Osteoblastic induction on calcium phosphate cement–chitosan constructs for bone tissue engineering

Abstract

Calcium phosphate cement (CPC) is osteoconductive and moldable, and it can conform to complex cavity shapes and set in situ to form hydroxyapatite. Chitosan could increase the strength and toughness of CPC, but there has been no investigation on recombinant human bone morphogenic protein-2 (rhBMP-2) delivery via CPC-chitosan composite and its effect on osteogenic induction of cells. The objective of this research was to investigate the mechanical properties and osteoblastic induction of MC3T3-E1 cells cultured on CPC-containing chitosan and rhBMP-2. Cell viability for CPC with chitosan and rhBMP-2 was comparable with that of control CPC, whereas the CPC-chitosan composite was stronger and tougher than CPC control. After 14 days, osteoblastic induction was quantified by measuring alkaline phosphatase (ALP) activity. ALP (mean +/- SD; n = 6) of cells seeded on conventional CPC without rhBMP-2 was (143 +/- 19) (mM pNpp/min)/(mug DNA). The addition of chitosan resulted in an ALP of 161 +/- 27. Further addition of rhBMP-2 to the CPC-chitosan composite increased the ALP to 305 +/- 111 (p < 0.05). All ALP activity on CPC composites was significantly higher when compared with the 10.0 +/- 3.3 of tissue culture polystyrene (p < 0.05). Flexural strength of CPC containing 15% (mass fraction) chitosan was 19.8 +/- 1.4 MPa, which is more than double the 8.0 +/- 1.4 MPa of conventional CPC (p < 0.05). The addition of chitosan to CPC increased the fracture toughness from 0.18 +/- 0.01 MPa.m(1/2) to 0.23 +/- 0.02 MPa.m(1/2) (p < 0.05). The relatively high strength, self-hardening CPC-chitosan composite scaffold is promising as a moderate load-bearing matrix for bone repair, with potential to serve as an injectable delivery vehicle for osteoinductive growth factors to promote osteoblastic induction and bone regeneration. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.