Polydimethyl siloxane (PDMS) is an excellent implant material for biomedical applications, but often fails as it is prone to microbial colonization which forms biofilms. In the present study CuO, CTAB capped CuO, and ZnO nanoparticles were tested as nanofillers to enhance the antibiofilm property of PDMS against Staphylococcus aureus and Escherichia coli. In general S. aurues (Gram positive and more hydrophobic) favor PDMS surface than glass while E. coli (Gram negative and more hydrophilic) behaves in a reverse way. Incorporation of nanofillers renders the PDMS surface antibacterial and reduces the attachment of both bacteria. These surfaces are also not cytotoxic nor show any cell damage. Contact angle of the material and the cell surface hydrophobicity influenced the extent of bacterial attachment. Cell viability in biofilms was dependent on the antimicrobial property of the nanoparticles incorporated in the PDMS matrix. Simple regression relationships were able to predict the bacterial attachment and number of dead cells on these nanocomposites. Among the nanocomposites tested, PDMS incorporated with CTAB (cetyl trimethylammonium bromide)-capped CuO appears to be the best antibacterial material with good cyto-compatibility. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1075-1082, 2017.

In the present work, hydrophobic (contact angle 108) poly methyl methacrylate (PMMA) films were developed by a simple room temperature drop-cast method based on slow solvent evaporation process. Further, PMMA nanocomposites (NCs) were developed by impregnating PMMA with nanoparticles (0.1% w/v) of copper oxide (CuO), cetyltrimethyl ammonium bromide (CTAB) capped CuO (CuO-CTAB) and zinc oxide (ZnO). The PMMA and NCs were tested against attachment of marine bacteria, microalgae (diatoms) and barnacle larvae in laboratory as well as in the sea. At low loading of nanoparticles (0.1% w/v), the PMMA NCs inhibited bacterial settlement (24 h assay) by 97-99% in the laboratory and by 40-69% in the field exposure studies. They also inhibited diatom attachment (24-38%) in laboratory and in the sea (80-95%). NCs successfully inhibited (100%) barnacle settlement and metamorphosis and caused mortality to the extent of 22-44% in exposed cypris larvae. Incorporation of nanoparticles in PMMA confers antifouling property to the polymer at greatly reduced metal release rates as compared to conventional antifouling paints. Results of the study indicate that PMMA NCs are promising as low cost antifouling coatings for static moored/submerged structures in the ocean due to their efficacy at low environmental metal release. (C) 2016 Elsevier Ltd. All rights reserved.

Polydimethyl siloxane (PDMS), in spite of possessing excellent foul-release properties, is prone to microbial fouling caused by organisms such as bacteria and diatoms. In the present study, we incorporated metal oxide nanoparticles in PDMS matrix to create composites with enhanced antifouling properties. The nanocomposites were prepared by incorporating small amounts (0.1 wt per cent) of CuO, CTAB-capped CuO and ZnO nanoparticles in PDMS. Their antibiofilm properties were tested in vitro against a marine bacterium and a diatom and also in the field. ZnO nanocomposite, exhibiting highest hydrophobicity, surface roughness and good antimicrobial activity, prevented biofouling in the sea for 45 days. PDMS with CTAB-capped CuO showed minimum roughness and hydrophobicity and performed well against the bacterium Bacillus flexus and the diatom Navicula sp. Metal leaching rates from the nanocomposites were quite low when compared to reported data, indicating that environmental effects of the nanocomposites would be minimal. The study indicates that the antifouling property of a foul-release polymer such as PDMS can be further increased by incorporation of nanoparticles, so that the formulation remains fouling-free even without extra shear forces. (C) 2015 Elsevier Ltd. All rights reserved.

Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availability D. radiodurans R1 exists in three morphologies viz. monococcal, diplococcal and tetracoccal. In this study, we examined whether nutrition-induced morphotypes of D. radiodurans showed similar DNA damage upon gamma radiation exposure. Total DNA damage after radiation exposure was estimated by comparing percent double-strand breaks (DSBs) in genomic DNA. It was found that all three morphotypes exhibited different radiation tolerances which were also dependent on the radiation dose given. Monococcal forms were found to be most radio-tolerant at most of the tested radiation doses. Results showed that these nutrient-starved-condition induced morphotypes show lesser DNA DSBs upon irradiation, hence show higher radio-tolerance.