L. Lelli

Hydrogels of poly(vinyl alcohol) and collagen as new bioartificial materials Part I Physical and morphological characterization

Poly(vinyl alcohol) was used to make hydrogels containing various amounts of collagen. These “bioartificial materials”, made of synthetic and biological polymers, were studied to investigate the effect of the presence of the collagen on the structural properties of the hydrogels. A comparison between thermal and morphological properties of collagen-containing hydrogels and hydrogels of pure poly(vinyl alcohol) was made.

Physical and biological properties of dehydro-thermally cross-linked collagen-poly(vinyl alcohol) blends

Dehydro-thermal treatments for 3, 24 and 72 h were used to crosslink blends of collagen and poly(vinyl alcohol) with various compositions. This crosslinking method increases the biological stabilityin vitro of collagen, as was established by an enzymatic test. When the poly(vinyl alcohol) content is not more than 20% the resistance of collagen to enzymatic digestion is not affected by the presence of the synthetic component. A higher content of poly(vinyl alcohol) produces a steric hindrance screening that enhances the resistance of collagen to the collagenase. Dehydro-thermal treatment performed for 24 and 72 h increases the crystallinity of poly(vinyl alcohol), thus reducing the solubility of this component of the blend. Calorimetric analysis was carried out by differential scanning calorimetry to investigate the structure and the thermal stability of the blends. Dehydro-thermal treatments carried out for 24 and 72 h induce high degrees of crosslinking in collagen and high crystallinity in poly(vinyl alcohol). The two components of the blend seem to create independent structures and the blend can show interpenetrating-network-like behaviour.

Blends of hyaluronic acid derivatives with ethylene-vinyl alcohol copolymers as potential biomaterials

Films were prepared by solution casting from blends of hyaluronic acid derivatives and ethylene-vinyl alcohol copolymers. A chemico-physical and biological characterization was carried out on these “bioartificial materials” made of synthetic and biological polymers. The morphological and chemical properties of the films were investigated by scanning electron microscopy and differential scanning calorimetry. The transport properties of these films were tested in liquid systems to evaluate their possible use in dialysis and/or haemodialysis. The biocompatibility was investigated by a haemocompatibility test based on the contact activation of plasma prekallikrein. No particular interaction between the two components was observed. The results of the permeation tests were compared with those obtained using commercial products such as Cuprophane and poly(acrylonitrile) membranes. These tests indicate that the permeability of the blends decreases as the content of the synthetic polymer increases. The good haemocompatibility of these materials suggests their possible use as biomaterials.

Blood-Compatible Polymers and Their Characterization: A Simple Sensitive Assay for Hemocompatibility Evaluation

Abstract The contact activation of plasma prekallikrein to kallikrein has been used as a blood compatibility test for two series of materials. Samples of diluted human plasma were held in contact with the materials to be tested, the activated plasma was then reacted with the chromogenic substrate H-D-Pro-Phe-Arg-pNA, which releases p-nitroaniline under the proteolytic action of kallikrein. The two series of materials tested are: an ethylene-vinyl alcohol copolymer (EVAL) and three graft copolymers (EVAL-SMA) obtained by reacting EVAL with a styrene-maleic anhydride alternating copolymer; four fluorinated polyurethanes (FPU). Each series of materials was compared with borosilicate glass, the high-activation reference; silicone, the low-activation reference; Cardiothane® 51, a blend of poly(ether-urethane) and poly(dimethylsiloxane) used for cardiovascular applications. Both series of materials show a low thrombogenicity; in particular, the FPUs are less activating than Cardiothane 51. To check the correlat...