One-Pot Reducing Agent-Free Synthesis of Silver Nanoparticles/Nitrocellulose Composite Surface Coating with Antimicrobial and Antibiofilm Activities.

Nitrocellulose with silver nanoparticle (AgNP/NC) composite was prepared in situ using Ag(CH3CO2) and nitrocellulose without any reducing agent. The composite materials synthesized were spray coated onto glass substrates to obtain thin films. The AgNPs/NC composites were characterized by ultraviolet-visible, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The antimicrobial activity of AgNPs/NC composite was investigated by tube method and time-kill kinetic studies against three microbial species, including Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923), and Candida albicans (ATCC 10231). The antibiofilm activities were qualitatively determined against all three organisms. Prepared AgNPs/NC films exhibited good antimicrobial activity and significant inhibition of biofilm development against all three microbial species. The effective dispersion of AgNPs/NC in biofilm was responsible for the significant antibiofilm activity of the prepared material. The reported AgNPs/NC composite can be used as coating additive in bacteriocidal paint which can be applied onto surfaces such as in healthcare environments.

Synthesis, Characterization and Antimicrobial Activity of Garcinol Capped Silver Nanoparticles.

Garcinol, a well-known medicinal phytochemical, was extracted and isolated from the dried fruit rinds of Garcinia quaesita Pierre. In this study, garcinol has successfully used to reduce silver ions to silver in order to synthesize garcinol-capped silver nanoparticles (G-AgNPs). The formation and the structure of G-AgNPs were confirmed by UV-visible spectroscopy, transmission electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial activity of garcinol and G-AgNPs were investigated by well diffusion assays, broth micro-dilution assays and time-kill kinetics studies against five microbial species, including Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Candida albicans (ATCC 10231) and clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). The formation of G-AgNPs is a promising novel approach to enhancing the biological activeness of silver nanoparticles, and to increase the water solubility of garcinol which creates a broad range of therapeutic applications.

TiO2 Nanoparticles from Baker's Yeast: A Potent Antimicrobial.

Titanium dioxide (TiO2) has wide applications in food, cosmetics, pharmaceuticals and manufacturing due to its many properties such as photocatalytic activity and stability. In this study, the biosynthesis of TiO2 nanoparticles (NPs) was achieved by using Baker's yeast. TiO2 NPs were characterized by X-ray Diffraction (XRD), UV-Visible spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray analysis (EDX) studies. The XRD pattern confirmed the formation of pure anatase TiO2 NPs. According to EDX data Ti, O, P and N were the key elements present in the sample. SEM and TEM revealed that the nanoparticles produced were spherical in shape with an average size of 6.7 ± 2.2 nm. The photocatalytic activity of TiO2 NPs was studied by monitoring the degradation of methylene blue dye when treated with TiO2 NPs. TiO2 NPs were found to be highly photocatalytic comparable to commercially available 21 nm TiO2 NPs. This study is the first report on antimicrobial study of yeast-mediated TiO2 NPs synthesized using TiCl3. Antimicrobial activity of TiO2 NPs was greater against selected Gram-positive bacteria and Candida albicans when compared to Gram-negative bacteria both in the presence or absence of sunlight exposure. TiO2 NPs expressed a significant effect on microbial growth. The results indicate the significant physical properties and the impact of yeast-mediated TiO2 NPs as a novel antimicrobial.

Comparison of Antimicrobial Properties of Silver Nanoparticles Synthesized from Selected Bacteria.

Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions and the microbial source. The antimicrobial activity of AgNPs biosynthesized by Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Acinetobacter baumannii (confirmed clinical isolate) were investigated in this study. Biosynthesis conditions (AgNO3 concentration, pH, incubation temperature and incubation time) were optimized to obtain the maximum AgNP yield. Presence of AgNPs was confirmed by observing a characteristic UV-Visible absorbance peak in 420-435 nm range. AgNP biosynthesis was optimal at 0.4 g/L AgNO3 concentration under alkaline conditions at 60-70 °C. The biosynthesized AgNPs showed higher stability compared to chemogenized AgNPs in the presence of electrolytes. AgNPs synthesized by P. aeruginosa were the most stable while NPs of S. aureus were the least stable. AgNPs synthesized by P. aeruginosa and S. aureus showed good antimicrobial potential against E. coli, P. aeruginosa, S. aureus, MRSA and Candida albicans. AgNPs synthesized by S. aureus had greater antimicrobial activity. The antimicrobial activity of NPs may vary depending on the size and the morphology of NPs.

Enhanced antibacterial activity of TiO2 nanoparticle surface modified with Garcinia zeylanica extract.

BACKGROUND: The antibacterial activity of 21 nm TiO2 nanoparticles (NPs) and particles modified with Garcinia zeylanica (G. zeylanica) against Methicillin resistant Staphylococcus aureus was investigated in the presence and absence of light. RESULTS: Surface modification of TiO2 NPs with the adsorption of G. zeylanica extract, causes to shift the absorption edge of TiO2 NPs to higher wavelength. TiO2 NPs, G. zeylanica pericarp extract showed significant bactericidal activity which was further enhanced in contact with the TiO2 modified G. zeylanica extract. CONCLUSIONS: The antimicrobial activity was enhanced in the presence of TiO2 NPs modified with G. zeylanica and with longer contact time.

Inadequacy of the risk factor based approach to detect gestational diabetes mellitus.

OBJECTIVE: To evaluate the present risk factor based approach in diagnosis of gestational diabetes mellitus (GDM) in Sri Lanka in comparison with new guidelines proposed by the International Association of Diabetes and Pregnancy Study Groups (IADPSG). METHODS: A community based cross sectional descriptive study was conducted among pregnant women with gestational age of 24-28 weeks and residing in Anuradhapura district. All eligible pregnant women from selected Medical Officers of Health areas were invited to participate. The 75 g oral glucose tolerance test was carried out among all participants. RESULTS: According to IADPSG criteria, 36 (8.9%) of pregnant women had GDM, compared to 29 (7.2%) according to WHO criteria. Prevalence of GDM in the study population (positive by one or both methods) was 10.6% (n=43) (95% CI 7.9-13.9%). Of these 43 women,22 (51.1%) had positive results by both methods. Seven (16.3%) and 14 (32.6%) mothers were positive only according to WHO and IADPSG criteria respectively. Out of 29 mothers who fulfilled WHO criteria, only one had an abnormal fasting plasma glucose, but 28 had abnormal 2 hour values. A total of 170 (42.0%) participants had at least one risk factor or early indicator of GDM. A risk based approach would have detected only 22 GDM patients according to IADPSG criteria, missing 14 cases (38.9%) who did not have any of the risk factors for GDM. CONCLUSIONS: The risk factor based approach misses more than one third of GDM cases. Urgent revision of current GDM screening guidelines is recommended.