Preparation And Properties Of POSS-PEG Hybrid Hydrogels

Hydrogel is a kind of gel with water as the dispersion medium,which is a cross-linked polymer formed by interconnecting between polymers,and its 3D network structure can hold a large amount of water but can not dissolve in water.Polyethylene glycol(PEG)hydrogel is formed by cross-linking of PEG end groups.It has the characteristics of good biocompatibility,non-toxicity,low immunogenicity,can be completely metabolized in vivo,and has been approved by the American Food and Drug Administration(FDA),which is a very attractive biomedical material.However,due to its soft texture,the application of PEG hydrogel is limited in some certain conditions.In particular,as a scaffold material for tissue engineering,its mechanical strength is far from meeting the practical needs.Therefore,in order to make PEG hydrogel more widely used,it is necessary to modify it to enhance its mechanical properties but not change its original good biocompatibility.Polyhedral oligomeric silsesquioxane(POSS)is a kind of nano-scale material with a cubic cage structure and a variety of functional vertices,which has been proven to have special surface properties,strong hydrophobicity,high mechanical strength,good biocompatibility,and has been widely used in the modification of biomedical polymeric materials.In this thesis,POSS nanoparticles were introduced into the 3D network structure of PEG hydrogels through grafting and cross-linking,and biological macromolecules with good biocompatibility were chosen as cross-linkers.Three kinds of POSS-PEG hybrid hydrogels were prepared by Michael-type addition reaction of “thiol-ene” and the Schiff-base reaction of“aldehyde-amino”,and their various properties were studied.1.Firstly,POSS-SH nanoparticles with single sulfhydryl group were gratfted into the monomer 4-arm-PEG-MAL to prepare the POSS-PEG-MAL prepolymers by Michael-type addition reaction,and then the prepolymer was gelled with the crosslinker MMP(W)x.In this chapter,four different contents of POSS were designed to study the performances of POSSPEG hybrid hydrogels,and the influence of POSS content on the properties was discussed in detail.The surface properties,blood compatibility and anti-calcification properties of the hydrogels were mainly discussed.Results showed that the POSS-PEG hybrid hydrogels not only have enhanced mechanical and surface properties,but also have excellent biocompatibility.The results of AFM and in vivo animal experiments indicated that the nano-scale of POSS in the PEG hydrogel plays an important role on its surface,which helps to improve its biological characteristics and reduce thrombosis on the surface of hydrogels compared to DVS.In addition,in vitro experiments and subcutaneous model in rats confirmed that the introduction of POSS nanoparticles also makes the hydrogel have better anti-calcification performance.These studies further proved that POSS-PEG hybrid hydrogel is a potential material for artificial valve scaffold.2.The crosslinked POSS-PEG hybrid hydrogel was prepared by octa-functional monomer POSS-PEG-CHO and the crosslinker chitosan.Firstly,octa-thiol-substituted POSS-8SH was synthesized by condensation and dehydration reaction of(3-mercaptopropyl)-trimethoxysilane,and then it was mixed with monoallyl polyethylene glycol(Allyl-PEG-OH)to prepare POSSPEG-OH through the click reaction of "thiol-ene".The cross-linking monomer POSS-PEGCHO was prepared by Steghlich esterification with POSS-PEG-OH and 4-formylbenzoic acid,and crosslinked with acidic chitosan solution via Schiff-base reaction to obtain the POSS-PEG hybrid hydrogel with self-healing properties.The micromorphology,mechanical properties,degradation rate and swelling properties of the prepared hydrogel were investigated before and after self-healing test.The cell compatibility of POSS-PEG-CHO,chitosan and hydrogel were carried out by direct contact and immersion method.Results showed that the prepared hydrogel had uniform network structure,good mechanical properties,proper swelling ratio,biodegradability and excellent cell compatibility,which could be used as injectable hydrogels and a candidate material for wound excipients.3.The previously prepared POSS-PEG-CHO was used as the cross-linking monomer and the quaternized chitosan was used as cross-linker,three POSS-PEG hybrid hydrogels with different solid content were prepared.The pore structure,mechanical properties,swelling ratio,degradability and cell compatibility of POSS-PEG hybrid hydrogels were also investigated.Results showed that POSS-PEG hybrid hydrogels with three different solid contents had similar network structure,high mechanical strength,proper swelling ratio,biodegradability and excellent cell compatibility.In particular,their mechanical properties were greatly improved compared to the self-healing hydrogel,so this kind of hydrogel has the potential as scaffold material for tissue engineering.In this thesis,three kinds of POSS-PEG hybrid hydrogels with different properties were prepared by Michael-type addition reaction and Schiff-base reaction.On the one hand,the POSS-PEG hybrid hydrogel with POSS grafting prepared by Michael-type addition reaction shows excellent anti-calcification performance and biocompatibility;on the other hand,two kinds of POSS-PEG hybrid hydrogel with different properties were prepared by Schiff-base reaction between crosslinking monomer(POSS-PEG-CHO)and two different crosslinkers,and their micromorphology,mechanical properties,swelling ratio,degradability and cell compatibility were studied.The results showed that these three kinds of POSS-PEG hybrid hydrogels all had uniform cross-linked network structures,good swelling properties,biodegradability and good biocompatibilities,which have potential application prospect in the field of biomedical materials.