Synthesis Routes of Silver Nanoparticles and Their Influence on Size, Shape, and Biological Activity

Abstract

AgNP formulations are frequently assessed in the same nominal concentration of silver, despite differences arising in synthesis that can alter numerous characteristics that govern the exposure of a biological target. This important narrative review provides an evaluation of how these changes, taken together, impact biological activity. Scope comparison of the seven previous reviews is undertaken, and another PubMed search is documented where all 388 unique records obtained from four focused searches are screened. The selected primary research is analyzed in terms of controls and measures used for exposures in order to justify the conclusions drawn by the authors. Two major issues, which arise repeatedly, are described in numbers: changing of potency ranking with the change of the dose metric and difference between administration concentration and actual dose. There are also changes in the properties of surface coatings when they come into contact with biological solutions, and formation of a corona can make the difference between the primary particles undetectable. Extracellular ionic regulation does not help solve the problem of silver release inside cells. In studies on antimicrobials and cancer research, activity should be taken into account together with cytotoxicity toward the host system; data on clinical wounds pertain to full preparations. This review highlights those comparisons that may differentiate a synthesis effect from changes in the means of delivery or residual components or interference in the assays. Reproducible synthesis, host compatibility, and environmental efficacy continue to be requirements in optimizing the applications.