A Study On The Preparation Of PHEMA/SiO₂/n-HA Hydrogel Films And Its Biocompatibility

Articular cartilage injury is a common disease in orthopaedics. Articular cartilage injury repaired ineffectively would lead to the disorder of histological environment of articular cartilage, mechanical environment and biological environment, then expand the lesion area, and eventually result into osteoarthritis and other serious diseases. It is a key to find the ideal materials for bone trauma in the treatment of such diseases.Natural materials and synthetic materials are the main kinds of scaffolds used for research in cartilage tissue engineering. Natural materials have good repairing effect but poor biomechanical property, so they can not provide timely stress support after transplantation, which results in harmful stress damage of transplanted tissue and abnormal stress concentration around the cartilage and affects the recovery effect. Synthetic materials have good biomechanical property but poor hydrophilicity, so water molecules are difficult to diffuse in the synthetic materials and the transport of nutrition is restrained due to their hydrophobicity.Poly-Hydroxyethyl methacrylate(PHEMA) hydrogel films has good pliability, mechanical strength, oxygen permeability and hydrophilicity, which are beneficial to exchange nutrition and metabolites between internal and external of joint. The biomechanical and mechanical properties of PHEMA are not ideal, so it is necessary to synthesize PHEMA composite to improve its properties. In this paper, SiO₂ and n-HA are introduced to PHEMA in order to improve the biomechanical and mechanical properties. Addition n-HA into PHEMA makes the synthetic material closer to the natural biomimetic materials for osteocyte growth. A double frame of PHEMA/SiO₂/n-HA inorganic composite hydrogel films is prepared by introducing two kinds of inorganic components (SiO₂ and n-HA ) into the PHEMA. Biological study has proved that the material has good biocompatibility and is suitable to be used as bionic repairing material for bone trauma.The main work of this paper:1.PHEMA hydrogel films are prepared by using H2O as solvent and MBA as crosslinking agent. The micro appearance of PHEMA was characterized by SEM. Effect of the addition amount of MBA on the swelling property and shrinking dynamics of PHEMA were studied. The results showed that the surface of PHEMA hydrogel films with 7.5wt%MBA is smooth and has less folds and grooves, close to the structure of cartilage. The addition of 7.5wt%MBA increases the strength and reduces the friction without significantly reducing the water absorption. This material is stable under physiological temperature and closer to human articular cartilage.2. PHEMA/SiO₂ and PHEMA/n-HA inorganic composite hydrogel films were prepared respectively. Two kinds of inorganic ingredients can be mixed very well with HEMA. Subchondral bone is rich in calcium, so two kinds of inorganic ingredients were introduced into bionic perichondrium to make the synthetic PHEMA composites closer to original material. PHEMA/SiO₂/n-HA inorganic composite hydrogel films were prepared by polymerization HEMA with nano-SiO₂ and n-HA through the initiator. The physical and chemical properties, swelling properties and mechanical properties of PHEMA/SiO₂/n-HA inorganic composite hydrogel films were discussed.PHEMA inorganic composite hydrogel films containing 0.5 wt%SiO₂/ and 1 wt%n-HA is a double-frame structure. It has better swelling property and water retention property than PHEMA, PHEMA/ SiO₂ and PHEMA/ n-HA inorganic composite hydrogel films respectively. PHEMA/SiO₂/n-HA inorganic composite hydrogel films have better tribological properties and can meet the request of normal friction after replacement of damaged articular cartilage. Protein adsorption experiments showed that the double-frame structure material has good adsorption of protein, and can not occur protein denaturation in the biological protein solution. The result indicated the prepared inorganic composite hydrogel films—PHEMA/SiO₂/ n-HA have good biocompatibility and will provide a good living environment to the growth of biological cells. 3.The effect of PHEMA inorganic composite hydrogel films on proliferation of the rabbit chondrocyte and on the recovery and inflammatory reaction of transplanted joint in vivo were observed. Rabbit hip chondrocytes is cultured by collagenase digestion. Immunity cell chemical method is used to identify the chondrocytes of the rabbit joint. Chondrocyte proliferation was determinded by MTT. Chondrocyte growth cycle was measured by flow cytometer. The basic phosphatase activity of the rabbit chondrocyte was detected by chromatometry. Joint fluid IL-1β, TGF-β, TNF-αare measured by ELISA. Joint recovery was observed by using HE staining. In vivo test, 10 rats (derived from healthy adult New Zealand white rabbits) were prepared with bilateral knee defect model 1.5cm in diameter, using the same body control methods with the experimental side (left) transplant synthetic material and the control side autotransplant bone tissue of defect part. The result indicated that PHEMA /0.5% SiO₂ inorganic composite hydrogel films can not change the proliferation activity of the rabbit chondrocyte. The proliferation reactivity of the chondrocyte is related to the content of n-HA in PHEMA/0.5%SiO₂/n-HA inorganic composite hydrogel films. PHEMA/0.5%SiO₂/n-HA inorganic composite hydrogel films containing 1%n-HA is best for the growth of the chondrocyte and promote the defect repair of the cartilage injury.