Papers by Author: D.S. Lee

Abstract: Fibrin is a natural polymer with excellent biocompatibility and widely used as a cell delivery vehicle in tissue engineering. However, fibrin of low concentration is not able to promote cell growth and differentiation within a desired time because of contraction and biodegradation of cell-seeded matrices. In this study we investigated effects of combining fibrin with collagen on growth and osteogenic differentiation of bone marrow stromal cells (BMSCs). Rabbit BMSCs-populated fibrin hydrogels with or without collagen were fabricated and cultured by the free floating method for 4 weeks. The DNA content of fibrin/collagen matrix significantly increased the growth of BMSCs compared to the fibrin-only matrix at 2week. Alkaline phosphatase activity was significantly higher in the fibrin/collagen matrix (71.0 nmol of p-nitrophenol /min/disc) than the fibrin-only matrix (45.1 nmol of p-nitrophenol /min/disc). Deposition of calcium was not significantly different between two groups. Histological examination also revealed more matured organization and deposition of collagen fibers and more concentric calcium deposition in the fibrin/collagen matrix compared to the fibrin-only matrix. These results indicated that fibrin/collagen matrix could be more effective than fibrin alone in supporting growth and osteogenic differentiation of BMSCs.

Abstract: To improve the mechanical properties of concretes containing recycled aggregates, pozzolanic materials such as Silica Fume and Meta Kaolin were used to decrease the porosity of the recycled aggregates. These pozzolanic aterials were adhered on the surface of recycled aggregates and closed the open pores so that the water absorption was decreased 1~2% as the amount of adsorption was increased. Compressive strength of cement mortars and concretes using surface treated recycled aggregates reached above 95% of the strength of its natural counterparts. Investigation of the microstructures using the scanning lectron micrographs showed the formation of dense interface after the adsorption treatment of pozzolanics to recycled aggregates.

Abstract: To improve the mechanical properties of concretes containing recycled aggregates, pozzolanic materials were used to decrease the porosity of the recycled aggregates. These pozzolanic materials were adhered on the surface of recycled aggregates and closed the open pores so that the water absorption was decreased 1~2% as the amount of adsorption was increased. Compressive strength of cement mortars and concretes using surface treated recycled aggregates reaches above 95% of the strength of its natural counterparts. Investigation of the microstructures using the scanning electron micrographs showed the formation of dense interface after the adsorption treatment of pozzolanics to recycled aggregates.