Aptamer-functionalized terahertz metasensor for sensitive and specific determination of alpha-fetoprotein.

Alpha-fetoprotein (AFP) is a key serum biomarker for the early diagnosis of hepatocellular carcinoma (HCC). In this study, a dual-band terahertz (THz) metasurface sensor (metasensor) was developed and functionalized with computationally selected aptamers for sensitive and specific detection of AFP. A 1000-sequence ssDNA library was screened using an in silico systematic evolution of ligands by exponential enrichment (SELEX) pipeline combining Mfold secondary structure prediction, RNA Composer 3D modeling, and dual-platform docking (HDOCK/ZDOCK) with Z-score consensus ranking. The lead candidate, Seq69, was immobilized on the metasurface and compared with a commercial anti-AFP antibody and a literature aptamer (AP273, hereafter apt2) to enable a three-way performance comparison on the same platform. The sensor achieved a refractive-index sensitivity of 315 GHz/RIU. The Seq69 aptamer-functionalized THz metasurface (AFTM) biosensor exhibited a concentration-dependent frequency shift over 0.02-100 ng/mL AFP, with an apparent dissociation constant of 0.058 ng/mL (0.83 pM) and a limit of detection of 5.68 pg/mL (81.1 fM), outperforming both the antibody- and AP273-modified counterparts in sensitivity and specificity. This work provides a promising strategy for early HCC screening and offers insights into the rational selection of biorecognition elements for THz metamaterial biosensors.