Illuminating the cellular and molecular mechanism of the potential toxicity of methacrylate monomers used in biomaterials.

The cytotoxicity of methacrylate-based biopolymers crosslinked by in situ photopolymerization has been attributed mainly to residual methacrylate monomers released due to incomplete polymerization. The residual monomers, primarily triethyleneglycol dimethacrylate or 2-hydroxyethyl methacrylate, may irritate adjacent tissue, or be released into the bloodstream and reach practically all tissues. Increased production of reactive oxygen species, which may be connected to concomitant glutathione depletion, has been the most noticeable effect observed in vitro following the exposure of cells to methacrylates. Radical scavengers such as glutathione or N-acetylcysteine represent the most important cellular strategy against methacrylate-induced toxicity by direct adduct formation, resulting in monomer detoxification. Reactive oxygen species may participate in methacrylate-induced genotoxic or pro-apoptotic effects and cell-cycle arrest via induction of corresponding molecular pathways in cells. A deeper understanding of the biological mechanisms and effects of methacrylates widely used in various bioapplications may enable a better estimation of potential risks and thus, selection of a more appropriate composition of polymer material to eliminate potentially harmful substances such as triethyleneglycol dimethacrylate.

Modulation of Skin Inflammatory Response by Active Components of Silymarin.

In this study, we compared selected silymarin components, such as quercetin (QE), 2,3-dehydrosilybin (DHS) and silybin (SB), with the anti-inflammatory drug indomethacin (IND) in terms of their wound healing potential. In view of the fact that pathological cutaneous wound healing is associated with persistent inflammation, we studied their anti-inflammatory activity against inflammation induced by bacterial lipopolysaccharide (LPS). We investigated the regulation of crucial pro-inflammatory transcription factors-nuclear factor kappa-B (NF-κB) and activator protein 1 (AP-1)-as well as the expression of downstream inflammatory targets by Western blotting, real-time PCR (RT-PCR), electrophoretic mobility shift assay (EMSA), and/or enzyme-linked immunosorbent assay (ELISA) in vitro using primary normal human dermal fibroblasts (NHDF). We demonstrated the greater ability of DHS to modulate the pro-inflammatory cytokines production via the NF-κB and AP-1 signaling pathways when compared to other tested substances. The prolonged exposure of LPS-challenged human dermal fibroblasts to DHS had both beneficial and detrimental consequences. DHS diminished interleukin-6 (IL-6) and interleukin-8 (IL-8) secretion but induced the significant upregulation of IL-8 mRNA associated with NF-κB and AP-1 activation. The observed conflicting results may compromise the main expected benefit, which is the acceleration of the healing of the wound via a diminished inflammation.

Effect of AgNPs on the human reconstructed epidermis.

Nanoparticles are utilized in a wide range of industries. The most studied silver nanoparticles (AgNPs) are used in medicine and also in several wound dressings due to their antimicrobial properties. The inflammatory response or potential morphological changes of skin cells after their application are not well known yet. In our study we used the model of human reconstructed epidermis (RHE), prepared in our laboratory, to evaluate whether the AgNPs penetrate through RHE, induce some morphological changes of keratinocytes or influence the production of pro-inflammatory cytokines (IL-6 and IL-8). After the application of three different concentrations (25 ppm, 2.5 ppm, 0.25 ppm) of AgNPs to of RHE for 24 hours we verified that AgNPs did not affect the production of pro-inflammatory cytokines (IL-6 and IL-8) and neither did they influence the expression of keratin K14 and loricrin. The morphology of the cells was likewise unchanged. Based on these results we conclude that AgNPs do not have any negative effect on the morphological changes and do not increase the production of pro-inflammatory cytokines.

Effects of silver nanoparticles on primary cell cultures of fibroblasts and keratinocytes in a wound-healing model.

BACKGROUND: Nanoparticles are widely used in different technological fields, one of which is medicine. Because of their antibacterial properties, silver nanoparticles (AgNPs) are used in several types of wound dressings for the treatment of burns and nonhealing wounds, but their influence on each component of the wound-healing process remains unclear. In the present study, we evaluated the effects of AgNPs on normal human dermal fibroblasts (NHDFs) and normal human epidermal keratinocytes (NHEKs). Both cell types are important for wound healing, including with regard to inflammation, proliferation and tissue remodeling. Each phase of wound healing can be characterized by the secretion of cytokines, chemokines and growth factors. METHODS: The production of inflammatory parameters (tumor necrosis factor α [TNF-α], interleukin-6 [IL-6], IL-8 and IL-12 and cyclooxygenase-2 [COX-2]), angiogenesis parameters (vascular endothelial growth factor [VEGF], granulocyte macrophage colony-stimulating factor) and matrix metalloproteinases (MMP-1, MMP-2, MMP-3 and MMP-9) by NHDFs and NHEKs were examined by ELISA or Western blot after 24 and 48 hours of incubation with AgNPs. RESULTS: We found that AgNPs decreased some inflammatory cytokines (TNF-α and IL-12) and growth factors (VEGF) that were produced by NHDFs and NHEKs after 24 and 48 hours and decreased the expression of COX-2 after 24 hours but only at the highest concentration of AgNPs (25 parts per million). CONCLUSIONS: The results indicate that NHEKs are more susceptible to the application of AgNPs than NHDFs, and AgNPs may be useful for medical applications for the treatment of wounds.