Anisotropic Porous Biodegradable Scaffolds for Musculoskeletal Tissue Engineering

Abstract

It has been generally accepted that tissue engineered constructs should closely resemble the in-vivo mechanical and structural properties of the tissues they are intended to replace. However, most scaffolds produced so far were isotropic porous scaffolds with non-characterized mechanical properties, different from those of the native healthy tissue. Tissues that are formed into these scaffolds are initially formed in the isotropic porous structure and since most tissues have significant anisotropic extracellular matrix components and concomitant mechanical properties, the formed tissues have no structural and functional relationships with the native tissues. The complete regeneration of tissues requires a second differentiation step after resorption of the isotropic scaffold. It is doubtful if the required plasticity for this remains present in already final differentiated tissue. It would be much more efficacious if the newly formed tissues in the scaffold could differentiate directly into the anisotropic organization of the native tissues. Therefore, anisotropic scaffolds that enable such a direct differentiation might be extremely helpful to realize this goal. Up to now, anisotropic scaffolds have been fabricated using modified conventional techniques, solid free-form fabrication techniques, and a few alternative methods. In this review we present the current status and discuss the procedures that are currently being used for anisotropic scaffold fabrication.

Solid Free-form Fabrication Technology and Its Application to Bone Tissue Engineering

“…The main advantages of the FDM method are that it does not require a toxic solvent and offers flexibility in material handling and processing (8,9,40). Filament material also lessens the manufacturing time required in the heating compartment and allows for continuous production without the need for replacing feedstocks.…”

“…Filament material also lessens the manufacturing time required in the heating compartment and allows for continuous production without the need for replacing feedstocks. However, the main difficulty of the FDM technique is the requirement for preformed fibers with a consistent size and material properties to feed through the rollers and nozzle (7)(8)(9) ). The porosity ranged from 60 to 65% and the pore size ranged from 300 to 580 μm.…”

“…These techniques permit researchers to control scaffold parameters, such as pore size, porosity, and interconnectivity. SFF methods that are applicable to bone tissue engineering include stereolithography (SL), fused deposition modeling (FDM), selective laser sintering (SLS), and 3D printing (3DP) (9)(10)(11)(12). As 3D bone scaffolds are developed using SFF technology, the selection of appropriate biomaterials will be one of the most challenging problems for bone tissue regeneration (1,2,4).…”

A New Biphasic Dicalcium Silicate Bone Cement Implant

“…Mercury porosimetry detected an average pore size of between 50–100 μm. A minimum pore size of 100 μm has been described to allow bone tissue formation inside the pores of materials [41,42], and the optimum pore size falls within the 200–400 μm range. Nevertheless, the most important factor is pore interconnectivity.…”

Simple method to generate and fabricate stochastic porous scaffolds

“…In contrast to solid structures, porous structures typically have larger internal surface areas and higher strength-to-weight ratios [1], their interconnected pores can govern cell attachment [2], and they provide efficient cell seeding into a scaffold [3], the mass transfer metabolites [4], the delivery drugs or growth factors [5], and a sufficient regeneration space for newly formed tissue [6].…”