An Organic Field-Effect Transistor-Based NANOFLEX-BIOCHIP for Ultrasensitive and Rapid Detection of HBV and HIV Biomarkers Using Atangana-Baleanu-Caputo Fractional-Order Modeling

Abstract

Christian Idogho* and Peter Idoko

Early and accurate detection of viral infections remains a major challenge in global healthcare, particularly for Hepatitis B virus (HBV) and Human Immunodeficiency Virus (HIV), where biomarker concentrations during early infection fall below the detection limits of conventional diagnostic assays. Here, we report the design, fabrication, and experimental validation of an organic field-effect transistor (OFET)-based NanoFlex-BioChip for ultrasensitive and rapid detection of hepatitis B surface antigen (HBsAg) and HIV-1 p24 antigen. The device employs a bottom-gate, top-contact architecture based on solution-processed poly(3-hexylthiophene) (P3HT) and a selectively biofunctionalized interface with covalently immobilized antibodies. Biomolecular binding induces electrostatic gating of the semiconductor channel, resulting in measurable threshold voltage shifts of up to 0.5 V and a 15–20% suppression of drain current. These electrical signatures enable direct, label-free transduction of antigen–antibody interactions. The NanoFlex-BioChip achieves limits of detection of 12 fM for HBsAg and 17 fM for HIV p24, with sensitivities of 2.5 nA/fM and 1.8 nA/fM, respectively, over a dynamic range spanning 10 fM to 10 nM. Rapid signal transduction is observed within 60 s with microliter-scale sample volumes (2–5 μL). Device-to-device reproducibility is confirmed across multiple fabricated devices (N = 12), with signal variation below 8%. Device performance was further evaluated using spiked human serum samples, demonstrating reliable detection in complex biological matrices. Validation studies using clinical samples from confirmed patient cases are currently underway, with initial sample collection completed and data analysis expected within the next 3 months. This ongoing process aims to confirm clinical utility and support further translational development. To interpret the complex sensing dynamics inherent to organic bioelectronic systems, a fractional-order modeling framework based on the Atangana–Baleanu–Caputo (ABC) derivative is introduced. This model captures nonlocal memory effects, charge trapping, and anomalous transport phenomena, reducing prediction error by over 60% compared to classical integer- order approaches and accurately reproducing both transient response and long-tail relaxation behavior. The device demonstrates stable performance across physiologically relevant pH (6–8), temperature (20–37 °C), and ionic strength, while maintaining compatibility with flexible substrates and scalable fabrication processes. These results establish the NanoFlex-BioChip as a robust, low-cost platform for decentralized viral diagnostics and highlight the critical role of fractional-order physics in advancing organic bioelectronic sensing technologies.

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