Synthesis And Properties Of Nanoparticle Reinforced Hybrid Hydrogels

Natural polymer hydrogels have been widely used in various fields includingbiomedical engineering, whereas the poor mechanical strength limited their furtherapplicability. In this work, double bond introduced nanoparticles were used asreinforcer to improve mechanical strength of hydrogel materials. An amphiphilictriblock copolymers (PECL) consisting of poly (ethylene glycol)(PEG) as hydrophilicsegment and poly (ε-caprolactone)(PCL) as hydrophobic block were prepared bycoupling reaction. The product from the reaction of PECL and propylene chloride byesterification reaction formed nanoparticles by self-emulsifying and evaporationdrying method. The results of~1H-NMR and FT-IR showed that the prepared PECLwas copolymer, and carbon-carbon double bonds were successfully introduced intothe PECL triblock copolymer. The PECL nanoparticle was a spherical core-shellstructure as observed by transmission electron microscope (TEM). Covalentlycrosslinked hybrid hydrogel was prepared by Michael-type addition reaction ofthiolated chitosan and PEGDA. Double bond carried PECL nanoparticles were usedas reinforcer for the hybrid hydrogels. When the molar ratio of thiol and double bondsfrom PEGDA and double bonds from nanoparticles was1:2:1, the hybrid hydrogelexhibited the highest compressive strength.Thiolated gelatin and thiolated heparin were prepared and then added into thehybrid hydrogel which resulted in the formation of composite hydrogel. Thecytotoxicity and mechanical strength of the composite hydrogel showed the bestcombination effect when the mass ratio of chitosan and gelatin was8:2. Hydrophobicindomethacin (IMC) was loaded in the composite hydrogel through entering thehydrophobic core structure of the PECL nanoparticles, whereas bFGF was introducedinto the hydrogel by specific interaction with heparin molecules. The results of releaseindicated that there were no burst releases for both IMC and bFGF. IMC and bFGFreleased from the composite hydrogels in constant speed at the initial16days, andthen slowed down. When the heparin content in the composite hydrogel was2%andthe IMC joined content was20%, the hydrogel exhibited the best dual releasebehaviour.