Preparation And Characterization Of Oxygen-Carrying Scaffold For Tissue Engineering

The ideal scaffolds should not only sustain cells physically, but also possess some biological functions, which can rugulate the growth and metabolism of cells. It is known that oxygen is an important component of the celluar microenvironment, serving as both metabolic substrate and signaling molecule. However, hypoxia is a common problem in tissue engineering,which is urgently to be solved. Therefore,there is potential value to develop such a scaffold that could carry proper oxygen. Hemoglobin based oxygen-carriers (HBOCs) have favourable property of oxygen-carring and oxygen-releasing. A novel scaffold which possesses the function of carrying oxygen could be developed by grafting HBOCs to the surface of traditional scaffold. In this paper, the preparation, modification and biocompatibility of poly-L-lactic acid(PLLA)/HAP composite scaffold was studied. First, the 3D scaffold with high porisity, fine interconnectivity and controllable pore size was prepared by the combination of Thermal-Induced Phase Separation and Porogen method. Then the HBOCs were grafted to the surface of scaffold by photooxidation and chemical surface modification, which not only improved biocompatability of the scaffold, but also endowed the scaffold with the function of oxygen-carrying. Lastly, the L929 cells were impanted on the surface of the scaffold, and were cultured in vitro, which was used to study the effect on biocompatibility by modification.PLLA/HAP porous scaffolds were prepared by Porogen/Phase Separation with porogen of the paraffin spheres. Effects of paraffin sphere size,paraffin sphere dosage, heating treatment of paraffin sphere, PLLA centration, HAP dosage and coaring time on the microstructure and properties of the PLLA scaffold. The porous scaffolds with proper pore size(200-400μm), high porosity(above 90%) and good interconnection could be prepared under required conditions.By treatment under vacuum, the fluid was easily filled in the 3D scaffold. The Scaffold was immersed into hydrogen peroxide solution(30%wt) under UV-light in order to introduce hydroperoxide groups on the interface of the scaffold. The content of hydroperoxide groups among the interface of the scaffold was measured with Iodometry method. The effect of photooxidization time and temperature on the content of hydroperoxide groups was discussed. It turned out that the content of the hydroperoxide groups increased initially and then decreased with the photooxidization time, and the process of photooxidization can be accelerated under a high temperature.Using the hydroperoxide groups on the photooxidized interface of the scaffold as initiators, hydrophilic mononer methacrylic acid(MAA) was polymerized on the interface of the scaffold under Fe2+ induction, wherein, carboxyl groups were introduced to the interface of the scaffold. Using 1-ethyl-3-(3-dimethylamino propyl)-carbodiimide(EDAC) as the activiator, the amino groups in the protein reacted with the carboxyl groups, resulting that HBOCs were grafting on the intersurface of the scaffold. The result of contact angle testing indicated the improvement of hydrophilicity of the surface. By FT-IR testing, there were remarkeble absorption peaks between 3000-3700cm-1, respectively corresponding to-COOH and -CONH2 which demonstrated that HBOCS were successfully grafted on the scaffold. The oxygen absorption was increased by oxygen-carrying testing, which demonstrated that the scaffold had the function of oxygen-earring.L929 cells were implanted into the 3D scaffold,and cultured in vitro, and the effect of scaffold midification on the biocompatibility was studied. Observig under Scanning Electronic Microscope, the modified scaffold had noteble advantage over the controled scaffold for the growth of L929 cells.The MTT assay also demonstrated that the surface modified scaffold had better ability for cell attachment and preliferation.