A Peptide Nucleic Acid‐Functionalized Heterojunction Thin Film Transistor as a Scalable and Reusable Platform for Label‐Free Detection of MicroRNA

Abstract Miniaturized, reusable, and scalable biosensors are key enablers of precision diagnostics and accessible healthcare. Among emerging liquid biopsy cancer biomarkers, microRNAs (miRNAs) have demonstrated transformative potential; however, conventional detection methods rely on expensive enzymes, labels, and bulky instrumentation, limiting clinical utility. Field effect transistor (FET) biosensors offer a promising alternative owing to their miniaturized size, intrinsic amplification capacity, user‐friendliness, and scalability. This study introduces a probe‐functionalized thin film transistor‐based miRNA biosensor, called miR‐TFT, enabling label‐free, enzyme‐free, ultrasensitive, and specific detection of miRNA. The highly scalable device features a tri‐channel heterojunction thin‐film transistor (HJ‐TFT) with an In 2 O 3 /ZnO channel, functionalized with bespoke peptide nucleic acid (PNA) probes via phosphonic acid anchor groups. Compared to conventional oligonucleotides, PNAs offer superior specificity, stability, and resistance to degradation. Sequence‐specific binding between the target miRNA and PNA probes induces charge modulation at the buried heterointerface, altering the transistor's electrical properties. This interaction produces an amplified signal, yielding an ultra‐low 0.6 fM limit‐of‐detection with single‐nucleotide specificity. Moreover, the device supports facile surface regeneration through O 2 plasma treatment, enabling device reuse without compromising performance. In addition to its exceptional analytical performance, miR‐TFT offers portability, reusability, and compatibility with wafer‐scale manufacturing, positioning it as a transformative solution to drive decentralized precision diagnostics.