Introduction: Biopolymers are extensively used in tissue engineering due to their properties[1],[2]. Chitosan (Ch) and xanthan gum (X) can form polyelectrolyte complexes (Ch-X) useful as scaffolds for tissue regeneration[3]. Scaffolds must present high porosity, interconnected pores and suitable pore size to promote cell migration and proliferation, as well as nutrients diffusion[1]. However, as the porosity of the matrix increases, the biomaterial mechanical properties are impaired[1],[4]. In this work, the surfactant Pluronic F68® (Pl) was added to Ch-X matrices to obtain porous scaffolds and the silicone rubber Silpuran® 2130A/B (S) was used to improve their mechanical properties.
Materials and Methods: Ch and X scaffolds were prepared according to Veiga and Moraes[5], but adding 10% and 25% (w/w) of Pl and 10% (w/w) of S. Morphology was analyzed by scanning electron microscopy. Uptake capacity (UC) and weight loss (WL) in culture medium (DMEM supplemented with 10% fetal bovine serum and 1% Penicillin/Streptomycin) were determined gravimetrically, while exposure of samples to blood for 60 min was performed to assess thrombogenicity. The relaxation behavior in unconfined compression was assessed in a bath of phosphate-buffered saline. Initial thickness of wet samples was determined by the equipment. The thickness of the dry material was measured using a micrometer.
Results and Discussion: The addition of Pl leads to the formation of highly porous matrices however there is no significant difference between the pores present in the formulations containing 10% or 25% of surfactant (Fig.1a). The pores are interconnected, with average diameter ranging from 500 to 1200 μm. According to the thickness results, dry and wet scaffolds containing 25% Pl have higher porosity (Fig. 1b). As a consequence, these scaffolds are more fragile than formulations with 10% of Pl regarding stress response to deformation (Fig. 2a). The addition of S increased the stiffness of all formulations. Porous scaffolds can uptake great amount of culture medium, which facilitates the transport of nutrients and metabolites within the matrix (Fig. 2b). However, their WL is relatively high given that the uptaken medium may promote polymer chains flexibilization and consequent leaching, mainly for formulations with 25% of Pl. Thrombogenicity of porous scaffolds is lower when compared to dense matrices (Fig. 2c). Pl is reported to decrease thrombus formation by increasing the hydrophilicity of surfaces due to its polyethylene oxide segments[6].
Conclusion: Porous formulations have appropriate properties regarding porosity, culture medium UC and thrombogenicity. The scaffolds prepared with 10% of Pl are the stiffest among the porous formulations. Addition of S enhances the mechanical properties of the samples, being then adequate to improve their characteristics. Further studies will be performed to evaluate the influence of the additives on cells behavior.
NSERC-Canada; CIHR-Canada; CFI-Canada; FRQ-NT-Quebec; MRI-Quebec; CAPES-Brazil; CNPq-Brazil
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