Label-free biosensor for trace insulin-like growth factor-I assay based on rGO-SnS2 heterostructure nanocomposite

Abstract

Insulin-like growth factor-I (AgIGF-I) is a key biomarker in tumor progression. In this work, a novel label-free electrochemical impedance biosensing platform for detection of AgIGF-I was developed on the basis of a nanocomposite of reduced graphene oxidetin sulfide (rGO-SnS2) loaded with gold nanoparticles (AuNPs). The rGO-SnS2 surface serves as an interfacial matrix, exhibiting outstanding electrochemical activity because of its large surface area; meanwhile, the abundant active sites in rGO-SnS2 promote AuNP deposition and improve antibody (Ab) immobilization. The specific recognition between IGF-I antibody (AbIGF-I) and antigen (AgIGF-I) at the interface induces changes in electrochemical impedance, which can distinguish AgIGF-I from a complex biological media to ensure the selectivity. Electron transfer resistance (Rct) corresponds to the number of analytes on the interface, which serves as the basis for the design of an electrochemical impedance biosensor. Under optimized conditions, the designed biosensor exhibits a linear response range of 0.25–750.0 pg/mL and an ultralow detection limit of 0.12 pg/mL (S/N = 3), and the results based on an electrochemical method are consistent with those of enzyme-linked immunosorbent assay (ELISA). Such an electrochemical biosensor is highly effective for IGF-I sensing in human plasma samples, which broadens the application of the heterostructure [email protected]2 nanocomposite in bioanalysis and clinical diagnosis.