Degradation and intrahepatic compatibility of albumin-heparin conjugate microspheres

Preparation, characterization and in vivo distribution of terbutaline sulfate loaded albumin microspheres

Terbutaline sulfate is widely used as a bronchodilator for the treatment of bronchial asthma, chronic bronchitis and emphysema. As it has a short biological half-life, a long acting terbutaline sulfate formulation is desirable to improve patient compliance. Bovine serum albumin microspheres were prepared by an emulsion polymerization method using glutaraldehyde as the crosslinking agent. All microspheres were spherical and smooth with the mean particle size in the range of 22-30 microm. Drug release from the BSA microspheres displayed a biphasic pattern characterized by an initial fast release, followed by a slower release. The released amount was decreased with an increase in the glutaraldehyde concentration. In the absence of trypsin, the time required for complete degradation of microspheres was increased from 144 to 264 h when the glutaraldehyde concentration increased from 0.1 to 0.7 ml. In the presence of trypsin, a linear relationship was obtained between the degradation rates and trypsin concentrations, indicating that saturation was not reached under the experimental conditions. Biodistribution studies indicated that the degree of uptake by the lungs was higher than that of the other organs. All these results demonstrated that terbutaline sulfate loaded microspheres can be used for passive lung targeting.

Adjuvancy enhancement of muramyl dipeptide by modulating its release from a physicochemically modified matrix of ovalbumin microspheres. I. In vitro characterization

The weak immunogenicity of subunit vaccines has necessitated research into the development of novel adjuvants and methods to enhance the adjuvancy associated with vaccine delivery systems. The purpose of the present study was to modulate the release of muramyl dipeptide (MDP) from a physicochemically modified matrix of ovalbumin microspheres (OVA-MSs). A two-component MS vaccine delivery system was fabricated, which utilized OVA as the antigen and delivery matrix, and MDP as the adjuvant. The MSs were prepared from OVA using a water/oil emulsion method, followed by suspension cross-linking using glutaraldehyde. The MS matrix was modified with respect to the degree of cross-linking by varying the concentration of glutaraldehyde and matrix density, a function of disulfide-bond formation. The modifications in the MS matrix were characterized using SDS-PAGE, scanning electron microscopy, differential scanning calorimetry, and thin layer wicking (TLW). The in vitro release of MDP and OVA from the various preparations of OVA-MSs exhibited triphasic and biphasic profiles, respectively. The degree of cross-linking and the matrix density were found to be significant physicochemical parameters that affected the release profiles of MDP and OVA through two mechanisms: controlled surface erosion and bulk degradation of the MSs.