Study On The Detection Of Pb²⁺ Based On Aptamer-InP/ZnS@GO Fluorescent Probes

Fluorescent probes have several advantages for biomedical research, such as high sensitivity, good selectivity, simple and low cost. The design and application of quantum dots (QDs) based fluorescent probes for biomedical research have become a focus in recent years because of their unique photophysical properties, such as broad-band absorption, size-dependent narrow-band emission and resistance to photobleaching. Metal ions, especially the heavy metal ions, is closely related to the ecological environment and human health. For example, lead ions (Pb2+) can cause damage to human’s kidneys, liver, central nervous system and cardiovascular system, especially on children’s intelligence. In this paper, a single emission florescent probe and a ratiometric florescent probe have been designed based on aptamer-InP/ZnS@GO florescent probe system, and they realize the detection of Pb2+successfully. The main contents are as follows:1. InP/ZnSquantum dots are synthesized based on the one-pot method and gQD@SiO2 are synthesized beasd on the reverse microemulsion method. Then the surface of the silica was modified amino group. Both the two kinds of QDs have excellent optical performance and environmental interference resistance, and they lay a good foundation for the design of the fluorescent probes.2. Using InP/ZnS quantum dots as a fluorophore, the graphene oxide (GO) as a quencher, and the aptamer as a recognition molecule, we build a novel kind of nano-fluorescent probes for realizing the high sensitive detection of Pb2+. Sulfydryl modified aptamer, the recognition molecule of Pb2+, connected with InP/ZnS QDs through the covalent bond. GO can conjugate with single-stranded aptamer via the π-π stacking interactions and then quench the fluorescence of QDs through nano-metal surface energy transfer (NSET) mechanism.Single-strandedaptamer transform to G4 chain structure after combining with Pb2+specifically, meanwhile, the reduction of the energy transfer efficiency cause the recovery of the fluorescence of QDs. We realize the quantitativedecetion of Pb2+through the"turn-on" mode and the detection limit can be up to 10 pM.3. Based on aptamer-InP/ZnS@GO fluorescent probe system, a new type of double emission ratiometric fluorescent probe has been constructed by modifying the GO with gQD@SiO2, andrealize the ratio detection of Pb2+.Positively charged gQD@SiO2 adsorbed on the edge of the negatively charged GO by electrostatic interaction, and then GO conjugate withaptamer-InP/ZnS via the π-πstacking interactions, the aptamer-InP/ZnS@GO @gQD/SiO2 nano-fluorescent probe has been constructed successfully. Identically, single-stranded aptamer transform to G4 chain structure after combining with Pb2+specifically, the fluorescence of InP/ZnSQDs recover, while the fluorescence ofgQD@SiO2remain the same, so the ratio of fluorescence intensity I585/I525 increases linearly. According to the ratio of the change of the ratiometric fluorescence intensity, we can quantitatively determine the concentration of Pb2+in aqueous solution. Due to the ratiometric detection method, the visual detection performance of probes has been enhanced.