Studies On The System Of Polyacrylic Acid/polyacrylamide In Drug Release

With the continuous development of new drug formulations and polymer materials science,polymer delivery systems has became a new research field of pharmaceutics which depends on its unique advantages.Temperature-sensitive gel is a kind of smart hydrogel.With its unique temperature sensitivity,good biocompatibility and low immunogenicity,it has been used in controlled drug release as carrier and obtained more and more attention of pharmaceutical scholars.Temperature-sensitive hydrogel can be divided into negative and positive type gels.Negative thermosensitive hydrogel belongs to heat-shrinking gel because the gel volume decreases with increasing temperature and it has lower critical solution temperature(LCST).The LCST changes with the sort and proportion of gel materials.This kind of liquid materials can turn into semi-solid state in the affected area immediately when environmental temperature rises.Positive thermosensitive hydrogel belongs to heat-swelling gel.The volume of gel can increase with increasing temperature,so it has upper critical solution temperature(UCST),most of it are the traditional structure with interpenetrating polymer network(IPN).The interlocking network segment and restricting phase separation of IPN can improve the stability of surface and volume morphology of hydrogel,thereby the mechanical strength of the gel significantly was improved.Most of the thermosensitive hydrogel research work have focused on the negative thermosensitive hydrogel system.However,the information about positive temperature sensitive gel is few,which most of the base materials are polyacrylic acid(PAAC)-polyacrylamide(PAAM)with IPN structure.Based on the properties of PAAM-PAAC complex solution,this experiment designs a new way to release drug.The first process is about preparation of PAAM solution,PAAC solution,PAAM gel sphere and PAAC gel sphere,separately.The second step is to study the interaction and release behavior between solution and solution,solution and sphere,sphere and sphere at different temperatures by breaking IPN structure of PAAM/PAAC,which helps to provide new ideas and methods for the thermosensitive hydrogel administration.The first chapter mainly introduces the application of negative thermosensitive hydrogel in the field of controlled drug delivery and tissue engineering,and proved the broad application prospects of thermosensitive hydrogel.In addition,it introduces the structure of IPN gel,as well as the recent advances and problems of positive temperature sensitive hydrogel,proposes purpose and significance of this paper.Content of the second chapter is the preparation technology of polyacrylic acid / polyacrylamide gel spheres which are uesd in the subsequent experiments.It also evaluates the effects of three factors including water/oil ratio,dosage of dispersants and stirring speed on particle size and size distribution.The results displayed that the average particle size and dispersion coefficient of the gel sphere had little change with the change of oil-/water ratios.However,Span 80 dosage and stirring speed had a great influence on the system stability.By adjusting the ratio of oil,polyacrylamide gel spheres meeting require of late experiments are prepared in the same way.The third chapter studies the interaction between the polyacrylic acid solution and the polyacrylamide solution,the polyacrylic acid and polyacrylamide gel sphere solution,the polyacrylic acid solution and polyacrylamide gel spheres.The results displayed that two kinds of solution were physical crosslinking,and turbidity change was reversible.When the ratio is 1: 1,the turbidity could be maximized and the interaction was the strongest.And the trend of turbidity is most evident when the temperature is between 15 ℃and 20 ℃,which indicated that this segment maybe the phase transition temperature.Polyacrylamide chains could hinder the drug release of polyacrylic acid spheres,and the phenomenon is more obvious when the temperature is low.This conclusion is the same with the complex interaction solution.PAAM gel spheres do not have release behavior.The fourth chapter studies the interaction between the two kinds of gel spheres from microlevel and drug release.The results showed that PAAM and PAAC gel spheres had interaction under the microscope,and the interaction was influenced by temperature.The ability of PAAC spheres to absorb VB12 was stronger than PAAM gel spheres.There was "on-off effect" between PAAM and PAAC spheres.