Studies On Production And Medicine Application Of Poly(3-Hydroxybutyrate-co-3-Hydroxyoctanoate)

Polyhydroxyalkanoates(PHAs) are polymers that are produced by many bacteria and accumulated as intracellular granules. It not only has the characteristic of petrochemical plastics but also has the biodegradability and biocompatility. These biopolymers have been evaluated for a variety of medical applications and new kinds of environment-friendly material that provide a novel way to resolve white-pollution. The most common polyhydroxyalkanoate produced by microbiology is polyhydroxybutyrate (PHB). PHB has a relatively high melting point and less flexile elasticity which restrict its application in medicine. Middle-chain-length PHAs, which consist of HB monomer and long-carbon-chain monomers are new type of PHAs family. Their mechanical properties are better than PHB, which made them more useful in medicine application.This paper describes the production of poly(3-hydroxy-butyrate-co-hydroxyoctanoate) [P(HB-HO)] by a Sinorhizobium fredii strain using sodium dodecanoate as auxiliary carbon source and glucose as the primary carbon source. The results showed that the technique of fermentation and purification of P(HB-HO) has been optimized. This technique has fewer steps which are easy to operate. The recovery rate of P(HB-HO) was above 95 per cent and the purity reached 98 per cent. Its molecular weight was between 11.2 × 10~4Da and 22.1 × 10~4Da. P(HB-HO) can be used as controlled-release and tissue-inducing material. A patent application has been submitted to Chinese Patent Office.At the same time, the rapid detection of endotoxin in P(HB-HO) removal of endotoxin were studied. The chromogenic technique of limulus test was adopted to detect the bacterial endotoxin in P(HB-HO) latex. This technique which has higher repeatability, sensitivity and simple operating procedures was considered to be the best detection method of endotoxin. It was found that the endotoxin content in P(HB-HO) could be controlled less than 20 EU/g by using chloroform extraction under optimized conditions and usinghydrogen peroxide removal endotoxin.Based on those experiments, biodegradability of P(HB-HO) was also investigated. According to the results of degradation tests in vitro, it was showed that the degradation rate of P(HB-HO) was 13 per cent when immerged into the lysozym/PBS buffer solution for 42 days. The degradation rate of P(HB-HO) was lower than PHB. The result of P(HB-HO) degradation in vivo demonstrate that the 5mm X 5mm P(HB-HO) had been completely digested after implanted into hypoderm of mice for 5 weeks.The acute and chronic toxic tests of P(HB-HO) were also studied. The results of acute and chronic toxic tests displayed that P(HB-HO) had no acute toxicity. The result of chronic toxic test demonstrated that there were no significant differences between the results of test and control groups.To sum up, this new medical biodegradable material which purified by the optimal extract method and removal of endotoxin has good biocompatibility and biological safety.