Developing a highly-sensitive aptasensor based on surface energy transfer between InP/ZnS quantum dots and Ag-nanoplates for the determination of insulin

Abstract

A novel optical aptasensor with excellent sensitivity and high selectivity was fabricated as a tool for insulin determination in human blood plasma. The performance of the probe is based on surface energy transfer (SET) between thioglycolic acid capped indium phosphide/zinc sulfide quantum dots (TGA-InP/ZnS QDs) (donor) and Ag-nanoplates (acceptor). Initially, low-risk TGA-InP/ZnS core–shell QDs with high fluorescence quantum yield (ФF = 73%) were synthesized via the stepwise method. Ag-nanoplates with well surface plasmon resonance (SPR), high extinction coefficient, viability, good optical and chemical stability act as fluorescence signal quencher. Insulin aptamer strands (Ap) was used as the biorecognition element and linked to the QDs surface by the covalent bonds (Ap-QDs). In the absence of insulin, Ap-QDs are adsorbed on the Ag-nanoplates surface and fluorescence intensity quenched. By adding insulin to the media, due to the high aptamer affinity to the insulin, AP-QDs getting away from Ag-nanoplates and the fluorescence signal of QDs was restored related to the insulin quantity. In the optimized situations probe works in the dynamic range (DR) (0.001–5000 nM) with a limit of detection (LOD = 0.5 pM). This method was used to measure insulin in blood plasma and its accuracy was estimated by comparison obtained results with the standard method (HPLC).