Thermo-responsive self-assembled polymeric micelles for drug delivery in vitro

Cholic acid (CA) was coupled with amine-terminated poly (N-isopropylacrylam ide) (ATPNIPAAm) using N,N'-dicyclohexyl carbodiimide as a coupling agent. Self-assembled CA/PNIPAAm conjugate (abbreviated as CN) micelles were prepa red by diafiltration method in water. The CN micelles exhibited the lower c ritical solution temperature (LCST) at 31.5 degrees C. The CN micelles were observed as spherical shapes and their dried sizes were ranged between 30 and 50 nm by the transmission electron microscope (TEM) images. Hydrated mi celle sizes measured by photon correlation spectroscopy (PCS) were ranged 3 37.5 +/- 67.8 nm. And reversible size changes of CN micelles were observed with two point temperature 10 and 40 degrees C, respectively. From the fluo rescence spectra, fluorescence intensity of pyrene in the CN micelles was i ncreased and red-shifted as the concentration of CN increased, indicating t he formation of self-assembled polymeric micelles in water. The critical mi celle concentration (CMC) was evaluated as 8.9 x 10(-2) g/l. Much more indo methacin (IN) was released from the CN micelles at 10 than at 40 degrees C due to the thermo-sensitivity of the PNIPAAm in the CN polymer. (C) 2000 El sevier Science B.V. All rights reserved.