Biodegradable Microspheres for Sustained Delivery of α-Proteinase Inhibitor
One of the adverse effects of smoking is related to the deterioration of α-i-proteinase inhibitor activity. There is a strong evidence that deficiency in α-1-proteinase inhibitors (α-PI) may predispose persons to the development of pulmonary emphysema. Since therapeutic administration of α-PI has been suggested it is possible that such therapy would be more efficient if delivered directly to the target organ, i.e., lung in this case. A selective administration of α-PI to the lung can be achieved via inhalation or intravenously, if the protein is available in the form of spherical particles of appropriate size, i.e., in the range 1–5 µm for the delivery to the lower airways or in the range 8–20 µm for an intravenous delivery to the lung capillaries and/or precapillary vessels. The methodology for preparation of microspheres from a biodegradable hydrogel of controllable size range has been developed. Microspheres have been characterized by light and electron scanning microscopy and factors affecting the yield of incorporated protein and the rate of its release have been studied. The amount of a diffusion-released fraction of incorporated protein can represent up to 25% of the mass of microspheres and the rate of its release can be controlled through control of the matrix properties. Retention of a substantial part of the inhibitory activity of incorporated α-PI has been documented. Biodegradable hydrogel microspheres constitute an attractive system for parenteral delivery of α-PI and other biologically active proteins; however, its appropriateness for particular purposes should be considered with respect to the capacity of the system and the required amount of the protein to be delivered.