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BACKGROUND: Nowadays, the scaffold for tissue engineering have low properties of physical mechanics, poor biocompatibility and has not free regulating degradation as matrix materials.OBJECTIVE: To develop a composite of scaffold for cartilage tissue engineering with higher porosity and good mechanical characteristic, biocompatibility and free regulating degradation as matrix materials.DESIGN, TIME AND SETTING: This experiment was conducted at the Research Institute of Engineering Materials, Lanzhou Jiaotong University from June 2006 to June 2008.MATERIALS: Gelatin, calcium polyphosphate fiber (diameter 10-20 μm) and rosin (size: 355-450μm) were used in the present study.METHODS: Calcium polyphosphate fiber was selected as reinforced materials and gelatin as matrix materials. The calcium polyphosphate/gelatin composite of the scaffold for cartilage tissue engineering were fabricated with a solvent-casting,particulate-leaching method.MAIN OUTCOME MEASURES: The microstructures, properties of physical mechanics and degradation were tested.RESULTS: ①Microcosmic observation: The composites had the 3-D, connectivity network microstructures. ②Physical and mechanical properties of scaffold composite: The experimental value of calcium polyphosphate/gelatin composite of the scaffold was consistent with calculated value. Experimental value of porosity was 60%-80%, meeting the requirement of porosity of tissue engineering scaffold composite. The compress modulus of scaffold would be increased with the crossllnkage increasing; ③The degradable rate of the scaffolds composites deteriorated quickly during 0-2 weeks, and slowly after 2 weeks and reduced with increased crosslinkage; the degradable liquid pH value was maintained between 5 and 7.CONCLUSION: The mechanical property and biodegradable property of calcium polyphosphate/gelatin composite can meet the demand of cartilage tissue engineering. This composite might be one of cartilage scaffold materials for cartilage tissue engineering with potentially broad applicability.
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AIM: To prepare α-tricalcium phosphate (α-TCP)/calcium polyphosphate (CPP) fiber and to study the feasibility of CPP fiber to reinforce calcium phosphate bone cement composites. METHODS: Firstly,α-TCP powder was synthesized using chemical sediment method. Secondly, the α-TCP was mixed with CPP fiber according to different contents and lengths. Finally, bone cement was tempered with firming agent. Solidification time and mechanical property of the samples were measured. Microstructure of hardened sample was observed with scanning electron microscope. RESULTS: When the amount of CPP fibers was 10% and the length was 2 mm, the compressive strength reached 62.5 MPa and the rupture strength reached 12.4 MPa. Scanning electron microscope suggested that CPP fibers with great associativity were well distributed in bone cement. After immersing in Ringer fluid for two months, the CPP fibers did not biodegrade obviously and still had certain function to increase strength and toughness. CONCLUSION: To a certain extent, the CPP fiber can increase strength and toughness of bone cement. Furthermore, α-TCP/CPP composites have good mechanical properties and biocompatibility.
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AIM: A new type of unsaturated poly (ester-amide) viz maleic anhydride-phthalic anhydride-propylene glycol-neopentylene glycol-hexane diamine copolymer was prepared by melt polycondensation and characterized.METHODS: To use it as biodegradable bone fixation polymer materials, the flexural strength of unsaturated poly (ester-amide) prepared under different heat treatment conditions was measured after depth cross-linking. The degradation and hydrolysis of the polymer were investigated in phosphate buffer (0.1 mol/L, pH7.4) at 37 ℃ and in 0.1 mol/L NaOH standard solution at room temperature.RESULTS: The results obtained indicate that increasing heat treatment time or temperature can dramatically increase the flexural strength of cross-linked unsaturated poly (ester-amide). The maximum flexural strength of the cross-linked polymer containing 50 wt% of cross-linker was 123 MPa. After degradation 3 months, the flexural strength of the cross-linked polymer that contained 50 wt% of cross-linker and was heated at 195 ℃ for 18 hours could maintain as high as 114.3 MPa.Heat treatment conditions and cross-linker content play an important role to control the mass loss of the cross-linked polymer during the hydrolysis. The polymer exhibits bulk erosion property.CONCLUSION: The preliminary results obtained suggested that the copolymer might be used as bone internal fixation material.
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BACKGROUND:When bone cement solidifies fast,the bone cement consistency will be decreased.resulting in difficulty in molding.DESIGN,TIME AND SETTING:Open experiment,performed in the Laboratory of Department of Materials,Lanzhou Jiaotong University between March 2005 and August 2006.gelatin were mixed with citric acid to produce hardening liquid.Then bone cement power and hardening liquid were mixed to form a paste,I.e.,bone cement.METHODS:Setting time of bone cement was determined using a Vicat apparatus.The compressive strength of bone cement at different proportions was tested using MTS-810 material tester.After 2 months of physiological saline soaking at 37℃.the microstructure of solidified bone cement was observed using scanning electron microscope.MAIN OUTCOME MEASURES:Setting time and compressive strength of bone cement,pH value of hydrated bone cement and the microstructure.RESULTS:After adding chitosan and gelatin in the hardening liquid.the consistency of the concoction obviously increased,the setting time became a little longer and the water-resistance of samples was enhanced.therefore the samples could be easily molded.But the compressive strength of the bone cement decreased a little.The pH value of the hydrated bone cement increased gradually with time and was close to the pH value of physiological saline at hour 24.The compressive strength of bone cement was achieyed at 24 hours and it almost did not change after 48 hours.the drawback of ceramic HA,including sintering and difficulties in shaping.It has the characteristics of simple-producing,easy application and low heat energy.
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Drug slow release in osteomyelitis treatment is an important biomedical problem, to prepare the high effect drug sustained-release bead is the sticking point. A sustained-release bead system consisting of gentamicin sulfate in biodegradable poly(dimer acid-tetradecandioic acid) copolymer [P(DA-TA), WDA: WTA= 50: 50] is prepared by melt casting which may be useful in osteomyelitis treatment. The stability at room temperature and the in vitro release profile in distilling water, in 0.9% saline buffer and in 0.1 mol/LpH7.4 PBS at 37 degrees C of the bead are determined, the drug release behavior in vitro follows the first order release kinetics and Peppas release kinetics equation. In vitro bacteriostatic activity studies demonstrated that the beads possessed desired bacteriostatic activity and lasted for 50 days for Staphylococcus aureus and Escherichia coli, which are common bacteria for infections in bone. All the above suggest that the biodegradable sustained-release beads may be a new treatment device for osteomyelitis treatment.