Synthesis and Characterization of Sulfur Nanoparticles of Citrus limon Extract Embedded in Nanohydrogel Formulation: In Vitro and In Vivo Studies

Abstract

The study aimed to synthesize non-noxious, clean, reliable, and green sulfur nanoparticles (SNPs) from Citrus limon leaves. The synthesized SNPs were used to analyze particle size, zeta potential, UV–visible spectroscopy, SEM, and ATR-FTIR. The prepared SNPs exhibited a globule size of 55.32 ± 2.15 nm, PDI value of 0.365 ± 0.06, and zeta potential of −12.32 ± 0.23 mV. The presence of SNPs was confirmed by UV–visible spectroscopy in the range of 290 nm. The SEM image showed that the particles were spherical with a size of 40 nm. The ATR-FTIR study showed no interaction, and all the major peaks were preserved in the formulations. An antimicrobial and antifungal study of SNPs was carried out against Gram-positive bacteria (Staph. aureus, Bacillus), Gram-negative bacteria (E. coli and Bordetella), and fungal strains (Candida albicans). The study showed that Citrus limon extract SNPs exhibited better antimicrobial and antifungal activities against Staph. aureus, Bacillus, E. coli, Bordetella, and Candida albicans at a minimal inhibitory concentration of 50 μg/mL. Different antibiotics were used alone and in combination with SNPs of Citrus limon extract to evaluate their activity against various strains of bacteria and fungal strains. The study showed that using SNPs of Citrus limon extract with antibiotics has a synergistic effect against Staph.aureus, Bacillus, E. coli, Bordetella, and Candida albicans. SNPs were embedded in nanohydrogel formulations for in vivo (wound healing) studies. In preclinical studies, SNPs of Citrus limon extract embedded within a nanohydrogel formulation (NHGF4) have shown promising results. To be widely used in clinical settings, further studies are needed to evaluate their safety and efficacy in human volunteers.

Plant-Based Extracts as Reducing, Capping, and Stabilizing Agents for the Green Synthesis of Inorganic Nanoparticles

“…Sulfur nanoparticles (SNPs) are biocompatible compounds with a high surface area and catalytic activity, which have great potential for diverse biomedical and agricultural applications [131]. These SNPs have been green-synthesized using aqueous extracts from various plant materials and their parts, including Rosmarinus officinalis [132], Citrus limon [131], Aloe vera [133], Allium sativum [134], and Cinnamomum zeylanicum [135]. Sodium thiosulfate pentahydrate is commonly used as a precursor for spherical SNPs, ranging from 40 to 69 nm in size [131][132][133][134][135].…”

“…These SNPs have been green-synthesized using aqueous extracts from various plant materials and their parts, including Rosmarinus officinalis [132], Citrus limon [131], Aloe vera [133], Allium sativum [134], and Cinnamomum zeylanicum [135]. Sodium thiosulfate pentahydrate is commonly used as a precursor for spherical SNPs, ranging from 40 to 69 nm in size [131][132][133][134][135]. After mixing the plant extract and sulfur precursor, a yellow color indicates the formation of SNPs [135].…”

“…These SNPs have been used as plant-growth-promoting and nematicidal agents [132,134,135] and are effective antimicrobial agents [131]. Furthermore, SNPs were embedded in a chitosan nanohydrogel for wound-healing applications [131]. Table 12 lists some green-synthesized sulfiur SNPs and their applications.…”

Improved Solubility and Activity of Natural Product in Nanohydrogel

“…For example, polysaccharides consisting of monosaccharide chains held together by glycosidic bonds have successfully enhanced drug delivery into and across the skin in nanohydrogel formulations. Furthermore, the saccharide polymers used include cellulose, chitosan, and their semisynthetic derivatives, such as alginate, pectin, HPMC, PLGA, carrageenan, and others [40,41].…”

“…Based on research by Kaur et al (2022), ionic gelation is the primary technique for forming milk protein nanohydrogel [36]. The milk protein-based nanohydrogel-forming system can improve various functions, such as food nutrition and health, food engineering and processing, and food safety [41]. Therefore, milk protein nanohydrogels have many applications in the food industry because denaturation, aggregation, and gelation of proteins have special meaning in making new nanostructures, such as nanohydrogels, in various scientific fields of application [41,42].…”