Abstract

 The emerging properties of noble metal nanoparticles (NPs) are attracting huge interest from the translational scientific community and have led to an unprecedented expansion of research and exploration of applications in biotechnology and biomedicine. An array of physical, chemical and biological methods has been used to synthesize nanomaterials. In order to synthesize noble metal NPs of particular shapes and sizes, specific methodologies have been formulated. Although ultraviolet irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques have been used successfully to produce NPs, they remain expensive and involve hazardous chemicals. Therefore, there is a growing concern about developing environment-friendly and sustainable methods. Since the synthesis of nanoparticles of different compositions, sizes, shapes and controlled dispersity is an important aspect of nanotechnology, new cost-effective procedures are being developed. Microbial synthesis of NPs is a green chemistry approach that interconnects nanotechnology and microbial biotechnology. Biosynthesis of gold, silver, gold–silver alloy, selenium, tellurium, platinum, palladium, silica, titania, zirconia, quantum dots, magnetite, and uraninite nanoparticles by bacteria, actinomycetes, fungi, yeasts, and viruses have been reported. However, despite stability, biological NPs are not monodispersed, and the rate of synthesis is slow. To overcome these problems, several factors, such as microbial cultivation methods and extraction techniques, have to be optimized, and the combinatorial approach, such as photobiological methods, may be used. Cellular, biochemical and molecular mechanisms that mediate the synthesis of biological NPs should be studied in detail to increase the rate of synthesis and improve the properties of NPs.