Green synthesis of silver nanoparticles using P. guajava L. extract prepared by ultrasonic-assisted extraction, as reducing agent for wound dressing application: In vitro and in vivo evaluation

P. guajava L. leaf extract prepared by ultrasonic sound, is used as green reducing agent for silver nanoparticles (AgNPs) synthesis. Ultrasonic-assisted extraction provides not only a shortened process at low temperature but also a higher amount of reducing agents, compared to magnetic stirring method in same condition. A highly efficient radical scavenging activity of guava leaf extract, prepared by sonication (15 mins, 37 kHz, 150W), possesses the 50% inhibitory concentration (IC50) of 43.29 μg/mL (1,1-diphenyl-2-picrylhydrazyl (DPPH)). The synthesized AgNPs were confirmed by UV–vis spectrophotometry at 405 nm and X-ray diffraction. Field emission scanning electron microscopy and dynamic light scattering showed that the average sizes of the AgNPs were 20 to 40 nm and 27.3 nm respectively. Guava leaf extract also acts as stabilizer for AgNPs. Zeta potential measurements (−56.5 mV) showed that the synthesized AgNPs had reasonably good stability. Antimicrobial activity assays of the AgNPs showed inhibition against selected bacteria E. coli. Healing effect on a second-degree burn of prepared AgNPs in an in vivo test is comparable to povidone. This study revealed the low-cost, fast and environmentally friendly synthesis of AgNPs, from P. guajava L. leaf extract, obtained by ultrasonic method and prepared AgNPs can be used as antimicrobial agent in nanobiotechnology field.