Regeneration of defects in the bone tissue due to disease or trauma continues to be a major challenge in orthopedics and dentistry. Autologous transplants that are commonly used in the clinic suffer from limited availability of harvestable tissue in addition to significant patient discomfort. Engineered tissues offer a promising alternative to transplants and there is a growing need to develop three-dimensional (3D) scaffolds for tissue regeneration.
Owing to their excellent osteoconductive properties, calcium phosphate-based materials have emerged as promising candidates for bone tissue regeneration. Typically, these materials require processing at a high temperature (hundreds of degree Celsius) for mechanical integrity which renders them unsuitable for encapsulation of bioactive molecules like drugs and growth factors to enhance the therapeutic effects. In a recent study, researchers from Dankook University in South Korea have prepared ceramic microparticles for sustained delivery of biomolecules at room temperature in an aqueous environment that afford easy encapsulation of drugs and proteins.
Self-setting calcium phosphate cements (CPCs) are being widely studied as potential injectable biomaterials to fill bone defects of any shape. Reporting in the February issue of the Journal of the American Ceramic Society (DOI: 10.1111/j.1551-2916.2010.04314.x; p. 351), J.-H. Park, H.-W. Kim, and their colleagues introduce a technique to fabricate self-hardening microspheres with sizes of hundreds of micrometers for use as 3D bone tissue matrix prepared by emulsification of α-tricalcium phosphate (α-TCP)-based CPC mixed with collagen. CPC-collagen composites constitute the two major components of the calcified bone matrix. Biomolecules can be easily incorporated into these microparticles by adding them to the collagen liquid phase during emulsification.
Scanning electron micrograph of calcium phosphate cements-collagen composite microparticle morphology and surface microstructure (inset) prepared by aqueous emulsification at room temperature.
Release kinetics of encapsulated bovine serum albumin indicated a two-step sustained release well-suited for controlled delivery of encapsulated drugs or growth factors to enhance cell function in these scaffolds. Furthermore, the surface of the α-TCP microspheres was covered by nanocrystals of bone mineral-like hydroxyapatite phase when the particles incubated in simulated body fluid. Results from in vitro cell studies indicated that osteoblasts adhere, spread, and proliferate on these microsphere substrates. Thus, these protein-releasing CPC-collagen microspheres hold promise as a 3D scaffold for bone tissue regeneration.
