Implants of polyanionic collagen matrix in bone defects of ovariectomized rats

In recent years, there has been a great interest in the development of biomaterials that could be used in the repair of bone defects. Collagen matrix (CM) has the advantage that it can be modified chemically to improve its mechanical properties. The aim of the present study was to evaluate the effect of three-dimensional membranes of native or anionic (submitted to alkaline treatment for 48 or 96 h) collagen matrix on the consolidation of osteoporosis bone fractures resulting from the gonadal hormone alterations caused by ovariectomy in rats subjected to hormone replacement therapy. The animals received the implants 4 months after ovariectomy and were sacrificed 8 weeks after implantation of the membranes into 4-mm wide bone defects created in the distal third of the femur with a surgical bur. Macroscopic analysis revealed the absence of pathological alterations in the implanted areas, suggesting that the material was biocompatible. Microscopic analysis showed a lower amount of bone ingrowth in the areas receiving the native membrane compared to the bone defects filled with the anionic membranes. In ovariectomized animals receiving anionic membranes, a delay in bone regeneration was observed mainly in animals not subjected to hormone replacement therapy. We conclude that anionic membranes treated with alkaline solution for 48 and 96 h presented better results in terms of bone ingrowth1913411348sem informaçãosem informaçã

Characterization of the physical and mechanical properties of femoral bone defects filled with polyanionic collagen scaffolds in ovariectomized rats

The aim of this study was to evaluate the effect of scaffolds native or polyanionic collagen matrix (submitted to alkaline treatment for 48 or 96 hours, PCM48 or PCM96, respectively) on the repair of osteoporosis bone fractures resulting from the gonadal hormone alterations caused by ovariectomy in rats undergoing hormone replacement therapy. The physical and mechanical characteristics of bone were analyzed. Macroscopic analysis revealed the absence of pathological alterations in the implanted areas. The percent mineral matter and bone mineral density of the femurs were lower in ovariectomized rats. The mechanical strength of newly formed bone was greater in the area receiving the PCM96 scaffolds compared to the area implanted with the native scaffolds. The PCM96 scaffold is the best choice for bone repair in animals with hormone deficiency since it promotes faster bone growth and good mechanical strength.23924

Géis de colágeno aniônico: ransana como biomateriais. Preparação e caracterização físico-química Anionic collagen: rhamsan gels as biomaterials. Preparation and physicochemical characterization

Este trabalho descreve o efeito da ransana, um polissacarídeo bacteriano, sobre géis de colágeno aniônico. A interação colágeno:ransana ocorreu independentemente do pH, mesmo com baixas concentrações de ransana, e os materiais obtidos no estado sólido foram caracterizados por serem mais estáveis térmicamente à medida em que se aumenta a concentração do polissacarídeo. Nenhuma alteração na estrutura secundária em tripla hélice do tropocolágeno foi observada. O efeito mais significativo da ransana sobre os géis aniônicos de colágeno foi um aumento significativo da viscosidade, e as variações observadas em função de pH e temperatura sugerem que nesta interação, não estão envolvidas forças de natureza eletrostática ou hidrofóbica. Micrografias de colágeno aniônico e colágeno aniônico:ransana mostraram a presença de estruturas vesiculares, diferente do padrão fibrilar característico de colágeno nativo. Um modelo de interação baseado na ação da ransana sobre a água estruturada, associada à organização macromolecular do colágeno em solução é proposto. Mais importante, géis de colágeno aniônico:ransana mostraram uma estabilidade térmica compatível com aquelas desejáveis para um biomaterial injetável de colágeno, evitando o uso do glutaraldeído como agente de estabilização.This work reports the effects of rhamsan, a bacterial polysaccharide, over anionic collagen gels. Collagen: rhamsan interaction occurred independently from pH even at extremely low collagen:rhamsan ratios and materials were characterized in the solid state by an increase in thermal stability with an increase in polysaccharide concentration. No disruption of the triple helix secondary structure of tropocollagen was observed. The most striking effect of rhamsan addition over anionic collagen gels was the high increase in viscosity. A dependence study on pH and temperature suggests that electrostatic or hydrophobic forces are probably not involved in the process. Anionic collagen and anionic collagen: rhamsan gel micrographs at neutral pH showed the presence of spherical vesicles, different from the expected fibrillar pattern of native collagen. A model based on the action of rhamsan over structured water associated to collagen assembly in solution is proposed. Most important, anionic collagen:rhamsan gels showed a thermal stability compatible for its use as an injectable collagen biomaterial, thus avoiding the use o glutaraldehyde as an stabilizing agent

Characterization and in vitro release studies of tetracycline and rolitetracycline imobilized on anionic collagen membranes

This work reports the covalent immobilization of tetracycline and rolitetracycline over anionic collagen membranes and the drug release studies as an effort to develop a two stage drug release based on diffusion (fast release) and on the rate of membrane biodegradation (slow release). Independent from casting conditions antibiotics incorporated by dispersion were released in the range from 80 to 100% within 7 hours in concentrations significantly higher than those described for the prevention of bacterial growth. Antibiotic release within this period was predominantly diffusion controlled. Covalent immobilization by a modified azide procedure occurred with preservation of collagen structure independently from pH of casting and reaction conditions. Its expected that anionic collagen membranes with dispersed and covalently bound rolitetracycline or tetracycline, in association with conventional therapy, may significantly reduce membrane induced infections observed post-implantation, one of the major problem associated with periodontal ligaments reconstruction by the Guided Tissue Regeneration procedure

Compósitos colágeno aniônico: fosfato de cálcio. Preparação e caracterização Collagen: calcium phosphate composites. Preparation and characterization

<abstract language="eng">Anionic collagen: calcium phosphate composite was obtained by controlled mixing of collagen and calcium phosphate until the consistence of a past. Material was characterized by a Ca/P ratio of 1.55, with a X-ray diffraction pattern similar to that for hydroxyapatite. Differential Scanning Calorimetry showed that the protein is not denatured under the processing conditions. Scanning Electronic Microscopy showed that the mineral phase are regularly covered with collagen fibers, indicating that anionic collagen is efficient in the preparation of stable form of calcium phosphate ceramic paste