Abstract

Green nanotechnology offers immense opportunities as it applies principles of green chemistry for synthesis of nanomaterial for various applications. Green gold nanoparticles (AuNPs) provide eco-friendly materials at low cost and toxicity, high chemical and thermal stability, enhanced degradation activity for environmental remediation and used in numerous biomedical fields. For biomedical application, the toxic chemical agents used for synthesis via conventional methods are a major deterrent. To address this, green synthesized of gold nanoparticles (AuNPs) were extensively studied. Continuous efforts have been focused on facile, low cost, pure, non-toxic and environment friendly approach for their synthesis. Their biocompatibility, photonic properties and their possible solubility in aqueous phases enabled the assimilation of AuNPs in diverse biomedical field. Different biological resources normally existing in the environment have been used for biosynthesis of biogenic nanoparticles that include bacteria, fungi, algae, yeast, cyanobacteria, actinomycetes, viruses and plants This review provides a comprehensive overview of synthesis and characterization of biogenic AuNPs with their broad applications in biomedical fields have also been elucidated along with their future prospects.

Introduction

Nano-science and technology is the new-fangled approach that becomes an inexorable element of the modern Era and are still garnering considerable interest in witnessing the ease of technology at the scientific and commercial level. The small-dimensions nanoparticles (1–100 nm) govern the entire research globally, due to its remarkable applications in physical, chemical, environmental and biological sciences [1]. Among all the synthetically classified nanoparticles, metal-based nanoparticles have enraptured, due to their unique physicochemical characteristics, highly active, reproducibility and antibacterial properties attributed to their enormous surface area to volume ratio [2,3]. Metallic nanoparticles that have achieved immense attention recently due to their imperative significance are aluminium, silver, gold, iron, zinc, copper and palladium [4]. Specifically, gold nanoparticles have an extensive history for medical purpose such as management of various aliments due to their biocompatible nature, high thermal and electrical conductivity, surface-enhanced Raman scattering, chemical stability, catalytic activity and antimicrobial activity [5]. The characteristics of metal nanoparticles contribute to several biomedical purposes assisted by optical device, sensing components, photothermal therapy, catalysts and targeted drug delivery [2]. There are various studies that described the different mode of gold NPs formulation- include chemical, radiation, electrochemical, Langmuir-Blodgett, photochemical methods and biological techniques. Generally, conventional mode of synthesis has serious limitations like as upfront use of toxic reagents that are extremely harmful for the living system and environment, high cost, exposure to radiation, requires high-energy input, high temperature and less productivity. The chemical diluters used during fabrication later on leads to troubles in nanoparticles extraction and also exhibit considerable obstacles to biomedical applications. Furthermore, during the application of gold nanoparticles as drug delivery carriers the extra of precursor constituents may causes cytotoxicity of healthy cells. Some reports states that function of heart and its vasculature can be affected by AuNPs that have to be cautiously evaluated [6]. Therefore, there is an emergent need to develop an environmentally benign method for the gold nanoparticles synthesis. This draws attention to the researchers and industrial sector in the field of nanoparticle synthesis and assembly to utilize some biocompatible natural compounds for the reduction of Au-containing salts for the synthesis of Au nanoparticles is very important, that further generate numerous imperative pharmaceutical molecules relevant for various biomedical applications as toxic substances are abolished [6,7]. The biogenic synthesis method has several advantages with respect to clean, cost effective, effortless procedure and eco-friendly approach. The use of various fungi, bacteria and plant tissues have been stated for the biosynthesis of gold nanoparticles. The biological mode of AuNPs synthesis is categorically classified into two approaches: first category involves the use of microorganisms such as- algae, bacteria, and fungi while the other is based on the plant-based extracts as reducing and stabilising agents [8,9]. The advantage of plant-based extract to serve as excellent reducing and stablishing agents are responsible in reducing particle size and enhance their reactivity in a one-pot synthesis of AuNPs. Here, we discuss the formulation of biogenic gold nanoparticles through green synthesis. The synthesis of green AuNPs is explained and various environmental parameters affecting their synthesis are introduced.

Conclusion

The green production of AuNPs is an evolving technique, in present day the development of reliable, unconventional, remarkable, and sustainable solutions is promising for the researchers and scientists with broad range of application in various biomedical fields. This review summarises the current understanding of synthesis and characterization of biogenic AuNPs in the field of biomedical application that holds eminent potential to address and explore the diverse areas such as chemistry, medicine, technology and industry.

Special interest is focused on the prospective effect of AuNPs in mediating the anti-microbial, anti-oxidant, anti-cancer and anti-diabetic effect. Along with this it also offers suitable platform for efficient delivery (drugs and gene) system and potent sensitive biosensor for detecting various ailments. The synthesis based on green reducing agents is executed in a modest way without pre-requisite need for higher temperature and pressure. Innumerable evidenced demonstrated the interdisciplinary ways for the production of biogenic AuNPs from several plant and microorganism extracts including the use of harmless components that mediates the reduction, capping of AuNPs and removing the risk associated to environmental pollutants. Usually, plant based reducing agents provide fastest reaction in comparison with microbial based green synthesis. Therefore, the biological synthesis of nanoparticles is extremely quicker, cost- effective process that can be developed as an economic and valuable substitution for the commercialization and large-scale production of biogenic gold NPs suitably applied in biomedical and clinical fields. Conclusively, emergence of green and sustainable nanotechnology provides a promising eco-friendly strategy and its utilization in multiple fields, but still its implementation as an in-vivo delivery vehicle and its efficacy along with clinical studies are critically required.

References

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