In vitro slow release profile of endothelial cell growth factor immobilized within calcium alginate microbeads

Although a variety of angiogenic growth factors have been isolated, its appropriate in vivo delivery remains problematic due to nonspecific, uncontrolled delivery by conventional methods. We have investigated calcium alginate microbeads as a vehicle for the controlled slow-release of endothelial cell growth factor (ECGF). Three different microbead compositions, dependent on ECGF amount and alginate percentage were studied. Microbeads were incubated in a 1.5% calcium chloride solution and release of ECGF into solution was measured spectrophotometrically at specific timepoints. Our results show release rate and amount released after the first 2 hours are dependent on initial quick delivery of ECGF in the first 2 hours after which a sustained controlled release occurred for 4-5 days. Beyond this point, release at a slower rate was noted for at least approximately 2 weeks. Calcium alginate microbeads demonstrated a controlled and predictable rate of release and that the amount of ECGF delivered can be varied by varying the initial concentration of ECGF in the microbeads. Based on these observations we conclude that calcium alginate microbeads are a convenient and practical vehicle for sustained ECGF delivery.