The Development Of Novel PDLA/PLLA Hydrogel For Bone Regeneration

Alveolar bone loss due to periodontal disease, cleft palate and other congenital maxillofacial deformities, trauma and tumors can lead to insufficient bone quantity or defects, and affect chewing function, facial beauty and health of patients. These had become the important clinical stomatology problems, so it has become an emphasis point to study the bone augmentation and repairation in oral medicine research. The application of traditional methods of autograft or allograft bone tissue is expensive and risky, and the second surgery will increase the suffering of patients, induce resulting in trauma and increase risk of infection. In addition, allogenic graft material has also led to the spread of infectious diseases and immune rejection response. With the continuous development of bone tissue engineering, new scaffolds for the repair and regeneration of bone tissue provides an alternative method of treatment.Currently, a variety of marine organisms such as coral skeleton, sea urchins and sponges have been a three-dimensional scaffold and the template for the regeneration of bone tissue. Compared with other structural or genetic engineering techniques, these materials are inexpensive, widely available, having the desired density for bone regeneration, shape, and hole formation. However, the rate of degradation of these materials can not be controlled, and there is a certain risk of infection, thus limiting its application. PLA, PGA and PLGA copolymers are the most widely used biodegradable synthetic polymer materials for tissue engineering. Its application forms include fiber scaffold, porous foam and tubular structures. PLA and PGA and PLGA belong to α- polyesters, has been used as scaffolds for bone tissue engineering with good biocompatibility and biodegradability.Because of the specific features and nanometer-sized, nano-materials show the important applications in the biomedical field. Research shows that the nanocomposite has a plurality of controllable aspects of osteogenic effects, such as bone formation, adsorption, migration, proliferation, cell signaling, gene expression and differentiation. With the development and maturity of nanotechnology, biomaterials design increasingly committed to the introduction of nano-sized elements, to produce cell behavior, promote the formation of functional tissue.Due to their possess of bionic structure and highly hydrophilic compatibility, hydrogels have become an important form of bone tissue engineering. Hydrogels have a controlled degradation, unique cell compatibility and injectable. As a new low-cost material, the hydrogel scaffold can induce the complex cellular responses by simple chemical functional groups, without the high cost of complex biological molecules. As a drug delivery system, the hydrogel can direct parcel biological agents by the surface functionalized particles or chemically cross-linked systems(such as cyclodextrins). Thus, the hydrogel stent has been successfully used for bone tissue engineering drugs, antibodies, growth factors, nucleic acids and targeted release. This study was prepared the PDLA-PLLA-dimensional composite hydrogel, and verified biological properties of bone regeneration by in vitro and in vivo experiments.Firstly, water-soluble PDLA-PEG-PDLA and PLLA-PEG-PLLA copolymer were prepared. At the same time, master inorganic components of human bone tissue nano hydroxyapatite(n HA) were added to provide the necessary sites of cell adhesion. Anti-inflammatory drugs rifampin was used as a model, and genipin was used to make the system more stable. Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD) analysis were employed to study the internal interactions. SEM results showed the rich holes, strong connectivity and moderate size. Swelling index experiments confirmed the decrease of the swelling degree. The scaffold can wrap drugs such as model drug rifampicin, which can release the drug slowly.The MC3T3-E1 cells were seeded in PDLA-PLLA-dimensional composite hydrogel scaffold surface. The cell adhesion, proliferation and bone differentiation were detected by scanning electron microscopy SEM, DAPI staining, MTT, quantitative real-time PCR and Alizarin Red staining. SEM results showed that, Gel + PDLA / PLLA + n HA + Gen was helpful to cell adhesion and proliferation. After be cultured with PDLA-PLLA-dimensional composite hydrogel for 24 h and 72 h, MC3T3-E1 cells were fully stretched. DAPI staining and MTT assay showed that, compared with the control groups, the adhesion quantity were increased in the experimental group. Alizarin Red staining results showed that, compared with the control group, Gel+PDLA/PLLA+n HA+Gen osteogenic cells capacity enhancement. The real time-PCR detection indicated that PDLA-PLLA-dimensional composite hydrogel in vitro can promote mouse osteoblasts to differentiate into bone cells, confirming PDLA-PLLA composite hydrogel has a good perspective of osteoblast compatibility.To further study the osteogenic role of scaffold in vivo, calvaria critical size defect model were established in SD rat, and the hydrogel scaffolds were implanted in the skull defect. Micro-CT and hematoxylin- eosin staining were employed to detect the histological changes and evaluate the feasibility and effectiveness of the gel material prepared for guided bone tissue regeneration. The results showed, Gel+PDLA/PLLA+n HA+Gen guide the new bone formation in the bone area.In order to further expand the application of perspective PDLA-PLLA composite hydrogel material. An anti-cancer drug, tetravalent platinum complexes was prepared through oxaliplatin and demethylated cantharidin(DMC) synthesis, and built into the polymer–conjugate system for the drug combination chemotherapy. PDLA-PLLA as a three-dimensional scaffold of the drug release carrier, oxaliplatin can release from the polymer- conjugaterelease drug system, attack the tumor cell DNA, followed by hydrolysis of DMC released.The results showed that oxaliplatin and demethylated cantharidin synthetic polymers can kill ovarian cancer cell SKOV-3, and the killing effect was higher than medication alone. This enhanced cytotoxicity was due to the synergistic effect of oxaliplatin and DMC. Cellular uptake may also be seen by confocal laser microscope(CLSM) clearly. Anti-cancer drugs was added to the PDLA-PLLA-dimensional hydrogel system, which further extends the application of the hydrogel system in terms of repairing bone tissue to kill tumor cells while guided bone repair, to achieve the original bone cancer median treatment.