Synthesis of Biogenic Silver Nanoparticles Using Caesalpinia digyna and Investigation of Their Antimicrobial Activity and In Vivo Biocompatibility.

Among metallic nanoparticles, silver nanoparticles (AgNPs) have a wide spectrum of medical applications. Herein, biogenic silver nanoparticles (bAgNPs) were prepared from extracts of Caesalpinia digyna leaf as a reducing agent at different pH values (i.e., 5, 7, 8, and 10). The as-synthesized bAgNPs were characterized using UV-vis and Fourier transform infrared (FTIR) spectroscopies, scanning transmission electron microscopy, powder X-ray diffraction analysis, dynamic light scattering, and ζ-potential analysis. The sizes of bAgNPs prepared at pH 5, 7, 8, and 10 were 45.4, 11.3, 11.4, and 40.8 nm, respectively, and all of the nanoparticles were negatively charged. The antimicrobial activity of the as-prepared bAgNPs was investigated against Bacillus subtilis, Escherichia coli DH5α, E. coli K12, enteropathogenic E. coli (EPEC), and Salmonella typhi. The bAgNPs prepared at pH 8 showed the highest antibacterial propensity against all of the bacterial strains as exhibited in the zone of inhibition (ZOI) as well as the CellTox green assay, which can be due to their relatively small size, stability, and higher surface area-to-volume ratio. The bAgNPs synthesized at pH 8 showed the highest ZOI against B. subtilis, which was ∼25 mm in diameter. The lipid peroxidation assay demonstrated the formation of the malondialdehyde-thiobarbituric acid (MDA-TBA) adduct while treating the bacteria with bAgNPs due to the oxidation of fatty acids present in the membrane. The highest amount of MDA-TBA adduct was observed when Gram-positive B. subtilis was exposed to bAgNPs. On the contrary, rats treated with bAgNPs demonstrated no significant toxicity in terms of hematological and biochemical parameters. The bAgNPs also showed excellent compatibility with human red blood cells. Overall, bAgNPs synthesized at pH 8 have superior antimicrobial activity and excellent biocompatibility and, therefore, can be used as potential antibacterial agents.

Functionalization of Elongated Tetrahexahedral Au Nanoparticles and Their Antimicrobial Activity Assay.

Gold nanoparticles are inert for the human body, and therefore, they have been functionalized to provide them with antibacterial properties. Here, elongated tetrahexahedral (ETHH) Au nanoparticles were synthesized, characterized, and functionalized with lipoic acid (LA), a natural antioxidant with a terminal carboxylic acid and a dithiolane ring, to generate ETHH-LA Au nanoparticles. The antioxidant activity of Au nanoparticles was investigated in vitro, showing that LA enhances the 2,2-diphenyl-1-picrylhydrazyl free-radical scavenging and Fe3+ ion reducing activity of ETHH-LA at higher amounts. The antimicrobial propensities of the nanoparticles were investigated against Gram-positive ( Bacillus subtilis) and Gram-negative ( Escherichia coli) bacteria through propidium iodide assay as well as disk diffusion assay. ETHH-LA Au nanoparticles showed significantly higher antimicrobial activity against B. subtilis compared with E. coli. Furthermore, ETHH-LA Au nanoparticles also showed significantly better antimicrobial activity against both bacterial strains when compared with ETHH. ETHH Au nanoparticles also bring about the oxidation of bacterial cell membrane fatty acids and produce lipid peroxides. ETHH-LA showed higher lipid peroxidation potential than that of ETHH against both bacteria tested. The hemolytic potential of Au nanoparticles was investigated using human red blood cells and ETHH-LA showed reduced hemolytic activity than that of ETHH. The cytotoxicity of Au nanoparticles was investigated using human cervical cancer cells, HeLa, and ETHH-LA Au nanoparticles showed reduced cytotoxicity than that of ETHH. Taken together, LA enhances the antimicrobial activity of ETHH Au nanoparticles and Au nanoparticles interact with the bacteria through electrostatic interactions as well as hydrophobic interactions and damage the bacterial cell wall followed by oxidation of cell membrane fatty acids.

Surface-Functionalized Polypropylene Surgical Mesh for Enhanced Performance and Biocompatibility.

Polypropylene (PP) surgical mesh has attracted vast attention due to its chemical inertness and excellent mechanical properties. However, improvement is necessary to enhance its biocompatibility and to prevent unwanted tissue adhesion. This study addresses these issues through surface modification of plasma-activated PP mesh with a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer. Reaction time and monomer concentration have been optimized to achieve the optimal biocompatibility with reduction in protein adsorption. Attenuated total reflection-Fourier transform infrared spectra confirmed the grafting of the MPC polymer (PMPC) to the plasma-activated polypropylene (PPP) mesh. Scanning electron microscopy images and energy-dispersive X-ray (EDX) line spectra exhibited morphological changes and specifically PMPC grafting to the surface of PPP mesh, due to the presence of a significant amount of phosphorus (P) on the grafted PPP mesh. PMPC-grafted polypropylene (PPP-PMPC) showed a significant reduction in contact angle as well as the amount of adsorbed bovine serum albumin (BSA) protein in comparison with pristine PP mesh. The highest reduction in protein adsorption and the lowest contact angle were achieved at the monomer concentration of 0.3 M and the reaction time of 90 min. A longer reaction time and higher monomer concentration resulted in clogging within the mesh pores. MTT assay results (∼90% cell viability) confirmed the nontoxicity of the PMPC-grafted mesh, while optical microscopic and SEM images showed increased resistance of cell attachment to the surface of PMPC-grafted mesh. The results show that PPP-PMPC can be a promising biomaterial to address the current issues in biocompatibility and reduction in adhesion after surgery.