Study On Modification Of Poly(hydroxybutyrate) And Construct Of Scaffold Used In Tissue Engineering

Tissue engineering has emerged as a new multi-disciplinary field combing engineering science and life science to provide living tissue products that restore, maintain, or improve tissue function. Acting as templates for cell adhesion and growth, scaffolds play an important role in construct of engineering tissue. Thus, scaffold biomaterials should meet a series of physical, chemical and mechanical requirements such as surface and degradation characteristics, blood and cell compatibilities etc. Polyhydroxybutyrate(PHB) is a microbially produced materials with many excellent properties such as biodegradability, biocompatibility, non-toxicity, piezoelectricity etc. But due to its high crystallinity and large spherulite, it shows high brittleness and strong hydrophobic property. At the same time, its process window is rather narrow.In this paper, physical blend and chemical modification were used to improve the properties of PHB using Poly (ethylene glycol)(PEG) with different molecular weight as the second component. At the same time, three-dimensional scaffolds were prepared by freeze-drying techniques and templates method. The biodegradability and biocompatibility were also investigated. The results showed that the PHB/PEG blend and copolymer could be prepared by physical blend and chemical methods. The crystallinity and size of spherulite of PHB decreased after modification. Thus, the thermal stability, hydrophilicity and brittleness of PHB were improved by whether physical blend or chemical modification. PHB three-dimensional porous scaffolds were prepared by freeze-drying technique and microemulsion templates method. The pore size of scaffold prepared by freeze-drying was about several hundred micrometers. While, microemulsion templates was shown to be capable of producing scaffolds of PHB with median pore sizes ranging from 5μm to 30μmin diameter and with micro-pore size ranging from 100nm to 500nm inside the pore wall. This multi-distribution of pore size may be in favor of transferring nutrient fluid and waste effectively so as to benefit the cell growth in three-dimensional porous scaffolds. The degradation of PHB was tested in the presence of distilled water and　lysozyme/PBS buffer solution, respectively. The result revealed that enzyme accelerated the degradation and because of high specific surface area and the hydrophilic addition of PEG, the weight loss of scaffolds was larger than that of membranes. The biocompatibility test showed that biocompatibility of PHB was improved with the PEG content increasing.