Search

The silver (0.5–3 at %) substituted nanosize hydroxyapatites (AgHAs) were synthesized by microwave processing. The X-ray diffraction (XRD) peaks are very broad, indicating that the AgHAs were of nanosize (30 nm). Transmission electron microscopy analysis shows needle-like morphology of AgHA, having length 60–70 nm and width 15–20 nm. The AgHA phase was stable up to 700°C without any secondary phases. The antibacterial effect of AgHA against Escherichia coli and Staphylococcus aureus was observed by spread plate method, even for low concentration of silver ions (0.5%) with 1 × 105 cells/mL of respective bacterial culture, after a 48 h incubation period. However, some colonies of E. coli were seen with a high dose of 1 × 108 cells/mL after 24 h. The zone of inhibition by disc diffusion test method was found to vary with the amount of silver in the sintered AgHA pellets, for both the bacteria, after 24 h of inoculation. Osteoblast cell attachment in varying density was noticed on AgHA samples with 0.5, 1.0, and 1.5% silver substitution. However, osteoblast spreading was significantly greater on 0.5% AgHA compared to 1.0 or 1.5% substituted AgHA samples. Thus, the low amount of AgHA has a potential of minimizing the risk of bacterial contamination, without compromising the bioactivity, and is expected to display greater biological efficacy in terms of osseointegration. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007

Commercial synthetic polymers namely Polycarbonate (PC), Low density polyethylene (LDPE), High density polyethylene (HDPE), and Polypropylene (PP) coupons were immersed for a period of 12 months (Feb 2006 - Feb 2007) in Bay of Bengal, East coast, India. Samples were retrieved every month and the extent of biofouling and biodegradation were monitored. Biofouling was found to depend not only on the season but also on the chemical nature of the polymer. Surface energy of all the four polymers is positively correlated with fouling only at the initial stages (three months) while surface roughness had a negative correlation. The later increased during the study period. Total suspended solids and organic matter were more abundant on HDPE, followed by PP and LDPE, indicating that among polyolefins hydrophobic surfaces (lower surface energy) favor biofouling over one year. Maximum fouling was observed on polycarbonate during initial three months. Chlorophyll a showed a decreasing trend during the study, as secondary foulers such as Balanus amphitrite, were dominant after the monsoon (6th month in the present study). Maximum weight loss was seen in LDPE (1.9%), followed by that in HDPE (1.6%), PC (0.69%) and finally in PP (0.65%) samples in the 12 months time period. FTIR spectra of PC displayed a decrease in carbonate carbonyl index, while an initial increase and a decrease in carbonyl index of polyolefins as a function of time indicated biodegradation. � 2009 Elsevier Ltd. All rights reserved.