiele, 2014).

5.3 Hazard as a Design Variable

The toxicological evidence summarised in Table 2 and Figure 3 has an encouraging implication, albeit a qualified one. Because harm appears to depend heavily on modifiable properties such as size, surface chemistry, aspect ratio, and degradability, it is at least partly within the designer's control (Maynard, 2006; Setyawati et al., 2014). Surface coatings that reduce ROS generation, avoidance of rigid high-aspect-ratio geometries, and preference for biodegradable matrices are all plausible design rules (Lam et al., 2006; Wu et al., 2020). The qualification is that most of this evidence comes from short-term in vitro or rodent studies; long-term human data remain almost entirely absent (Ma et al., 2024). The autophagy-lysosome pathway is a case in point: mechanistically it is compelling (Mao et al., 2016; Zhao et al., 2013), yet its clinical significance at therapeutic doses remains uncertain. We would argue, cautiously, that the field's next priority should be prospective long-term follow-up of patients already receiving approved nanomedicines, rather than further acute toxicity screens alone.

5.4 Occupational and Environmental Blind Spots

Occupational and environmental exposures seem to receive less attention than patient safety, which is somewhat surprising given that workers and ecosystems may experience higher cumulative doses than any individual patient (Choi & Ramachandran, 2009; Schulte & Salamanca-Buentello, 2007). The life-cycle perspective in Figure 4 makes clear that clinical benefit is only one stage of a longer chain that also includes synthesis, waste, and environmental transformation (Hannah, 2008; Purohit et al., 2017). Environmental aging may substantially alter particle toxicity, which means that hazard data generated on pristine laboratory materials may not apply to what organisms actually encounter (Ma et al., 2024). Life-cycle assessment and non-toxicological risk analysis remain underdeveloped (Ok & Benneyan, 2009), and integrating them into product development appears to be an important but neglected step.

5.5 Is Nanomedicine Ethically Novel?

Whether nanomedicine raises genuinely new ethical issues has been debated for nearly two decades. Allon et al. (2016) asked, provocatively, whether the debate was a "tempest in a teapot", while Kermisch (2012) suggested that novelty may emerge at particular stages of development rather than uniformly. Our synthesis (Table 3; Figure 5) tends to support a middle position. Consent, privacy, enhancement, and justice are familiar bioethical concerns, but nanomedicine appears to intensify them in specific ways: by making risks harder to quantify (Resnik & Tinkle, 2007), by generating more continuous and granular data (Kato, 2009), and by blurring the therapy-enhancement boundary through implantable and neural devices (Gordijn, 2006). Framing these issues as intensifications rather than novelties may actually be useful, since it allows existing ethical and legal instruments to be adapted rather than invented anew (van de Poel, 2008).

The "nano-divide" may be the issue with the most immediate practical consequences. If high-cost nanomedicines are developed mainly for affluent markets, the technology could widen rather than narrow global health inequities (Sahoo et al., 2010; Uskokovic, 2021). Concerns that financial interests can shape research agendas and bias reported findings (Resnik, 2004) add a further layer, and may also help explain the tendency towards overpromising noted by several authors (Mills & Fleddermann, 2005; Schaeffer & Olson, 2017). Tiered pricing, patent pools, and public investment directed at diseases of low-income countries have been proposed as remedies (Choi, 2005; Uskokovic, 2021), although evidence of their effectiveness in nanomedicine specifically is limited.

5.6 Governance and the Testing Paradigm

The regulatory picture (Table 4; Figure 6) is one of divergence rather than convergence. The US product-based approach offers flexibility but risks inconsistency, whereas the EU's definitional and precautionary approach offers clarity at the cost of complexity and a heavier evidentiary burden (Baran, 2016; Hogle, 2009; Yeagle, 2007). The distinction drawn by Renn and Roco (2006) between passive nanostructures and active nanosystems seems especially relevant here: as theranostic and responsive platforms move towards the clinic, frameworks designed for passive materials may prove inadequate. Mechanism-based ATS represent a realistic way forward (Krewski et al., 2010; National Research Council, 2007; Wu et al., 2020), but their regulatory acceptance will depend on demonstrating that invertebrate and zebrafish outcomes predict mammalian and human responses, which has not yet been shown convincingly (Johnston et al., 2018; Vinken & Blaauboer, 2017).

5.7 Implications for Research, Practice, and Policy

Several practical implications follow. For researchers, safety-by-design and full physicochemical characterisation should accompany efficacy studies from the outset (Ma et al., 2024; Maynard, 2006). For clinicians and ethics committees, consent processes for nanomedicine trials may need to communicate uncertainty explicitly rather than implying that risks are known (Resnik & Tinkle, 2007). For regulators, internationally harmonised definitions and acceptance criteria for alternative testing data would reduce fragmentation (European Commission, 2011; Mehlich & Thiele, 2014). And for funders, dedicated investment in ELSI research and public dialogue, together with RRI approaches, could help avoid the loss of public trust that has affected other emerging technologies (Mills & Fleddermann, 2005; Oftedal, 2014; Tegart, 2008).

5.8 Strengths and Limitations

The main strength of this review lies in its integrative scope, which allows connections across disciplines that are seldom examined together. Several limitations should nonetheless be acknowledged. As a narrative synthesis, it does not provide pooled quantitative estimates, and the selection and weighting of evidence involved judgement. Restricting the search to English-language sources may have omitted relevant regulatory and ethical work from non-English-speaking regions, including perspectives from the Global South (Sahoo et al., 2010). Much of the ethical and governance literature predates recent regulatory developments, so some debates may have moved on. Finally, the toxicological evidence relies heavily on in vitro and animal models, which limits confidence in conclusions about long-term human risk.

5.9 Future Directions

Future work would benefit from long-term pharmacovigilance and registry studies of approved nanomedicines, from validation studies linking alternative test outcomes to mammalian and clinical endpoints, and from life-cycle assessments carried out alongside product development (Ma et al., 2024; Wu et al., 2020). Empirical research on how patients and trial participants actually understand nanomedicine risks would also help ground ethical debates that have so far been largely theoretical (Kermisch, 2012; Schaeffer & Olson, 2017).

6. Conclusion

Nanomedicine has already delivered tangible clinical benefits, most notably in targeted chemotherapy, contrast imaging, and mRNA-lipid nanoparticle vaccination, yet much of its broader promise still remains at the preclinical stage. This review shows that benefit and hazard arise largely from the same nanoscale properties: the size and reactivity that enable targeted delivery also drive oxidative stress, lysosomal dysfunction, organ accumulation, and environmental persistence. Ethically, nanomedicine intensifies rather than replaces familiar dilemmas of consent under uncertainty, privacy, enhancement, and distributive justice, while regulation remains fragmented between product-based and precautionary models. Realising nanomedicine's potential will therefore require safety-by-design, mechanism-based alternative testing validated against human outcomes, harmonised

international definitions, long-term clinical surveillance, and genuine public engagement. Policies on pricing and research investment must also ensure that low-income populations share in the benefits. Treating safety, ethics, and equity as design requirements, rather than afterthoughts, offers the most credible path towards responsible, equitable clinical translation.

References