Surfaces modified with nanometer-thick silver-impregnated polymeric films that kill bacteria but support growth of mammalian cells

Abstract

Silver is widely used as a biocidal agent in ointments and wound dressings. However, it has also been associated with tissue toxicity and impaired healing. In vitro characterization has also revealed that typical loadings of silver employed in ointments and dressings (∼ 100 μg/cm2) lead to cytotoxicity. In this paper, we report the results of an initial study that sought to determine if localization of carefully controlled loadings of silver nanoparticles within molecularly thin films immobilized on surfaces can lead to antimicrobial activity without inducing cytotoxicity. Polymeric thin films of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were prepared by layer-by-layer deposition and loaded with ∼0.4 μg/cm2 to ∼23.6 μg/cm2 of silver nanoparticles. Bacterial killing efficiencies of the silver-loaded films were investigated against Staphylococcus epidermidis, a gram-positive bacterium, and it was determined that as little as ∼0.4 μg/cm2 of silver in the polymeric films caused a reduction of 6 log10 CFU/mL (99.9999%) bacteria in suspensions incubated in contact with the films (water-borne assays). Significantly, whereas the antibacterial films containing high loadings of silver were found to be toxic to a murine fibroblast cell line (NIH-3T3), the polymeric films containing ∼0.4 μg/cm2 of silver were not toxic and allowed attachment, and growth of the mammalian cells. Thus, the results of this study go beyond prior reports by identifying silver-impregnated, polymeric thin films that are compatible with in vitro mammalian cell culture yet exhibit antibacterial activity. These results support the hypothesis that localization of carefully controlled loadings of silver nanoparticles within molecularly thin polymeric films can lead to antimicrobial activity without cytotoxicity. More broadly, this strategy of modifying surfaces with minimal loadings of bioactive molecules indicates the basis of approaches that may permit management of microbial burden in wound beds without impairment of wound healing.

Commercial Metal-Based Nanocolloids - Evaluation of Cytotoxicity

“…Moreover, other authors have reported that, as in our experiments, AgNPs sometimes had a proliferative effect. Agarwal et al (1) found that low non-toxic doses of nanosilver stimulated the growth of mouse fibroblasts NIH/3T3, while Rosas-Hernandes et al (26) observed the proliferative activity of nanosilver towards coronary endothelial cells (CEC), although in this case the effect was in reverse proportion to the applied concentration. In contrast, our results did not confirm the hypothesis by Arora et al (4) about lesser sensitivity of primary cell cultures to nanosilver.…”

Antimicrobial and osteogenic effect of Ag-implanted titanium with a nanostructured surface

“…6,33 During the short period of testing, NT and Ag-NT did not show any cytotoxicity to osteoblasts through direct contact. At 3 days, the number of cells on the surfaces of NT and Ag-NT were higher than that on Ti, which suggests that Ag-NT has no adverse effect toward osteoblasts, and may slightly promote their growth.…”

“…Silver is effective against a broad spectrum of bacterial and fungal species, including strains that are resistant to antibiotics. 6 Silver nanoparticles are considered to be even more active due to their large surface area to volume ratio. 7 Previous work has indicated that silver nanoparticles embedded in titanium may be highly effective in inhibiting both Staphylococcus aureus and Escherichia coli.…”

Cytotoxicity of AgNPs/CS composite films: AgNPs immobilized in chitosan matrix contributes a higher inhibition rate to cell proliferation

“…3 However, the cytotoxicity and genotoxicity [4][5][6] of AgNPs raise risk for patient exposure. The cytotoxicity of AgNPs is directly proportional to the silver concentration, and 5-50 mg/ml AgNPs cause acute toxicity in rat liver cells (BRL 3A).…”