BSA-stabilized manganese phosphate nanoflower with enhanced nanozyme activity for highly sensitive and rapid detection of glutathione

The development of an efficient protein-inorganic nanohybrid with superior nanozyme activity for highly sensitive detection of glutathione (GSH) is essential for early diagnosis of human diseases. Herein, a rapid and highly sensitive colorimetric assay using self-assembled bovine serum albumin-hydrated manganese phosphate nanoflowers (MnPNF) as a biomimic oxidase is developed for GSH detection in human serum. The BSA can complex with Mn2+ to serve the nucleation center to produce MnPNF in the presence of phosphate-buffered saline (PBS). The morphology and surface characterization results show that the MnPNF is assembled with hierarchical nanoplates to form 500 nm nanoflowers. The oxidase-like activity of MnPNF is based on the redox reaction with 3,3',5,5'-tetramethylbenzidine. However, the addition of GSH can reduce MnPNF to Mn2+, and subsequently supresses the oxidase-like activity and a yellow color at 450 nm is observed in the presence of H2SO4. The MnPNF-based nanozyme exhibits excellent sensing ability toward GSH detection, and a good linear relationship between the change in absorbance at 450 nm and the added amounts of GSH at 50 nM-10 μM with low limits of detection of 20 and 26.6 nM in the PBS and diluted human serum, respectively, is observed. Moreover, the sensing probe shows a superior selectivity over the other 16 interferences, which drive the determination of GSH feasible in real human serum. Since the MnPNF can be simply prepared at room temperature and no functionalization is required, this assay can be used to design the highly efficient biomimic oxidase for effective sensing of GSH and other disease-related biomolecules in biological fluid samples.