Matrices and scaffolds for delivery of bioactive molecules in bone and cartilage tissue engineering

Regeneration of bone and cartilage defects can be accelerated by localized delivery of appropriate growth factors incorporated within biodegradable carriers. The carrier essentially allows the impregnated growth factor to release at a desirable rate and concentration, and to linger at injury sites for a sufficient time to recruit progenitors and stimulate tissue healing processes. In addition, the carrier can be formulated to have particular structure to facilitate cellular infiltration and growth. In this review, we present a summary of growth factor delivery carrier systems for bone and cartilage tissue engineering. Firstly, we describe a list of growth factors implicated in repair and regeneration of bone and cartilage by addressing their biological effects at different stages of the healing process. General requirements for localized growth factor delivery carriers are then discussed. We also provide selective examples of material types (natural and synthetic polymers, inorganic materials, and their composites) and fabricated forms of the carrier (porous scaffolds, microparticles, and hydrogels), highlighting the dose-dependent efficacy, release kinetics, animal models, and restored tissue types. Extensive discussion on issues involving currently investigated carriers for bone and cartilage tissue engineering approaches may illustrate future paths toward the development of an ideal growth factor delivery system.