Preparation and Mechanism of Novel Bioceramics with Controllable Morphology and Crystal Growth - Advanced Bioactive Inorganic Materials for Bone Regeneration and Drug Delivery - page 164

fixation. SBF soaking, hydrothermal homogeneous precipitation, and elec-
trodeposition have been widely used due to (1) the methods enable forma-
tion of highly crystalline deposits with low solubility in body fluids and low
residual stresses; (2) the ability to coat porous, geometrically complex, or
non-line-of-sight surfaces; (3) the ability to control the thickness, composi-
tion, and microstructure of the deposits; (4) the possible improvement of the
substrate and coating bond strength and (5) the availability and low cost
of equipment. The compositions of the precursor solutions, pH values, and
additives were found to significantly affect the Ca-P crystal phases, surface
morphologies, crystal sizes, and chemical compositions of the Ca-P deposits
in the electrocrystallization process (Eliaz and Sridhar 2008; Haders et al.
2008; Stenport et al. 2008).
Electrospinning is good technology to fabricate ultrafine and ultra long
fibers with diameters from nano- to micrometers under high electro-
static force. The main features of nonwoven fabrics composed of the fibers
include large surface area, high percentage of voids, and small pore size.
These features are highly desirable in scaffolds for tissue engineering
and in substrates for functional cell cultures such as in three-dimensional
model systems. Such scaffolds and substrates have been developed from a
variety of materials, including polymers, inorganics, and their composites
(Ramanan and Venkatesh 2004; Wu et al. 2004; Schnell et al. 2007; Chew et al.
2008; Yamaguchi et al. 2008; Franco et al. 2012; Xie et al. 2012; Zou et al. 2012).
Recently, the bioactive silicate fiber scaffolds were fabricated with a com-
bination of electrospinning technology and the sol-gel process (Yamaguchi
et al. 2008; Franco et al. 2012). The HAp fibers with porous surface and uni-
form fiber diameter of about 140 µm were fabricated by the electrospin-
ning sols of the 2-butanol solution of phosphorous pentoxide and calcium
acetate solution in distilled water, and lactic acid was added as a spinning
aid. Yamaguchi et al. (2008) prepared silicate electrospun nanofibers via the
sol-gel process. Xie et al. (2012) prepared the submicron bioactive glass tubes
using sol-gel and coaxial electrospinning techniques for applications in bone
tissue engineering. The heavy mineral oil and gel solution were delivered by
two independent syringe pumps during the coaxial electrospinning process.
Subsequently, submicron bioactive glass tubes were obtained by removal of
poly(vinyl pyrrolidone) and heavy mineral oil via calcination at 600°C for
5 h. The tubular structures possess high surface area, high protein-loading
capacity, and delayed release properties.
We prepared the nanocrystalline HAp assembled hollow fibers (NHAHF)
in the membrane form by combining the electrospinning technique and the
hydrothermal method. First, the electrospun bioactive glass fibers (BGF)
were prepared via mixtures of the bioactive glass precursor (molar ratio of
SiO 2 :CaO:P 2 O 5 = 70:25:5) and poly(vinyl butyral) (PVB). After calcining at
600°C for 4 h in air, the polymer PVB was removed and the resulting bioac-
tive glass nanofiber nonwoven membrane was obtained and then was used
as a self-sacrificial template. After hydrothermal treatment the bioactive