Three-cascade cycle amplification strategy for fluorescent detection of HIV-DNA in human blood with hybrid of pentaethylenehexamine-functionalized graphene quantum dot and NaGdF4:Yb,Er@NaGdF4

Abstract

Poor water solubility and low efficiency of upconversion luminescence limit the applications of rare earth (RE)-doped upconversion nanoparticles in bioanalysis. The paper reports hybrid of pentaethylenehexamine functionalized graphene quantum dots and NaGdF4:Yb,Er@NaGdF4 via coordination of RE with nitrogen in the presence of polyvinylpyrrolidone. The resulting hybrid offers hexagonal nanostructure with particle size of 25 nm, good dispersibility and rich functional groups. Interestingly, the hybrid promotes the enhancement of upconversion luminescence that depends on the structure of graphene quantum dots. The hybrid was used as fluorescence probe for construction of three-cascade cycle amplification for detection of HIV-DNA. Target DNA interacts with the pre-hybridized duplex DNA to induce release of assistant strand DNA, triggering target DNA-induced recycle. The utilization of three-cascade cycle allows one target DNA to produce many tetramethylrhodamine-labeled DNA fragments. These are connected on the hybrid by complementary base pairs, promoting a significant upconversion fluorescence quenching by fluorescence resonance energy transfer, due to proximity of tetramethyl rhodamine and hybrid. The fluorescence signal decreases with increasing HIV-DNA concentration in the range of 1.0 × 10−17-1.0 × 10-12 M with the detection limit of 4.8 × 10-18 M. The proposed method provides advantage of sensitivity, specificity and stability and was successfully applied in detection of HIV-DNA in human blood.