Volume 5 Number 1 2026
Single-Entity Electrochemistry for Ultrasensitive Molecular Diagnosis: Collision Dynamics, CRISPR Nanointerfaces, and Clinical Translation
Yee Mun Oon 1* Aya Elfiki 2
Biosensors and Nanotheranostics 5 (1) 1-8 https://doi.org/10.25163/biosensors.5110985
Submitted: 19 January 2026 Revised: 06 March 2026 Accepted: 15 March 2026 Published: 17 March 2026
Most electrochemical biosensors still report an average. The current recorded at a conventional electrode sums the behaviour of millions of nanoparticles or molecules, and in doing so it conceals the particle-to-particle differences in size, catalytic activity and interfacial kinetics that often decide whether a scarce biomarker is detected at all. Single-entity electrochemistry, which follows the stochastic collisions of individual nanoparticles with an ultramicroelectrode, offers a route around this averaging and is now moving from physical chemistry into molecular diagnostics. This review traces that transition. We first describe the transduction modes that underpin nano-impact measurements: catalytic spikes, adsorptive staircase steps and blocking events, alongside the edge effects and filtering artefacts that complicate their interpretation. We then examine how signal amplification has been rebuilt around the single-entity principle, from one-to-many nuclease recycling that liberates tens of millions of catalytic reporters per target to in-electrode Faraday cage-type architectures that bring every label into the electron-transfer zone. A third strand concerns CRISPR-Cas systems, whose programmable trans-cleavage has been paired with tetrahedral DNA scaffolds, hairpin-decorated magnetic beads and PAM-free strand-displacement circuits. Across the platforms compared, reported detection limits reach the attomolar to low-femtomolar range for microRNAs and viral RNA and sub-nanomolar levels for mercuric ions. Performance in serum, urine and food matrices is encouraging, though less consistent, and depends on antifouling chemistry and magnetic separation. We close by weighing the obstacles that still limit translation, including biofouling, fabrication reproducibility and signal deconvolution, and the extent to which microfluidic automation and machine learning may resolve them.
Keywords: single-entity electrochemistry; nano-impact; ultramicroelectrode; CRISPR-Cas12a; signal amplification; Faraday cage-type biosensor; molecular diagnostics; point-of-care testing
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