Breath figure plga films as implant coatings for controlled drug release
The breath figure method is a versatile and facile approach of generating ordered micro and nanoporous structures in polymeric materials. When a polymer solution (dissolved in a high vapor pressure organic solvent) is evaporated out in the presence of a moist air stream, the evaporative cooling effect causes the condensation and nucleation of water droplets onto the polymer solution surface. This leads to the formation of an imprinted porous structure upon removal of the residual solvent and water. The facile removal of the water droplet template leaving its structural imprint is a specifically appealing aspect of the breath figure film technology. The first part of the dissertation work involves the fabrication of drug loaded breath figure thin films and its utilization as a controlled drug release carrier and biomaterial scaffold. In a single fabrication step, single layer/multilayer porous thin films were designed and developed by combining the breath figure process and a modified spin or dip coating technique. Using biodegradable polymers such as poly (lactic-co-glycolic acid) (PLGA) and poly (ethylene glycol) (PEG), drug loaded films were fabricated onto FDA approved medical devices (the Glaucoma drainage device and the Surgical hernia mesh). The porosity of the films is in the range of 2-4 µm as characterized by scanning electron microscope. The drug coated medical implants were characterized for their surface and bulk morphology, the degradation rate of the film, drug release rate and cell cytotoxicity. The results suggest that the use of breath figure morphologies in biodegradable polymer films adds an additional level of control to drug release. In comparison to non-porous films, the breath figure films showed an increased degradation and enhanced drug release. Furthermore, the porous nature of the film was investigated as a biomaterial scaffold to construct three dimensional in vitro tissue model systems. The breath figure film with interconnected pores facilitates cell infiltration and tissue remodelling in vitro, suggesting its high potential in regenerative medicine and tissue engineering applications. In the second part of the dissertation, the versatility of breath figure polymers was explored as a reverse template to create micropatterned soft materials. Unlike traditional lithographic masters, the breath figure assembly is a simple and cost-effective approach to create micro/nano sized "bead" like uniform patterns on the surface of hydrogels and biopolymers. By incorporating iron nanoparticles into the pores, this technique was extended to form hydrogels decorated with nanoparticles specifically in the pattern. The morphology features and the functional characteristics were demonstrated through scanning electron microscopy. The potential applications of these micro-fabricated materials in biosensors and cell culture substrates are outlined.