A facile Pt-doped g-C3N4 photocatalytic biosensor for visual detection of superoxide dismutase in serum samples

In this work, we reported a photocatalytic biosensor for visual detection of superoxide dismutase (SOD) based on Pt-doped graphite phase carbon nitride (g-C 3 N 4 ). Upon illumination by a violet light-emitting diode (LED), Pt-doped g-C 3 N 4 absorbed the light energy and catalytically produced O 2 − which further oxidized the dyes into a colorless end product. In the presence of SOD, it can specifically catalyze O 2 − into oxygen and hydrogen peroxide, leading to a reduced photooxidation and a visual color display. After screening a series of dyes, the azo dye amaranth (AM) was proven to be the best indicator for O 2 − since the azo bond is active and easily oxidized by O 2 − , resulting in a low background. Such a simple photocatalytic sensor allows visual detection of SOD at a nM level without the need of any sophisticated instrument; using spectrometry, the linear response for SOD detection ranges from 1.5 to 4500 nM with a limit of detection (LOD, 3σ) down to 0.3 nM. The sensor was also successfully applied for label-free and wash-free detection of SOD in human serum samples with a satisfactory recovery.