Drug Release Of PH/Thermo-Sensitive Poly(N-acryloylglycinates)/Sodium Alginate Hydrogel

Responsive gels are sensitive to the external stimulus such as temperature, pH, ionic strength, magnetic field, electric field and some chemical substances. At present, it is particularly active on studying pH/temperature-sensitive hydrogels both in the field of academia and applications. More and more scholars have been focused their interesting on this "smart" hydrogels. The sensitive hydrogels have promising potential application in the field of drug delivery system, biomaterial culture, separation and enzyme immobilization, and so on. The main contents in this dissertation are that the natural macromolecules with biocompatibility and biodegradability are incorporated with the thermo-sensitive polymer containing amino acid residues. We have prepared the hydrogel bead with different structures, and investigated the drug release behaviors from these hydrogel beads.First, a series of pH/temperature sensitive hydrogel beads with semi-interpenetrating polymer network (Semi-IPN), composed of sodium alginate (SA) and poly(N-acryloylglycinate) were prepared as drug delivery carrier. Using indomethacin as a drug model, the release behaviors of indomethacin were investigated in the different temperature, pH value and ratio of SA/polymer. In pH=2.3 phosphate buffer solution (PBS), the release amount of indomethacin incorporated into the beads was about 9% within 610 min, while this value approached to 68% in pH=7.4 PBS. The release rate of indomethacin was much higher at 37℃than that at 20℃. Second, in this study, a pH/temperature sensitive bead with core-shelled structure, as a drug carrier, was prepared by grafting of N-acryloylglycinates on the surface of sodium alginate beads. SA was used as inner core, the thermo-sensitive poly(N-acryloylglycinates) as outer shell was grafted on the bead surface. The release of indomethacin was systematically investigated as a function of temperature, pH and SA concentration. The amount of indomethacin released from beads was as higher as 61.6% in pH=7.4 phosphate buffer solution (PBS) over 620 minutes whereas only 27.9% indomethacin was diffused into the pH=2.1 PBS. Additionally, the release rates of indomethacin at 37℃were faster than that at 20.0℃, and decreased with increasing the SA concentration in the beads.