Strain-induced PtCu nanozymes for paper-based portable colorimetric immunoassay of carcinoembryonic antigen with smartphone readout.

Rapid and accurate detection of carcinoembryonic antigen (CEA) is of significant clinical importance for early cancer screening and prognosis monitoring. In this study, highly active PtCu bimetallic nanozymes were constructed via strain-induced deformation engineering. By employing a lattice strain regulation strategy to optimize their peroxidase-like catalytic performance, efficient catalytic color development in the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system was achieved. The introduction of Cu into the Pt nanoclusters effectively reduced the activation energy for simulating peroxidase activity (Ea = 15.11 kJ mol-1) and increased the substrate affinity for H2O2 (Km = 4.95 mM). Based on this nanozyme, a low-cost, portable paper-based colorimetric immunoassay platform was developed. Through antigen-antibody-specific recognition, the CEA concentration is correlated with the color intensity in the detection zone, and semi-quantitative readouts are achieved by combining smartphone image acquisition with RGB value analysis. The platform has a detection range for CEA of 0.1-50 ng mL-1, and effectively resists interference from matrix components in clinical blood samples. Test results from clinical serum samples demonstrated good agreement with clinical methods (R2 = 0.993), meeting clinical screening requirements. This study provides a novel nanozyme-catalyzed tool and paper-based analytical platform for the rapid on-site detection of cancer biomarkers, offering broad application prospects for early cancer screening in resource-limited regions.