Prunella vulgaris-phytosynthesized platinum nanoparticles: Insights into nanozymatic activity for H₂O₂ and glutamate detection and antioxidant capacity

Artificial nanozymes (enzyme-mimics), specifically metallic nanomaterials, have garnered significant attention recently due to their reduced preparation cost and enhanced stability in a wide range of environments. The present investigation highlights, for the first time, a straightforward green synthesis of biogenic platinum nanoparticles (PtNPs) from a natural resource, namely Prunella vulgaris (Pr). To demonstrate the effectiveness of the phytochemical extract as an effective reducing agent, the PtNPs were characterized by various techniques such as UV–vis spectroscopy, High-resolution Transmission electron microscopy (HR-TEM), zeta-potential analysis, Fourier-transform infrared spectroscopy (FTIR), and Energy dispersive spectroscopy (EDS). The formation of PtNPs with narrow size distribution was verified. Surface decoration of PtNPs was demonstrated with multitudinous functional groups springing from the herbal extract. To demonstrate their use as viable nanozymes, the peroxidase-like activity of Pr/PtNPs was evaluated through a colorimetric assay. Highly sensitive visual detection of H₂O₂ with discrete linear ranges and a low detection limit of 3.43 μM was demonstrated. Additionally, peroxidase-like catalytic activity was leveraged to develop a colorimetric platform to quantify glutamate biomarker levels with a high degree of selectivity, the limit of detection (LOD) being 7.00 μM. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) test was used to explore the scavenging nature of the PtNPs via the degradation of DPPH. Overall, the colorimetric assay developed using the Pr/PtNP nanozymes in this work could be used in a broad spectrum of applications, ranging from biomedicine and food science to environmental monitoring.