Microparticles as tissue engineering scaffolds: manufacture, modification and manipulation

Tissue engineering, a field which focusses on the replacement, repair and regeneration of damaged or diseased tissue by the application of biomaterials, cells and associated biological molecules, has advanced rapidly due to the intense demand for tissue substitutes. A key principle in tissue engineering involves growing the appropriate cells in vitro for the desired application before delivery into the body of a patient. The implantable devices, biological constructs or scaffolds, developed in tissue engineering aim to provide the initial architecture required for supporting the cells as well as define the micro and macrostructure of the final engineered product. Furthermore, these scaffolds may be exploited to release drugs and/or growth factors in a controlled manner, thus facilitating the repair and regeneration of the target tissue. Microparticles, spherical carrier scaffolds, have recently received extensive interest for their potential therapeutic applications in a diverse range of clinical and regenerative medical settings. Not only can these versatile subunits be used as cell culture scaffolds, their innate structure reduces the degradation of encapsulated biologically active molecules and also allows their exploitation as a localised injectable delivery system. The purpose of the present article is to review the tissue engineering applications of these microparticles and to provide a brief overview of the critical factors considered during their formulation and use - including the range of materials used and the different modification protocols and technologies exploited to improve and enhance their mechanical properties and biocompatibility for regenerative medicine.