| Microgels are polymer colloid particles that can swell/deswell in response to changes in the local environment,the matter has many advantages such as small particle size,large specific surface area,good biocompatibility and fast response.These years,with resort to its particular properties,microgels have been made good achievements and potential applications in drug delivery.Methacrylic acid(MAA)and 2-(diethylamino)ethyl methacrylate(DEA)are known to be pH-responsive and good biocompatible.First,a series of polyampholyte microgel particles,with different mole percentages of monomers,containing MAA and DEA used as an anionic and a cationic monomer respectively,have been prepared by inverse microemulsion polymerization and conventional emulsion polymerization.The polymerization was prepared in the presence of PEGMA and N,N'-methylenebisacrylamide(MBA)as macromolecules stabilizer and crosslinker respectively.This polyampholyte microgels,containing weak acid or base groups,can be marked as Gn(xM-yD-zP),where x,y is on behalf of the mole percentage of MAA and DEA respectively,z is on behalf of the mass fractions of MAA and DEA.n =1 is on behalf of the inverse microemulsion polymerization,n=2 is on behalf of the conventional emulsion polymerization.The chemical structure and composition of microgels were characterized and analyzed through conductometric titration;pH-responsive behavior and swelling property were investigated by Dynamic Light Scattering(DLS)and UV-Vis spectrophotometry(UV-Vis);effects of PEGMA on the colloidal stability of microgel were mainly researched.The results indicated that the microgel particles swelled at low and high pH and possessed a compact structure near the IEP,microgels with different mole percentages of monomers have different IEP values.The results also indicated that the colloidal stability of microgels which grafting macromolecules stabilizer have been greatly improved,especially at the isoelectric point near;it can be concluded that the carboxyl distribution of microgels prepared by inverse microemulsion polymerization and conventional emulsion polymerization were different,the carboxyl group of G2(xM-yD-zP)was mainly distributed in the periphery of the gel.In order to investigate the microgel as a drug carrier whether can achieve the controlled release and the slow release,we made a systematic investigation on the uptake and release of bovine serum albumin from polyampholyte microgel particles.Effects of the amount of microgel,pH,the degree of crosslinking and ionic strength on the adsorption properties were researched by UV-Vis and other instruments.With microgel G1(6M-4D-30P)as an example,the results of the study showed that:in the microgel dosage for 0.3 mg/mL,crosslinking agent for 1 wt%and pH = 5,the adsorption quantity could achieve maximum;in the process of absorption,electrostatic interactions played a dominant role;the increase of ionic strength would impede the adsorption of microgel to BSA;the distribution of carboxyl groups also had a significant effect on the adsorption;the microgel grafting macromolecules stabilizer was not easy to aggregate,it could increase the amount of microgel and value in the actual applicationThrough investigating its release behavior,we found that the microgel which absorbed BSA could have done slow release and controlled release to BSA.The compound almost didn't release the BSA in pH = 5,but the biggest release quantity could reach to 65.5%in pH = 3 or 9,and the release behavior could achieve in balance at the 24th h.The factors Influenced the release rate and release amount include pH,ionic strength,crosslinking degree and the gel structure,etc.The dynamics of the release behavior were discussed,the results showed that the release of BSA mechanism mainly was controled by spread and skeleton relaxation. |
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