Known for its antimicrobial properties, silver is widely used in implantable device coatings to prevent bacterial growth and ward off infections. However, because of their cytotoxicity, silver nanoparticles have possible adverse effects on the body. Andrea Travan, a materials engineer at the Università degli Studi di Trieste (Italy), remarks, “So far, to the best of our knowledge, water-based biomaterials able to successfully combine antibacterial properties of silver nanoparticles with demonstrated absence of cytotoxicity have not yet been reported in the literature.”
To remedy this deficiency, Travan and his colleagues have conducted research into developing a noncytotoxic nanocomposite hydrogel material for antimicrobial applications based on the polysaccharide alginate and silver nanoparticles. This hydrogel appears to be nontoxic toward three different eukaryotic cell lines because the nanoparticles, immobilized in the gel matrix, can exert their antimicrobial activity by simple contact with the bacterial membrane without being uptaken and internalized by eukaryotic cells.
Relying on the simultaneous presence of a sugar-based bioactive polymer for cell stimulation and silver nanoparticles for antibacterial activity, the nanocomposite hydrogels developed by Travan and his team display antibacterial activity without being harmful to mammalian cells. “In our cytotoxicity studies we show how the lack of physical barriers to nanoparticle diffusion into cells determines their generalized bio-availability, with the risk of a massive uptake by eukaryotic cells, which eventually leads to their death,” Travan explains. “Conversely, the nanocomposite materials we have developed are able to solve the cytotoxicity problem by creating a gel structure that efficiently immobilizes the metal nanoparticles and ions within the material.”
In addition to their cytotoxicity, silver nanoparticles tend to aggregate, losing their nanoscale properties. Travan and his team have also conducted experiments using the branched polysaccharide chitlac (lactose-modified chitosan), which they say helps to form and stabilize well-dispersed silver nanoparticles with a mean diameter of about 35 nm.
