The collagen sponge was completely decomposed in 1 day and the impregnated rhBMP-2 was fully released within 1 day (Fig. 4). In contrast, the hyaluronic acid-based powder gel composite showed slow release compared to the collagen sponge, and the amount of rhBMP-2 released was less than 20 % of the total after 7 days.
Fig. 4 In vitro release of BMP-2 (A: Hyaluronic acid (HA)-based powder-gel; Control: collagen sponge)