Combining xanthan and chitosan membranes to multipotent mesenchymal stromal cells as bioactive dressings for dermo-epidermal wounds.

The association between tridimensional scaffolds to cells of interest has provided excellent perspectives for obtaining viable complex tissues in vitro, such as skin, resulting in impressive advances in the field of tissue engineering applied to regenerative therapies. The use of multipotent mesenchymal stromal cells in the treatment of dermo-epidermal wounds is particularly promising due to several relevant properties of these cells, such as high capacity of proliferation in culture, potential of differentiation in multiple skin cell types, important paracrine and immunomodulatory effects, among others. Membranes of chitosan complexed with xanthan may be potentially useful as scaffolds for multipotent mesenchymal stromal cells, given that they present suitable physico-chemical characteristics and have adequate tridimensional structure for the adhesion, growth, and maintenance of cell function. Therefore, the purpose of this work was to assess the applicability of bioactive dressings associating dense and porous chitosan-xanthan membranes to multipotent mesenchymal stromal cells for the treatment of skin wounds. The membranes showed to be non-mutagenic and allowed efficient adhesion and proliferation of the mesenchymal stromal cells in vitro. In vivo assays performed with mesenchymal stromal cells grown on the surface of the dense membranes showed acceleration of wound healing in Wistar rats, thus indicating that the use of this cell-scaffold association for tissue engineering purposes is feasible and attractive.

Produçäo e caracterizaçäo de alfa-amilase produzida por Rhizopus sp / Production and characterization of alfa-amilase from Rhizopus sp

A strain of Rhizopus sp. screened among more than 800 filamentous fungi showed great ability to produce a thermostable alfa-amylase by solid state fermentation. The best production was obtained with a bran moisture content of 40 per cent when the enzyme activity reached 60 EU/g. of medium. During the purification procedures, a column of DEAE- Sephadex A-50 separeted the enzyme in two fractions and the larger (85 per cent of the total activity) showed optimum pH in a range from 4.0 to 5.6. Optimum temperature was found at 60-65§ C and in this range no loss of activity was observed after 60 min. of treatment in pH 5,0. Its Km and Vm are, respectively, of 5.0 mg/ml of starch and 10,01 uMol of reducing sugar/min./mg. of protein. Its molecular weight was calculated in 64.000 by gel filtration in Sephadex G-200. The dextrinization power of the enzyme was observed preferentialy on substrates compound by chain with higher ramifications, traht is: amylopectin > starch> amylose. Other aspects of the enzyme pattern action are also discussed