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In this study, green-ZnS nanoparticles (g-ZnS NPs) were synthesized via chemical precipitation using aqueous solutions of ZnCl2 and Na2S at the presence of green tea solution. The ternary hybrid nanocomposite of green-ZnS@ Graphen oxide@Chitosan (g-ZnS@GO@CS) was also prepared through in situ chemical deposition of g-ZnS nanoparticles on GO@CS composite. The obtained nanostructures were characterized by FTIR, SEM, XRD, EDX, X-map, photoluminescence (PL), TGA, and UV-DRS analyses. Based on the results, the g-ZnS@GO@CS composite possessed cauliflower morphology in which ZnS NPs were homogeneously distributed on the composite matrix. Crystallographic investigations revealed the fcc phase of ZnS NPs. Moreover, the crystallite sizes of ZnS, g-ZnS, and g-ZnS@GO@CS samples were estimated as 28.8, 17.9, and 14.8 nm, respectively. Using UV–vis spectroscopy, the bandgap energy of g-ZnS@GO@CS composite, pure ZnS, and g-ZnS were determined 3.02, 3.37, and 4.42 eV, respectively; suggesting a significant reduction in the bandgap of the composite sample due to the synergic effect of GO@CS. Among various g-ZnS@GO@CS composites with different GO@CS contents (4, 8, and 12 wt%) the sample containing 4 wt% GO@CS exhibited the highest photoluminescence intensity. The g-ZnS@GO@CS nanocomposite displayed higher antibacterial activity (growth inhibition zone of 27.6 mm) on Gram-positive Staphylococcus aureus bacteria compared to g-ZnS NPs (growth inhibition zone of 23.5 mm). No significant bioactivity was, however, observed against Gram-negative bacteria (Escherichia coli). According to the results, g-ZnS@GO@CS composite with reduced bandgap, enhanced PL intensity, and smaller ZnS NPs can offer better antibacterial activity as compared to pristine g-ZnS NPs.

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Background and Objective: Nowadays, incidence of antibiotic-resistance among pathogenic bacteria has increased due to indiscriminate use of antimicrobial drugs for treatment of diseases, especially urinary tract infections. Medicinal plants are also of great importance as antibacterial agents. Therefore, the aim of this study was to determine the antibacterial effect of ethanolic extract of nettle (Urtica dioica L.) leaves using two methods of disk diffusion and well diffusion.Methods: Ethanolic extract of nettle leaves was prepared by the percolation method. Effect of different concentrations of the extract on Escherichia coli (PTCC1399), Staphylococcus aureus (PTCC 1431), Staphylococcus epidermidis (PTCC 1435) and Staphylococcus saprophyticus (PTCC1440) was evaluated using the disk diffusion and well diffusion methods by measuring diameter of growth inhibition zone. Gentamicin and propylene glycol were used as positive and negative control, respectively.Results: In both methods, especially in the well diffusion, the ethanolic extract of nettle leaves had favorable inhibitory effect on the growth of S. aureus, S. epidermidis and S. saprophyticus. In the well diffusion method, the highest rate of susceptibility to the extract (89%) was related to S. saprophyticus and S. epidermidis. Conclusion:The ethanolic extract of nettle leaf has good inhibitory effect on the growth of S. aureus (especially in the well diffusion method), which confirms the traditional use of this plant for the treatment of urinary tract infections.

Background: Variations in the viral receptor human angiotensin-converting enzyme 2 (ACE2) may specify the susceptibility of a certain population to severe acute respiratory syndrome coronavirus 2. Objective: Evaluation of the affinity of severe acute respiratory syndrome coronavirus 2 spike glycoprotein to the Iranian genetic variants of ACE2. Materials & methods: Single nucleotide polymorphisms of ACE2 among the Iranian population were collected from the Iranome database. Missense mutations in the N-terminal peptidase domain were selected for in silico analysis. Results: 17 missense single nucleotide polymorphisms were found at ACE2. Viral glycoprotein had the lowest affinity to ACE2 mutant V485L. Discussion: The V485L variant of ACE2 could be a natural resistance mutation among the Iranian population. In addition, variant S331F can increase slightly the susceptibility to infection with the virus.

In this study, the effect of sub-minimum inhibitory concentrations of the zinc oxide nanoparticle on the expression of the α-haemolysin gene as a significant virulence factor of Staphylococcus aureus is assessed. The effect of sub-minimum inhibitory concentration (312.5 μg/ml) of the zinc oxide nanoparticle on the haemolysis phenomenon was studied phenotypically on blood agar media with and without zinc oxide nanoparticles and genetically by real time polymerase chain reaction method in media containing and without zinc oxide. The haemolysis phenomena of all S. aureus isolates in a blood agar with a sub-minimum inhibitory concentration and 1/2, 1/4 and 1/8 minimum inhibitory concentration of zinc oxide nanoparticles was completely restrained. After performing real time polymerase chain reaction, the amount of hla gene expression in 12 h culture in media with 1/2 and 1/4 minimum inhibitory concentration of zinc oxide nanoparticles was reduced, but gene expression in the 1/8 minimum inhibitory concentration was did not decrease. Haemolysis by S. aureus was decreased in the presence of sub-minimum inhibitory concentration of zinc oxide nanoparticles. The use of zinc oxide nanoparticle in sub-minimum inhibitory concentration as cover of artificial instruments such as catheter, intravascular catheters or shunts to control bacterial infection is suggested for further study.

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