▎ 摘　　要

This research describes the synthesis of a covalent bioconjugate of graphene quantum dots (GQDs) and glutaminase (10 units.mg(-1)) for electrochemical and photoluminescent (PL) detection of L-glutamine (Gln). As synthesized GQDs exhibited uniform size distribution, (average diameter similar to 5-10 nm, and discrete blue emission characteristics (lambda(ex) = 391 +/- 2 nm and lambda(em) = 480 +/- 2 nm)). Accordingly, the immobilization of glutaminase over the surface of the GQDs was confirmed by the characteristic Fourier-transform infrared (FTIR) spectroscopy peaks of the amide bond at 1,703 and 1,390 cm(-1). The conjugate was used to detect Gln using electrochemical and PL approaches on a parallel basis over a concentration range of 100-1,000 mu M. Electrochemical analysis of Gln using cyclic voltammetry revealed a limit of detection (LOD) and limit of quantification (LOQ) values of 360.4 mu M and 1,100 mu M, respectively. In comparison, quantification of Gln based on the PL approach yielded a Stern-Volmer quenching constant, LOD, and LOQ values of 2.2 x 10(3) M-1, 9.42 mu M, and 28.57 mu M, respectively. As such, the PL spectroscopy-based analysis was seen to have better sensitivity for Gln quantification than the electrochemical analysis. The PL-based approach is a more recommendable option for Gln quantification with high sensitivity and rapidity.