Silver: an age-old treatment modality in modern times

Plant-mediated synthesis of silver nanoparticles: unlocking their pharmacological potential-a comprehensive review

In recent times, nanoparticles have experienced a significant upsurge in popularity, primarily owing to their minute size and their remarkable ability to modify physical, chemical, and biological properties. This burgeoning interest can be attributed to the expanding array of biomedical applications where nanoparticles find utility. These nanoparticles, typically ranging in size from 10 to 100 nm, exhibit diverse shapes, such as spherical, discoidal, and cylindrical configurations. These variations are not solely influenced by the manufacturing processes but are also intricately linked to interactions with surrounding stabilizing agents and initiators. Nanoparticles can be synthesized through physical or chemical methods, yet the biological approach emerges as the most sustainable and eco-friendly alternative among the three. Among the various nanoparticle types, silver nanoparticles have emerged as the most encountered and widely utilized due to their exceptional properties. What makes the synthesis of silver nanoparticles even more appealing is the application of plant-derived sources as reducing agents. This approach not only proves to be cost-effective but also significantly reduces the synthesis time. Notably, silver nanoparticles produced through plant-mediated processes have garnered considerable attention in recent years due to their notable medicinal capabilities. This comprehensive review primarily delves into the diverse medicinal attributes of silver nanoparticles synthesized using plant-mediated techniques. Encompassing antimicrobial properties, cytotoxicity, wound healing, larvicidal effects, anti-angiogenesis activity, antioxidant potential, and antiplasmodial activity, the paper extensively covers these multifaceted roles. Additionally, an endeavor is made to provide an elucidated summary of the operational mechanisms underlying the pharmacological actions of silver nanoparticles.

Metallodrugs, an approach against invasion and metastasis in cancer treatment

Cancer is a heterogeneous and multifactorial disease that causes high mortality throughout the world; therefore, finding the most effective therapies is a major research challenge. Currently, most anticancer drugs present a limited number of well‐established targets, such as cell proliferation or death; however, it is important to consider that the worse progression of cancer toward pathological stages implies invasion and metastasis processes. Medicinal Inorganic Chemistry (MIC) is a young area that deals with the design, synthesis, characterization, preclinical evaluation, and mechanism of action of new inorganic compounds, called metallodrugs. The properties of metallic ions allow enriching of strategies for the design of new drugs, enabling the adjustment of physicochemical and stereochemical properties. Metallodrugs can adopt geometries, such as tetrahedral, octahedral, square planar, and square planar pyramid, which adjusts their arrangement and facilitates binding with a wide variety of targets. The redox properties of some metal ions can be modulated by the presence of the bound ligands to adjust their interaction, thereby opening a range of mechanisms of action. In this regard, the mechanisms of action that trigger the biological activity of metallodrugs have been generally identified by: (a) coordination of the metal to biomolecules (for instance, cisplatin binds to the N7 in DNA guanine, as Pt‐N via coordination of the inhibition of enzymes); (b) redox‐active; and (c) ROS production. For this reason, a series of metallodrugs can interact with several specific targets in the anti‐invasive processes of cancer and can prevent metastasis. The structural base of several metal compounds shows great anticancer potential by inhibiting the signaling pathways related to cancer progression. In this minireview, we present the advances in the field of antimetastatic effects of metallodrugs.

Designing metallodrugs with nuclease and protease activity

The accidental discovery of cisplatin some 50 years ago generated renewed interest in metallopharmaceuticals. Beyond cisplatin, many useful metallodrugs have been synthesized for the diagnosis and treatment of various diseases, but toxicity concerns, and the propensity to induce chemoresistance and secondary cancers make it imperative to search for novel metallodrugs that address these limitations. The Amino Terminal Cu(ii) and Ni(ii) (ATCUN) binding motif has emerged as a suitable template to design catalytic metallodrugs with nuclease and protease activities. Unlike their classical counterparts, ATCUN-based metallodrugs exhibit low toxicity, employ novel mechanisms to irreversibly inactivate disease-associated genes or proteins providing in principle, a channel to circumvent the rapid emergence of chemoresistance. The ATCUN motif thus presents novel strategies for the treatment of many diseases including cancers, HIV and infections caused by drug-resistant bacteria at the genetic level. This review discusses their design, mechanisms of action and potential for further development to expand their scope of application.

In vitro evaluation of antimicrobial and antibiofilm potentials of silver nanoparticles biosynthesised by Streptomyces griseorubens

This study was performed to determine the antimicrobial and antibiofilm activities of silver nanoparticles (AgNPs) biosynthesised using Streptomyces griseorubens AU2 isolated from soil. The antimicrobial activity of the AgNPs was determined by agar well diffusion, disc diffusion and broth microdilution methods. Diameters of the zone of inhibition results clearly displayed that the microbially biosynthesised AgNPs have potent antimicrobial activity against Candida albicans , Bacillus subtilis , Escherichia coli , Pseudomonas aeruginosa and Staphylococcus aureus . The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of the nanoparticles that had been determined by broth microdilution method were found to be 20 and 50 µg/ml for C. albicans , B. subtilis and S. aureus ; 10 and 20 µg/ml for E. coli and P. aeruginosa , respectively. For determining the effect of AgNPs on biofilm formation under in vitro conditions, MIC and subMICs were studied on P. aeruginosa and S. aureus biofilms by using microplate biofilm assay. Treatment of the AgNPs resulted in a decrease in the biofilm formation of S. aureus and P. aeruginosa as 26.52 and 25.50%, respectively. As a result of this study, it can be suggested that actinobacterially synthesised AgNPs have an effective potential to be used for pharmaceutical applications against multi‐resistant microorganisms.

Silver toxicity with the use of silver-impregnated dressing and wound vacuum-assisted closure in an immunocompromised patient

Silver-containing topical agents are used to help prevent infectious complications in wound therapy. Toxicity from topical silver agent exposure was initially reported in 1975 and was clinically characterized by granulocytopenia. Currently, the data regarding potential toxicity associated with silver-impregnated devices are limited. A 23-year-old patient receiving chemotherapy for acute lymphoblastic leukemia presented with necrotizing fasciitis of the abdominal wall and scrotum from a Crohn disease-related psoas-enteric fistula. Surgical debridement of the soft-tissue and abdominal musculature was performed to the peritoneum. Silver-containing foam sponges and wound vacuum-assisted closure were applied directly to the peritoneum 2 weeks after initial debridement. Subsequently, the patient developed leukopenia, and workup revealed the serum silver level was 4 times normal level. Silver-impregnated sponges were discontinued and silver-free sponges and wound vacuum-assisted closure therapy resumed, followed by leukopenia resolution. Silver toxicity associated with routine application of silver-impregnated sponges has not been previously reported.