A label-free fluorescent biosensor for determination of bovine serum albumin and calf thymus DNA based on gold nanorods coated with acridine orange-loaded mesoporous silica

A simple fluorescent assay for sensing bovine serum albumin (BSA) and calf thymus DNA (ctDNA) was developed based on the gold nanorods-based probe. Gold nanorods coated with mesoporous silica coated (Au@SiO 2 ) which loading acridine orange (AO) was prepared by one-pot synthesis method. Interestingly, BSA is detected based on the quenching fluorescence signal while ctDNA is determined based on the enhanced fluorescence signal by the proposed method. Under the optimal conditions, the declined values of the fluorescent intensity of the biosensor are proportional to the BSA concentration in the range of 0.75–33.86   μmol/L. The limit of detection is 0.25   μmol/L. The enhanced values of the fluorescent intensity of the biosensor are linear with the ctDNA concentration in the range of 0.5–10   μg/mL, and the detection limit is 0.1667   μg/mL. The proposed method shows a good selectivity for BSA and ctDNA and can be applied to the determination of the analytes in real samples. The strategy of Au NRs@SiO 2 -AO complex as a novel fluorescent probe paves a new way to design fluorescent sensor.