Bone Repairing Application Of A Novel Injectable PEG-hydrogel Loaded With RBMSC

The ever-increasing demands for perfect osteoplastic surgery and oral implant prosthesis make doctors and scholars focus on how to promote or accelerate bone regeneration and repair. The present study is to design and synthesize a new kind of injectable in-situ forming poly(ethylene glycol) (PEG) hydrogel. A series of comprehensive In vitro and In vivo tests have been carried out to test it, and the main research results and conclusions are as follows:1. Water-soluble hydrogel precursors with "clickable" mercapto groups or double bonds were facilely synthesized by direct polycondensation of oligo(ethylene glycol) (OEG) diol with mercaptosuccinic acid (MSA) or maleic acid (MA) catalyzed by scandium trifluoromethanesulfonate (Sc(OTf)3), The 1H NMR results showed that the ratio of corresponding protons’integrals in hydrogel precursors (POEGMS and POEGM) matched the theoretic value, and the molar ratio of OEG to diacid in polymer was close to the feed ratio. The monomodal peak of GPC traces of the two kinds of hydrogel precursors also demonstrated the successful synthesis of clickable PEG derivatives. Under human physiological conditions(pH7.4,37□), the two hydrogel precursors rapidly formed a 3D PEG-based network via thiol-ene "click" reaction within 30 seconds.In the FTIR results, the disappearance of absorption peaks ascribing to the double bonds and thiol groups in the spectra of hydrogel indicated the high conversion of the thiol-ene "click" reaction.2. Through a series of comprehensive experiments in vitro, the hydrogel has been proved to have a excellent biological compatibility, enough mechanical strength(G’ approximately equals 69.2kPa), low swelling rate (< 50%) and proper degradation speed(very little weight loss within 2 weeks). Preosteoblast (MC3T3-E1) and rat bone marrow-drived mesenchymal stem cells (rBMSC) can surivived and proliferated on/in the PEG hydrogel, and be successfully induced into osteogenetic differentiation in osteogenetic culture medium. The hydrogel can also be loaded with rhBMP-2 and keep releasing to promote the proliferation and osteogenetic differentiation of the seeded cells with a effective loading concentration of 1μg/ml. All of these make it a suitable candidate as an injectable hydrogel for further biomedical applications.3. In vivo animal experimental results showed that the hydrogel itself can enhance bone regeneration and repair rat cranial CSD. After the hydrogel loaded with rBMSC was implanted, the bone defects could be calcified and closed within 8 weeks. When the hydrogel was loaded with both rhBMP-2 and rBMSC at the same time, the speed of bone repair and regeneration have soared. It can almost finish the most parts of the CSD repairing within 4 weeks, and the new-bone volume fraction and the trabecular structure were both superior to other groups.In a word, the injectable in-situ forming PEG hydrogel developed in the present study can be facilly made and also is a new type bone implant substitute with great expectation in future clinical application; it could be an excellent bone grafting method to utilize a PEG hydrogel matrix loaded with active rhBMP-2 and/or rBMSC.