(14e) Periosteum-Mimetic Polysaccharide-Based Coatings for Cortical Bone Allografts towards Orthopedic Tissue Engineering Applications

Bone allografts are commonly used in surgery as a means to replace degraded or broken bone. The periosteum is usually removed before implantation in order to avoid immune rejection. On large defects; however, these allografts fail to promote new bone formation and often they are susceptible to bacterial infection. Thus, engineering periosteum-mimetic coatings for the modification of bone allografts might restore the osteoinductive properties of native bone; allowing new tissue to be regenerated in implantation. To this end, ovine bone was coated with polysaccharide-based polyelectrolyte multilayers (PEMs).

The periosteum of ovine bone pieces from the femur was removed via sonication in 70 % ethanol and freezing. PEMs were constructed using either the polycation chitosan or N,N,N-trimethyl chitosan and the sulfated glycosaminoglycan heparin as the polyanion. X‑ray photoelectron spectroscopy was used to determine PEM deposition. Increase of the sulfur peak (S2p) as well as attenuantion of the calcium (Ca2p) and phosphorus (P2p) peaks after deposition of PEMs confirms adsorption of the polysaccharides onto the bone.

Bone marrow derived ovine mesenchymal stem cells (MSCs) were seeded onto the PEM-coated bone to test their viability over a culture period of 4 days. It was observed that MSCs grow well on the PEM coated decellularized bone. The antimicrobial activity of the PEM-coated bone samples was tested against E. coli and S. aureus. PEM-coated bone samples demonstrated significant antimicrobial activity for both bacteria when compared to uncoated bone. PEMs provide an attractive and simple method for creating periosteum-mimetic coatings for bone allografts, which supports mammalian cell growth, has antimicrobial properties, and could be used for growth factor delivery.