Synthesis and Bioactivity of Selenium Nanoparticles Stabilized by Biocompatible Agents

Abstract

In recent past, the domain of nanobiotechnology has progressively transitioned towards the creation of eco-friendly, biologically inspired techniques for nanoparticle production, focusing on biocompatible and ecologically safe procedures. Endophytic fungi are prolific makers of secondary metabolites and exopolysaccharides (EPS), both of which are significant for applications such as nanoparticle fabrication and the identification of bioactive compounds. The presented research work was aimed to investigate the biofunctionalization potential of secondary metabolites that were extracted from an endophytic fungal source. The isolation and antimicrobial screening were done of fungal isolates obtained from a plant source, Nerium oleander, commonly known as the Ganer plant. Upon the basis of antimicrobial screening of the fungal extracts, one of the isolates showing good antimicrobial potential was selected for further studies, i.e., NL(C). Following the morphological and molecular identification, the strain was observed to be Nigrospora spp. Moving forward, the fungal strain’s secondary metabolites, viz., fungal extract (NL(C)) and exopolysaccharide (EPS), were employed for the stabilization of selenium nanoparticles (SeNPs). Selenium nanoparticles have garnered significant interest in the last decade for their multifunctional uses in medicinal, environmental, and industrial fields. The study aimed at the green production of selenium nanoparticles utilizing endophytic fungal extracts (NL(C)) and exopolysaccharides (EPS). The study demonstrates a biological approach that effectively facilitates the synthesis and stabilization of SeNPs with the help of secondary metabolites, i.e., fungal extract rich in phenolic and flavonoids, which was obtained from endophytic fungi Nigrospora spp. termed as NL(C)-SeNPs. The nanoparticles formed were characterized via various techniques i.e., UV- visible spectroscopy, FTIR, DLS, and TEM. The synthesized NL(C)-SeNPs were spherical with a size of 55 ± 7.0 nm. These capped SeNPs (NL(C)-SeNPs) showed prominent bioactivity in terms of in-vitro anti-oxidant properties and anti-microbial activity on Escherichia coli, Enterobacter faecalis, and Staphylococcus aureus and antifungal activity on Aspergillus niger and Fusarium laterium. The results indicated NL(C)-SeNPs portray enhanced anti-oxidant and anti-microbial activity in a dose-dependent manner. Apart from their antimicrobial efficacy NL(C)-SeNPs was also successful in showing cell cytotoxic effect against HepG2 cells. In the second stage, of this study, green synthesis was obtained by using EPS extracted from the same strain N. guilinensis. The primary objective of this work was to investigate the synthesis and the bioactivity of SeNPs encapsulated with exopolysaccharide (EPS). The EPS. was mainly composed of 395 ± 13.20 mg/g carbohydrate and 121 ± 3.21 mg/g protein, the following moiety was used for surface stabilization of selenium nanoparticles (SeNPs). Bioactive SeNPs i.e., EPS-SeNPs. with an average size of 43.7 ± 13.7 nm were successfully synthesized. The antibacterial bioactivity of EPS-SeNPs was seen to be showing inhibition against Gram-positive bacteria, viz., Bacillus subtilis, Staphylococcus aureus, and Enterococcus faecalis, as well as Gram-negative bacteria, such as Escherichia coli and Salmonella enterica. In addition, the study also demonstrated antifungal activity against Alternaria alternata, Fusarium laterium, and Aspergillus niger. The cytotoxic activity of synthesized EPS-SeNPs exhibited a dose-dependent response against liver carcinoma cell lines, i.e., the HepG2. Upon juxtaposition, it was observed that although both the SeNPs are showing broad spectrum activity, yet EPS-SeNPs was shown to be more bio-actively potent than NL(C)-SeNPs. Additionally, these findings also support the hypothesis that these nanoparticles hold potential as an emerging material in the field of therapeutics. The synthesized EPS-SeNPs were converted into a functional material to improve the antibacterial performance of commercial gauze textiles. The challenge of bacterial contamination, which triggers an immune response, remains a significant hurdle in the biomedical field. As the conventional wound dressings lack antimicrobial efficacy, to enhancement of the antibacterial activity of dressing material was considered with the help of EPS-SeNPs, which may indirectly support wound healing. This study explored the use of exopolymeric substance-capped selenium nanoparticles (EPS-SeNPs) to enhance the antibacterial properties of cotton gauze. The modification of the gauze involved using chitosan as an adhesive agent to improve the deposition of EPS-SeNPs. The resulting functionalized gauze, termed EPS-SeNPs@CH_CG, was further analysed using physicochemical techniques such as XRD, FTIR, and FE-SEM. This functionalized gauze exhibited both anti-adhesive and bactericidal properties against Escherichia coli and Staphylococcus aureus. A prolonged antibacterial effect was also observed to be facilitated by the sustained release of selenium from the gauze. This study underscores the potential of EPS-SeNPs@CH_CG-functionalized cotton gauze for anti-microbial enhancement, which can be an asset for biomedical applications.