Injectable gels of anionic collagen : rhamsan composites for plastic correction: Preparation, characterization, and rheological properties

The present article describes the preparation and characterization A anionic Collagen gels obtained from porcine intestinal submucosa after 72 h of alkaline treatment and in the form of rhamsan composites to develop injectable biomaterials for plastic for construction. All materials were characterized by SDS/polyacrylamide gel electrophoresis, infrared spectroscopy, thermal stability, potentiometric titration, rheological properties, and fluidity tests. Biocompatibility was appraised after the injection of anionic collagen:rhamsan composites at 2.5% in 60 North Folk rabbits. Independently of processing, the Collagen's secondary structure was preserved in all cases, and after 72 h of hydrolysis the Collagen was characterized by a carboxyl group content of 346 :L 9, which, at physiological pH, corresponds to an increase of 106 17 negative charges, in comparison to native Collagen, due to the selective hydrolysis of asparagine and glutamine carboxyamide side chain. Rheological studies of composites at pH 7.4 in concentrations of 2, 4, and 6% (in proportions of 75:1 and 50:1) showed a viscoelastic behavior dependent on the frequency, which is independent of concentration and proportion. In both, the concentration of the storage modulus always predominated over the loss modulus (G' > G and delta < 45 degrees). The results from creep experiments confirmed this behavior and showed that anionic collagen:rhamsan composites at pH 7.4 in the proportion of 50:1 are less elastic and more susceptible to deformation in comparison to gels in the proportion of 75:1, independent of concentration. This was further confirmed by flow experiments, indicating that the necessary force for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic Collagen, was significantly smaller and with a smooth flow. Biocompatibility studies showed that the tissue reaction of anionic collagen:rhamsan composites at 2.5% in the proportion of 75:1 was compatible with the application of these gels in plastic reconstruction. These results suggest that the association of Collagen with rhamsan may be a good alternative in the replacement of glutaraidehyde to stabilize the microfibril assembly of commercial Collagen gel preparations. (c) 2005 Wiley Periodicals, Inc

Bovine osteoblasts cultured on polyanionic collagen scaffolds: An ultrastructural and immunocytochemical study

Collagen is the most abundant protein in the body and is also the most important component of the extracellular matrix. Collagen has several advantages as a biomaterial such as lack of toxicity, biocompatibility, biodegradability, and easy reabsorption. In this study, we examined bovine osteoblasts cultured on native or anionic collagen scaffolds prepared from bovine pericardium after selective hydrolysis of glutamine and asparagine side chain amides for periods from 24 (BP24) and 48 h (BP48). The cells were cultured in control and mineralization medium at 37 degrees C in the presence of 5% CO2. Transmission and scanning electron microscopy, energy dispersive spectroscopy, and an immunocytochemical marker were used for analysis. Cells with an irregular morphology forming a confluent multilayer were observed on matrices kept in control medium. Most of these cells presented a polygonal or elongated flattened morphology. Several spherical deposits of calcium crystal associated with phosphorus were observed on the native and BP48 matrices. Similar results were observed in samples kept in control medium except with lower calcium/phosphorus ratio. Vesicles actively expelled from the cell membrane were also seen (do this vesicles corresponds to calcium/phosphorus deposits). Osteocalcin was clearly visible on matrices kept in mineralization medium and was more expression on the surface of BP48 matrices. The results showed that anionic collagen is able to support osteoblastic differentiation, regardless of the medium used. Finally, the BP48 matrix promoted better osteoblast differentiation than the native matrix. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1827, 2013.101B1182

ANGIOTENSIN-LIKE and ANTAGONISTIC ACTIVITIES of N-TERMINAL MODIFIED [8-LEUCINE]ANGIOTENSIN II PEPTIDES

ESCOLA PAULISTA MED,DEPT BIOPHYS & PHYSIOL,04023 São Paulo,BRAZILESCOLA PAULISTA MED,DEPT BIOPHYS & PHYSIOL,04023 São Paulo,BRAZILWeb of Scienc