A highly sensitive multicolor quantum dots-polylysine@FLISA platform for the simultaneous detection of serum PD-L1, SORL1, and GDF-15 levels

Background Colorectal cancer (CRC) requires accurate diagnostic approaches for effective clinical management. Serum biomarkers PD-L1, SORL1, and GDF-15 offer valuable diagnostic information, but their simultaneous detection is hindered by the limited sensitivity and multiplexing capacity of conventional immunoassays. This work addresses the critical need for a highly sensitive multiplexed platform for precise CRC diagnosis. Results We constructed a multicolor QDs-K@FLISA platform employing K24 polylysine-conjugated CdTe quantum dots with distinct emissions (543/587/647 nm). The K-peptide enabled multi-QD loading, significantly amplifying fluorescence signals and facilitating ultrasensitive triplex detection. The assay achieved exceptional sensitivity with detection limits of 0.996 pg/mL (PD-L1), 1.101 pg/mL (SORL1), and 1.035 pg/mL (GDF-15), along with wide linear ranges (7.8-500 pg/mL for PD-L1/SORL1; 6-1600 pg/mL for GDF-15). High reproducibility was demonstrated (RSD < 2.3%). Clinical validation using 120 serum samples revealed strong correlation with reference methods (R 2 > 0.99) and effective discrimination between CRC patients and healthy controls. Significance and Novelty This work establishes a novel peptide-mediated multi-QD loading strategy that enables ultrasensitive multiplexed detection of CRC biomarkers. The platform presents significant potential for clinical applications in CRC diagnosis and biomarker profiling.