Synthesis of Layered, Graded Bioscaffolds - Structural Interfaces and Attachments in Biology - page 347

Analysis of the multi-compartment scaffold showed a modulus of 23 2 kPa, with
the low modulus suggestive of compartmentalization of all scaffold deformation in
the softer CG region. Serial microCT analysis has been used to depict the behavior of
individual compartments within the multi-compartment osteochondral scaffold; the
softer cartilagenous compartment experienced more deformation compared to the
osseous compartment (negligible strain) [ 47 ]. Recently, ultrasound elastography
approaches have been used to depict local strain in the discrete scaffold
compartments of a multi-compartment scaffold, confirming localized scaffold
deformation in the non-mineralized region under compressive loads (Fig. 16.4 ).
Scaffold permeability varies significantly across the multi-compartment CG
scaffold. Permeability of tissue engineering scaffolds is a critical design parameter
to be controlled as it influences the diffusion of cytokines, nutrients, and waste
throughout the scaffold prior to material vascularization; further, biomaterial
permeability has also been shown to significantly impact cell migration processes
and scaffold biodegradation rates, amongst others [ 59 ]. Material permeability also
affects fluid pressure fields and shear stresses within the construct, additional
potential stimuli for functional adaptation [ 60 ]. Permeability of tissue engineering
scaffolds is dictated by a variety of microstructural characteristics including poros-
ity, pore size and orientation, pore interconnectivity, fenestration size and shape,
specific surface area, and applied strain. Cellular solids approaches have been
utilized to build descriptive models of scaffold permeability that accurately capture
the effect of scaffold pore size, relative density, and applied strain on overall
scaffold permeability [ 58 ]. When examining the model multi-compartment scaf-
fold, the permeability of each compartment was found to behave as predicted by the
previously described cellular solids model; however, the permeability of the entire
multi-compartment scaffold was found to match that of the mineralized layer. Here,
the mineralized compartment provided the limiting resistance due to its smaller
pore size and higher relative density. The findings that multi-compartment scaffold
mechanical properties match the CG compartment while the bulk permeability
matches the CGCaP compartment, while not surprising, underscore the importance
of continuing to develop methods to quantitatively analyze region-specific
properties within heterogeneous biomaterials.
16.3.3 Clinical Application of Multi-compartment
CG-CGCaP Scaffolds
The weak antigenicity/immunogenicity of the collagen/GAG content within the CG
scaffold as well as its controllable biodegradability, previous FDA-approval, and
overall history in clinical applications [ 34 , 35 ] make CG scaffolds an attractive
target for clinical translation. Multi-compartment CG-CGCaP scaffolds are cur-
rently being developed and tested for orthopedic interface regeneration applica-
tions. The first generation multi-compartment CG-CGCaP scaffold is currently