The Preparation of Polymer Composites for Bone Regeneration and Osteosarcoma Treatment

Author:Shao Zuo Zuo

Supervisor:huang yu bin


Degree Year:2019





There are 213 bones(including the sesamoid bones)composed of the adult human skeleton.They can be divided into four categories:long bones,irregular bones,flat bones and short bones.With the structure support of the skeleton,the movement of the body parts and muscles can be allowed.Besides,the inner organs in our body also need the protection of the skeleton.Bones are served not only as storage of cytokines and growth factors but also used to regulate the acid-base or the mineral balance.It also provides enough spaces for hematopoiesis within the marrow.Osteons are the main component of cortical and trabecular bone.Moreover,the cortical bone accounts for 80%of the human skeleton,which is usually formed in a lamellar pattern with the collagen fibrils filling in.The periosteum and endosteum are on the outer and inner surface of the cortical bones,respectively.There are nerve fibers,osteoclasts,osteoblasts and nerve fibers in them,which are critical for the bone regeneration.Because when the rate of bone formation is faster than resorption on the surface of periosteum,the bones regenerate.However,when the rate of bone resorption is faster than formation on the surface of endosteum,the marrow space expands and bone loss.It is reported that Bone defects are usually formed by the following reasons:trauma,infection,tumor removal,surgical debridement of osteomyelitis.Subsequent therapy caused by bone loss,defect and fracture,is a major issue in orthopedics.It is placing social and financial burdens on our society with the increase of the aging population.Because of the limited availability,postoperative infection and hemorrhage of an autograft,immune rejection,and the epidemic spreading risks of allografts and xenografts,natural bone grafts are unable to meet the clinical demand.Hence,based on the causes of bone defects,the corresponding polymer composites have been made.Their effects on bone regeneration,anti-inflammation,anti-infection and osteosarcoma treatment have also been investigated.The research contents and conclusion are as follows:(1)The bioactive Gel/(nHAp-BMP-2)composite hydrogel was produced and its effects on skull bone regeneration in vivo were also investigated.This hydrogel was mainly made of gelatin methacrylamide(GelMA)and four-armed PEG10K methacrylamide(four-armed PEGMA)with the combination of nHAp-BMP-2.It not only mimicked the chemical components of collagen matrix but also had good mechanical strength.The introduction of nHAp-BMP-2 endowed the hydrogel with sustainable bioactivity,which benefited the 2D and 3D culture,proliferation,differentiation of bone marrow mesenchymal stem cells.Besides,after treatment of a rat calvarial defect model for 12 weeks,the Gel/(nHAp-BMP-2)group showed the highest ratio of new bone(64.38±17.22%)compared to those of the other groups.(2)Through RAFT polymerization,a mesoporous silica nanoparticle-poly(N-isopropylacrylamide-b-(2-(dimethylamino)ethyl methacrylate),MSN-PNI-PDMA,was synthesized to be a multi-functional carrier with bacteriostasis function.Then its application potentials in anti-inflammation and enhanced osteoblast calcification were also investigated.Specifically,DXMS was loaded into MSN-PNI-PDMA(D@MPP)to improve its ability of anti-inflammation and promote homeostatic equilibrium for calcification formation.Besides,with the combination of the ECM-derived peptides(Sequence:Succinic acid-GTPGPQGIAGQRGVV,P15-Suc),the target product,P15 and D@MPP composite nanoparticles(P15/D@MPP)revealed a significant improvement of mineralization and alkaline phosphatase expression in the preosteoblasts(MC3T3-E1).After intramuscular implantation in mice for four weeks,the results analyzed from computed tomography(CT)images and histological examination indicated that P15/D@MPP drug delivery system could promote ectopic bone formation.(3)IR-780 iodide was loaded by the mercaptopropionic acid grafted poly(ethylene glycol)-block-poly(ε-caprolactone)-block-poly(allyl glycidyl ether)[mPEG5K-PCL10KPAGE6(MPA)]copolymer to form nanomicelles(IR-780@TBMPA)in aqueous solution.On account of the hydrophobic and electrostatic interaction between mPEG5K-PCL10K-PAGE6(MPA)and IR-780,the IR-780@TBMPA micelle was structurally stable with improved solubility,light stability and biocompatibility.The encapsulation of IR-780 indicated no influence on its original physicochemical property,showing good optical and thermal characteristics.The drug-loaded micelles had appropriate microscopic size for endocytosis,displaying significant cytotoxicity to Saos-2 cells under NIR laser irradiation.In addition,the phototoxicity generated by photothermal and photodynamic effect of IR-780@TBMPA under 808 nm laser irradiation was also investigated against Saos-2 cells.Furthermore,the superior accumulation of IR-780@TBMPA in tumor tissues provided sufficient hyperthermia to kill tumor cells,indicating its potential in cancer clinical treatment.(4)Combining with Au,nano-hydroxyapatite and chitosan,the double-layered Au@nHAp/chitosan hydrogel was produced.The top layer was the thermal-protect coating,consisting of chitosan and benzaldehyde-terminated four-armed PEG10k(four-armed PEGBA).The bottom layer had photothermal properties by introducing the Au@nHAp nanoparticles.These two layers could be self-healed together due to the existence of Schiff base.And under the radiation of 653 nm laser,the difference of the temperature tested on the top and bottom site of this hydrogel was significant and kept stable after irradiation for multiple times.Moreover,it could be also adjusted by the Au content of Au@nHAp nanoparticles.By co-culture with the osteosarcoma cells(MG-63)and human umbilical vein endothelial cells(HUVEC)in the dark conditions for 48 h,the hydrogel was proved to have good biocompatibility.Next,whether the double-layer gel can prevent skin bums while treating osteosarcoma with light will be tested in vivo.Besides,whether the porous structure of the gel will adsorb exudate and free tumor cells after tumor resection,and prevent tumor recurrence under thermal therapy will be also investigated.