Delivery of Osteogenic Regulatory Growth Factors - Engineered Bone: Tissue Engineering Intelligence Unit - page 112

Figure 2. Bone scores for rhBMP-2, rhBMP-4 and succinylated rhBMP-2 implanted with collagen sponge
and poly (glycolic acid) mesh. 0, 2, 5, 15 µ g for rhBMP-2, 0, 2, 5, 15, 45 µ g for rhBMP-4 and 0, 5, 15,
45, 135 µ g for succinylated rhBMP-2 were implanted in a rat ectopic site for 14 days. The bone score of
0, 0.5, 1, 2, 3, 4 and 5 corresponded to implants containing 0%, < 10%, 10-20%, 20-40%, 40-60% and
80-100% of newly formed bone, respectively. Figure adapted from Ref. 29. Copyright© 2000 John Wiley
& Sons. Reprinted by permission of John Wiley & Sons, Inc.
Inorganic Matrices
Inorganic matrices offer the advantages of being structurally strong, immunologically inert,
variably biodegradable and osteoconductive i.e., providing a favourable scaffolding for ingrowth
of bone tissue. A variety of ceramics (e.g., coralline, hydroxyapatite (HAP), tricalcium phos-
phate (TCP)), calcium sulfates, bioactive glass, and metals have been used as inorganic carrier
devices for the BMPs. 39,40
Hydroxyapatite and Tricalcium Phosphate Ceramics
Ceramic implants made of hydroxyapatite (HAP) and tricalcium phosphate (TCP) have been
investigated extensively because they are composed of minerals similar to natural tissue. 41-43 It has
been clearly established that incorporation of an osteoinductive protein (BMP) in HAP/TCP
ceramics greatly accelerates bone formation in various models of bone healing. 44-48
HAP is the major mineral component of bone with the chemical formula, Ca10(PO4)6(OH)2.
This material can be hydrothermally converted from coral or synthetically manufactured. HAP
can be supplied as a powder, granule, disk or block. Its geometry appeared to significantly
affect the osteoinductive ability of BMPs with the key parameter being the porosity of the