Preparation of self-assembled microspheres and their potential for drug delivery

Dextran solutions intended for use as plasma extenders have been observed to form insoluble precipitates. Earlier studies of precipitation have shown that in solutions of 50% and 60% w/w of dextran molecular mass 6000 g mol(-1) beaded precipitates are formed over a two-week period. This study considers dextran precipitation over a wider molecular mass range and the kinetics, of formation, morphology and potential utility of these precipitates is investigated. Results show precipitation occurs over the dextran molecular mass range 6000-17,000 g mol(-1), with lower molecular mass material showing more rapid precipitation. As bead formation is accompanied by an increase in turbidity, formation kinetics were quantified spectrophotometrically confirming that precipitation rates were inversely proportional to molecular mass. The utility of these precipitates for drug delivery applications was assessed using bovine serum albumin as a protein drug analogue. The results showed that the inclusion of protein did not prevent bead formation and that entrapped protein was subsequently released from dextran beads in a time dependant manner. This suggests that dextran beads of this type may find application in the drug delivery area, as they combine the advantages of mild entrapment conditions with the use of an unmodified clinically approved polymer.