[Injectable borate glass/chitosan composite as drug carrier for treatment of chronic osteomyelitis].

OBJECTIVE: To evaluate the characterization, biocompatibility in vitro and in vivo, and antimicrobial activity of an injectable vancomycin-loaded borate glass/chitosan composite (VBC) so as to lay the foundation for its further clinical application. METHODS: The solid phase of VBC was constituted by borate glass and vancomycin, liquid phase was a mixture of chitosan, citric acid, and glucose with the proportion of 1 : 10 : 20. Solid phase and liquid phase was mixed with the ratio of 2 : 1. Vancomycin-loaded calcium sulfate (VCS) was produced by the same method using calcium sulfate instead of borate glass and saline instead of chitosan, as control. High performance liquid chromatography was applied to detect the release rate of antibiotics from VBC and VCS, and minimum inhibitory concentration (MIC) was tested by using an antibiotic tube dilution method. The structure of the VBC and VCS specimens before and 2, 4, 8, 16, and 40 days after immersion in D-Hank's was examined by scanning electron microscopy, and the phase composition of VBC was analysed by X-ray diffraction after soaked for 40 days. Thirty-three healthy adult New Zealand white rabbits (weighing, 2.25-3.10 kg; male or female) were used to establish the osteomyelitis models according to Norden method. After 4 weeks, the models of osteomyelitis were successfully established in 28 rabbits, and they were randomly divided into 4 groups (groups A, B, C, and D). In group A (n=8), simple debridement was performed; in groups B and C (n=8), defect was treated by injecting VCS or VBC after debridement; and in group D (n=4), no treatment was given. The effectiveness of treatment was assessed using radiological and histological techniques after 2 months. RESULTS: The releases of vancomycin from VBC lasted for 30 days; the release rate of vancomycin reached 75% at the first 8 days, then could reached more than 90%. The releases of vancomycin from VCS lasted only for 16 days. The MIC of VBC and VCS were both 2 microg/mL. The VCS had a smooth glass crystal surface before immersion, however, it was almost degradated after 4 days. The fairly smooth surface of the VBC pellet became more porous and rougher with time, X-ray diffraction analysis of VBC soaked for 40 days indicated that the borate glass had gradually converted to hydroxyapatite. After 2 months, the best result of treatment was observed in group C, osteomyelitis symptoms disappeared. The X-ray scores of groups A, B, C, and D were 3.50 +/- 0.63, 2.29 +/- 0.39, 2.00 +/- 0.41, and 4.25 +/- 0.64, respectively; Smeltzer scores were 6.00 +/- 0.89, 4.00 +/- 0.82, 3.57 +/- 0.98, and 7.25 +/- 0.50, respectively. The scores were significantly higher in group D than in groups A, B, and C (P < 0.05), and in group A than in groups B and C (P < 0.05). The scores were higher in group B than in group C, but no significant difference was found (P > 0.05). CONCLUSION: The VBC is effective in treating chronic osteomyelitis of rabbit by providing a sustained release of vancomycin, in addition to stimulating bone regeneration, so it may be a promising biomaterial for treating chronic osteomyelitis.

Archaefructaceae, a new basal angiosperm family.

Archaefructaceae is proposed as a new basal angiosperm family of herbaceous aquatic plants. This family consists of the fossils Archaefructus liaoningensis and A. sinensis sp. nov. Complete plants from roots to fertile shoots are known. Their age is a minimum of 124.6 million years from the Yixian Formation, Liaoning, China. They are a sister clade to all angiosperms when their characters are included in a combined three-gene molecular and morphological analysis. Their reproductive axes lack petals and sepals and bear stamens in pairs below conduplicate carpels.