A bioinspired nanozyme cascade sensor for fluorometric and smartphone-assisted colorimetric cholesterol analysis in serum and food samples.

Analyzing cholesterol (Chol) levels in serum and food samples is essential for monitoring cardiovascular health, diagnosing lipid-related disorders, and evaluating the dietary impacts on Chol concentrations, thus guiding both preventive and therapeutic strategies. In this context, we present a bioinspired nanozyme-based cascade sensor designed for rapid, label-free, and dual-mode Chol detection in complex biological and food samples. This sensor integrates cholesterol oxidase (CholOx) with chromium-doped vanadium oxide nanobelts (Cr@VO₂ NBs), which exhibit remarkable peroxidase-mimetic activity under physiological conditions. The system enables highly sensitive fluorometric detection of Chol over a wide concentration range of 0-850 μM with an ultra-low limit of detection of 0.01 μM, while also providing smartphone-assisted colorimetric visualization for convenient on-site semi-quantitative analysis. Unlike conventional Chol sensors, our platform eliminates the need for costly instrumentation and complex procedures, positioning it as an ideal solution for point-of-care applications. The method was rigorously validated with clinical serum and food samples, demonstrating outstanding correlation with established assays. In addition, a smartphone-assisted colorimetric readout was developed as a portable auxiliary mode, showing a linear relationship between the digital color parameter (R + G)/B and Chol concentration, with a detection limit of 0.25 μM. With its superior selectivity, reproducibility, and long-term stability, the system offers substantial promise for widespread adoption in Chol monitoring and the early diagnosis of Chol -related diseases. This study not only advances the field of Chol biosensing but also establishes the foundation for next-generation, multifunctional biosensing platforms with vast potential in both clinical diagnostics and food quality control.