Biomedical Engineering Reference
In-Depth Information
Triethyl phosphate
75°C, hydrolysis 48 h
Ca(NO
3
)
2
R.T., aging, 120 h
Sol-gel
PAN, DMF
Electrospinning
Hot-stretched
Preoxidation
carbonization
FIGURE 18.9
Schematic illustration for the preparation of
β
-TCP@/CNF membranes.
[101,102]
. However, the inappropriate rheological properties and rapid hydrolysis rates of precursors
make it very hard to control the electrospinning process because an inorganic sol is a thermostatically
unstable system. To make the solution spinnable, one method is to introduce a polymer into the solu-
tion to regulate the rheological properties. This is very easy and involves simply co-dissolving the
precursor and polymer in a cosolvent. Poly(vinyl pyrolidone) (PVP) is one of the most popular poly-
mers employed as a matrix. Other polymers, such as poly(vinyl alcohol) (PVA), poly(vinyl acetate)
(PVAc), PAN, PMMA, and poly(acrylic acid) (PAA) have also been widely used. Inorganic/polymer
composite nanofibers are obtained via electrospinning from the above solutions. In the following
steps of calcinations, the organic phase is burnt out while the nanofibers evolve into ceramic nanofi-
bers
[103,104]
. As we have learnt, a popular and simple way to produce CNFs is from electrospin-
ning the PAN/DMF solution, followed by oxidation and carbonization. This has provided us an
excellent opportunity to modify CNFs. If we add PAN as the matrix to CaP precursor sol
gel solu-
tion to modify rheological properties, the electrospun CaP precursor/PAN composite nanofibers can
be envisioned into CaP ceramic/CNF hybrids under proper calcination condition. In the calcination
process, the precursors transform into CaP ceramic like HA or
-TCP depending on the feeding ratio
of Ca/P, and meanwhile PAN transforms into CNFs. This is such an easy way to embed bioactive
CaP nanoparticles into CNFs, to improve their biological properties.
Our lab has done some work on preparing
β
β
-TCP or bioglass-embedded CNFs via sol
gel/
electrospinning. As shown in
Figure 18.9
, to produce
-TCP@CNFs, TEP is dissolved in distilled
water and hydrolyzed first, followed by dissolving calcium nitrate tetrahydrate into the hydrolyzed
β
