Lian Qin

Preparation of chitosan–gelatin hybrid scaffolds with well-organized microstructures for hepatic tissue engineering

The structural organization of natural liver is instrumental in the multifunctionality of hepatocytes, and mimicking these specific architectures in tissue-engineered scaffold plays an important role in the engineering of an implantable liver equivalent in vitro. To achieve this goal, we have developed a novel fabrication process to create chitosan-gelatin hybrid scaffolds with well-organized architectures and highly porous structures by combining rapid prototyping, microreplication and freeze-drying techniques. The scaffolds obtained not only have analogous configurations of portal vein, central vein, flow-channel network and hepatic chambers, but also have high (>90%) porosity, with the mean pore size of 100microm. Swelling and degradation studies showed that the scaffold has excellent properties of hydrophilicity and biodegradability. A hepatocyte culture experiment was conducted to evaluate the efficiency of the well-defined chitosan-gelatin scaffold in facilitating hepatocyte growth in the inner layer of the scaffold in vitro. Scanning electron microscopy and histological analysis showed that hepatocytes could form large colonies in the predefined hepatic chambers, and these cavities could the completely filled with hepatocytes during 7 day culture. Albumin secretion and urea synthesis further indicated that the well-organized scaffolds were more suitable for hepatocyte culture.

Mechanical Performance of Chitosan Fiber/Calcium Phosphate Cement Composite for Artificial Bone

Chitosan fiber(CF)as reinforcement to improve the mechanical properties of calcium phosphate cement(CPC)is presented,while CF/CPC composite artificial bone with concentric fiber structure that mimics the microstructure of natural bone is fabricated.Special resin precise moulds produced by rapid prototyping(RP)are used to prepare two types of cylindrical CF/CPC artificial bones(φ20mm×20 nun andφ10 mm×20mm),which are evaluated respectively by initial intensity and in vivo intensity experiment.The initial strength of the CF/CPC composite specimens is 11～26 MPa,significantly higher than CPCs 4～10 MPa.And the porous structure and the macropores,which are gradually achieved for bone growth with the dissolution of chitosan fibers during the canine condyle defect repairing,do not lower mechanical properties of the implanted CF/CPC composite artificial bone.In conclusion,the existence of chitosan fibers can achieve the needed initial strength for CFC while tissue regeneration is occurring,and create porous structure for bone growth to turn to strengthen the implant when the fiber is dissolved,and this alleviate s the conflict between artificial bones porous structure and its strength.

The Research of Technique on Fabricating Hydrogel Scaffolds for Cartilage Tissue Engineering Based on Stereo-lithography

Based on stereo-lithography, the polyacrylamide hydrogel scaffolds with controlled accurate internal structures were fabricated. The structure accuracy of the scaffolds was evaluated by the size measurement compared with the CAD model. The mechanical property evaluation showed that the hydrogel compressive modulus of elasticity reached 4.54MPa, which was similar to that of the articular cartilage, therefore meeting the basic requirements of cartilage tissue engineering. The technique based on stereo-lithography showed promising in fabricating cartilage scaffolds.

3D Printing and application of large-size joint os-teochondral scaffolds

Implantation and long-term failure of artificial joints can cause unrecoverable tissue loss, whereas small-scale biodegradable osteochondral scaffolds can restore the mechanical environment and induce tissue regeneration within articular lesions, thus providing a new therapeutic strategy for repairing large-size defects. However, treatment development has been challenging because of the complex physical structure and mechanical environment of the lesions, and the demanding manufacturing techniques and surgical implantation strategies for multi-material composite scaffolds. This paper presents a novel multi-material osteochondral scaffold, and its bio-manufacturing technique and implantation. To induce tissue growth, PEG (polyethylene glycol), β -TCP ( β -tricalcium phosphate), and PLA (polylactide) biomaterials are selected to develop the new scaffolds. Based on limited radiological image data, techniques for reverse engineering, finite element analysis, and 3D printing are used to establish the cartilage lesion model in a sheep knee joint. Based on the mapping relationship between the scaffold physiological characteristics and joint defect mechanical properties, large-size biomimetic osteochondral scaffolds and their fixations are designed to fasten themselves securely to defects. Experiment results show that scaffold implantation restores the defects initial mechanical environment. Therefore, the proposed large-size osteochondral scaffolds through 3D printing technique is expected to provide a new treatment strategy for repairing large osteochondral defects.