BACKGROUND:Calcium phosphate bone cement has been applied to clinical surgery because of its good biocompatibility and osteoconduction. However poor mechanical properties and lack of osteoinductivity limit its wide application.
OBJECTIVE:To develop calcium phosphate cement incorporated with N-acetylcysteine (NAC) loaded silk fibroin microspheres (SFM), which is a kind of new injectable bone graft material with slow-release function, and evaluate its physical and chemical properties and cel compatibility.
METHODS: Empty SFMs were prepared with emulsion solvent evaporation to absorb NAC solution of different concentrations by NAC-SFM and the concentration of NAC at the maximum drug loading ratio was determined. Then, NAC-SFM was loaded into calcium phosphate bone cement to test the drug release propertiesin vitro. MC3T3-E1 osteoblasts were cultured on the surface of NAC-SFM calcium phosphate bone cement and cel attachment and growth were observed by scanning electron microscope. Additionaly, MC3T3-E1 cels were cultured with three kinds of bone cement extracts (calcium phosphate cement, SFM-calcium phosphate cement, NAC-SFM-calcium phosphate cement, as wel as cultured in theα-minimum essential medium containing a volume fraction of 10% fetal bovine serum and 1% penicilin-streptomycin double antibody as the control. MTS assay was used to evaluate cel proliferation.
RESULTS AND CONCLUSION:Microspheres in the composite bone cement presented with smooth surface, same size, diffused distribution and no obvious destroy. Thus, the SFM could remain stable in the reaction process of the composite bone cement. The double slow release system which contained silk fibroin microspheres and calcium phosphate bone cement showed a significant decrease in the cumulative release percentage of NAC within the first 24 hours compared with the control group (P < 0.05). In the next 28 days, the release speed of NAC was significantly lower in the NAC-SFM-calcium phosphate cement group than the calcium phosphate cement group (P< 0.05). In addition, different extracts had no significant cytotoxicity to the growth of MC3TC-E1 cels. Thus, the NAC-SFM-calcium phosphate cement has good cytocompatibility, which provide a new insight into the development of bone repair biomaterials.

BACKGROUND:Calcium phosphate cements (CPCs) possess the bio-degradation and osteoconduction, and its final hydration product, hydroxyapatite, is the main inorganic constituent of bones. However, its poor mechanical property makes it unable to be used for repairing weight-bearing bone defects. OBJECTIVE:To develop a kind of bioactive bone cements with decent biomechanical property and biocompatibility. METHODS:6%silk fibroin aqueous solutions containing different concentrations of N-acetylcysteine (0, 10 and 25 mmol/L) were prepared. Each cement sample was prepared by mixing the curing liquid andα-tricalcium phosphate powder with the ratio of 0.4 mL:1 g;α-tricalcium phosphate powder mixed with ddH2O as control group. The compressive strength, setting time of the cements were measured. The crystal components of the cements were characterized using X-ray diffraction and the microstructure was observed using scanning electron microscope. MC3T3-E1 cel s were seeded onto the material in each group, and cel morphology was observed under scanning electron microscope at 24 hours. MC3T3-E1 cel s were cultured in the extract of each material, cel proliferation was detected at 1, 3, 5 and 7 days, and the lactate dehydrogenase level was detected at 1 and 3 days. RESULTS AND CONCLUSION:X-ray diffraction and scanning electron microscope showed that the final hydration products ofα-tricalcium phosphate in al specimens were hydroxyapatite. When the concentration of N-acetylcysteine was 25 mmol/L, the compressive strength of the material reached (49.39±1.68) MPa, with the initial setting time of (21.77±1.07) minutes and the final setting time of (31.88±1.69) minutes. There was no significant difference in cel morphology among cements. These results suggest that the cement containing N-acetylcysteine exhibites good biocompatibility and high mechanical strength.

Objective: To explore the protective effect of Baoyuan Qiangshen Capsule No. Ⅱ (BYQS) and its mechanism in treating chronic renal failure (CRF). Methods: Sixty CRF patients were divided into 2 groups randomly, the treated group used BYQS combined with Lotensin and the control group administered with essential amino acid combined with Lotensin. Changes of renal functions and tubular labelled proteins were observed. Results: The markedly effective rate and total effective rate of the treated group were 63.3% and 93.3% respectively, and those of the control group were 30.0% and 56.7% respectively, the effect of the treated group was obviously better than that of the control group (P<0.01). In the treated group after medication, blood urea nitrogen, serum creatinine and clearance rate of creatinine were improved significantly (P<0.01), while Tamm-Horfau protein increased significantly (P<0.01). Conclusion: BYQS could alleviate tubular interstitial injury significantly so as to improve the renal function and enhance the effective rate in treating CRF.