Highly sensitive CdSe/ZnS quantum dots immunosensor via DNA tetrahedra nanostructure-assembled with multiple hybridization chain reaction

Abstract

Quantum dots (QDs) based fluorescence immunosensor (QD-FLIS) has shown promise in target analysis on account of its superior characteristics. However, conventional QD-FLIS lacks signal amplification strategy for target molecules, resulting in limited fluorescence signal output. Herein, a programmable and high-sensitive DNA tetrahedra nanostructure-assembled with multiple hybridization chain reaction (DTN-mHCR) was designed to achieve the signal amplification of QD-FLIS. HCR served as signal amplified unit and the binding site for QDs signal tag; DTN provided multiple HCR initiations and maintained initiators in extended state, promoting signals generation by enhancing the hybridization dynamics and efficiency of HCR, which was confirmed through theoretical simulations and experimental studies. Upon recognition of the target protein (C-reactive protein, CRP, in this instance), a sandwich immune complex is formed, prompting the binding of DTN-mHCR nanostructures via biotin-streptavidin interaction and nucleic acid tether. This process anchors DNA-functionalized QDs (DNA-QDs) probes, yielding amplified photoluminescence (PL) signals for detection. Under optimized conditions, this DTN-mHCR based QD (DTN-mHCR-QD) immunosensor exhibits a wide linear response to CRP from 0.25 to 100 ng/mL, with a detection limit of 0.069 ng/mL, 31.1-fold lower than QD-based immunosensor (2.148 ng/mL). Furthermore, this immunosensor had competitive detection results in clinical samples. The proposed immunosensor is a multifunctional biosensing platform with universality, providing a new direction for the highly sensitive detection of targets in the sensing field.