Thermo-Responsive Polymer/Cerium–Gold Nanoparticle-Decorated UiO-66-NH ₂ Nanozymes for Colorimetric Sensing of Captopril

Although nanozymes offer tunable catalytic activity for bioanalysis, conventional monometallic formulations are often constrained by suboptimal efficiency and a lack of environmental adaptability. Herein, thermo-responsive polymer-functionalized bimetallic nanozymes, UiO-66-NH2-poly(N-isopropylacrylamide-co-2-vinyl-4,4-dimethylazlactone)-bovine serum albumin/cerium–gold nanoparticles (U-PNV-BSA/Ce–AuNPs), were successfully designed for the high-performance colorimetric detection of captopril. Comprehensive characterization (TEM, XPS, EDS, XRD) confirmed the material’s structural integrity. Mechanistically, the nanozymes integrates the synergistic electron transfer of Ce3+/Ce4+ and Au0/Au+ redox couples with temperature-regulated nanoconfinement induced by the polymer coating. This dual mechanism significantly amplified reactive oxygen species (ROS) generation, resulting in a 100-fold and 13-fold enhancement in peroxidase-like activity compared to monometallic AuNPs and CeNPs nanozymes, respectively. Based on this, a colorimetric sensing platform was constructed, demonstrating a good linear relationship (R2 = 0.996) and a low limit of detection (0.18 μM). Furthermore, the method exhibited excellent reliability in mouse serum samples with satisfactory recoveries ranging from 97.2% to 102.1%. This work demonstrates that integrating stimuli-responsive components with synergistic bimetallic catalysts offers a promising strategy for pharmaceutical analysis.