RESUMO
Understanding the chemical absorption process of silver ions helps the rational design of functional materials for effective release to minimize unwanted toxicity. To this end, a histidine-containing aliphatic peptide (IH6) was designed to immobilize the silver ion (Ag+) through coordinate interaction. Using circular dichroism spectroscopy, Ag+ was found to dose-dependently induce parallel ß-sheet conformation of IH6 to a saturation molar ratio of 1:2. A conformational switch of IH6 from antiparallel to parallel ß-sheet assembly upon Ag + coordination was further revealed by Fourier transform infrared spectroscopy. The resultant Ag-IH6 hydrogel displayed substantially enhanced mechanical strength as well as controlled release of Ag+. Ag-IH6 hydrogel thus exhibited strong dose-dependent bactericidal activities that can be tuned selectively, sparing the cocultured human keratinocytes in normal. Overall, the study demonstrates an unusual silver ion-induced peptide conformational switch between ß-structure subtypes and the bilateral effects on hydrogel-based chemical control of silver ion absorption and release, thus, revealing the potential in antibacterial applications.
Assuntos
Antibacterianos/química , Histidina/química , Hidrogéis/química , Oligopeptídeos/química , Prata/química , Antibacterianos/farmacologia , Linhagem Celular , Liberação Controlada de Fármacos , Humanos , Queratinócitos/efeitos dos fármacos , Conformação Proteica em Folha beta , Pseudomonas aeruginosa/efeitos dos fármacos , Prata/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Polímeros Responsivos a Estímulos/químicaRESUMO
Escin, a natural mixture of triterpenoid saponin isolated from the seed of the horse chestnut, is reported to have a potent antiulcer activity against ethanol-induced gastric mucosal lesions. This study investigated the possible mechanisms underlying the gastroprotective effect of escin against indomethacin-induced gastric ulcer in mice. Gastric ulceration was induced by a single intragastric administration of indomethacin (18 mg/kg). The mice underwent intragastric treatment with escin at doses of 0.45, 0.9 or 1.8 mg/kg. Gastric lesion was estimated morphometrically and histopathologically 6 h after the indomethacin administration. The antioxidative parameters in gastric mucosa were measured. Moreover, the activity of myeloperoxidase and the contents of TNF-α, P-selectin and VCAM-1 in gastric tissues were determined. The results showed that escin protected gastric tissues against indomethacin-induced gastropathy as demonstrated from a reduction in the ulcer index and an attenuation of histopathologic changes. Escin caused significant reductions of the contents of malondialdehyde, TNF-α, P-selectin, VCAM-1 and myeloperoxidase activity. The altered activities of superoxide dismutase, catalase and glutathione peroxidase in the stomach tissues were also ameliorated by escin treatment. The present study demonstrated that escin had a protective effect against indomethacin-induced gastric ulcer in mice, not only by virtue of its antioxidant potential, but also due to its anti-inflammatory effect.