Toxicity Testing in Vitro and Biocompatibility Scaffold for Transplantation of Stem Cells in Spinal Cord Injury
Authors: Falavigna Asdrubal , Marinowic Daniel Rodrigo , Machado Denise Cantareli , Palloma Gabriela , de Assis Denis , Valente Cristiane Alvin , Costa e Ferro Zaquer Suzane , Salamoni Simone Denise , dal Bello Chariston , Basso Nara Regina Souza , DaCosta Jaderson , da Silva Pedro Guarise 
Published: May 2015

Introduction Spinal cord injury occurs mainly in young healthy individuals, causing motor impairment and temporary or sensory loss and leading to chronic disability. An attractive possibility of treatment for TRM is the use of stem cells for restoration of neural cells in the spinal cord. Support Matrices for use in cell therapy must be able to provide structural and microenvironmental support to ensure the viability of the transplanted cells and to facilitate integration in the target tissue. Materials and Methods Biocompatible polymeric films composed of polylactic acid-co-acid (PLGA) polymer nanofiber polypyrrole (PPy) were used polypyrrole nanofibers and films made containing 10% (W/W) PLGA in PPy by solvent evaporation method were synthesized. The PPy nanofibers showed electrical conductivity of semiconductor and the dispersion of the nanofibers in PLGA resulted in PPy films with fibrous topographical morphology with suitable for use as scaffolds for cell growth driven by PPy nanofiber voids. Cell toxicity test method of extraction was performed. Samples of the polymers were maintained in DMEM culture medium obeying the proportions established by ISO 10993 (2013) by 24, 48, 72 hours, 7 and 14 days. After each time period, NIH3T3 fibroblasts were cultured for 24 hours with the film exposed to the environment, and then was held cellular toxicity test by MTT assay. Wistar rats were anesthetized and underwent laminectomy of the eighth thoracic vertebra. On the local display of the spinal cord was placed a cut polymer approximately 3 mm wide and 8 mm long. The motor recovery of the animals 24 hours and 7, 14, and 28 days after injury was assessed. To assess the degree of inflammation generated by the polymer in tissues other than the spinal cord, a 1 cm incision in the flank and placement polymer was performed. In the region against lateral incision was performed only. Histological evaluation of the spinal cord and the fabric flank was held. Results The electrical conductivity of PPy fibers showed values of 8.10 to 4 S/cm, lying within the range of semiconductors. The molecular structure of PPy was evaluated in the range of 400 to 4,000/cm and all spectra were similar. There was no change in cell viability after exposure of the cells to the conditioned medium with the polymer in both seasons. Cell viability was maintained at 100% when compared with the control. The motor functional assessment of mice showed no alteration in any evaluation period are because of the surgical procedure or a possible effect of inflammatory irritation of the polymer on the spinal nerve tissue. Histological evaluation showed no changes suggestive of inflammation or infection of the marrow tissue adjacent to the polymer or the flank of the animal tissues. Conclusion PLGA/PPy polymer has conductivity expected for semiconductors and structural heterogeneity, without any type of cell toxicity in periods. The polymer is safe to be used as a scaffold in the TRM model because it does not cause any functional, structural, or inflammatory change.