BIODEGRADABLE LONG-CIRCULATING POLYMERIC NANOSPHERES

Injectable nanoparticulate carriers have important potential applicati ons such as site-specific drug delivery or medical imaging. Convention al carriers, however, cannot generally be used because they are elimin ated by the reticulo-endothelial system within seconds or minutes afte r intravenous injection. To address these limitations, monodisperse bi odegradable nanospheres were developed from amphiphilic copolymers com posed of two biocompatible blocks. The nanospheres exhibited dramatica lly increased blood circulation times and reduced liver accumulation i n mice. Furthermore, they entrapped up to 45 percent by weight of the drug in the dense core in a one-step procedure and could be freeze-dri ed and easily redispersed without additives in aqueous solutions.