Microporous and nanoporous characteristics of polymer films formed by the ´breath figure´ process for tissue engineering and drug delivery

Summary form only given. We report studies of ordered microporous and nanoporous polymer films formed by the evaporation of polymer solutions following exposure to a humid atmosphere. High speed microphotographic studies of the formation process reveal that near the surface of the polymer solution, vapour condensation produced near mono-disperse water droplets which form a close-packed monolayer (or ´breath figure´). An interesting feature found in the present study is the occurrence of nano-scale pores at the film surface and at (and within) the walls of the sub-surficial microscopic pores. This finding is particularly important in the context of the possible use of such films as biodegradable scaffolds for Tissue Engineering applications involving extracellular matrix production, or as candidate systems for drug delivery containment systems. Clearly, a failure to account for the presence of large populations of nanoscopic pores at (and within) the walls of the micron-scale pore structure will lead to significant overestimates of the mass of polymer available for bio degradation and hence of the likely lifetime of such structures in vivo. Similarly, given the potential application of porous scaffolds generated using the breath figure technique for slow release in drug delivery processes, the results of the present work suggest the presence of the smaller population of pores could have a significant influence on drug delivery timescale