Plasmid BMP-2–embedded gelatin sponge as a gene-activated matrix for preosteoblast differentiation

Gene-activated matrices (GAM), a combination of scaffolds and plasmid delivery systems, are widely used in regenerative medicine, but few compared plasmid BMP-2 in hemostatic gelatin sponge. We compared the osteogenic differentiation ability of bone morphogenetic protein-2 (BMP-2)–transfected preosteoblasts cultured into a hemostatic gelatin sponge with that of non-transfected cells cultured into BMP-2–activated hemostatic gelatin sponge. GAM was prepared from hemostatic gelatin sponge embedded with complexes (plasmid BMP-2 mixed with TransIT-2020^® transfection reagent). The standard transfection method using mouse preosteoblasts (MC3T3-E1) mixed with the complex loaded onto the scaffold was compared with the GAM group. Non-transfected cells were loaded onto the scaffold as the control group. Transmission and scanning electron microscopy results revealed that TransIT-2020^®/plasmid BMP-2 complexes formed homogeneous non-aggregated structures, which were round in shape and 200–250 nm in size. Alkaline phosphatase activity, the marker of bone differentiation, was significantly higher in GAM group compared to that in standard and control groups on differentiation days 14, 21, and 28. The concentration of released BMP-2 was significantly higher in GAM group than that in standard group on days 3 and 7, consistent with confocal microscopy results.