Fabrication Techniques and Properties of Scaffolds - Biodegradable Polymer-Based Scaffolds for Bone Tissue Engineering - page 38

when a highly porous well-interconnected PHBV structures were seeded with
fibroblasts, it sustained a cell proliferation rate similar to that observed in collagen
sponges for 35 days, with a maximum cell density observed on day 28 in culture
(Rivard et al. 1995 ). It was also reported that PHBV polymers kept their structural
integrity throughout the culture (Rivard et al. 1995 ).
2.7.2 Alkaline Phosphatase Assay
In vitro studies with the osteoblast-like cells can offer insights into the biologi-
cal performance of bone implant materials. Alkaline phosphatase (ALP) activ-
ity, type 1 collagen synthesis, secretion of osteocalcin, and production of a
mineralized matrix are the set of properties associated with the osteoblast phenotype
(Rea et al. 2004 ). Among these properties, ALP is a widely accepted marker of
osteoblastic differentiation. With the aid of an alkaline phosphatase assay kit, ALP
can be determined according to the manufacturer's instruction. It was reported that
differentiated osteoblastic function was monitored by measuring alkaline phos-
phatase activity of PLLA skeleton covered with bonelike apatite or apatite/colla-
gen composites (Chen et al. 2006 ) to measure the interactions between osteoblasts
and the polymer scaffolds. It was also found that collagen has a positive effect on
ALP activity of osteoblasts. From another study it was found that ALP is an early
marker of mechanically-induced differentiation of osteoblasts (Pavlin et al. 2000 ).
In vitro biocompatibility of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copol-
ymer in fibroblast cells was evaluated (Siew et al. 2007 ). The cytotoxicity, mode
of cell death, geno-toxicity of the copolymer against fibroblast cells were assessed
using MTT assay, acridine orange/propidium iodide staining, alkaline comet assay
respectively. The results demonstrated that the polymer poly(3HB-co-4HB) treated
on both cell lines were comparable with clinically used Polyglycan 910, where more
than 60 % of viable cells were observed following 72 h treatment at 200 mg/ml. The
mode of cell death showed an increase in apoptotic cells in a time-dependent man-
ner in both cell lines. Using alkaline comet assay following 72 h treatment, it was
observed that poly(3HB-co-4HB) polymers did not show any genotoxic effects. This
study concluded that poly(3HB-co-4HB) compounds possessed good biocompatibil-
ity in fibroblast cells.
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Anderson JM (1995) Perspectives on the in vivo responses of biodegradable polymers.
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