Microbial mediated biological synthesis of metallic nanoparticles was carried out ecofriendly in the present study. Silver nanoparticles (AgNPs) were extracellularly biosynthesised from Streptomyces griseorubens AU2 and extensively characterised by ultraviolet–visible (UV–vis) and Fourier transform infrared spectroscopy, high‐resolution transmission electron microscopy, scanning electron microscopy and X‐ray diffraction analysis. Elemental analysis of nanoparticles was also carried out using energy dispersive X‐ray spectroscopy. The biosynthesised AgNPs showed the characteristic absorption spectra in UV–vis at 422 nm which confirmed the presence of metallic AgNPs. According to the further characterisation analysis, the biosynthesised AgNPs were found to be spherical and crystalline particles with 5–20 nm average size. Antioxidant properties of the biosynthesised AgNPs were determined by 2,2‐diphenyl‐1‐picrylhydrazyl free radical scavenging assay and was found to increase in a dose‐dependent matter. The identification of the strain was determined by molecular characterisation method using 16s rDNA sequencing. The present study is the first report on the microbial biosynthesis of AgNPs using S. griseorubens isolated from soil and provides that the active biological components found in the cell‐free culture supernatant of S. griseorubens AU2 enable the synthesis of AgNPs.

Bacterial adherence to a suture material is one of the main causes of surgical site infections. An antibacterial suture material with enhanced wound healing function may protect the surgical site from infections. Thus, the present study aimed to investigate the synergistic effect of propolis and biogenic metallic nanoparticles when combined with silk sutures for biomedical use. Silver nanoparticle (AgNP) synthesis was carried out via a microbial-mediated biological route and impregnated on propolis-loaded silk sutures using an in situ process. Silk sutures fabricated with propolis and biosynthesized AgNPs (bioAgNP-propolis-coated sutures) were intensively characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The antibacterial characteristics of the bioAgNP-propolis-coated sutures were evaluated using the agar plate method. The biocompatibility of the bioAgNP-propolis- coated sutures was evaluated using 3T3 fibroblast cells, and their wound-healing potential was also investigated. BioAgNP-propolis-coated sutures displayed potent antibacterial activity against pathogenic gram-negative and gram-positive bacteria, Escherichia coli and Staphylococcus aureus, respectively. BioAgNP-propolis-coated silk sutures were found to be biocompatible with 3T3 fibroblast cell culture. In vitro wound healing scratch assay also demonstrated that the extract of bioAgNP-propolis-coated sutures stimulated the 3T3 fibroblasts’ cell proliferation. Coating the silk sutures with propolis and biogenic AgNPs gave an effective antibacterial capacity to surgical sutures besides providing biocompatibility and wound healing activity.

Denture soft liners, especially used for elders who have poor disinfection habits, provide a favourable environment for accumulation and colonization of microorganisms. This in vitro study is aimed to investigate the effectiveness of natural carvacrol incorporation into soft lining material on the inhibition of oral pathogens. Antimicrobial susceptibility of carvacrol was primarily determined by disc diffusion method. Soft lining material was prepared as recommended by the manufacturer and 10 μL carvacrol was added aseptically to the soft liner discs. Inhibition zones for the control discs without carvacrol (C) and carvacrol-incorporated discs (CL) were determined by disc diffusion method. The biofilm inhibition percentages of carvacrol on soft liner was determined by MTT assay and also observed by Scanning Electron Microscopy (SEM). Carvacrol displayed great antimicrobial activity for yeast, Gram-negative and Gram-positive strains. The highest inhibition zone of carvacrol (41.33 ± 1.53 mm) was measured for Bacillus subtilis strain which is followed by Candida albicans and Streptococcus sanguis (34.00 ± 1.73 mm and 32.33 ± 0.58 mm, respectively). The inhibition zones were also similar for soft liner discs with carvacrol, with the highest inhibition zones against B. subtilis, Streptococcus mutans and C. albicans (43.67 ± 0.58 mm, 40.33 ± 0.58 mm and 38.33 ± 1.15 mm, respectively). Incorporation of carvacrol into the soft liner decreased (98.03 ± 0.2%) of the biofilm formation for C. albicans. Carvacrol-incorporation obviously decreased the colonization and plaque formation of oral pathogens, especially C. albicans accumulation. Carvacrol may be useful as a promising agent for antibacterial and antifungal management for denture soft lining materials.

This study was performed to determine the antimicrobial and antibiofilm activities of silver nanoparticles (AgNPs) biosynthesised using Streptomyces griseorubens AU2 isolated from soil. The antimicrobial activity of the AgNPs was determined by agar well diffusion, disc diffusion and broth microdilution methods. Diameters of the zone of inhibition results clearly displayed that the microbially biosynthesised AgNPs have potent antimicrobial activity against Candida albicans , Bacillus subtilis , Escherichia coli , Pseudomonas aeruginosa and Staphylococcus aureus . The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of the nanoparticles that had been determined by broth microdilution method were found to be 20 and 50 µg/ml for C. albicans , B. subtilis and S. aureus ; 10 and 20 µg/ml for E. coli and P. aeruginosa , respectively. For determining the effect of AgNPs on biofilm formation under in vitro conditions, MIC and subMICs were studied on P. aeruginosa and S. aureus biofilms by using microplate biofilm assay . Treatment of the AgNPs resulted in a decrease in the biofilm formation of S. aureus and P. aeruginosa as 26.52 and 25.50%, respectively. As a result of this study, it can be suggested that actinobacterially synthesised AgNPs have an effective potential to be used for pharmaceutical applications against multi‐resistant microorganisms.