Vinita Vishwakarma

Antibacterial copper―nickel bilayers and multilayer coatings by pulsed laser deposition on titanium

Biofouling, especially microfouling, is a major concern with the use of titanium (Ti) in the marine environment as a condenser material in cooling water systems. Earlier, copper–nickel (Cu/Ni) alloys were extensively used in marine environments due to their high corrosion and biofouling resistance. However, the choice of condenser material for the new fast breeder reactor in Kalpakkam is Ti to avoid steam side corrosion problems, which may pose a threat to steam generator parts having sodium as the secondary coolant. This study evaluates the surface modification of Ti using nano films of copper (Cu) and nickel (Ni) to utilize the antibacterial property of copper ions in reducing microfouling. The surface modification of Ti was carried out by the deposition of a Cu/Ni bilayer and (Cu/Ni)10 multilayer films using a pulsed laser deposition technique. Various surface characterization studies revealed that the deposited Cu/Ni films were thin and nanocrystalline in nature. The antibacterial properties were evaluated using total viable count and epifluorescence microscopic techniques. The results showed an apparent decrease in bacterial attachment on multilayered and bilayered Cu/Ni thin films on Ti surfaces. Comparative studies between the two types of films showed a bigger reduction in numbers of microorganisms on the multilayers.

Antibacterial effects of silver-zirconia composite coatings using pulsed laser deposition onto 316L SS for bio implants

Bacterial invasion on biomedical implants is a challenging task for long-term and permanent implant fixations. Prevention of initial bacterial adherence on metallic implants is an important concern to avoid extracellular matrix (biofilm) secretion from bacteria that is resistant to antibacterial agents. In order to overcome this defect, recently, surface coatings such as zirconia (ZrO2) with higher smoothness have been shown to improve implants durability. In the present study, pulsed laser deposition (PLD) was used to deposit ZrO2 and silver (Ag)-ZrO2 composite coatings onto 316L stainless steel (316L SS). Phase purity, surface roughness and surface morphology, thickness of the coatings and elemental compositions of the coatings were analyzed using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). Total viable count (TVC) and epifluorescence microscopy analysis were studied to evaluate antimicrobial efficiency of ZrO2 and Ag–ZrO2 composite coatings using gram negative (gram −ve) Escherichia coli (E.coli) and gram positive (gram +ve) Staphylococcus aureus (S.aureus). On the basis of the present study, it could be speculated that ZrO2 coatings exhibited antibacterial activity against only E.coli, whereas Ag–ZrO2 composite coatings showed superior activity against E.coli and S.aureus strains.

Studies of detailed Biofilm characterization on fly ash concrete in comparison with normal and superplasticizer concrete in seawater environments

In cooling water systems, many concrete structures in the form of tanks, pillars and reservoirs that come in contact with aggressive seawater are being deteriorated by chemical and biological factors. The nuclear industry has decided to partially replace the Portland cement with appropriate pozzolans such as fly ash, which could densify the matrix and make the concrete impermeable. Three types of concrete mixes, viz., normal concrete (NC), concrete with fly ash and superplasticizer (FA) and concrete with only superplasticizer (SP) were fabricated for short- and long-term exposure studies and for screening out the better concrete in seawater environments. Biofilm characterization studies and microscopic studies showed excellent performance of FA concrete compared to the other two. Laboratory exposure studies in pure cultures of Thiobacillus thiooxidans and Fusarium oxysporum were demonstrated for the inhibition of microbial growth on fly ash. Epifluorescence and scanning electron microscopic studies supported the better performance of the FA specimen. Thus, the present study clearly showed that FA concrete is less prone to biofilm formation and biodeterioration.

Isolation and characterization of biogenic calcium carbonate/phosphate from oral bacteria and their adhesion studies on YSZ-coated titanium substrate for dental implant application

Biogenic calcium carbonate/phosphate were isolated and characterized from oral bacteria (CPOB). The crystalline nature and morphology of calcium carbonate/phosphate were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. XRD analysis revealed the cubic phase of YSZ coating as well as biogenic calcium carbonate (rhombohedral) and calcium phosphate oxide (hexagonal) was observed from CPOB. FESEM confirmed the extracellular synthesis of calcium compounds. Bacterial adhesion result reveals that YSZ coating drastically reduce bacterial invasion than titanium substrate.

Corrosion, haemocompatibility and bacterial adhesion behaviour of TiZrN-coated 316L SS for bioimplants

TiZrN coating was deposited on 316L stainless steel (SS) by the reactive magnetron co-sputtering technique. Cubic phase of TiZrN with uniform surface morphology was observed by X-ray diffraction and atomic force microscopy. Bacterial adhesion, haemocompatibility and corrosion behaviour of TiZrN coating were examined in order to evaluate the coating’s compatibility for ideal implant. Results revealed that TiZrN coatings exhibited less bacterial attachment against Staphylococcus aureus and Escherichia coli bacteria, negligible platelets activation and superior corrosion resistance than the uncoated 316L SS.

Green synthesis of silver nanoparticles using hypericin-rich shoot cultures of Hypericum hookerianum and evaluation of anti-bacterial activities

The paper reports a green chemistry approach for the synthesis of silver nanoparticles (AgNPs) using hypericin-rich shoot cultures of Hypericum hookerianum as reducing agent. Normal green shoot cultures deficient in hypericin and red-pigmented shoot cultures rich in hypericin (3.01% DW) were raised in Murashige and Skoog nutrient medium containing 1.0 mg/L kinetin (KIN) and 0.2 mg/L naphthaleneacetic acid (NAA), respectively. Dried powder extracts of whole shoots were used for AgNPs formation. The effect of temperature on the formation of AgNPs is investigated. The nanoparticles obtained were characterised using UV–Vis spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The UV–Vis spectra of AgNPs gave surface plasmon resonance (SPR) at 440 nm. The synthesised AgNPs were effective against different multidrug-resistant human pathogens such as Bacillus subtillis (Gram positive) and Pseudomonas aeruginosa (Gram negative) species. Further, the effect of hypericin concentration on anti-bacterial activity was investigated and was found to increase with increase in concentration.

Identification of potential anti-hepatitis C virus agents targeting non structural protein 5B using computational techniques: POLAMREDDY et al.

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) is an RNA‐dependent RNA polymerase that plays a key role in HCV replication, and, hence, NS5B is an attractive target for hepatitis C drug discovery. Hepatitis C is a chronic liver disease affecting the global population significantly. Many NS5B inhibitors targeting active site were launched in recent years, however, still there exists a pressing need for cost‐effective therapies with pan genotypic activity and therapies targeting niche HCV population with comorbities and resistant to earlier therapies. The objective of the current study is to identify potential anti‐HCV agents from FDA approved drugs that are already in the market for a different disease—Drug repurposing approach. A combination of computational chemistry and computational biology techniques was used to discover potential therapies for hepatitis C targeting the NS5B Thumb I allosteric site. Computational chemistry analysis emphasized the fact that fluvastatin, a lipid lowering agent, and olopatadine, an antihistamine, exhibited good binding affinity to NS5B. In addition, gene set enrichment analysis brought to light the significant overlap between disease characteristic features and the mechanism of action of fluvastatin and olopatadine. The current study concludes the potentially beneficial use of fluvastatin in niche hepatitis C patient population suffering from nonalcoholic fatty liver diseases.

Surface Modification of Fly Ash Concrete Through Nanophase Incorporation for Enhanced Chemical Deterioration Resistance

The global warming gas, CO2, is liberated when clay and limestone are crumbled for the production of cement. About 8–10% of the universal CO2 emissions are emitting from the cement factories. With concerns arising over environmental issues associated with cement usage, it is the need of the hour to reduce its consumption. Fly ash, the waste material from thermal power plants, is a widely used supplementary cementitious material that extends the life of the concrete structures. The intervening of nanotechnology into construction industry has provided wider opportunities to better the performance of concrete in rigorous conditions, especially acids and alkali environment. This work endeavours to study the effect of surface-modified fly ash concrete through the addition of nanoparticles against sulphate attack and calcium leaching. Nanophase modification was performed by integrating nano-TiO2 and CaCO3 for enhanced durability and corrosion resistance. Four types of concrete mix, namely fly ash concrete (FA), FA with 2% TiO2 nanoparticles (FAT), FA with 2% CaCO3 nanoparticles and FA with 2% TiO2:CaCO3 (FATC) nanoparticles, were designed and casted as cylindrical concrete blocks. The specimens were immersed in 1% sulphuric acid solution and sea water to study the resistance of concrete against sulphate attack and calcium leaching, respectively. Results showed that nanophase modification of fly ash concrete improved the resistance to sulphuric acid attack and calcium leaching. Among the nanophase-modified specimens, FAT and FATC specimens showed superior performance.

Bacterial Adhesion and Hemocompatibility Behavior of TiN, TiO2 Single and TiN/TiO2 Multilayer Coated 316L SS for Bioimplants

Magnetron sputtering techniques was used to deposit TiN, TiO2 single layer and TiN/TiO2 multilayer coatings on 316L stainless steel (316L SS) substrates. The crystallinity, surface topography and roughness parameters of uncoated (316L SS) and coated specimens were examined. The anti adhesion and antibacterial behavior of S.aureus (gram (+) ve) and E.coli (gram (-) ve) strains on uncoated and coated substrates were determined by live/dead staining using epifluorescence microscopy. Results demonstrate that the coated samples undergo drastic reduction of bacterial adhesion and negligible effect of antimicrobial activity. Further, coated substrates exhibit less platelets activation than that of uncoated substrates.

Structural and corrosion behaviour of bilayer and alloyed films of Cu-Ni

Bilayer and alloyed thin films of Cu-Ni were successfully prepared by RF magnetron sputtering method. XRD analysis showed polycrystalline film with preferred orientation for both bilayer and alloyed thin films. Nanograins were observed by FESEM. The results of electrochemical experiments indicated that the alloyed films exhibited superior corrosion resistance followed by bilayer and bare 316L stainless steel in 3.5% NaCl solution.