Physical And Chemical Properties Of Hydroxypropyl Chitosan Hydrogel Research, And Drug Delivery Applications

Hydroxypropyl chitosan (HPCS), which has good water solubility, hygroscopicity and moisture retention, surfactivity, foaming capability and emulsifying property, is derived from chitosan. It shows good compatibleness with other kinds of surfactants and has different effects on their microemulsion systems. The following results are approved: (1) The input of HPCS aqueous solution will improve the water and oil solubility in the system of H2O/BRIJ35/ n-C4H9OH +10%n-C8H18, at the same time, the higher the HPCS concentration is, the stronger this effect is; (2) As to the system of H2O/CTAB/n-C4H9OH +10%n-C8H18, HPCS solution has the same effect on it as (1); (3) At low concentration, HPCS solution 'vill improve the solubility between water and oil of SDS system, the effect is increased by increasing the HPCS concentration. But it is the other way round at high HPCS concentration; (4) HPCS has no remarkable effect on the system of H2O/ C12BE/n-C4H9OH +10%n-C8H18.Glutaraldehyde, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, epichlorohydrin and glyceryl glycidyl ether are applied to crosslinking HPCS respectively and a series of microsparticles which have crosslinking HPCS molecular as its net framework are prepared. The preparation methods are discussed and the swelling behavior of all the microsparticles in different mediums are examined. The results are shown as following: (1) The amount of crosslinking agent is the most important factor to affect the properties of the hydrogel products, more or less crosslinking agent is not favorable for the appearance and swelling property of hydrogel microparticles; (2) All of the hydrogels crosslinked with glutaraldehyde, diisocyanate, epichlorohydrin or glyceryl glycidyl ether belong to acid-sensitive hydrogels. Their volume phase can be changed remarkably according to the change of pH. The high swelling degrees are discovered in acidic mediums but low in basic mediums. The change may be attributed to protonation of amino-group and the change of interaction forces in the net framework. PH sensitivities of hydrogels are different in terms of different crosslinking agents; (3) A semi-interpenetrating polymer network (semi-IPN) is prepared by crosslinking reaction of HPCS with epichlorohydrin in presence of polyacryamide. The semi-IPN product belongs to basic-sensitive hydrogel. Volume phase change not much in the mediums below pH7.0 because protonation of some of -NH2 happens. It's swelling degree (SD) change remarkably between pH7.0~9.0 with a high SD in basic medium. The reason may be hydrolysis of some of -COONH2 , the produced -COO- results inthe repulsion between the negative charges and the increasing of the SD; (4) A full-IPN is prepared by crosslinking co-polymerization reaction of acrylic acid and MBAA in the presence of HPCS-ECH rriicrogel. The full-IPN also belongs to basic-sensitive hydrogel and exhibits similfir pH-sensitivity to the semi-IPN of (3). The induction of polyacrylic acid improves the swelling degree in basic medium more than the semi-IPN. In different salt solutions with equal metal ionic valence and ionic strength the swelling degrees of the full-IPN are on the same level, but swelling degree increases with increasing metal ionic valence.The sustained-release drug micropellets of Ibuprofen, Hydrocortisone and Dichlofenac potassium are prepared by applying hydrogel of epichlorohydrin crosslinked HPCS as the drug carriers. The preparation processes are optimized and the patterns of drug release are evaluated. The results have shown that: (1) The drug micropellets with reasonable drug entrapment ratio and release velocity will be obtained if the amount of crosslinking agent and drugs is controlled successfully; (2) The Ibuprofen micropellet has a suitable release rate in artificial intestinal juice but a very low release rate in artificial succus gastrius because it has a low solubility in acid medium, the cumulative release percentage after 10h is 89.2% and 23.6% respectively, the release pat...