ABSTRACT
Cell therapy is actively used to treat skin defects, particularly burn lesions. The effectiveness of its application may depend on the appropriate choice of wound dressings used together with any cellular material. The aim of the study was to investigate the interaction of 4 hydrogel dressings used in clinical practice with human cells in an in vitro model to determine if their use in combination with cell therapy is possible. The effect of the dressings on the growth medium was assessed by considering the changes caused in the medium's acid-base equilibrium (pH) and viscosity. Cytotoxicity was determined by applying an MTT-assay and by direct contact methods. Cell adhesion and viability on the dressing surfaces were analyzed using fluorescence microscopy. Proliferative and secretory cell activity were determined concurrently. Characterized human dermal fibroblast cultures were used as the test cultures. Results: The tested dressings interacted differently with the growth medium and the test cultures. 1-day extracts of all dressings had almost no effect on the acid-base balance, but, after 7 days, the pH of the dressing Type 2 extract had sharply acidified. The viscosity of the media under the influence of dressings of Types 2 and 3 had also markedly increased. MTT-assays showed nontoxicity of all the 1-day-incubated dressing extracts, while incubation for 7-days resulted in extracts with evident cytotoxicity, which was reduced upon dilution. Cell adhesion to the surfaces of the dressings differed, being observed occurring on dressings 2 and 3, and to a limited extent on dressing 4. Cells under dressing 1 showed evident proliferative and secretory activity whereas the other dressings impaired either proliferation or secretion processes. These effects indicate that, in general, comprehensive studies including a variety of methodological approaches at the in vitro stage are needed to allow the selection of appropriate dressings if they are to be used in combination with cell therapy to act as cell carriers. Of those investigated, the Type 1 dressing can be recommended as a protective dressing for use after transplantation of cells into a wound defect area by some other method.
ABSTRACT
One of the key and actively developing areas of regenerative medicine is tissue-engineering. There is no doubt that the use of tissue-engineering products can have a significant impact on the efficiency of repair of damaged tissues and organs. However, before being used in clinical practice, tissue-engineering products require thorough preclinical studies to confirm their safety and efficacy, both with in vitro models and in experimental animals. This paper presents preclinical studies of a tissue-engineered construct, based on a hydrogel biopolymer scaffold carrier (consisting of blood plasma cryoprecipitate and collagen) with encapsulated mesenchymal stem cells, to evaluate its biocompatibility in vivo. The results were analyzed using histomorphology and transmission electron microscopy. It was shown that when implanted into animal (rat) tissues, the implants were completely replaced by connective tissue components. We also confirmed that no acute inflammation occurred in response to the scaffold implantation. The observed processes of cell recruitment to the scaffold from the surrounding tissues, the active formation of collagen fibers and the absence of acute inflammation testified that the regeneration process was ongoing in the implantation area. Thus, the presented tissue-engineered construct shows promise for becoming an effective tool for regenerative medicine in the future and may be used, in particular, to repair soft tissues.
ABSTRACT
A study is presented on four polymers of the polyurethane family, obtained using a two-stage process. The first composition is the basic polymer; the others differ from it by the presence of a variety of fillers, introduced to provide radiopacity. The fillers used were 15% bismuth oxide (Composition 2), 15% tantalum pentoxide (Composition 3), or 15% zirconium oxide (Composition 4). Using a test culture of human fibroblasts enabled the level of cytotoxicity of the compositions to be determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay, along with variations in the characteristics of the cells resulting from their culture directly on the specimens. The condition of cells on the surfaces of the specimens was assessed using fluorescence microscopy. It was shown that introducing 15% bismuth, tantalum, or zinc compounds as fillers produced a range of effects on the biological characteristics of the compositions. With the different fillers, the levels of toxicity differed and the cells' proliferative activity or adhesion was affected. However, in general, all the studied compositions may be considered cytocompatible in respect of their biological characteristics and are promising for further development as bases for bone-substituting materials. The results obtained also open up prospects for further investigations of polyurethane compounds.
ABSTRACT
Graft copolymers of collagen and polyacrylamide (PAA) were synthesized in a suspension of acetic acid dispersion of fish collagen and acrylamide (AA) in the presence of tributylborane (TBB). The characteristics of the copolymers were determined using infrared spectroscopy and gel permeation chromatography (GPC). Differences in synthesis temperature between 25 and 60 °C had no significant effect on either proportion of graft polyacrylamide generated or its molecular weight. However, photomicrographs taken with the aid of a scanning electron microscope showed a breakdown of the fibrillar structure of the collagen within the copolymer at synthesis temperatures greater than 25 °C. The mechanical properties of the films and the cytotoxicity of the obtained copolymer samples were studied. The sample of a hybrid copolymer of collagen and PAA obtained at 60 °C has stronger mechanical properties compared to other tested samples. Its low cytotoxicity, when the monomer is removed, makes materials based on it promising in scaffold technologies.
