Alina Sionkowska

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.

Surface modification of thin polymeric films by air-plasma or UV-irradiation

Abstract Commercial, purified poly(vinyl chloride) (PVC) in a form of thin film was used for modification by low-temperature air-plasma or short-wavelength UV-irradiation. The changes of surface properties were monitored by contact angle measurements allowing for calculation the surface free energy as well as its polar and dispersive components. Both modification sources cause surface oxidation of PVC films, which is connected with formation of functional groups enhancing polymer wettability. This process is very fast and efficient in air-plasma but slower during PVC exposure to UV. Storage of modified PVC indicates that in plasma also conformational changes occur. In case of UV-irradiated PVC secondary, dark reactions (mainly oxidation) take place during storage at ambient conditions.

THERMAL HELIX-COIL TRANSITION IN UV IRRADIATED COLLAGEN FROM RAT TAIL TENDON

The thermal helix-coil transition in UV irradiated collagen solution, collagen film and pieces of rat tail tendon (RTT) were compared. Their thermal stabilitys were determined by differential scanning calorimeter (DSC) and by viscometric measurements. The denaturation temperatures of collagen solution, film and pieces of RTT were different. The helix-coil transition occur near 40 degrees C in collagen solution, near 112 degrees C in collagen film, and near 101 degrees C in pieces of RTT. After UV irradiation the thermal helix-coil transition of collagen samples were changed. These changes depend on the degree of hydratation.

Modification of collagen films by ultraviolet irradiation

Abstract This work describes photochemical modification of collagen films, which are widely used in medical and consumer applications. Modification of collagen films by UV irradiation (254 nm) was investigated using differential scanning calorimetry and scanning electron microscopy. It was found that the denaturation temperature of collagen decreased during irradiation and the surface of the films was changed. Changes of denaturation temperature and surface of films under UV irradiation point to the loss of water bonded to collagen. This is confirmed by IR spectra.

Characterization of collagen/hydroxyapatite composite sponges as a potential bone substitute

Hydroxyapatite and collagen composites (HAp/Col) have the potential in mimicking and replacing skeletal bones. Their combination should prove beneficial for bone tissue engineering due to their natural biological resemblance and properties. In this study, hydroxyapatite and collagen isolated from animal tendons were used in different proportions as composites. Sponges were prepared by freezing and lyophilization of corresponding composite solutions. The properties of composite sponges, such as microstructure, chemical and physical properties were studied. In the present investigation, a collagen sponge and a composite sponge made of composite of HAp/Col were prepared in our lab and characterized by attenuated total reflection Fourier transform infra-red spectroscopy, thermogravimetric analysis and scanning electron microscopy (SEM). Infrared spectroscopy (IR) in combination with attenuated total reflection (ATR) spectroscopy is one of the most widely used technique for surface infrared analysis. The ATR-IR analysis did not indicate shift of the band corresponding to -COO(-) for none of the used HAp/Col ratios. Thermogravimetric results suggested that collagen chains had been embedded with HAp to several complexes with different thermal stabilities. SEM was used to observe the morphology and pore size of the sponges. SEM observations showed the sponges of HAp/Col with fully interconnective macroporosity.

Chemical and thermal cross-linking of collagen and elastin hydrolysates

Chemical and thermal cross-linking of collagen soluble in acetic acid and elastin hydrolysates soluble in water have been studied. Solutions of collagen and elastin hydrolysates were treated using variable concentrations of 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Moreover, diepoxypropylether (DEPE) has been used as cross-linking agent. Films made of collagen and elastin hydrolysates were also treated with temperature at 60°C and 100°C to get additional cross-links. The effect of cross-linking has been studied using FTIR spectroscopy, thermal analysis, AFM and SEM microscopy. Mechanical and surface properties of materials have been studied after cross-linking. It was found that thermal and mechanical properties of collagen and elastin materials have been altered after thermal treatment and after the reactions with EDC/NHS and/or DEPE. Surface properties of collagen materials after chemical cross-linking have been modified. Thermal and chemical cross-linking of collagen films lead to alteration of polarity of the surface.

Interaction of collagen and poly(vinyl pyrrolidone) in blends

The interaction between collagen and poly(vinyl pyrrolidone) (PVP) in blends has been studied by viscometry, differential scanning calorimetry (DSC) and by Fourier transform infrared spectroscopy (FTIR). It was found that the amide A and amide I bands position in FTIR spectra of collagen were shifted after blending with PVP to higher wavenumbers. DSC measurements showed different melting temperature, glass transition temperature and enthalpy for the blends and for the single components. Viscosity measurements showed interaction between collagen and PVP also in a dilute water solution. The results have shown, that the interactions between collagen and PVP exist due to the strong interactions between the synthetic and biological component, mainly by hydrogen bonds. These interactions caused that collagen and PVP are miscible at molecular level. The blending of collagen with PVP may give the possibility of producing new materials for potential biomedical applications. � 2003 Elsevier Ltd. All rights reserved.

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.

Characterization of chitosan composites with various clays

The structural properties, thermal behaviour and mechanical properties of composites of chitosan (Ch) with nanoclay (montmorillonite, MMT) and/or nanoclays after surface modification have been characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and a tensile tests. The microstructure obtained by SEM and AFM microscopy for unmodified chitosan and its composites showed that particles are relatively well dispersed in the chitosan matrix. However, the increasing concentration of the chitosan solution from 1% to 2% decreases the homogeneity of the surface of the composites. In the case of chitosan composite with modified nanoclay (contains 25-30 wt.% of octadecylamine), the lack of particles aggregates in polymer matrix independent of the concentration of chitosan solution was observed. Generally, addition of nanoclay after its surface modification improved the mechanical and thermal properties of the composite much more than montmorillonite without modification.

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.