Green synthesis of metal nanoparticles: Biodegradable polymers and enzymes in stabilization and surface functionalization

Current breakthroughs in green nanotechnology are capable of transforming many of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and non-renewable resources. Successful use of metal nanoparticles and nanocomposites in various catalytic applications, electronics, biology and biomedical applications, material science, physics, environmental remediation and interdisciplinary fields as well as their toxicity essentially depends on the structural features such as size, shape, composition and the surface chemistry of nanomaterials. Moreover, to prolong the life span of metal nanoparticles and avoid undesired effects such as aggregation in aqueous solutions and organic solvents, to prevent contamination of the environment as well as to reuse and recycle nanoparticles, it is vital to select stabilizing agents and functionalization pathways that are environmentally friendly, non toxic and easy to implement. In recent years, stabilization and surface functionalization of metal nanoparticles became 'greener' to the extent that biocompatible stabilizing agents, e. g. biodegradable polymers and enzymes among others were introduced. These agents were able to produce a great variety of extremely stable spherical-, rod- or flower- shaped metal nanoparticles that opened up vast opportunities for their utilization and potential mass production. This review summarizes the state-of-the-art in the use of biocompatible and biodegradable homo- and copolymers as well as enzymes for the production of stable, environmentally benign, selective and active metal nanoparticles for desired applications.