Controlling environmental conditions to generate homogeneous biodegradable polymeric films for nerve guide conduits

INTRODUCTION: Biodegradable polymeric conduits can be applied in peripheral nerve regeneration following trauma and nerve damage. We have developed a method to make biodegradable conduits using polycaprolactone (PCL) films by solvent casting. An environmental chamber has been modified and utilised in the experiments. The aim of the present study was to evaluate the effect of the environmental factors on the surface structure of the PCL films in order to optimise cell attachment, proliferation and nerve regeneration. METHODS: Films were made in environmental chamber with glove ports and controlled conditions. The 3% wt/v PCL (Mn ~ 70,000-90,000g/mol) in dichloromethane (99% purity) was cast on the glass cover slip (18 X 18mm). Films were imaged by scanning electron microscopy and interferometer and analysed by imaging processing and analysis software .The statistical analysis was performed by GraphPad Prism5.03. One way ANOVA with P<0.05 was used to determine the statistical difference. RESULTS: Preliminary study on PCL/PLA (80/20%) films was comparing the surface structure of the nine batches in uncontrolled and controlled T-RH (temperature-relative humidity) conditions. Only four batches in uncontrolled condition produced pitted films. However all samples in controlled conditions (23°C -50%) were pitted with average depth and width of 2.32µm, 4.33 µm, receptively. Further study was performed in the environmental chamber with the constant temperature (23°C) and variable humidity (20-80%). Analysis of SEM images was carried out to measure the pit size and the area fraction of the surface covered by pits. The pit size was in a range of 1-700 µm2 and divided in to two groups; pits larger than 80 µm2 and smaller than 80 µm2. Humidity affects the surface morphology by changing the pit size and porosity. The large pits formed randomly, however the size of the small pits and its porosity, increased by increasing the humidity up to 50%. DISCUSSION & CONCLUSIONS: This study has demonstrated that environmental temperature and humidity affect the surface structure and morphology of the solvent cast films. By altering the environmental conditions, the pit size, porosity and pit distribution could be controlled. It is most likely that the changes in the environmental conditions affect the rate of the solvent evaporation directly. This has enabled us to produce pitted or non-pitted polymer surface. By controlling the rate of evaporation, it is possible to tailor the final structure with the desired surface morphology. The ability to control the surface features of biopolymers used in regenerative medicine is essential, for appropriate cell differentiation and tissue repair. Further work will analyze the combined effects of all the variables on the final morphology of the film with structured experiments and multivariate data models.REFERENCES: Jiang, X., et al (2010), Experimental Neurology. 223(1): p. 86-101. ACKNOWLEDGEMENTS: This abstract presents independent research commissioned by the National Institute for Health Research (NIHR) under the invention for Innovation (i4i) programme (ll-AR-0209-10050). The views expressed in this abstract are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.