Controlled Release of Endothelial Cell Growth Factor from Chitosan-Albumin Microspheres for Localized Angiogenesis: In Vitro and in Vivo Studies

Abstract

Endothelial cell growth factor (ECGF) stimulates vascularization, however its relatively short half-life requires this angiogenic factor to be frequently administrated by non-specific and uncontrolled methods. This work describes the use of biocompatible chitosan, a polysaccharide having structural similarity to glycosaminoglycans, -albumin microspheres, as well as its fiber form, as a potential delivery system for the controlled and localized release of ECGF. Chitosan-albumin microspheres (400-600 μm) and fibers, formed in 0.5 M sodium hydroxide-methanol solution were incubated with ECGF. In vitro release was performed in PBS at 37^oC, under constant stirring. In vivo experiments were realized by implanting ECGF loaded matrices subcutaneously into rat groin fascia. After an initial ECGF burst of 1.32-1.62 mg (22-27%) within the first 2 hours, a daily release of 120-420 μg (2-7%) during the first, and 60-240 μg (1-4%) during the second week was observed from M_r 70.000, 750.000, and 2.000.000 chitosan containing microspheres of 6 mg/ml loading. ECGF release rate of <30 μg (0.5%)/day was maintained during the third week of experiments. By the increase in ECGF loading (12 mg/ml polymer), while the amount of release increased, percent release decreased. Chitosan-albumin fibers gave a ECGF release rate nearly similar to microspheres, and in vivo studies demonstrated a high degree of neovascularization for both types of implants, starting from 7 day-post implantation. Control animals that received ECGF injection did not show any significant neovascularization, after same period of time.

Key Words:

• Endothelial cell growth factor
• Angiogenesis
• Neovascularization
• Controlled release
• Chitosan-albumin
• Microspheres
• Fibers