Detection of Four Early Tumor Biomarkers Using Micron-Sized Silica Microspheres Encoded With QDs (CQDs) for Tumor Early Screening

Detection of tumor biomarkers is critical for early cancer diagnosis and cancer therapeutic monitoring, but traditional methods often lack sufficient sensitivity and specificity, especially at low biomarker concentrations. To address this challenge, in this study a multiplex detection platform based on core–shell quantum dot-encoded silica microspheres was developed for highly sensitive, simultaneous detection of multiple tumor biomarkers in a single assay. The core–shell silica architecture provides a high surface area for bioconjugation, while embedded quantum dots (QDs) offer strong fluorescence, making them ideal labels. Carbon quantum dots (CQDs), which have low toxicity, superior biocompatibility, and high photostability, were used as reporter molecules instead of organic dyes. This choice improved detection sensitivity and reduced the detection system’s environmental toxicity relative to traditional dye-based assays. After optimizing QD–silica conjugation and immunoassay conditions, the platform achieved highly sensitive multiplex detection of four tumor biomarkers (AFP, CEA, CA125, CA19-9) commonly used in early cancer screening. Results demonstrated specific detection of all four targets within a short time frame, with excellent stability and reproducibility. By enhancing sensitivity for these biomarkers and reducing assay toxicity while improving stability, this platform shows significant potential to greatly improve early cancer screening and cancer therapeutic monitoring in clinical practice.