High-density AuNP-decorated microneedle electrochemical aptasensor for minimally invasive CEA detection in interstitial fluid.

A high-density microneedle (MN) electrochemical aptasensor integrated with gold nanoparticles (AuNPs) and aptamer recognition elements, enabling label-free, minimally invasive, and rapid detection of carcinoembryonic antigen (CEA) in interstitial fluid (ISF) is proposed. The AuNP-functionalized MNs enhance electrochemical signal transduction owing to their substantial electroactive surface area and high density of catalytic sites. Concurrently, CEA aptamers enable their covalent immobilization onto the nanostructured AuNP-modified electrode surface through gold-thiol (Au-S) bonds. Electrochemical analyses demonstrate a wide linear detection range (0.05-500 ng/mL), low limits of detection (0.012 ng/mL in phosphate buffer solution (PBS), 0.028 ng/mL in artificial interstitial fluid (ISF)). The biosensor also exhibited excellent stability, repeatability, and specificity. As a proof of concept, skin model tests further confirmed the ability of the MN biosensor to extract and electrochemically detect CEA levels in artificial ISF, with a detection limit of 0.034 ng/mL. This sampling-detection integrated biosensor provides a new approach for wearable point-of-care technologies in early cancer diagnosis.