Joanna Skopinska

Molecular interactions in collagen and chitosan blends.

Molecular interactions between collagen and chitosan (CC) have the potential to produce biocomposites with novel properties. We have characterised the molecular interactions in CC complexes by viscometry, wide angle X-ray scattering and Fourier transform infrared spectroscopy. It was found that CC are miscible at the molecular level and exhibit interactions between the components; X-ray diffraction of CC blends indicate that the collagen helix structure is lost in CC films with increasing chitosan content. Non-linear viscometic behaviour with decreasing chitosan content is interpreted as evidence of a third structural phase formed as a complex of CC. The blending of collagen with chitosan gives the possibility of producing new bespoke materials for potential biomedical applications.

Photochemical stability of collagen/poly (vinyl alcohol) blends

Abstract The photochemical stability of blends of collagen and poly(vinyl alcohol) has been studied by Fourier transform infrared spectroscopy (FTIR), UV–vis spectrophotometry, differential scanning calorimetry (DSC) and viscometry. Mechanical properties of the blends before and after UV irradiation were studied. Surface properties before and after UV irradiation were monitored using atomic force microscopy (AFM) and optical microscopy. The new materials obtained have different thermal, mechanical and photochemical stability than those of single components. They are more stable thermally and photochemically, but they have worse mechanical properties than pure collagen films.

The photochemical stability of collagen-chitosan blends

Abstract The photochemical stability of collagen–chitosan blends in solution and film form was investigated using viscosimetry measurements, UV-Vis spectrophotometry, FTIR spectroscopy and wide angle X-ray diffraction. It was found that the relative viscosity of collagen decreased upon UV irradiation. The initial relative viscosity of collagen–chitosan blends were greater than the viscosity of collagen; upon UV irradiation the viscosity of the blends decreased rapidly. The absorption/scattering of collagen in solution increased during irradiation of the sample as shown by UV-Vis, indicating a conformational transition in the sample. FTIR showed that the amide A, B, I and II bands from collagen are shifted after UV irradiation to lower wave numbers; these shifts in collagen–chitosan blends are less well pronounced. Wide angle X-ray diffraction indicated that collagen and collagen–chitosan blends in film form retain much of their structural characteristics after irradiation. The viscosimetry and UV-Vis spectrophotometry results have shown that solutions of collagen–chitosan blends are less stable photochemically than a pure collagen solution. FTIR spectra have shown, that collagen–chitosan blended films are also less stable photochemically than pure collagen films. Wide angle X-ray diffraction indicates that collagen and collagen–chitosan blend samples in film form are less susceptible to conformational change than equivalent samples in solution.

UV-vis and FT-IR spectra of ultraviolet irradiated collagen in the presence of antioxidant ascorbic acid.

The influence of deleterious UV radiation on collagen molecules in the absence and presence of ascorbic acid using UV-vis and FT-IR spectroscopy has been studied. Intensity of UV-vis absorption spectrum of collagen with a maximum at 275 m due to the aromatic residues (tyrosine and phenylalanine) increases with the increasing dose of UV radiation. This effect is significantly hindered in the presence of antioxidant ascorbic acid. Intensities of FT-IR bands (amide A, B, I and II) of collagen decrease with the increase of the UV radiation dosage. Intensities of bands are also decreased in the presence of ascorbic acid. Results suggest that increasing the concentration of ascorbic acid increases the photo-stability of collagen, and the collagen becomes less sensitive to UV radiation. It is possible that hydrogen bonds form between the groups N-H of collagen and C=O of ascorbic acid. It is believed that under UV radiation free radicals appear in acid soluble collagen and resulting in photodegradation of the macromolecule restore due to the ability of ascorbic acid donating one or two electrons. Increasing the dose of radiation causes more molecules of ascorbic acid to slow down, and their antioxidant effect is diminished accordingly.

Effects of Solar Radiation on Collagen-Based Biomaterials

The effect of solar radiation on collagen and collagen/synthetic polymer blends in the form of thin films and solutions has been studied by UV-VIS and FTIR spectroscopies. Films and solutions of collagen blended with poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were irradiated by solar light. It was found that UV-VIS spectra, which characterize collagen, collagen/PVA, and collagen/PVP blended films, were significantly altered by solar radiation. FTIR spectra of collagen, collagen/PVA, and collagen/PVP films showed that after solar irradiation, the positions of Amide A bands were shifted to lower wavenumbers. There was not any significant alteration in the position of Amide I and Amide II bands of collagen and its blends after solar radiation. The effect of solar UV radiation in comparison with artificial UV radiation has been discussed.