Fluorescent sensor assay for β-lactamase in milk based on a combination of aptamer and graphene oxide

•Graphene oxide (GO) is proposed to be able to quench the fluorescence signal.•β-lactamase aptamer was used to replace the traditional antibody.•Based on aptamer assembled onto GO, a new, sensitive and direct determination of β-lactamase was established.•The established method was verified by ELISA.

Fluorescent sensor assay (FSA) was developed by using a fluorescein-labeled aptamer assembled onto Graphene oxide (GO) in order to determine β-lactamase in milk. Under optimal conditions, FSA indicated a detection range from 1 to 46 U/mL with a limit of detection (LOD) of 0.5 U/mL (R2 = 0.999, n = 3). In addition, commercial milk samples tainted with β-lactamase were detected by the established FSA with a recovery rate between 96.04 and 119.67%. Additionally, the reliability and sensitivity of FSA was validated by enzyme-linked immunoassay (ELISA) with a high correlation of 0.993. Thus, these data, combined with the ease and speed of the assay, suggest that the developed FSA may represent a promising method for monitoring β-lactamase contamination in milk.