| Intelligent hydrogels are sensitive to the external stimulus such as temperature,pH, magnetic field,electric field,ionic strength,light.They have attracted considerable attention in recent research work for their potential applications in biomedical and biotechnological field,including controlled drug release,sensor,tissue engineering,and separation of cells,etc. Intelligent hydrogels have attracted great interest from both fundamental and application fields at present.The different kinds of pH responsive hydrogels were prepared,their pH-sensitivity was discussed in a deeper degree and their appliance in drug controlled delivery system(DCDS) was also investigated preliminarily in this thesis.The main contents and conclusions in this paper are as follows:1.A semi-interpenetrating polymer networks hydrogel was prepared with konjac Glucomannan and polyvinylpyrrolidone using glutaraldehyde as crosslinking agent.The structure of the semi-IPN hydrogel was studied by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy.The effect of the mass ratio of konjac Glucomanna to polyvinylpyrrolidone and the content of crosslinking agent on the swelling ratio was investigated.Meanwhile,the effect of the degree of the hydrogel crosslinking on the swelling kinetics and the release profiles of the drug in vitro were also examined in pH 2.2 and 7.4.The results showed that the mass ratio of KGM to PVP influenced swelling capability of the hydrogel.That is,the swelling ratio of hydrogel,when the mass ratio of KGM to PVP was close to 1,reached to maximum.The swelling ratio and rate of the hydrogel were increasingly decreased with the increase of the content of crosslinking agent. The mass and rate of controlled release for drug also were increasingly decreased with the increase of the content of crosslinking agent.The hydrogel in pH 2.2 showed better swelling ratio,swelling rate and controlled release for the drug than that of it in pH 7.4.2.A pH-sensitive semi-interpenetrating polymer network(semi-IPN) hydrogels were prepared by using Konjac Glucomannan(KGM) and poly(aspartic acid)(PAsp) with trisodium trimetaphosphate(STMP) as the crosslinking agent.The effects of their composition,cross-linking density(STMP concentration),pH and ionic strength on the swelling properties of hydrogels were investigated.The structure of the semi-IPN hydrogels were characterized by fourier transform infrared spectroscopy(FT-IR),surface area analyzer and scanning electron microscopy(SEM).The equilibrium swelling characteristics and the release profiles of the drug in vitro were investigated for the hydrogels at 37℃in buffer solutions of pH 2.2 and 7.4 as simulated gastric and intestinal fluids,respectively.At pH= 2.2,the release amount of 5-Fluorouracil(5-FU) incorporated into the hydrogel was about 23%within 180 min,while this value approached to 95%at pH=7.4.These results showed that the semi-IPN hydrogels could be a suitable polymeric cartier for site-specific drug delivery in the intestine.3.A semi-IPN hydrogels with pH responsive based on starch and poly(aspartic acid) (PAsp) were prepared by trisodium trimetaphosphate(STMP) as the crosslinking agent. The goal was to obtain a colon specific drug delivery system,exploiting the pH-sensitive behavior of the hydrogels.The hydrogels obtained have been characterized by using fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),and scanning electron microscopy(SEM).The hydrogel prepared with a suitable ratio between the starch and the poly(aspartic acid) was investigated regarding its swelling behavior in gastrointestinal simulated conditions.Moreover,the drug release studies were carried out using 5-Flurouracil as a model of anticancer drug.The obtained hydrogel,due to its excellent pH-sensitive release property,could be potentially used as system for the oral treatment of colonic cancer.
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