Self-interpreting quasi-site-rich electroanalytical interface for autonomous biosensing of hepatotoxic drugs

A carbon microfiber is engineered into a self-interpreting electroanalytical interface for on-site monitoring of therapeutic drug-levels. Through a voltammetric self-regulation strategy, the microfiber reconstructs into nanocrystalline domains enriched with naturally occurring quinone/hydroquinone (Q/HyQ) redox moieties, evolving into quasi-site architectures with a high electroactive site density (2.42 × 10^-8 mol cm^-2), which delivers an exceptional electron-transfer interface with a turnover frequency of 0.134 s^-1. This metal-free interface enables sensitive and selective detection of acetaminophen (APAP) and diclofenac (DCF) drug molecules, even at low abundance (LOD's: 0.89 ± 0.04 nM, 4.61 ± 0.32 nM), exhibiting strong selectivity against physiological interferents (<10% deviation) and stable analytical performance in PBS and human serum (∼97% signal retention) with excellent serum recovery (∼98%), demonstrating its potential for on-site monitoring. The engineered interface is experimentally calibrated for practical purposes and digitally integrated with a smartphone-deployable application, HepatoAI, enabling rapid interpretation of electrochemical signals into actionable therapeutic decisions. This work demonstrates that engineered carbon microinterfaces can be seamlessly integrated into intelligent fiber-based devices and electronics for autonomous human healthcare monitoring.