Pd/Pt-decorated poly(tannic acid) nanospheres as a multifunctional label for ultrasensitive lateral flow immunoassay of methamphetamine

Methamphetamine (METH) abuse remains a pressing global health threat, driving the demand for on-site, ultra-sensitive detection tools. Herein, we design and fabricate a triple-functional nanozyme through a rational structural design strategy, involving the in situ reduction of Pd/Pt precursors on poly(tannic acid) nanospheres (PTAN). The phenolic-rich surface of PTAN@Pd/Pt allows for one-step, covalent-free antibody immobilization while preserving bioactivity and, concurrently, creates a synergistic catalytic interface. When integrated into a lateral flow immunoassay (LFIA), the platform affords visual limits of detection of 1.0 ng/mL (colorimetric signal) and 0.5 ng/mL (catalytic signal), representing 15- and 30-fold improvements over conventional gold nanoparticle-based LFIAs, and lowers the drug concentration cut-off value (critical value) to 19 ng/mL and 40 ng/mL, respectively. Quantitative analysis showed excellent linearity, and validation in spiked hair, serum, and urine samples yielded high recoveries and low coefficients of variation (CVs). The PTAN@Pd/Pt nanozyme therefore offers a powerful and practical tool for rapid METH screening in clinical diagnostics and forensic science.