Construction and comparison of BSA-stabilized functionalized GQD composite fluorescent probes for selective trypsin detection

Abstract

Herein, three kinds of functionalized fluorescent graphene quantum dots (GQDs), as molecule-like building blocks, were used to prepare bovine serum albumin (BSA)-stabilized composite probes. The properties of three types of GQDs and their corresponding BSA-stabilized GQD composite probes were compared using various characterization methods, including FT-IR, TEM, zeta potential measurements, and fluorescence spectroscopy. These three types of BSA-stabilized functionalized GQD composite fluorescent probes were applied to selective trypsin detection. The optimized conditions for preparing composite nanoprobes and optimal detection circumstances were further investigated. Different BSA-stabilized GQD composite probes were used as novel selective label-free fluorescent biosensors for trypsin, proving to have a marked fluorescence enhancement effect, high selectivity, and sensitivity. The most suitable composite probe of the three was selected. The BSA-stabilized amino-functionalized GQDs were the best trypsin sensors among the three tested, with a lower limit of detection of 0.004 μg mL⁻¹. The selective detection mechanism for trypsin was also further studied. This represents the first use of BSA-stabilized GQDs as selective trypsin sensors. Differently functionalized GQD composite probes for trypsin detection were compared and discussed to investigate the selective detection mechanism.