Improved detection limit for an electrochemical γ-aminobutyric acid sensor based on stable NADPH detection using an electron cyclotron resonance sputtered carbon film electrode

We report an electrochemical γ-aminobutyric acid (GABA) sensor with an improved detection limit based on stable β-nicotinamide adenine dinucleotide phosphate (NADPH) oxidation with an extremely low background current using an electron cyclotron resonance (ECR)-sputtered carbon film electrode. The sensor comprised an ECR carbon electrode modified with gabase co-immobilized bovine serum albumin. We obtained stable responses for NADPH without any electrode surface fouling by electrochemically pretreating the ECR carbon electrode because ECR carbon has an extremely flat surface even after pretreatment and increasing the surface oxygen made the surface more hydrophilic thus suppressing oxidized NADPH (NADP+) fouling of the surface. As a result, we obtained a very low detection limit of 10 nM for NADPH, which was more than one order of magnitude better than that of a conventional glassy carbon electrode (250 nM). We also achieved a low detection limit of 30 nM GABA within 2 min by modifying the pretreated ECR carbon electrode with gabase. The proposed electrochemical GABA sensor exhibited a lower detection limit than any previously reported GABA sensor.