The Synthesis And Characteristic Of Thermosensitive Materials Based On Poly (N-Isopropylacrylamide)-B-Poly(L-Alanine) For Controlled Release Of Adriamycin

Poly(N-isopropylacrylamide) is a typical thermosensitive polymeric material, which exhibits a reversible thermoresponsive phase transition to respond to these changes in their external environment. PNIPAAm is water-soluble and hydrophilic at the environmental temperature below its 33℃, but after undergoing a phase transition it becomes an insoluble and hydrophobic aggregate as the temperature exceeds 33℃. Owing to the thermal-sensitive property, the PNIPAAm polymers have been used in many fields, especially for the control and release of drugs. The main content of this research consists of:1,The amino-terminated PNIPAAm is prepared by radical polymerization using thiol compounds as a chain transfer agent. The effects of initiating agent and chain transfer agent on the molecular weight of PNIPAAm-NH2 are investigated respectively. L-Ala-NCA is synthesized by triphosgene method and PNIPAAm-b-PAla is prepared by thermal ring-opening polymerization of L-Ala-NCA. Copolymers of different poly(L-alanine) molecular weights are obtained by changing the concentration ratio of L-Ala-NCA.2,The products are characterized by FT-IR and 1H NMR spectra and TEM. The PNIPAAm-b-PAla copolymer micelles in aqueous solution form a spherical core-shell structure. Temperature-responsive property of block copolymer micelles is measured by a turbidity method and differential scanning calorimeter (DSC). With the increase of the composition of the PAla block, the LCST decreases. However, the LCST changes of the copolymer is slight, almost the same as the unmodified PNIPAAm. The hydrodynamic diameters of the particles in water measured by the quasi-elastic light scattering are larger than measured by TEM. The size distribution of micelle increases with the temperature. It is because the micelles show intermicellar aggregations in response to temperature cycles through the LCST. the micelles show reversible temperature-responsive of PNIPAAm-b-PAla hydrogels in response to impulse temperature changes between 22℃and 37℃.3,An adriamycin delivery system is synthesized by using PNIPAAm-b-PAla block copolymers to investigate the loading and release properties of drugs. It is found that PNIPAAm-b-PAla drug carrier could prolong the release time and control the release amount by changing the temperature. Therefore, the PNIPAAm-b-PAla copolymer is very promising drug carrier for the delivery and controlled release application.