(114g) A Novel Method of Forming Self-Assembled Polycaprolactone Matrixes and Immobilization of the Natural Polymer

Introduction: Polycaprolactone (PCL) is the biocompatible polyester which is explored in forming various medical devices, templates in tissue regeneration and drug delivery systems. Typically used halogenated hydrocarbon solvents such as Chloroform have been shown to generate a hydrophobic surface with smooth surface characteristics. We have discovered that PCL can be dissolved in glacial acetic acid (AA) which allows spontaneous aggregation of PCL upon contact with water. The aim of this study was to compare the characteristics of self assembled matrices to those formed using chloroform. Formed matrices were evaluated for surface characteristics, tensile properties, cellular interactions and effect of mixing gelatin, chitosan, and Dextran sulfate in the same solution.

Materials and Methods: 10% (wt/v) PCL (80kDa MW) solution was prepared in glacial acetic acid, and the same MW PCL solution was prepared in chloroform to compare the effect of solvent. PCL matrices were made in 5 cm diameter Teflon by dispensing 3 to 4 mL PCL solution drop-wise on the top of a water bath. Some of those PCL matrixes were incubated in 10% gelatin solution for 30 min, 0.5% chitosan solution for 30 min, and 0.1% Dextran sulfate for 10 min. Then PCL-gelatin and PCL-Dextran sulfate were allowed to air dry, and PCL-Chitosan was lyophilized for overnight. Formed matrices were also analyzed using a scanning electron microscope (SEM) and an atomic force microscopy (AFM-DI Nanoscope V Multimode Scanning Probe Microscope) for surface roughness and charge distribution. Tensile properties were assessed in both dried and hydrated conditions using INSTRON 5842. Human Foreskin Fibroblasts (American Type Culture Collection Walkersville, MD) cells were seeded uniformly onto control and PCL matrices. They were stained for actin fibres using Alexa Fluor 546 phalloidin (Molecular Probes) and counterstained with DAPI following vendor's protocol (Invitrogen Corp).

Results: PCL solution in water bath formed matrices quickly. AFM analysis showed a significant increase in nanoscale roughness relative to chloroform-casted matrices. Matrices formed in acetic acid had positive surface charge where as chloroform casted membranes had negative surface charge. However, AFM and SEM analysis showed sidedness in architectures. The bottom side where contacts with water had a net positive surface charge, and the top side had both negative and positive charges. Toluidine Blue staining indicated the presence of Dextran sulfate on the PCL membrane. Tensile properties decreased relative to chloroform casted membranes. Cell retention was significantly increased in self assembled matrix compared to chloroform casted matrix. Addition of gelatin improved the retention of seeded cells on the surface. In summary, PCL matrixes generated using the novel technique show significant promise in biomedical applications.