Polycaprolactone-based Scaffolds Fabricated Using Fused Deposition Modelling or Melt Extrusion Techniques for Bone Tissue Engineering - Biointerfaces: Where Material Meets Biology - page 230

It is widely accepted that PCL, alone and without surface modification, is a
poor substrate for cells to attach to and modification techniques are widely
reported. 22-24 It should be noted, however, that cells can and have been
cultured successfully on untreated PCL. It would appear that initially, cells
attach and retain a spherical shape but after 2-3 days, matrix deposition and
cell migration lead to cell-scaffold interactions typically seen in treated
scaffolds. 15,17
It also appears that the raster angle of PCL scaffolds has little effect on cell
attachment and proliferation within parameters and under methods typi-
cally assessed. Hoque et al. 15 demonstrated that with three different RAs
(0/301, 0.601 and 0/901) there was no significant influence on attachment or
proliferation of rat smooth muscle cells.
Studies of untreated PCL scaffolds were taken a step further by Schantz
et al. 25,26 when they assessed porous PCL constructs in vivo. Porous PCL
scaffolds were generated with a triangular structure (0/60/1201) and an
etching process was first reported whereby sodium hydroxide was used to
roughen the PCL surface with the aim of increasing cell attachment by way
of increasing the surface hydrophilicity of the PCL. Cells were seeded onto
the scaffolds and fibrin glue was utilised to assist cell seeding and attach-
ment. Attachment, proliferation and extracellular matrix (ECM) synthesis
were all observed within the construct. 25

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9.4 Polycaprolactone-based Composite Scaffolds
Initial studies indicated that PCL scaffolds are a viable option for bone
scaffolds, owing to their superior formability, relative low cost, high mech-
anical strength, biocompatibility, potential for high purity and ease of
characterisation. The next step was to increase the bioactivity of these con-
structs with the aim of producing a bioactive scaffold able to compete with
the clinical gold standard of autograft. PCL is bioinert; this is an advantage
in that it does not initiate a response or interact with surrounding biological
tissue in a negative way; unfortunately, it is also unable to induce bone
formation. To overcome this drawback, various PCL-based composite scaf-
folds have been developed for tissue engineering applications. For bone
regeneration, a bioactive material is capable of creating an osteogenic en-
vironment; promoting the development of a mineralised interface as a
natural bonding junction between living tissues and non-living materials
(i.e., the scaffold itself) and subsequently encouraging regeneration of
the defect sites into which the scaffold has been placed. 27 It is thus an
imperative to emulate this through creation of an artificial 3D bioactive
scaffold.

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9.4.1 Polycaprolactone with Hydroxyapatite
Bioactive ceramics are biocompatible compounds that can either be related
to the body's own material or more durable metal oxides. Bioceramics have a