The influence of KrF excimer laser irradiation on the surface of collagen and collagen/PVP films

The surface properties of collagen and collagen/poly(vinyl pyrrolidone) (PVP) films after KrF excimer laser irradiation (λ=248nm) were investigated by means of the technique of scanning electron microscopy (SEM) and optical microscopy (OM). The laser irradiation of the used specimens caused an expansion of materials above their surface with pronounced sings of its melting. The height of the ablated volume in a case of collagen film at a fluence of 1.1J/cm2 was approximately 5μm. A white damage appears on the treated surfaces at a threshold of 0.5J/cm2 with a single pulse and becomes more visible for a higher fluence. It is also noteworthy that along with increasing fluences (beginning from the fluence of 1.7J/cm2), the characteristic filaments at the spot edges are observed. The local heat and pressure generated by the laser radiation were able to induce bubble formation on the surface. Further bubble colliding and bursting produce a three-dimensional polymer “microfoam” structure with interconnected pores. These results can be of interest for some new applications

Angiogenic Activity of Sera from Pulmonary Tuberculosis Patients in Relation to IL-12p40 and TNFα Serum Levels

The role of angiogenesis in the pathogenesis of tuberculosis (TB) is not clear. The aim of this study was to examine the effect of sera from TB patients on angiogenesis induced by different subsets of normal human mononuclear cells (MNC) in relation to IL-12p40 and TNFα serum levels. Serum samples from 36 pulmonary TB patients and from 22 healthy volunteers were evaluated. To assess angiogenic reaction the leukocytes-induced angiogenesis test according to Sidky and Auerbach was performed. IL-12p40 and TNFα serum levels were evaluated by ELISA. Sera from TB patients significantly stimulated angiogenic activity of MNC compared to sera from healthy donors and PBS (p < 0.001). The number of microvessels formed after injection of lymphocytes preincubated with sera from TB patients was significantly lower compared to the number of microvessels created after injection of MNC preincubated with the same sera (p < 0.016). However, the number of microvessels created after the injection of lymphocytes preincubated with sera from healthy donors or with PBS alone was significantly higher (p < 0.017). The mean levels of IL-12p40 and TNFα were significantly elevated in sera from TB patients compared to healthy donors. We observed a correlation between angiogenic activity of sera from TB patients and IL-12p40 and TNFα serum levels (p < 0.01). Sera from TB patients constitute a source of mediators that participate in angiogenesis and prime monocytes for production of proangiogenic factors. The main proangiogenic effect of TB patients’ sera is mediated by macrophages/monocytes. TNFα and IL-12p40 may indirectly stimulate angiogenesis in TB

The photochemical stability of collagen–chitosan blends

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. © 2004 Elsevier B.V. All rights reserved

The influence of UV irradiation on the mechanical properties of chitosan/PVP blends

Abstract The mechanical and surface properties of chitosan, poly(vinyl pyrrolidone) (PVP) and chitosan/PVP blends before and after UV irradiation have been investigated by mechanical testing (Instron) and by contact angle measurements. Air-dried specimens were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in mechanical properties, such as breaking strength, percentage elongation and Young\u2019s modulus have been investigated. The results have shown that the mechanical properties of the blends were greatly affected by UV irradiation, but the level of the changes of these properties were smaller in the blend than in pure chitosan and strongly dependent on the time of irradiation and the composition of the samples. The contact angle and the surface free energy were altered by UV irradiation, which indicates photooxidation and an increase of polarity. The range of these changes points to greater sensitivity of chitosan to photooxidation in comparison with PVP and chitosan/PVP blends

Biological effects of conjugated linoleic acids supplementation

Conjugated linoleic acids (CLA) are a group of polyunsaturated fatty acids (PUFA) with a single pair of conjugated double bonds. The major natural CLA isomer is 18:2 cis-9, trans-11 (c9, t11) linoleic acid, or rumenic acid (RA). Chemically synthesized CLA is also available, mostly as a mixture of RA and 18:2 trans-10, cis-12 (t10, c12) isomers in equal amounts (50:50). Consumption of ruminant meat (beef and lamb) and dairy products (milk and cheese) is the main source of dietary exposure to CLA. Despite numerous studies on animal and human models (tumorigenesis, obesity, immune response) it has not been established whether additional supplementation of CLA is of benefit. Moreover, some studies, conducted both in animals and in humans, reveal that CLA isomers may induce insulin resistance. Presently, balanced diet rich in CLA from natural sources is recommended. The purpose of this review was to sum up the results available in the literature

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. © 2003 Elsevier Ltd. All rights reserved