Fusarium oxysporum fungal strain was screened and found to be successful for the inter- and extracellular production of platinum nanoparticles. Nanoparticle formation was visually observed, over time, by the colour of the extracellular solution and/or the fungal biomass turning from yellow to dark brown, and their concentration was determined from the amount of residual hexachloroplatinic acid measured from a standard curve at 456 nm. The extracellular nanoparticles were characterized by transmission electron microscopy. Nanoparticles of varying size (10-100 nm) and shape (hexagons, pentagons, circles, squares, rectangles) were produced at both extracellular and intercellular levels by the Fusarium oxysporum. The particles precipitate out of solution and bioaccumulate by nucleation either intercellularly, on the cell wall/membrane, or extracellularly in the surrounding medium. The importance of pH, temperature and hexachloroplatinic acid (H(2)PtCl(6)) concentration in nanoparticle formation was examined through the use of a statistical response surface methodology. Only the extracellular production of nanoparticles proved to be statistically significant, with a concentration yield of 4.85 mg l(-1) estimated by a first-order regression model. From a second-order polynomial regression, the predicted yield of nanoparticles increased to 5.66 mg l(-1) and, after a backward step, regression gave a final model with a yield of 6.59 mg l(-1).

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Nanotechnology is relevant to diverse fields of science and technology. Due to the many advantages over non-biological systems, several research groups have exploited the use of biological systems for the synthesis of nanoparticles. Among the different microbes used for the synthesis of nanoparticles, fungi are efficient candidates for fabrication of metal nanoparticles both intra- and extracellulary. The nanoparticles synthesized using fungi present good polydispersity, dimensions and stability. The potential applications of nanotechnology and nanoparticles in different fields have revolutionized the health care, textile and agricultural industries and they are reviewed here.

Changes in the drug-taking behaviour of drug users after imprisonment vary according to the type of drug being taken. Prisoners were much more likely to continue to use heroin than either cocaine or amphetamines while in prison. Heroin was most likely to be used by those who had been using heroin during the immediate pre-imprisonment period, and particularly by the two-thirds of heroin users who considered themselves dependent. In view of the high prevalence of prior use of these drugs by individuals currently imprisoned, continuing attention is required to study of their behaviour and of the impact of interventions that may be introduced during or following their incarceration.