Composite scaffolds for cartilage tissue engineering

Abstract

Tissue engineering remains a promising therapeutic strategy for the repair or regeneration of diseased or damaged tissues. Previous approaches have typically focused on combining cells and bioactive molecules (e.g., growth factors, cytokines and DNA fragments) with a biomaterial scaffold that functions as a template to control the geometry of the newly formed tissue, while facilitating the attachment, proliferation, and differentiation of embedded cells. Biomaterial scaffolds also play a crucial role in determining the functional properties of engineered tissues, including biomechanical characteristics such as inhomogeneity, anisotropy, nonlinearity or viscoelasticity. While single-phase, homogeneous materials have been used extensively to create numerous types of tissue constructs, there continue to be significant challenges in the development of scaffolds that can provide the functional properties of load-bearing tissues such as articular cartilage. In an attempt to create more complex scaffolds that promote the regeneration of functional engineered tissues, composite scaffolds comprising two or more distinct materials have been developed. This paper reviews various studies on the development and testing of composite scaffolds for the tissue engineering of articular cartilage, using techniques such as embedded fibers and textiles for reinforcement, embedded solid structures, multi-layered designs, or three-dimensionally woven composite materials. In many cases, the use of composite scaffolds can provide unique biomechanical and biological properties for the development of functional tissue engineering scaffolds.

Figure 1

SEM photomicrograph of knitted PLGA/collagen composite scaffold. Reproduced with permission [63].

Figure 2

(A) Bilayered PLA/HA composite scaffold for osteochondral tissue engineering. (B) Colorized μCT of bilayered scaffold showing internal pore structure and integration of the two phases. Reproduced with permission [36].

Figure 3

Colorized SEM photomicrograph showing PLA foam sponge (yellow) within SFF fabricated HA scaffold (blue). Reproduced with permission [39].

Figure 4

(A) Patella-shaped natural bovine trabecular bone substrate. (B) Patellar osteochondral construct after 14 days in culture. Reproduced with permission [47].

Figure 5

Schematic diagram of a 3-D orthogonally woven structure. Reproduced with permission [55].

Figure 6

Mechanical properties of PCL vs. PGA scaffolds. (A) Compressive Young’s modulus (E) as determined by unconfined compression. (B) PGA scaffolds had significantly higher ultimate tensile stress than did PCL scaffolds. (C) Tangent moduli (at 0 and 10%ε) were higher for PGA scaffolds than for PCL scaffolds. Data presented are mean ± SEM. Statistical significance determined by ANOVA with Fisher’s PLSD, * p < 0.05, **p < 0.0001.