Beyond drop-casting: A laser-sputtered TiO2/g-C3N4 photoanode for high-reproducibility photoelectrochemical immunosensing of PIVKA-II

Achieving consistent fabrication of photoelectrochemical (PEC) biosensors remains a challenge, largely due to the variability introduced by manual drop-casting of photoactive materials. To address this limitation, we report a one-step laser-sputtering technique that enables the construction of a standardized sensing platform for ultrasensitive detection of Protein Induced by Vitamin K Absence or Antagonist-II (PIVKA-II), a clinically relevant biomarker for hepatocellular carcinoma. In this process, a mixed target of titanium and melamine is irradiated, where laser-induced thermal and photon pressure effects simultaneously synthesize a TiO 2 /g-C 3 N 4 heterojunction and uniformly sputter-deposit it onto an ITO electrode. This laser-engineered photoanode exhibits excellent batch-to-batch consistency. After immobilizing anti-PIVKA-II antibody, the resulting immunosensor quantifies PIVKA-II based on the specific immunocomplex-triggered photocurrent decrease, achieving a wide linear range from 0.5 ng/mL to 1 μg/mL and a low limit of detection (LOD) of 0.13 ng/mL with high specificity, stability, and reproducibility. Beyond offering a dependable tool for clinical PIVKA-II analysis, this work establishes a generalizable laser-based manufacturing strategy that paves the way toward standardized production of next-generation PEC biosensors.