Iswary Letchumanan, Xin Jie Keith Ng, Subhashini Raj Kumal, Farid Nazer Faruqu, Hao Ing Yeoh, Chee Wun How, Thian Chee Loh, Jiunn Liang Tan, Yen-Chang Chen, Kevin C-W Wu, Sook Mei Khor, Bey Fen Leo
A highly sensitive label-free aptamer-based electrochemical biosensor is reported for the direct detection of extracellular vesicles (EVs), a promising circulating biomarker associated with disease progression and intercellular communication. The sensing platform was fabricated by modifying a glassy carbon electrode (GCE) with a ternary nanocomposite comprising a metal-organic framework (MOF), poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) conductive polymer, and gold nanoparticles (AuNPs), followed by immobilization of a CD63 aptamer for selective EV recognition. Comprehensive characterization using FESEM, EDX, TEM, FT-IR, XRD, and XPS analyses confirmed the morphological, structural, and chemical properties of the nanocomposite. The synergistic integration of the high surface area and abundant binding sites of the MOF, the mixed ionic-electronic conductivity of PEDOT: PSS, and the excellent bioconjugation capability of AuNPs enhanced the electrochemical sensing performance. Under optimized conditions, the biosensor achieved an ultralow limit of detection of 3.2 particles/µL, outperforming recently reported EV biosensors, with recovery rates ranging from 87 to 100% in serum samples. Importantly, the high sensitivity of the biosensor enables reliable detection of low-abundance tumor-derived EVs in complex biological matrices (as low as ~ 10 particles/µL) while also demonstrating good reproducibility, selectivity, and storage stability. Furthermore, the platform successfully differentiated EV profiles between healthy individuals and cancer patients, highlighting its promising potential for clinical translation as a rapid and minimally invasive cancer screening tool.