Green Synthesis of Silver Nanoparticles Using Hypericum perforatum L. Aqueous Extract with the Evaluation of Its Antibacterial Activity against Clinical and Food Pathogens

Abstract

The rapid development of nanotechnology and its applications in medicine has provided the perfect solution against a wide range of different microbes, especially antibiotic-resistant ones. In this study, a one-step approach was used in preparing silver nanoparticles (AgNPs) by mixing silver nitrate with hot Hypericum perforatum (St. John’s wort) aqueous extract under high stirring to prevent agglomeration. The formation of silver nanoparticles was monitored by continuous measurement of the surface plasma resonance spectra (UV-VIS). The effect of St. John’s wort aqueous extract on the formation of silver nanoparticles was evaluated and fully characterized by using different physicochemical techniques. The obtained silver nanoparticles were spherical, monodisperse, face-centered cubic (fcc) crystal structures, and the size ranges between 20 to 40 nm. They were covered with a capping layer of organic compounds considered as a nano dimension protective layer that prevents agglomeration and sedimentation. AgNPs revealed antibacterial activity against both tested Gram-positive and Gram-negative bacterial strains causing the formation of 13–32 mm inhibition zones with MIC 6.25–12.5 µg/mL; Escherichia coli strains were resistant to tested AgNPs. The specific growth rate of S. aureus was significantly reduced due to tested AgNPs at concentrations ≥½ MIC. AgNPs did not affect wound migration in fibroblast cell lines compared to control. Our results highlighted the potential use of AgNPs capped with plant extracts in the pharmaceutical and food industries to control bacterial pathogens’ growth; however, further studies are required to confirm their wound healing capability and their health impact must be critically evaluated.

Green Synthesis and Antimicrobial Activities of Silver Nanoparticles Using Calotropis gigantea from Ie Seu-Um Geothermal Area, Aceh Province, Indonesia

“…In the case of AgNPs-FCg, the colorless solution transformed into a yellow-brown solution (Figure 1). Similarly, previous reports have shown the color changing into yellow-brown [29][30][31][32] or dark brown [33][34][35][36][37][38] following the green synthesis of AgNPs.…”

Excellent Antimicrobial, Antioxidant, and Catalytic Activities of Medicinal Plant Aqueous Leaf Extract Derived Silver Nanoparticles

“…Concerning Ciprofloxacin, the observed inhibition zones against all the seven bacteria were 26 ± 0.3, 26 ± 0.9, 21 ± 0.8, 31 ± 0.4, 24 ± 0.1, 25 ± 0.5, 30 ± 0.8, whereas Kanamycin showed activity against MRSA, S. aureus, and E. coli and the observed zones diameters were 19 ± 0.6, 18 ± 0.3, and 20 ± 0.4, respectively, Figure 7i-l. Thus, C-AgNPs have proved to be effective against a wide range of bacterial pathogens, which is in agreement with the data reported for other various plant-based AgNPs [68][69][70]. Moreover, concerning the results presented in Figure 7a-g and Table 1, it was assessed that Gram-positive MRSA and S. aureus had inhibition zone sizes that were 7% higher than those produced by Gram-negative S. typhimurium and P. aeruginosa and 14% than Gram-positive E. faecalis and Gram-negative E. coli and K. pneumoniae.…”

Efficacy of Sterculia diversifolia Leaf Extracts: Volatile Compounds, Antioxidant and Anti-Inflammatory Activity, and Green Synthesis of Potential Antibacterial Silver Nanoparticles

“…This may be explained by the fact that nanoparticles in aqueous extracts have a larger negative charge and a narrower size distribution than those in ethanolic extracts, indicating that AgWPE is more stable than AgEPE ( Figure 2 and Figure 3 , Table 3 ). According to reports, AgNPs cause bacterial cell membrane damage by releasing Ag ions that build up in the membrane and then react with proteins and thiol groups to produce free radicals, which slowly kill the bacteria [ 41 , 42 , 43 ].…”