Controlled delivery of therapeutics from microporous membranes. I. Fabrication and characterization of microporous polyurethane membranes containing polymeric microspheres

This paper describes a process for the inclusion of polymer microspheres in microporous polyurethane tubes and membranes. These composites were fabricated via a spray, phase-inversion technique using Cardiothane 51, a medical grade polyurethane, and either spray-dried poly(D,L-lactide-co-glycolide 50:50) microspheres or commercially available fluorescent polystyrene-latex microspheres. Characterization of the polyurethane membranes was performed using Fouriertransform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, hydraulic permeability testing, scanning electron microscopy, and visible and fluorescence light microscopy. The results indicated the feasibility of layering microspheres throughout the microporous membrane or wall of the microporous tube, and the potential of such composite structures for local delivery of bioactive substances.