BACKGROUND:An ideal scaffold material needs appropriate degradation rate and certain mechanical properties, but the traditional colagen sponge scaffold has rapid degradation velocity and low mechanical strength, which is easy to colapse and difficult to maintain its natural form. Traditional cross-linking methods also have the problems of cytotoxicity or colagen denaturation, severely limiting the application of colagen. OBJECTIVE:To design a new cross-linking method for colagen and to optimize the self-assembly process so as to develop a colagen sponge scaffold with good mechanical properties and resistance to degradation. METHODS:Colagens were modified by self-assembly technology to prepare colagen fibrils which were then freeze-dried into fibrilar colagen sponges. Meanwhile, we optimized the conditions of self-assembly by using orthogonal experiment based on univariate analysis of the effect of initial colagen mass concentration, final phosphate concentration and pH value on the conversion yield of colagen self-assembly. RESULTS AND CONCLUSION:We optimized the conditions of self-assembly revealed that the optimum conditions to prepare colagen fibrils were determined as pH=8.0, initial colagen concentration=2 mg/mL, and final concentration of phosphate=15 mmol/L. The results of scanning electron microscope showed that fibrilar colagen sponges were characterized by refined porous structure which was connected by colagen fibrils. In addition, the fibrilar colagen sponges showed better equilibrium-sweling ratio, water retaining property and mechanical strength compared with unmodified colagen spondages (P < 0.05), to solve the problems in rapid degradation.

BACKGROUND:Studies have found that adipose-derived stem cells (ADSCs)/collagen complexes can promote the ADSCs differentiation and maturation into mature adipocytes and promote angiogenesis.OBJECTIVE:To explore the biological properties of the ADSCs/collagen sponge composite material and to detect its effect on angiogenesis.METHODS:(1) ADSCs were cultured on collagen sponge (experimental group) or cultured alone (control group).After 24 hours of culture,cell adhesive rate of ADSCs was determined with flow cytometry.After 2,4,6 days of culture,cell proliferation and level of vascular endothelial growth factor (VEGF) in the culture medium were detected.(2) Chick embryo chorioallantoic membranes were exposed and incubated for 7 days and then divided into four groups:0.2 mL of sterile PBS was added in the blank group,0.2 mL of 2× 108/L passage 3 ADSCs suspension was added in the ADSCs group,collagen sponge was added in the collagen sponge group,and collagen sponge with 0.2 mL of 2× 108/L passage 3 ADSCs suspension was added in the composite group.After 7 days of incubation,the microvessel count around the chorioallantoic membrane was measured.RESULTS AND CONCLUSION:(1) The cell adhesive rate of ADSCs to collagen sponge reached to (93.04±0.67)％.(2)The absorbance value (at 6 days of culture) and level of VEGF (at 4 and 6 days of culture) in the experimental group were significantly higher than those in the control group (P ＜ 0.01 or P ＜ 0.05).(3) Compared with the blank group,the number of microvessels was significantly higher in the ADSCs,collagen sponge and composite groups (P ＜ 0.05).Moreover,higher amount of microvessels were found in the composite group than the ADSCs and collagen sponge groups (P ＜ 0.05).To conclude,ADSCs can adhere well to the collagen sponge with good biocompatibility and their combined use can improve angiogenesis further by enhancing cell proliferation and VEGF secretion of ADSCs.