Ultrasensitive detection of alpha-fetoprotein via ZnO-mediated photo-ATRP signal amplification on...

Alpha-fetoprotein (AFP) is a key serum biomarker for the early detection and monitoring of hepatocellular carcinoma (HCC). However, conventional methods such as enzyme-linked immunosorbent assay (ELISA) and chemiluminescence immunoassay often lack the sensitivity and practicality required for point-of-care testing, due to their complex procedures, high cost, and moderate detection limits. To overcome these limitations, we developed a highly sensitive fluorescent biosensing platform that integrates chitosan-functionalized magnetic beads with a ZnO-enhanced photoinduced atom transfer radical polymerization (photo-ATRP) signal amplification strategy. Carboxyl-modified Fe₃O₄ magnetic beads were used to immobilize anti-AFP antibodies for specific target capture. An azide-terminated AFP aptamer was conjugated via click chemistry to a phenylboronic acid functional monomer, which then selectively bound to chitosan through boronate-diol interactions. Multiple ATRP initiation sites were grafted onto chitosan using an NHS-activated bromoisobutyrate initiator. Under UV light, ZnO nanoparticles facilitated efficient electron transfer, promoting the controlled growth of fluorescent polymer brushes from the chitosan backbone. This approach enabled significant signal amplification, yielding a wide linear detection range from 10.0 fg/mL to 10.0 ng/mL and an exceptionally low detection limit of 2.3 fg/mL. The biosensor also demonstrated high selectivity, good storage stability, and reliable performance in diluted human serum. This work presents a robust, cost-effective, and sensitive platform for AFP detection, showing promising potential for AFP monitoring in complex biological matrices.