Biomedical Engineering Reference
In-Depth Information
BiocompatibilityEvaluationoftheNanostructured
BioceramicCoatingsbyInVitroCellCulture
A material must be in contact with living tissues when used as implant during clinical
service, thus its biological performance, defined as the interaction between materials and
living systems, is important for a favorite functional life. Two aspects of the biological
performance, host response and material response, are responsible for overall bioactivity
of the implants. Host response (the reaction of a living system to the presence of a mate-
rial) controls the performance of the patient who received the placement of the implant.
It is, however, controlled by the characteristics of the material and especially its chemi-
cal stability in the body. These two characteristics—the susceptibility of the material to
degradation and the effect such degradation has on the tissue—are the central features
of biocompatibility. The mechanism of tissue attachment is directly related to the type of
tissue response at the implant interface. So far it seems clear that one of the original goals
of implantation, that is, to produce minimal host response, is an outmoded view that may
limit further development of implant materials and devices.
Generally, implant materials such as HA coatings must fulfill the following require-
ments (Wise et al. 2000):
• The elemental chemistry of primarily calcium and phosphate ion substances in
Ca/P ratio of 1.67, which is similar to natural bone.
• The controllability of crystalline and physical structures to provide a wide range
of in vivo interactions.
• The extensive availability of existing literature on biocompatibility.
• The opportunity for bonding to bone.
• The opportunity to enhance mechanical force transfer allowing for use in load-
bearing implants.
• A wide range of crystalline and structural forms can be constituted from reac-
tions between calcium oxide and phosphorous pentoxide, which allows for mate-
rial properties formulation that better matches requirement.
• The opportunity to introduce other elements or structural defects.
• Microstructures and densities can be varied to provide properties from relatively
stable to completely biodegradable.
Biocompatibility was defined as the ability of a biomaterial to demonstrate host and mate-
rial response appropriate to its intended application (Wise et al. 2000). To be biocompatible,
a bioceramic coating must not induce an activation of the immune system or be toxic and
carcinogenic, and finally should not disturb the blood flow, intrinsically or via waste prod-
ucts, after being in contact with blood. The simplest form of interaction between implant
materials and the biological environment is the transfer of material across the material-
tissue interface in the absence of reaction (Black 1999). It was revealed that once the implant
was put into the body, complicated behavior took place as a local host response.
In vitro tests have come to be seen as screening tests, serving as precursors for more
involved, more costly and time-consuming animal implantation. In vitro testing is a neces-
sary method to evaluate the changes of HA prosthesis in simulated body fluid (SBF) and/
or cell culture medium before its direct use in patients' body. Generally used SBF solution
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