Photodynamic-Driven Growth of Aqueous CdSe/ZnSe/ZnS//ZnS Quantum Dots for Inflammatory Factors Multiplexed Detection via a Ratiometric-Fluorescence Immunosensor

Core/shell quantum dots (QDs) with a low cadmium (Cd) content and an intermediate ZnSe-based shell have attracted significant attention due to their excellent fluorescence properties. However, their poor water and oxygen stability presents a major challenge for transferring QDs to the aqueous phase. Herein, we prepared CdSe/ZnSe/ZnS//ZnS core/shell/shell QDs exhibiting both high fluorescence and good stability through a photodynamically driven mild growth process conducted at low temperatures. Growing a thicker, wide bandgap ZnS shell can effectively limit the domain of the excitons within the core, preventing fluorescence bursting caused by the complexation of internal excitons during the ligand exchange process. Furthermore, the prepared red and green core/shell QDs were biofunctionalized to develop a ratiometric-fluorescent immunosensor for the quantitative detection of four inflammatory biomarkers: C-reactive protein (CRP), serum amyloid A (SAA), interleukin-6 (IL-6), and procalcitonin (PCT). The novel immunosensors detected CRP, SAA, PCT, and IL-6 antigens with a broad linear range and high sensitivity, reaching 0.128, 0.047, 0.041, and 0.047 ng/mL, respectively. Clinical validation of the proposed assay demonstrated its high accuracy in detecting serum samples. Based on tailored low Cd content CdSe/ZnSe/ZnS//ZnS QDs as fluorescent probes, this highly sensitive ratiometric-fluorescent immunosensor shows great potential for the quantitative detection of biomarkers in in vitro diagnostics.