Biomedical Engineering Reference
In-Depth Information
electrospun PLLA/MWCNTs/HA membranes. This new type of membrane showed excellent dual
biological functions and satisfied the requirement of the GTR technique
[109]
.
10.4.1
Fabrication of PLLA and PLLA/HA Composite Nanofibers
The two-solvent system was exploited to obtain a spinnable PLLA/HA dispersion
[97-99]
. HA nan-
oparticles (
Figure 10.1
) were dispersed in 1,4-dioxane to form a suspension, then dichloromethane
and PLLA particles were added to the suspension, and the suspension was homogenized by using
ultrasonic vibrator. The suspension was then electrospun at fixed parameters: voltage
10 kV, injec-
tion rate
1.0 ml h
1
, PLLA concentration
6 wt%, distance
100 mm, inner diameter of spin-
neret
0.7 mm. The resulted fibrous membranes were placed in a vacuum oven at 50°C over 2 days
to remove the solvent.
By using different solvent to dissolve PLLA, varied fiber surface morphology would be resulted.
As shown in
Figure 10.2
, the PLLA nanofibers electrospun from PLLA/dichloroform solution exhibited
microporous structures due to fast evaporation rate of dichloromethane. With the addition of dioxane
to slow the fiber solidification, smooth PLLA nanofibers could be obtained. Thus, this mixed solvent
system was applied to electrospin PLLA/HA composite nanofibers, in which, the presence of dioxane
helped to disperse HA particles in PLLA solution and ameliorate the fiber morphology. However, the
incorporation of HA nanoparticles resulted in more beaded in morphology than pure PLLA fibers.
10.4.2
Fabrication of PLLA/MWCNTs/HA Composite Nanofibers
Figure 10.3
shows a schematic diagram of the fabrication progress of the PLLA/MWCNTs/HA mem-
brane. MWCNTs were first modified by anodic oxidation (sulfonic acid/nitric acid, v/v
3/1, 80°C);
then, MWCNTs/HA nanoparticles (3 wt% MWCNTs) were in-situ synthesized by a wet method with
Ca(NO
3
)
2
·4H
2
O and (NH
4
)
2
HPO
4
(Ca/P
1.67) by using an ultrasonic sonicator. The needle-like HA
particles were about 40-70 nm in length and 15 nm in diameter, and well-combined on the surfaces of
anodic oxidized MWCNTs. The prepared MWCNTs/HA nanoparticles were washed with 1,4-dioxane
repeatedly to remove the water and dispersed again in 1,4-dioxane to form a suspension. Dichloromethane
FIGURE 10.2
Choice of solvents on the morphology of electrospun PLLA and PLLA/HA nanofibers: (A) PLLA in
dichloroform, (B) PLLA in dichloroform/dioxane, (C) PLLA/HA in dichloroform/dioxane.
