A facile enzymatic approach for selective detection of γ-aminobutyric acid using corn-derived fluorescent carbon dots

A facile and cost-effective enzymatic fluorescent method was developed by using eco-friendly carbon dots (CDs) synthesized from corn juice (Zea mays) via the hydrothermal method. The CDs derived from corn juice are termed as CCDs. Herein, we present a novel enzymatic fluorescence sensing approach for the detection of gamma-aminobutyric acid (GABA), a potential inhibitory neurotransmitter. For this purpose, CCDs were functionalized with 3-aminophenyl boronic acid (APBA) and Nicotinamide adenine dinucleotide phosphate (NADP⁺) via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-Hydroxy-succinimide (EDC/NHS) coupling reaction. After the functionalization of the CCDs, these are termed as CANs. The CANs by utilizing enzyme GABase were successfully employed to detect GABA by fluorescence quenching through electron transfer between enzyme and substrate owing to the formation of a reduced form of NADPH. The proposed method allows detecting GABA in the linear range of 0–90 μM with a detection limit of 6.46 μM. Further, this sensor was also applied in biological samples such as human cerebrospinal fluid (CSF) and serum for the determination of GABA, which demonstrated better recovery results of 93.2–101.5% and 96.4–104.6%, respectively.