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

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 nano -composite of reduced graphene oxide-tin 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 (R-ct) 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 AuNPs@rGO-SnS2 nanocomposite in bioanalysis and clinical diagnosis.

Automated summary

A label-free electrochemical impedance biosensing platform was developed for detection of AgIGF-I using a nano-composite of reduced graphene oxide-tin sulfide loaded with gold nanoparticles. The biosensor showed high sensitivity and selectivity for IGF-I detection in human plasma samples, expanding the application of the nanocomposite in bioanalysis and clinical diagnosis.