Immobilization of cross-linked enzyme aggregates on organic field-effect transistor for cholesterol detection on...

This study reports the development of an ultrasensitive cholesterol biosensing platform utilizing an organic field-effect transistor (OFET) with a functionalized extended-gate electrode. The sensing interface was engineered through the immobilization of a multi-enzyme system comprising cholesterol esterase (CE), cholesterol oxidase (COx), and horseradish peroxidase (HRP) within a chitosan biopolymer matrix, ensuring high specificity and enhanced catalytic efficiency. The detection mechanism relies on an enzymatic cascade reaction: CE-mediated hydrolysis of cholesterol esters liberates free cholesterol, which is subsequently oxidized by COx to yield H₂O₂. The generated H₂O₂ is then electrocatalytically reduced by HRP, producing a quantifiable electrochemical signal that is efficiently transduced and amplified by the OFET architecture. The chitosan matrix not only provides optimal enzyme immobilization but also improves biocatalytic stability and interfacial charge transfer. To ensure robust system performance, a custom-designed printed circuit board was integrated, enabling stable power delivery and energy-efficient operation. The fabricated biosensor demonstrates exceptional analytical performance, featuring a broad linear dynamic range, a remarkably low detection limit, and outstanding repeatability along with long-term operational stability. This work establishes a scalable and cost-effective methodology for fabricating portable cholesterol monitoring systems, highlighting significant potential for point-of-care diagnostics and personalized healthcare applications.