Study On Synthesis Of Poly(N-isopropylacrylamide)-g-Polyamidoamine And It's Drug Release Behaviors

The purpose of the investigation was to develop a novel derivative of Poly(N- isopropylacrylamide) (PNIPAm)-g-polyamidoamine (PAMAM) dendrimer as a kind of nano-scale drug delivery device for increasing the solubility of the hydrophobic drugs and controlling the release of the drugs.First of all, PAMAM dendrimers was synthesized from ethylenediamine (EDA) on the basis of repeatedly using two consecutive chain forming reactions, the Michael addition reaction and the amine reaction. After that the G1.5 ester-terminated half- generation PAMAM dendrimer was converted into a more water-soluble hydroxyl surface by reacting with amino ethanol. G2.0 PAMAM-OH was characterized by mass spectrum (MS) and 1H-NMR. Using mercaptoacetic acid (MAA) as a chain- transfer agent, 2, 2′-azobisisobutyronitrile (AIBN) as an initiator, radical polymeri- zation of N-isopropylacrylamide (NIPAm) was carried out. The molecular weight was 2400 determinated by 1H-NMR and gel permeation chromatography (GPC). Then, PNIPAm with carboxyl group terminal reactive groups was grafted to the PAMAM dendrimers in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydro- chloride (EDC?HCl) through esterification. The structure of this thermo-sensitive polymer-grafted dendrimer was characterized by 1H-NMR and the molecular weight was determinated by GPC. The thermo-sensitive properties of the resulted dendrimer derivatives were determined by UV-VIS photometer. The behaviors of the temperature controlled drug release from this novel polymer were studied at two different temperatures, 37℃vs 27℃and indomethacin was selected as a model drug. The loading of indomethacin was detected by UV-VIS photometer, which was about 17.53%. The release rate of the drug in the internal cavities of the dendrimer derivatives can be effectively controlled by the surrounding temperature.