Wettability-Enhanced Photothermal Vertical Flow Biosensor on a Syringe for PSA Detection Using TaTe₂ Nanosheets

Photothermal vertical flow biosensors (VFBs) have emerged as attractive tools for biomarker detection, addressing restricted sensitivity, insufficient quantitative accuracy, and geometric mismatch issues of traditional photothermal lateral flow biosensors (LFBs) while retaining rapid detection capability. Herein, we developed a syringe-based wettability-enhanced photothermal vertical flow biosensor (SW-PVFB) for prostate-specific antigen (PSA) detection, integrating tantalum ditelluride (TaTe₂) nanosheets as highly efficient photothermal probes and hydrophilic/hydrophobic patterned nitrocellulose (NC) membranes for precise fluid control and target enrichment. The 10-20-nm-thick TaTe₂ nanosheets exhibited a photothermal conversion efficiency of 50.74% and good stability, efficiently converting near-infrared irradiation to detectable heat signals. The hydrophilic/hydrophobic NC membrane confined fluid flow to the detection zone, enhancing the TaTe₂ accumulation and signal intensity. Under optimal conditions, SW-PVFB detected PSA in urine over 0-160 ng mL^-1 with a limit of detection (LOD) of 0.028 ng mL^-1, significantly outperforming conventional LFBs and standard VFBs. It showed high specificity against interfering proteins (e.g., CA9 and CEA), good reproducibility (RSD ≤ 3.8%), and recoveries of 89.1-112.7% in spiked urine. Integrated with a smartphone for portable signal readout, this SW-PVFB provides a sensitive, user-friendly point-of-care testing (POCT) platform for decentralized PSA diagnostics.