Andréa Cristiane Krause Bierhalz

Influence of Drying Conditions on Physical Properties of Alginate Films

The effect of drying conditions of the film-forming solution on thickness, moisture content, water vapor permeability, and tensile properties of alginate films were investigated. A long period of constant rate was observed in all conditions and the model proposed by Wang and Singh was able to adjust the drying data. As expected, there was a clear effect of temperature on drying kinetics; that is, increasing the drying temperature decreased the drying time. Considerable glycerol losses were observed when alginate gel was oven dried at temperatures above 40°C. Compared to other drying conditions, films oven dried at 60°C were thinner, had lower moisture content, and were less flexible.

BIOMATERIAIS: TIPOS, APLICAÇÕES E MERCADO

The types of compounds used in the production of biomaterials, namely metals, ceramics, synthetic and natural polymers, as well as composite materials, are discussed in the present work, together with details of their application and evolution from biocompatible to bioactive, biodegradable, and biomimetic clinical products. The chemical structure, the three-dimensional structure, and the molecular organization of compounds frequently used in the manufacture of relevant classes of biomaterials are discussed, along with their advantages and some of their major limitations in specific clinical applications. The main chemical, physical, mechanical, and biological requirements of biomaterials categories are presented, as well as typical tissular responses to implanted biomaterials. Reasons for the recent economic growth of the biomaterials market segment are addressed, and the most successful biomaterial categories are discussed, emphasizing areas such as orthopedic and cardiovascular implants, regenerative medicine, tissue engineering, and controlled drug release devices. Finally, the need for the development of innovative and more accessible biomaterials, due to the expected increase in the number of elderly people and the growing trend of personalized medical procedures, is pointed out.

Comparison of the properties of membranes produced with alginate and chitosan from mushroom and from shrimp.

Dense and porous chitosan-alginate membranes (1:1 in mass) useful as coverages of skin wounds treated through cell therapy were produced using chitosan of different chain sizes from fungal (white mushrooms) and animal (shrimp shells) sources. Porous materials were obtained by adding the surfactant Poloxamer 188 to the formulations. The influence of chitosan type on membranes physicochemical properties and toxicity to fibroblasts was evaluated. Porosity was noticed to be more pronounced in membranes obtained with fungal chitosan and increased with its molecular mass. These formulations showed the highest values of thickness, roughness, opacity, liquid uptake and water vapor permeability. The membranes were not toxic to fibroblasts, but the lowest cytotoxicity values (0.16-0.21%) were observed for membranes prepared with fungal chitosan in the presence of surfactant. In conclusion, it is possible to replace chitosan from animal sources by chitosan of fungal origin to produce membranes with negligible cytotoxicity while maintaining appropriate physicochemical properties.

Composite membranes of alginate and chitosan reinforced with cotton or linen fibers incorporating epidermal growth factor

Suture threads of cotton or linen, in crossed and random orientation, were added to alginate-chitosan membranes intended to wound coatings application to improve the mechanical properties. The elongation at break increased to about 5 and 8 times for membranes with linen and cotton, respectively, both in the crossed orientation. The addition of the threads increased roughness and opacity of the membranes and reduced the liquid absorption capacity and water vapor transmission rate. The lowest toxicity to human fibroblasts was observed for extracts of membranes produced with linen, and incorporation in them of epidermal growth factor was able to slightly increase cell proliferation.

Development of polysaccharide-based membranes incorporating the bioactive compound aloin

ABSTRACT Chitosan-alginate (CA) and chitosan-xanthan (CX) membranes containing aloin were developed for use as wound dressings. The effects of aloin-to-biopolymer ratio on membranes morphology, aspect, liquid uptake, mass loss, mechanical properties, thermal behavior, aloin incorporation efficiency, and release kinetics were analyzed. CA membranes showed higher stability in liquid media and greater elongation at break. CX membranes had more homogeneous microstructure and slightly higher tensile strength. The opacity and color intensity of both formulations increased with aloin incorporation. Maximum aloin incorporation efficiencies were 56.0% and 79.5% in CA and CX membranes, respectively, and slower aloin release was observed for CA membranes. GRAPHICAL ABSTRACT