Dual protecting encapsulation synthesis of ultrastable quantum-dot nanobeads for sensitive and accurate detection of cardiac biomarkers

Abstract The labeling material is a key factor that determines the ability of lateral-flow immunoassay (LFIA) for accurate and sensitive detection. Herein, a dual protection strategy with both polyvinylpyrrolidone (PVP) winding and SiO2 coating has been first developed for generating quantum dot beads@SiO2-COOH (QBs@SiO2-COOH) nanobeads with high fluorescence and extraordinary stability, which greatly improved the sensitivity and stability of rapid LFIA. QBs@SiO2-COOH showed outstanding colloidal stability in complex matrices and 1,967-fold higher luminescence than that of corresponding QDs. The novel LFIA nanosensor was constructed by utilizing synthesized QBs@SiO2-COOH as the reporter to realize rapid quantitative detection of cardiac troponin I (cTnI) within 10 min using only 60 μL of sample. The limit of detection (LOD) was 0.036 ng mL−1 with the excellent linearity relationship between 0.12 and 125 ng mL−1. Importantly, the detection method owned good reproducibility (CV