The influence of cosolvents and in situ-forming hydroxyapatite on permeation characteristics of collagen films

Collagen was processed into film in mixtures containing various ratios of water, propylene glycol, and ethanol. Hydroxyapatite (HAP) crystals were also introduced into collagen films by in-situ formation. Permeability studies were employed to characterize their influence on the permeation of various solutes through the collagen films with or without the presence of HAP. For a series of alkyl parabens and macromolecules, permeabilities across collagen films with and without the presence of HAP decreased with increasing chain length of alkyl parabens and molecular weight of macromolecules. There were significant alterations in permeabilities for alkyl parabens and macromolecules permeating through collagen films containing HAP. This is probably due to the introduction of HAP further modifying the network and the flexibility of collagen films, in turn affecting the permeation of solutes. However, results reveal that the influence of solvent mixtures that used to prepare collagen films on the permeation of various solutes through collagen films with and without HAP was similar. A linear correlation between the logarithm of permeability and the square of the radius of macromolecules was observed for permeation across collagen films without the presence of HAP. This relationship is similar to that for permeation through collagen films of different solvent mixtures.