Generally, silver is considered as a noble metal used for treating burn wound infections, open wounds and cuts. However, the emerging nanotechnology has made a remarkable impact by converting metallic silver into silver nanoparticles (AgNPs) for better applications. The advancement in technology has improved the synthesis of NPs using biological method instead of physical and chemical methods. Nonetheless, synthesizing AgNPs using biological sources is ecofriendly and cost effective. Till date, AgNPs are widely used as antibacterial agents; therefore, a novel idea is needed for the successful use of AgNPs as therapeutic agents to uncertain diseases and infections. In biomedicine, AgNPs possess significant advantages due to their physical and chemical versatility. Indeed, the toxicity concerns regarding AgNPs have created the need for non-toxic and ecofriendly approaches to produce AgNPs. The applications of AgNPs in nanogels, nanosolutions, silver based dressings and coating over medical devices are under progress. Still, an improvised version of AgNPs for extended applications in an ecofriendly manner is the need of the hour. Therefore, the present review emphasizes the synthesis methods, modes of action under dissipative conditions and the various biomedical applications of AgNPs in detail.

Of the various methods explored for the synthesis of nanoparticles, biogenesis of silver nanoparticles (AgNPs) received great attention due to their versatile properties. In this report, Daucus carota extract was used for the synthesis of AgNPs and ceftriaxone was conjugated with AgNPs to enhance their antimicrobial efficacy. The conjugated and unconjugated AgNPs were characterized by adopting UV-Vis spectroscopy, FTIR, AFM, DLS, and TEM, which revealed the SPR peak at 420 nm and spherical shaped nanoparticles of 20 nm size, respectively. The antimicrobial efficacies of the unconjugated AgNPs and ceftriaxone-conjugated AgNPs were tested against ceftriaxone-resistant human pathogens, Bacillus cereus, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The ceftriaxone-conjugated AgNPs showed high inhibitory action (23 mm) than the unconjugated AgNPs (18 mm) at the concentration of 50 μg/mL. Both the unconjugated and ceftriaxone-conjugated AgNPs were found to be non-toxic on EAC cells at 50 μg/mL. The dose-dependent cytotoxic activities were observed on increasing the concentration of the AgNPs. The ceftriaxone-conjugated AgNPs showed high activity than the unconjugated AgNPs. The enhanced activity could be useful to treat ceftriaxone-resistant human pathogens.

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Iron oxide nanoparticles were synthesized using Amaranthus spinosus leaf aqueous extracts reducing from ferric chloride. A. spinosus leaf extract is a rich source of amaranthine and phenolic compounds with high antioxidant and these molecules were used as reducing agents. The operating parameters of nanoparticles synthesis were optimized. Physicochemical, optical, and magnetic properties of synthesized nanoparticles were characterized using analytical techniques. Results confirmed that A. spinosus leaf extract mediated iron oxide nanoparticles are spherical shape with rhombohedral phase structure, smaller size, and large surface with less aggregation. The photocatalytic and antioxidant activities of leaf extract as well as sodium borohydride mediated iron oxide nanoparticles were studied. The percentage decolorization of methyl orange and methylene blue was 75% and 69%, respectively, for extract mediated iron oxide nanoparticles under sunlight. The antioxidant efficiency was also observed to be 93% against 2,2-diphenyl-1-picrylhydrazyl. The extract mediated iron oxide nanoparticles showed better photocatalytic and antioxidant capacity than sodium borohydride mediated nanoparticles.

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