ABSTRACT
BACKGROUND: Presently, the biomaterial used in ligament tissue engineering such as collagen protein, polylactic acid, polyglycolic acid, small intestinal submucosa, glycan and nanomaterial are characterized by rapid degradation, resulting in inflammatory reaction after applying in host.OBJECTIVE: To investigate mechanical strength and in vitro degradation of silk scaffold and explore the reaction to macrophages.DESIGN: Controlled experiment.SETTING: Experiments were performed at the Department of Orthopaedics, Union Hospital, Huazhong University of Science and Technology from September 2004 to January 2005.MATERIALS: White raw Bombyx mori silkworm fibers of size 20/22 (according to the manufacturer) were obtained from the market. Bundles of 30 parallel fibers were prepared for a bundle of scaffold, which was put into fervens 5g/L Na2CO3for degumming. Ratio of Na2CO3 solution (Ml) to raw silk (g) was 1000.METHODS: In vitro degradation: 8cm long silk scaffold was weighed after drying. Subsequently, the silk scaffold was separately dipped into phosphate buffer saline (PBS) and 1.0g/L collagenase prepared with PBS. Twelve weeks later, silk scaffold was weighed to calculate weight loss rate. Simultaneously, tensile test was performed to detect the ultimate tensile strength (UTS) of samples. Culture of monocyte strain RAW264.7:2×108L-1 macrophage suspension (1mL) were separately added in a silk scaffold group, a control group and a lipopolysaccharide (LPS) group. At days 1 and 7, cell supernatant was collected from each group. Tumor necrosis factor-α(TNF-α) levels were measured by enzyme linked immunosorbent assay (ELISA).MAIN OUTCOME MEASURES: ① Changes in weight loss rate and UTS of the silk matrices after incubated with collagenase and the PBS. ②TNF-αlevels in the supernatant of each groups at days 1 and 7.RESULTS: Mass of silk matrices reduced by over 50% after incubated with collagenase for 8 weeks, but no change was found in PBS. UTS decreased by over 50% 8 weeks after incubated with collagenase, but no change was detected in PBS. At days 1 and 7, TNF-α levels in the supernatant was less in the silk scaffold group; TNF-α levels in the supernatant was significantly higher in the LPS group than in the silk scaffold group (P<0.01), but no significant difference in TNF-α levels was measured between the silk scaffold group and the control group (P>0.05).CONCLUSION: After 12-weeks degradation, silk scaffold still has good mechanical properties. Macrophages possess immunological inertia at days 1 and 7 after inoculated with macrophages.