Enzymatic erosion of bioartificial membranes to control drug delivery

The preparation of an enzymatic controlled drug release system from blends of PVA/starch/alpha A, in the form of films, is described. It was shown that alpha A hydrolyses the starch within these films, resulting in a time-dependent change of the porosity in the matrix. Films were characterized by calorimetric analysis to study the interactions between the enzyme and the polymeric constituents at the molecular level. The presence of aA, in fact, influenced the PVA cristallization in the blends. Release tests and permeability experiments were carried out to evaluate the transport properties of the films. An increase in porosity and permeability was observed by increasing aA content (16-28 wt.-%). Films loaded with theophylline and caffeine were also prepared to analyze drug release properties of the matrix. Drug release kinetics were coherent with the measured changes in porosity: at higher aA concentrations the amount of released drug increased under the influence of diffusion and erosion processes. The results obtained are promising for the realization of drug delivery devices for a rapid release or for the release of poorly soluble drugs which usually remain entrapped in the matrix.