Biological synthesis and characterization of silver nanoparticles by Orthosyphan rubicundas: Silver nano particles

Abstract

Over the last two decades, nanoparticles have become an important alternative source, which is having the capability inhibit microbes that are highly resistant to different classes of antibiotics. Their wide array of physio-chemical properties makes them a good antimicrobial and anticancer agent. The potential efficacy, toxicity and production in reasonable costs is been assessed by studying different properties of nanoparticles. There are many metal nanoparticles, usually formed in the range of 1 to 100 nm size. Silver nanoparticles (AgNPs) have the unique properties of silver ions and hence are useful in molecular diagnostics, in therapies, as well as in devices that are used in several medical procedures. AgNPs are majorly synthesised by physical and chemical methods. But the methods used for synthesizing are very expensive and many toxic substances are absorbed on them. The biological methods have emerged as viable options and provides a feasible alternative. From the last two decades, biologically mediated synthesis of nanoparticles have been proved to be simple, cost effective, dependable and environmentally friendly. The attention has been given to high yield production of AgNPs of a defined size using various biological systems, including bacteria, fungi, plant extracts, and small biomolecules like vitamins and amino acids as an alternative method to chemical methods. The use of plants in the production of AgNPs has drawn attention due to their rapid, eco-friendly, non-pathogenic, economical protocol and a single step technique for the biosynthetic processes. Though till date, many researchers have explored biosynthesis of nanoparticles using different species belonging to Lamiaceae, This family plants possess high medicinal values due to rich phytocompounds occurrence. It is one of the largest families having a diverse type of plant species, which are widely spread across. The volatile oil is produced by the external glandular structures, mainly occurring in leaves of many Lamiaceae species. Orthosyphan rubicundas is the plant chosen from this family for the study as it is wildly grown in the as a weed and rarely studied in the nanoparticle synthesis. Two-third of the world’s population depends mainly on herbal medicine for primary health care and treatments [1]. The reasons for this is because of their better cultural acceptability, better compatibility and also adaptability with the human body and pose lesser side effects.

The silver based compounds were used as known as non-toxic inorganic antibacterial agents expressing their biocidal properties in many application [2].  AgNPs are the one of the most vital and fascinating nanomaterials among all other metallic nanoparticles that are used in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although, several noble metals have been used for various purposes, AgNPs have been focused for potential applications such as Antimicrobial and cancer diagnosis and therapy [3]. AgNPs have the ability to interact with various microorganisms and they inhibit the growth of bacterial biofilms and, therefore, could be used as broad spectrum antimicrobials [4]. The synthesis of nanoparticles has been carried out using three different approaches, including physical, chemical, and biological methods. However, the use of physical methods and chemical reducing agents are very harmful to living organisms [6]. To overcome this, a new green chemistry approach for the synthesis of AgNPs the biological synthesis of nanoparticles depends on three factors, including 1) the solvent; 2) the reducing agent; and 3) the non-toxic material. The major advantage of biological methods is that the availability of variety amino acids, proteins, or secondary metabolites present in the synthesis process. The elimination of the several extra step required for the prevention of particle aggregation, and the use of biological molecules for the synthesis of AgNPs is eco-friendly and pollution-free. Biological methods seem to provide a controlled particle size and shape, which is an important factor for all various biomedical applications [5].

For characterization of AgNPs the physicochemical properties of nanoparticles were studied which explained the detailed result of their behaviour, efficacy, safety and biodistribution. Characterization is performed using a variety of analytical techniques, mainly including X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) [7], scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM)