中文摘要：

为了开发天然安全、结构稳定的细胞包埋载体,本研究初次选取天然鲑鱼精DNA作为材料,层层自组装构建DNA/壳聚糖/海藻酸钙多层水凝胶球。通过显微镜及扫描电镜观察水凝胶球结构,并表征其性能,透析法评价其在模拟消化液中的稳定性。结果显示水凝胶球形态圆整,膜层清晰,平均粒径为（2.7±0.1）mm,冻干脱水后球体内部呈大孔网格结构,外膜层致密无孔隙。该水凝胶球失水产生明显形变而复水后恢复原有形状;可固定吸附阳离子小分子及与DNA特异结合的分子。水凝胶球在模拟消化液中可稳定存在,其中pH=7.8条件下2h仅有0.5%DNA释放。包埋酵母菌的水凝胶球孵育24h后可发生局部形变,但结构仍保持完整,未见酵母菌逸出。研究结果表明此多层水凝胶球具有良好的生物相容性、形状记忆性、膜透性及结构稳定性,为细胞生长提供了良好的微环境,可包埋酵母细胞并使其在寡营养条件下增殖。

英文摘要：

Cell immobilization is an attractive choice for high-throughput cell isolation and culture due to its advantageous such as protecting cell viability and improving the environmental stability of cell growth,which is widely used in the fields of food,medical application,and environmental protection,etc.In order to improve the micro-environment of cell growth,as well as the stability of the carrier media,bioavailable hydrogel beads composed of natural DNA was developed as a novel matrix for cell immobilization.Based on the biological compatibility and the double helix structure of DNA,DNA/chitosan/calcium alginate multi-layered hydrogels bead（DCS）was prepared by using layer-by-layer（LbL）technique.The morphology and inner micro-structure of DCS were observed by microscopy and scanning electron microscopy,respectively.The stability of DCS was evaluated by determining the cumulative DNA release content in different simulated digestive fluids by dialysis method.Yeast was used as a model cell for cell immobilization.DCS was composed of a soft condensed DNA/CS inner-core and a solid calcium alginate outer-layer through intermolecular electrostatic interactions between DNA,chitosan,and alginate.The prepared hydrogel beads were transparent with spherical shape.The average particle size of the beads was（2.7±0.1）mm,and the thickness of CS/SA layer and calcium alginate outer-layer was about 240 and 6μm,respectively.The interior morphology of the DCS demonstrated open,interconnected highly porous structure,which enabled the multi-layered hydrogel beads fast swelling/deswelling.Re-hydration test showed that the DCS had good shape memory,having obvious deformation in the process of water loss and recover its original shape after re-incubated in water.In addition,small molecules,such as positively charged molecules and specific DNA-binding molecules,can be absorbed and encapsulated in DCS.Stability studies showed that the beads could be stable in simulated gastric fluid,and only 0.5% DNA was released in 2hours in sim