Biomedical Engineering Reference
In-Depth Information
16.3.1 Fabrication of Osteochondral CG-CGCaP Multi-
compartment Scaffolds
In designing a multi-compartment scaffold, important factors to control include the
chemical and microstructural composition of each compartment and the interfacial
region. A
liquid phase co-synthesis
method was developed to enable fabrication
of multi-compartment CG scaffolds for osteochondral tissue engineering. This
multi-compartment scaffold was designed to be a single biomaterial construct
containing distinct osseous (bone) and cartilagenous (cartilage) regions
(compartments), each with distinct microstructural, chemical, and mechanical
properties that are connected via a continuous interface [
47
]. The osseous compart-
ment for subchondral bone regeneration was made from type I collagen, chondroi-
tin sulfate, and CaP while the cartilagenous compartment for cartilage regeneration
was composed of type II collagen and chondroitin sulfate. Using this new fabrica-
tion scheme, distinct CG and CGCaP suspensions are created containing ECM
components representative of each tissue compartment.
The continuous interface is created by layering the cartilagenous compartment
and the osseous compartment suspensions in a conventional freeze-drying mold,
but then incorporating a processing step to enable partial diffusive mixing between
the two suspensions near their interface. Once the region of interdiffusion was
created between the suspension layers, freeze-drying was used to form the final
multi-compartment scaffold microstructure (Fig.
16.2
)[
47
]. This fabrication
method prevents complications often observed in layered scaffolds containing
abrupt interfaces such as those created when suturing or gluing distinct phases
together post-fabrication. In these cases delamination due to stress concentrations,
foreign body contamination (from glue or other adhesive), and inefficient cellular
transport between scaffold phases can be a significant problem [
47
]. The differen-
tial chemistry, microstructure, and mechanics of the osseous and cartilagenous
compartments enable these layered scaffolds to exhibit compressive deformation
behavior that mimics behavior observed in natural articular joints [
47
,
52
]. The
continuous interface between scaffold regions may also be critical for the recapitu-
lation of native interfacial physiology for tissues such as ligament and tendon [
47
].
16.3.2 Methods of Characterizing Multi-compartment
CG-CGCaP Scaffolds
It is imperative to develop quantitative analysis techniques to consider the biophysical,
compositional, and biomechanical properties of multi-compartment scaffolds.
Experimental characterization of multi-compartment CG scaffold properties such
as chemical composition, pore morphology (size/shape), relative density, perme-
ability, and mechanics have been used to describe distinct scaffold features. Experi-
mental characterization has also been supplemented by modeling approaches that
enable a more complete understanding of the microenvironment presented by the
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