(197l) New Strategy for the Fabrication of Annular Cylindrical Polysaccharide-Based Scaffolds
Different types of organs and tissues show annular cylindrical geometry in vivo, such as ureters, trachea, blood vessels and heart valves. In the case of diseases related to atherosclerosis, direct replacement of damaged blood vessels through surgical intervention is already frequently performed. However, most of the materials currently available for this type of therapy are efficient only when used to substitute blood vessels with diameters greater than six millimeters, as complications may occur in smaller diameter devices, leading to vessel reocclusion. Recent advances in the development of vascular substitutes are consequences of tissue engineering approaches, focusing on the culture of vascular cells on biodegradable scaffolds. Once the seeded cells have deposited an extracellular matrix and the original scaffold is biodegraded, the tissue resembles and behaves as native tissue. Since the scaffold will act as a structural cast for neotissue formation, devices with annular cylindrical geometry are a prerequisite for vascular tissue engineering. Different approaches have been used for the fabrication of tubular scaffolds, including methods based on thermally induced phase-separation, particulate-leaching, dipping in polymeric solution, 3D printing, electrospinning, solvent casting/ freeze-drying and others. In this work, an alternative technique for the fabrication of tubular-shaped scaffolds was used, based on the casting of polymeric solutions by controlled crosslinking mediated by a semipermeable cast. A chitosan-alginate polymeric mixture was used for the production of the scaffold and CaCl2 was used for alginate crosslinking. The crosslinking was performed in two steps, as a single-step can lead to incomplete, heterogeneous reticulation and impairment of the scaffold mechanical properties. CaCl2 concentration and temperature for the secondary crosslinking step were varied. The surfactant Kolliphor® P188 was added to the polymeric mixture to improve the scaffolds porosity by foam formation. The use of a Ca+2 ions/polymers ratio of 12.3 g/g resulted in semi-solid tubular structures with c.a. 5 mm of internal diameter and 1.5 mm of wall thickness when the reticulation was performed at 4°C. The presence of the surfactant resulted in highly porous structures with both macro and micropores.
The authors are grateful for the financial support of this work by the Coordination for the Improvement of Higher Education Personnel (CAPES) and by the São Paulo Research Foundation (FAPESP), both from Brazil.