Temperature-responsive and Biodegradable Polymeric Micelles as drug carrier

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Site-specific drug delivery has been markedly focused on the enhancement of pharmacological efficacy and reduction of side effects. The polymeric micelle shows very high stability in aqueous media due to its low critical micelle concentration. In this project, we attemped to fabricate sitespecific drug carriers using temperature-responsive polymeric micelle. Namely, novel type of polymeric micelle were prepared from N-isopropylacrylamide (IPAAm)-D,L-lactide(DLLA) block copolymer. PIPAAm is known to be a thermo-responsive polymer which has lower critical solution temperature (LCST, 32ﾟC). Below the LCST, PIPAAm shows the hydrophilicity and is soluble in aqueous media due to strong hydration and it is insoluble due to dehydration above the LCST.This phase transition takes place in narrow temperature range. Moreover, poly(D,L-lactide) is well-known as a biodegradable polymer. The corresponding block copolymer formed the micellar structure with core (PDLLA)-shell (PIPAAm) below LCST.On ther other hand, abovel LCST the polymeric micelles fomed aggregation. This phenomena was completely reversible. It was expected to induce selective accumulation controlled by temperature modulation. Namely, in a body, the thermo-responsive polymeric micelle would accumulate at the locally heated place. This finding surely contributes to site-specific drug delivery.