Novel silver-platinum bimetallic nanoalloy synthesized from Vernonia mespilifolia extract: antioxidant, antimicrobial, and cytotoxic activities

Abstract In this study, bimetallic nanoparticles comprising silver and platinum with promising therapeutic activities were synthesized using ethanolic Vernonia mespilifolia plant extract for the first time. The bimetallic silver-platinum nanoparticles (AgPtNPs) were characterized using solid-state techniques including UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) techniques. The internal morphological structure showed that the AgPtNPs were spherical with a diameter of approximately 35.5 ± 0.8 nm, while FTIR confirmed the effective capping and formation of the nanoparticles by phytoconstituents. The polyphenolic contents of the green synthesized nanoparticles from the ethanolic extract of V. mespilifolia (AgNPs and AgPtNPs) was found to be (28.0 ± 0.8 and 13.6 ± 0.1 mg GAE/g) total phenol, while the flavonoids content was (366.2 ± 17.0 and 126.6 ± 0.2 mg QE/g), and proanthocyanins content was (161.8 ± 0.6 and 70.2 ± 0.6 mg CE/g). The AgPtNPs displayed a greater ability to scavenge free radicals, especially DPPH and ABTS (IC50 19.5 and 21.6 µg/mL) respectively when compared with AgNPs and ascorbic acid. Besides, the AgPtNPs had a higher ferric reducing antioxidant power (FRAP) (44.1 mg GAE/g) when compared to AgNPs (18.5 mg GAE/g). Moreover, the AgPtNPs showed a two-fold antimicrobial activity towards pathogenic microbes compared to AgNPs and a selective cytotoxic potency towards MCF-7 breast cancer cell line compared to HEK 293 normal cell line. In summary, these fascinating bioactivities displayed by the AgPtNPs highlighted their potential in therapeutic biomedical applications.