Biomedical Engineering Reference
In-Depth Information
or plasma modified and fibronectin coated), scaffolds with plasma modi-
fication and fibronectin exhibited the highest proliferation rates and sig-
nificantly higher osteoblast differentiation rates as indicated by alkaline
phosphatase and osteocalcin expression.
55
Higher osteoblast differen-
tiation means that a greater number of bone cells are being produced.
Alkaline phosphatase is often expressed by osteoblasts during/after dif-
ferentiation and osteocalcin is secreted solely by osteoblasts. In a similar
study, Berneel et al.
56
pre-activated PCL surfaces by subjecting the scaffolds
to 30 s of argon-plasma treatment, coating the scaffolds with gelatin type B
and finally dip-coating the scaffolds with fibronectin. SEM, X-ray photo-
electron spectroscopy and confocal laser scanning microscopy indicated
homogenous gelatin type B and fibronectin coating on the entire scaffolds.
Scaffolds were also seeded with human foreskin fibroblasts and
cultured for up to 21 days. Histological sections of cell-gelatin type B-
fibronectin-PCL scaffold constructs revealed that at day 7, cells migrated
towards the centre of the scaffolds and at day 21, the entire scaffold was
colonised.
56
This behaviour was not observed in PCL-only scaffolds. How-
ever, this study only presented qualitative results; further validation of the
findings through quantitative means would be necessary to draw signifi-
cant conclusions.
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9.5.5 Hydroxyl Functionalisation
The intrinsic hydrophobicity, coupled with an absence of bioactive func-
tional groups makes PCL unfavourable for cell adhesion and proliferation.
Seyednejad et al.
57,58
developed a hydroxyl-functionalised co-polymer based
on PCL, known as poly(hydroxylmethylglycolide-co-e-caprolactone)
(pHMGCL). In their studies, 3D pHMGCL scaffolds were fabricated using an
FDM technique with PCL scaffolds as controls. Assessments in vitro indi-
cated that pHMGCL scaffolds supported superior cell adhesion and pro-
liferation rates compared to PCL scaffolds. Cells were filling most of the
pores at day 7 of culture. Additionally, alkaline phosphatase activity was
significantly higher in pHMGCL scaffolds compared to PCL scaffolds. This
indicated improved osteogenic differentiation.
58
Following on from this,
pHMGCL and PCL scaffolds were implanted subcutaneously into balb/C
mice. Both pHMGCL and PCL scaffolds indicated good biocompatibility
in vivo. Tissue infiltration was observed on both pHMGCL and PCL scaffolds
1 month post-implantation. However, it was shown that pHMGCL scaffolds
induced a more intense tissue-biomaterial interaction, with the presence of
mononuclear inflammatory cells within the infiltrated tissue (1 month post-
implantation), progressing to a mild chronic inflammatory response as in-
dicated by presence of giant cells and progressing fibrosis (seen 3 months
post-implantation). Notably, pHMGCL scaffolds induced significantly higher
vascularisation within the infiltrated tissue than PCL scaffolds, indicating
better neotissue-scaffold integration.
57
.
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