ICP-AES analysis
The concentration of calcium and phosphorous ions existing
in the SBF solution after removing the samples from the soaking
solution is exhibited in Fig. 10. Due to the increase in amount of
nanoclay for GP3 composition, the concentration values of Ca and
P ions decrease from 100 ppm to 92.60 and 40.62 after the 28 days
of immersion, respectively. The event originated from the increase
of porosity of composite and subsequently strong chemical bond
with the bone tissue resulting in the consumption of the phosphorus
to form a layer of calcium phosphate on the surface of the fibre
composite.
The release of calcium ions from the surface into the SBF solution
leads to the formation of many silanol groups on the surface. Silanol
groups are heterogeneous nucleation sites for the apatite layers. As
can be seen from Fig. 9, the Ca ion concentration begins to decrease
for IGT/PVA and tends to be fixed in PVA/IGT–NC nanocomposites
after 2 weeks. To explain the event one can say that the SBF solution
eventually becomes saturated from the Ca ions (after 2 weeks),
so that the calcium ions tend to leave the solution [25]. In other
words a balance between the Ca ions release and Ca ions absorption
is achieved. It should be noted that there are two places for the
absorption of calcium ions [25].
It is clear from Fig. 9 that the optimum amount of pH has been
achieved after 28 days for PVA/IGT–NC nanocomposite samples
[25].
As the amount of NC increases, the weight loss begins to
decrease. Generally, bioceramics improve the chemical stability
and mechanical properties of the polymers. As the NC amount
increases, the pH value slowly begins to decrease. Fig. 10 shows
the curve of PVA/IGT nanofibres containing different amount of NC
after degradation for a period of 28 days. This figure shows that
by increasing the NC content in the nanocomposite samples, the
rate of degradation also increases. The morphology of pure PVA/IGT
nanofibre immersed in PBS solution for 28 days showed no changes
whereas a considerable degradation was observed for the nanofi-
bres containing 3% NC after 14 days. The increase of degradation
rate in the nanocomposite samples is due to this fact that the nanoclay
acts as a filler between the polymer chains and so it improves
the capability of microorganism growth, and subsequently easier
and faster destruction of polymer structure.