(188o) Generating Anatomically Relevant Structures of Self Assembled Polycaprolacton Matrixes

Polycaprolactone (PCL) is the biocompatible polyester which is explored in forming various medical devices, templates in tissue regeneration and drug delivery systems. Further, its low melting point (60?aC) allows processing into various forms by variety of techniques. However, wide use of PCL in biomedical applications in hindered by two properties: i) bioregulatory activity and ii) direct relationship of resorption rate with molecular weight. We have discovered that PCL can be dissolved in glacial acetic acid (AA) which allows spontaneous aggregation of PCL upon contact with water. This self assembly method makes the possible to form any shapes of scaffolds such as tissue, blood vessels, and organs. Current techniques utilize porous sheets and the surgeon molds into required shape (Atala, Bauer et al. 2007). However, they have uneven thickness due to wrinkling and overlap. Further, the quality of the regenerated tissue is dependent on the surgeons' ability to mold. Thus, it is important to develop anatomical relevant scaffolds appropriate to regenerating a specific tissue. Previously, we reported a novel process of generating PCL flat matrixes in aqueous medium, which decreased hydrophobic surface properties (Pok, Wallace et al. 2010), nevertheless self assembled matrixes showed hydrophobic characteristic. Hence, immobilizing with natural polymers, which provide uniform distribution of nutrients was necessary. 10% (wt/v) PCL (80, 46, 10kDa MW) blended solution was prepared in glacial acetic acid. 0.5 % (w/v) chitosan containing 0.5 % gelatin solutions was also prepared. 1 M of glacial acetic acid was added in gelatin-chitosan solution to give better chance of immobilization with PCL matrixes. Silicone rods of 6 mm outer diameter were used to make tubular shapes useful in vascular graft application. Spherical solid mold of 300 mL volume were used to make spherical shapes scaffolds similar to the bladder. Rods and balloons were immersed in PCL solution for few seconds and immersed in water bath immediately. This step was repeated three times in fresh PCL solution and water to form thicker matrixes. Formed 3-D PCL matrixes were neutralized in NaOH solution and air dried. 3-D PCL matrixes were immersed in gelatin-chitosan solution for 10 min, and dipped in liquid nitrogen tank to have uniform thickness of gelatin-chitosan layers. Then, multi layered matrixes were lyophilized for overnight to complete gelatin-chitosan matrix formation. Surface characteristics of immobilized matrices were analyzed using a scanning electron microscope (SEM). PCL solution in water bath formed desired shapes of matrices quickly. PCL matrixes immobilized with gelatin-chitosan and formed double layers. SEM analysis results showed that gelatin-chitosan solution formed matrixes on the PCL matrixes and penetrated through the perforations. Tensile properties will be assessed in both dried and hydrated conditions using INSTRON 5842. Cellular activity test will be performed using Human Foreskin Fibroblasts (American Type Culture Collection Walkersville, MD) cells onto control and matrices. Cell seeded scaffolds will be stained for actin fibres using Alexa Fluor 546 phalloidin (Molecular Probes) and counterstained with DAPI following vendor's protocol (Invitrogen Corp). We highly expected that gelatin-chitosan immobilized PCL matrixes will have strong mechanical properties due to presence of PCL layer, and also they will have improved cellular activity due to gelatin-chitosan layer.