Paper-based degradable, label-free microRNA sensing platform based on oxide thin-film transistor arrays

MicroRNAs have started being used as an effective marker in early diagnosis and preoperative monitoring of cancers in recent years. Traditional microRNA testing technology, such as quantitative reverse transcription polymerase chain reaction (qRT-PCR) and various fluorescent and colorimetric assays, often suffer from complicated operations and limited sensitivity. They also produce significant electronic waste posing threats to human health and environment. Here, we propose a degradable biosensor using indium-gallium-zinc oxide (IGZO) thin-film transistor (TFT) arrays for rapid and highly sensitive detection of microRNAs from glioma exosome extracts (g-miRNAs). The IGZO transistor arrays fabricated on nanofibrillated cellulose paper exhibit high electronic performance with a current on/off ratio >1.5 × 10⁶, a mobility of 9.6 cm² V^-1·s^-1, a subthreshold swing <0.5 V·dec^-1, and excellent bias stress stability. Specific DNA probes in the IGZO channel bind selectively with g-miRNA targets to form DNA-RNA double strands, offering high specificity even when coexisting with high concentrations of nonspecific microRNAs. The inherent negative charges in DNA and g-miRNA molecules sensitively modulate the IGZO channel conductivity, leading to a positive shift of threshold voltage and decrease of source-drain current. These changes are linearly correlated with microRNA concentrations from 1 fM to 100 pM, with a detection limitation of 350 aM. Furthermore, the paper-based IGZO transistor array nearly completely dissolves in a NaOH solution after 300 min. The proposed approach combines easy-to-operate, point-of-care microRNA testing with lightweight, low-cost, biocompatible, and degradable devices, showing great promise for early diagnosis of glioma and most likely also other tumors.