Target-induced tripedal G-quadruplex DNAzyme for multicolor visual point-of-care testing of biomarkers using Au nanorods-decorated electrospun nanofibrous films

Abstract

A target-induced tripedal G-quadruplex DNAzyme (TGD) for visual point-of-care testing (POCT) of PSA proteins by using solid Au nanorods (Au NRs)-decorated electrospun nanofibrous films was constructed. The TGD was formed by the recycling amplification cascades of target-triggered catalytic hairpin assembly (CHA), which exhibited superior horseradish peroxidase (HRP) mimicking activity to facilitate the degradation of H2O2 into hydroxyl radicals (·OH). The ·OH oxidized the 3,3′,5,5′-tetramethylbenzidine (TMB) into TMB+. Then, the TMB+ was converted into TMB2+ in the acidic environment, which can etch the Au NRs for further promoting the blue shift of their longitudinal surface plasmon resonance (LSPR) absorption peak. Thereby, with the increasing PSA concentrations, the proposed strategy presented palpable color variations from green, cyan, violet, and red by naked eyes. Significantly, the cutoff values near 4.0 and 10.0 ng/mL of PSA in human blood serum could be discriminated with naked eyes, which could provide a semi-quantitative process for the early diagnosis and prognosis evaluation. In addition, this portable, and label-free TDG biosensor exhibited remarkable improvements in sensitivity with a low detection limit of 61.1 fg/mL for PSA protein. This strategy showed the great versatility and potential for the visual biomedical detection with portable type and early diagnosis of diseases.