Biomedical Engineering Reference
In-Depth Information
bioagents, such as growth factors and other proteins into the coating during the fabri-
cation process, which further broadens the applications of electrophoretically deposited
coatings.
Heparin has already been codeposited with HAp-chitosan composite coatings, being
located in the top layer of multilayered or functionally graded composite microstructures
[149]. Heparin is an anticoagulant drug that has been used to modify different blood-
contacting materials surfaces. By incorporating it into the top layer of the coating, it can
improve the blood biocompatibility of the implant. This discovery has demonstrated the
feasibility of adding other drugs, such as proteins and growth factors, into the electro-
phoresis system, thereby facilitating codeposition onto implant surfaces for different bio-
medical applications. Besides heparin, silver also has been codeposited with HA-chitosan
composites to fabricate antimicrobial coatings [173]. The composite coating was attained
by adding AgNO 3 to the coating medium. It was found that the coating also provided cor-
rosion protection to the underlying 316L stainless steel substrate.
More broadly, the biocompatibilities of HAp coatings and HAp-polymer composite
coatings produced by electrophoretic deposition have been evaluated in vitro and in vivo.
Both silicon-substituted HAp coatings and silicon-substituted HAp-poly( ε -caprolactone)
composite coatings have the ability to induce bonelike apatite formation after immersion
in simulated body fluid for ~1 week, indicating the good bioactivity of these coatings
[130,167]. Moreover, these coatings support the attachment, proliferation, and mineraliza-
tion of osteoblast cells and stem cells [103,104,171]. In vitro studies have shown that HAp
coatings support the attachment and growth of human primary osteoblast cells (HOBs)
and they exhibit greater mineralization than uncoated substrates [104]. Laser-treated HAp
coatings have shown superior biocompatibility than Ti controls. After 11 days of culture
with the osteoblast precursor cell line (OPC1), coated surfaces indicated good cell spread-
ing and coverage [171]. Figure 3.16 shows the morphology of rabbit mesenchymal stem
cells (MSC) growing on nano-HAp coatings after 2 and 10 days of culture [103]. After 10
days, the cells were well spread on the substrate and formed a confluent monolayer.
(a)
(b)
5 µm
FIGURE 3.16
Scanning electron microscope (SEM) images of human primary osteoblast cells (HOBs) growing on the sur-
face of a nano-HAp coating produced by electrophoretic deposition. (a) After 2 days, the pseudopod of cells
can be seen clearly. (b) After 10 days, the surface is extensively covered by cells, which are flattened and
form a confluent monolayer. (Reproduced by courtesy of Journal of Biomedical Materials Research B: Applied
Biomaterials .)
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