Nanosilver: An innovative paradigm to promote its safe and active use

A general model useful to assess the applicability, in terms of safety and efficiency, of nanosilver sols in real applications was developed. This led to the definition of an operative parameter, named Quality Index (QI), able to rank the capacity of the samples to be applied effectively in safe concentration ranges on the basis of the mere knowledge of the toxicological and antibacterial limits of the samples and of the fraction of silver ions (Ag+) with respect the total silver in the samples and in the samples after application. The new approach was applied to three nanosilver formulations to be used as antibacterial agents on tile surfaces, differing, essentially, for the relative amount of silver ions and silver nanoparticles (Ag NPs): i) a (diluted) commercial sample (Ag1); ii) a sample arising from the latter after an ultrafiltration treatment applied as remediation strategy (Ag31); and iii) a sample synthesized at lab scale in controlled conditions (AgL). Such sols were characterized with in vitro toxicity and antibacterial tests to collect the inputs required by the model. A general rationale to classify partially soluble nanomaterials, exploitable in antibacterial applications, was thus introduced, opening a new perspective toward the promotion of a safer by-design management of nanomaterials.