Aptamer-Conjugated Multi-Quantum Dot-Embedded Silica Nanoparticles for Lateral Flow Immunoassay

Abstract

Lateral flow immunoassays (LFIAs) are widely used for their low cost, simplicity, and rapid results; however, enhancing their reliability requires the meticulous selection of ligands and nanoparticles (NPs). SiO2@QD@SiO2 (QD2) nanoparticles, which consist of quantum dots (QDs) embedded in a silica (SiO2) core and surrounded by an outer SiO2 shell, exhibit significantly higher fluorescence intensity (FI) compared to single QDs. In this study, we prepared QD2@PEG@Aptamer, an aptamer conjugated with QD2 using succinimidyl-[(N-maleimidopropionamido)-hexaethyleneglycol]ester, which is 130 times brighter than single QDs, for detecting carbohydrate antigen (CA) 19-9 through LFIA. For LFIA optimization, we determined the optimal conditions as a 1.0:2.0 × 10−2 ratio of polyethylene glycol (PEG) to aptamer by adjusting the amounts of PEG and aptamer, phosphate-buffered saline containing 0.5% Tween® 20 as a developing solution, and 0.15 μg NPs by setting the NP weight during development. Under these conditions, QD2@PEG@Aptamer selectively detected CA19-9, achieving a detection limit of 1.74 × 10−2 mg·mL−1. Moreover, FI remained stable for 10 days after detection. These results highlight the potential of QD2 and aptamer conjugation technology as a reliable and versatile sensing platform for various diagnostic applications.