Swelling Behaviour and Water Vapour Transmission Rates of Gellan Gum/Collagen Film Containing Gatifloxacin as Dressing Materials

In an effort to produce ideal wound dressing, gellan gum/collagen hydrogel films containing different concentrations of gatifloxacin were prepared via evaporative casting method. The films were examined in terms of physical appearances, water uptake and water vapour transmission rate (WVTR). All the films showed good physical appearances. Swelling percentages of the films were decreased, whereas WVTR values were increased as the addition of gatifloxacin was increased. Swelling percentage of gellan gum/collagen film with the lowest percentage of gatifloxacin (GG/C-GAT01) has the highest swelling ratio (2057%). Meanwhile, the WVTR value of GG/C-GAT1 has the highest WVTR value among all films which is 1245 g m-2 day-1. The formulation of GG/C films with the addition of gatifloxacin with good water absorbance and acceptable WVTRs value offered promising materials to be applied as wound dressing materials.

Proton Conduction via Water Bridges Hydrated in the Collagen Film

Collagen films with proton conduction are a candidate of next generation of fuel-cell electrolyte. To clarify a relation between proton conductivity and formation of water networks in the collagen film originating from a tilapia’s scale, we systematically measured the ac conductivity, infrared absorption spectrum, and weight change as a function of relative humidity (RH) at room temperature. The integrated absorbance concerning an O–H stretching mode of water molecules increases above 60% RH in accordance with the weight change. The dc conductivity varies in the vicinity of 60 and 83% RH. From those results, we have determined the dc conductivity vs. hydration number (N) per unit (Gly-X-Y). The proton conduction is negligible in the collagen molecule itself, but dominated by the hydration shell, the development of which is characterized with three regions. For 0 < N < 2, the conductivity is extremely small, because the water molecule in the primary hydration shell has a little hydrogen bonded with each other. For 2 < N < 4, a quasi-one-dimensional proton conduction occurs through intra-water bridges in the helix. For 4 < N, the water molecule fills the helix, and inter-water bridges are formed in between the adjacent helices, so that a proton-conducting network is extended three dimensional.

Effect of the Application of a Dehydrothermal Treatment on the Structure and the Mechanical Properties of Collagen Film

Dehydrothermal (DHT) treatment was used to improve the properties of collagen casings because of its non-cytotoxicity. Understanding the effects of DHT treatment on the structure and mechanical properties of collagen films is beneficial to developing satisfying collagen casings. Herein, DHT treatment with various temperatures (85–145 °C) and timescales (1–7 days) were investigated. It was clarified that the chemical crosslinking covalent bond between collagen molecules was formed after the DHT treatment. Crosslinking density increased with increasing DHT treatment temperatures, contributing to the increase of tensile strength up to over three times of that of the untreated collagen film. The increased crosslinking density was also found when increasing the DHT treatment time, and the maximum was obtained in 3 days. Further DHT treatment time did not change the crosslinking density. The damage in the triple helix structure and the self-assembly of collagen molecules were observed from IR and SAXS. The extent of denaturation increased with increasing DHT treatment temperature and time, although the effect of the DHT treatment time on the denaturation was more moderate. When the DHT treatment temperature was as high as 145 °C or the DHT treatment time exceeded 5 days, serious denaturation occurs, leading to the deterioration of mechanical properties.