Preparation of double layered nanosphere using dextran and poly(L-lactide-co-glycolide)

The initial burst of drug release is an important role in the controlled delivery of drug having high toxicity and narrow therapeutic ranges. Nanosphere composed of monolayer could not achieve precisely controlled drug release because of the initial burst of drug on surface. In this study, double layered nanosphere was prepared for sustained drug delivery without initial burst. Double layered nanosphere composed of dextran and PLGA was fabricated by using conventional W/O/W double emulsion method. To control surface tension on the outer layer of nanospheres, PVA was used as a surfactant. Release behavior of dextran as model drug was observed as the 3x1 mm wafers formed by compression mould in the deionized water for 7 days. Double layered nanosphere has sustained release behavior, in contrast to single layered nanospheres such as mechanical mixture and dextran nanospheres. Especially, nanosphere containing PVA 0.2% has shown nearly the zero-order release profile. As a result of this study, double layered nanospheres has more sustained release profile of drug without the initial burst and the release behavior of dextran on the double layered nanospheres was controlled by the contents of PVA as a surfactant.