Synthesis Of Hydroxypropylcellulose-Based Intelligent Microgels And Controlled Release Of Oral Insulin

The design and preparation of intelligent polymers which are able to respond to external or internal stimuli such as heat, light, pH, magnetic and electric fields and chemical substances have attracted a great deal of interest for their potential applications in drug delivery. Among the above-mentioned stimuli, temperature and pH may be the most important ones due to their physiological significance. In this dissertation, two kinds of temperature-and pH-responsive microgels which have interesting potential application in oral insulin controlled release have been successfully developed. The main contents can be summarized as follows:1. Temperature-and pH-responsive microgels composed of hydroxypropylcellulose-acrylic acid (HPC-AA) and poly(acrylic acid)(PAA) were prepared via precipitation polymerization. The particles undergo reversible volume phase transitions in response to both pH and temperature changes while keeping the inherent properties of PAA and HPC-AA. Dynamic light scattering measurements reveal that the hydrodynamic radius and hydrodynamic radius distributions of the microgel particles depend on temperature and pH. The microgels exhibit excellent pH sensitivity and a higher swelling ratio at higher pH in aqueous solution. In vitro release study shows that the amount of insulin released from the microgels is less at pH=1.2than at pH=6.8.2. Novel smart microgel particles composed of poly (L-glutamic acid-2-hydroxylethyl methacrylate)(PGH) and hydroxypropyl cellulose-acrylic acid (HPC-AA) were prepared via inverse emulsion polymerization. Dynamic light scattering measurements reveal that the average hydrodynamic radius and hydrodynamic radius distributions of the microgel particles depend on temperature and pH thus the microgel particles exhibits both pH-and temperature-sensitivity. In vitro release study shows that the amount of insulin released from the microgels is less at pH=1.2than at pH=6.8.