Cauliflower-like platinum nanostructures mediated photothermal and colorimetric dual-readout biosensor for sensitive cholesterol detection

Point-of-care testing has been extensively utilized for in-home diagnosis, customized testing, and pandemic monitoring. The current study aims to develop a nanozyme-mediated dual-readout (colorimetric and photo -thermal) bioassay for straightforward and sensitive detection of cholesterol. The nanozyme, cauliflower-like platinum nanostructures (CS@Pt NS) were synthesized by chemically reducing the Pt precursor in the chito-san (CS) solution. CS as a stabilizer excels at controlling the surface properties, enhancing peroxidase-like ac-tivity, and improving colloidal dispersion, and stability. The dual-readout sensor for cholesterol detection was proposed by combining cholesterol oxidase-catalyzed cholesterol oxidation with CS@Pt NS-catalyzed TMB oxidation. The oxidized TMB (TMBox) acts as a probe for both colorimetric and photothermal readouts because of having excellent absorbance in visible and near-infrared (NIR) regions. The absorption of NIR laser-driven light by the TMBox in the reaction solution generates heat, which is proportional to the concentration of cholesterol. The dual-readout sensor shows a linear detection range of 0-2 mM, with a limit of detection (LOD) of 45 mu M for the colorimetric assay and 25 mu M for the photothermal assay. Furthermore, the sensor successfully detects cholesterol in spiked human serum with acceptable accuracy.