Synthesis,Characteristic And Its Release Properties In Vitro Of PH/Temperature-Sensitive Intelligent Materials Based On Sodium Alginate/Poly (N-Isopropylacrylamide)

Synthesis , characteristic and its release properties in vitro of pH/temperature-sensitive intelligent materials based on Sodium Alginate/poly(N -isopropylacrylamide) were studied in this paper.N-isopropylacrylamide monomer , its polymers and hydrogels , such as PNIPAAm hydrogels, Calcium Alginate hydrogels; were synthesized and further temperature and pH sensitivity was studied in this paper. A novel temperature-sensitive/enteric functional biomaterial N-isopropylacrylamide-grafted-Sodium Alginate polymer(SA-g-PNIPAAm) with maximum percentage of grafting using CAN were prepared in an aqueous medium; A novel thermo- and pH-sensitive Calcium Alginate /PNIPAAm interpenetrating network hydrogels (CA-I-PNIPAAm) beads were prepared with both calcium alginate and PNIPAAm hydrogels which were synthesized by free-radical aqueous solution polymerization using APS(ammonium persulphate)/Na2S2O5(Sodium pyrosulfite) as redox initiator in a Simultaneous interpenetrating network process.The influences on swelling ratio, gelling time and phase transition point of PNIPAAm hydrogels were investigated, the mechanism of temperature sensitivity was discussed furtherly. The physicochemical paraments of sodium alginate were measured and Calcium Alginate hydrogels' pH sensitivive swelling property wereanalysed from its molecule structure. The optimized reaction conditions affording maximum percentage of grafting of NIPAAm onto sodium alginate are determined. The temperature and pH sensitivity of different SA-g-PNIPAAm was also studied. The microenviroment condition of CA-I-PNIPAAm and its temperature phase transition near LCST were studied By using fluorenscene probe Rhodamine B, and its controlled release characteristics containing pentoxifylline and naproxen sodium were studied respectively as model drugs.The results showed that: The amount of crosslinker and initiator prepared for PNIPAAm hydrogels had no effect on its lower critical solution temperature (LCST), ranging from 32-36℃,but swelling ratio as funtion of the extent of phase transition.The optimized reaction conditions affording maximum percentage of grafting of NIPAAm onto sodium alginate are determined under the following conditions:CcAN=10-3mol/L, CNIPAAM=0.1mol/L, Temperture=40℃, the reacting time =4 hours.CA-I-PNIPAAm show relative SR and distinct phase transition point under the condition: the amount of reducer lesser than 9.9% and Cnipaam more than 0.6mol/L and pH value is about 4; and show clear pH- sensitive and appropriate SR in the presence of CNipaam/CSa equals 5.9%. The microenviroment condition of CA-I-PNIPAAm and its temperature phase transition near LCST were detected By using fluorenscene probe Rhodamine B, the results showed that the polarity of microenviroment aroud Rhodamine B changed during this course, which was due to the change of interaction between hydrophilic and hydrophobic groups in polymer chains. Useing model drugs containing Pentoxifylline , Naproxen Sadium respectively, The CA-I-PNIPAAm beads exhibited thermo- and pH-sensitive release Characteristic in vitro. Temperature, solution pH values, drug solubility and solvent appeared to significantly affect gel swelling ratio and the drug release rate. The drug release is the coupled action of diffusion and erosion mechanism.In this paper, Oweing to its change of interaction between hydrophilic and hydrophobic groups in polymer chains, the temperature phase transition of CA-I-PNIPAAm were confirmed By using fluorenscene probe Rhodamine B. CA-I-PNIPAAm beads also exhibited its thermo- and pH-sensitive controlled drug...