A review on green synthesis of zinc oxide nanoparticles – An eco-friendly approach

Green synthesis, characterization and antimicrobial activities of zinc oxide nanoparticles from the leaf extract of Azadirachta indica (L.)

Nanotechnology is emerging as an important area of research with its tremendous applications in all fields of science, engineering, medicine, pharmacy, etc. It involves the materials and their applications having one dimension in the range of 1-100nm. Generally, various techniques are used for syntheses of nanoparticles (NPs) viz. laser ablation, chemical reduction, milling, sputtering, etc. These conventional techniques e.g. chemical reduction method, in which various hazardous chemicals are used for the synthesis of NPs later become liable for innumerable health risks due to their toxicity and endangering serious concerns for environment, while other approaches are expensive, need high energy for the synthesis of NPs. However, biogenic synthesis method to produce NPs is eco-friendly and free of chemical contaminants for biological applications where purity is of concerns. In biological method, different biological entities such as extract, enzymes or proteins of a natural product are used to reduce and stabilised formation of NPs. The nature of these biological entities also influence the structure, shape, size and morphology of synthesized NPs. In this review, biogenic synthesis of zinc oxide (ZnO) NPs, procedures of syntheses, mechanism of formation and their various applications have been discussed. Various entities such as proteins, enzymes, phytochemicals, etc. available in the natural reductants are responsible for synthesis of ZnO NPs.

A review on biogenic synthesis of ZnO nanoparticles using plant extracts and microbes: A prospect towards green chemistry.

Antimicrobial properties of ZnO nanomaterials: A review

Despite an array of cogent antibiotics, bacterial infections, notably those produced by nosocomial pathogens, still remain a leading factor of morbidity and mortality around the globe. They target the severely ill, hospitalized and immunocompromised patients with incapacitated immune system, who are prone to infections. The choice of antimicrobial therapy is largely empirical and not devoid of toxicity, hypersensitivity, teratogenicity and/or mutagenicity. The emergence of multidrug-resistant bacteria further intensifies the clinical predicament as it directly impacts public health due to diminished potency of current antibiotics. In addition, there is an escalating concern with respect to biofilm-associated infections that are refractory to the presently available antimicrobial armory, leaving almost no therapeutic option. Hence, there is a dire need to develop alternate antibacterial agents. The past decade has witnessed a substantial upsurge in the global use of nanomedicines as innovative tools for combating the high rates of antimicrobial resistance. Antibacterial activity of metal and metal oxide nanoparticles (NPs) has been extensively reported. The microbes are eliminated either by microbicidal effects of the NPs, such as release of free metal ions culminating in cell membrane damage, DNA interactions or free radical generation, or by microbiostatic effects coupled with killing potentiated by the host's immune system. This review encompasses the magnitude of multidrug resistance in nosocomial infections, bacterial evasion of the host immune system, mechanisms used by bacteria to develop drug resistance and the use of nanomaterials based on metals to overcome these challenges. The diverse annihilative effects of conventional and biogenic metal NPs for antibacterial activity are also discussed. The use of polymer-based nanomaterials and nanocomposites, alone or functionalized with ligands, antibodies or antibiotics, as alternative antimicrobial agents for treating severe bacterial infections is also discussed. Combinatorial therapy with metallic NPs, as adjunct to the existing antibiotics, may aid to restrain the mounting menace of bacterial resistance and nosocomial threat.

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M. Anbuvannan

Papers

Green synthesis of ZnO nanoparticles using Solanum nigrum leaf extract and their antibacterial activity.

Synthesis, characterization and photocatalytic activity of ZnO nanoparticles prepared by biological method

Anisochilus carnosus leaf extract mediated synthesis of zinc oxide nanoparticles for antibacterial and photocatalytic activities