Biomedical Engineering Reference
In-Depth Information
to their ease of processing and forming and superior mechanical proper-
ties. In the other hand, conventional ceramics such as alumina (Al
2
O
3
) and
zirconia (ZrO
2
) have been evaluated due to their excellent properties of
high strength, good biocompatibility and stability in physiological envi-
ronments [4]. Also, they are non-bioactive ceramics and are covered by a
non-adherent i brous layer at the interface at er implantation. In orthope-
dics they are mainly used as artii cial femoral heads due to their excellent
mechanical strength and durability [5]. Bioactive glasses (Bioglass) have
been widely used as bone void i llers in clinical settings. h ey mainly con-
sist of sodium, calcium, silicon and phosphorous oxides [6]. However, the
brittleness and low fracture toughness of bioglass hampers its application
for load-bearing applications.
2.2.3 Composites
Polymer-matrix composite materials are resins reinforced by i bers which
have diverse applications in dif erent industries; composite materials have
potential to be manipulated to obtain materials with combination of prop-
erties which cannot be obtained by conventional methods. Composite
materials have been recently considered for biomedical applications, since
they have mechanical and biological similarities to the human tissue being
replaced [7].
2.2.4 Metals
Metals have been usually used in biomedical i eld as implants. Permanent
metal implants based on stainless steel, cobalt- chromium (Co-Cr) alloys
and titanium or its alloys have been at the forefront of classical biomateri-
als research for decades. h e high tensile strength and fatigue resistance
of metal makes it suitable for load-bearing applications. Until now, hip,
knee, spinal and dental metal implants still cover up the majority of all
inserted implants worldwide. However, currently used metallic materials
are al icted with some limitations such as, corrosion which can cause tox-
icity or hypersensitivity reactions.
2.3
Responsive Polymers in Controlled Drug Delivery
Drug delivery systems can be classii ed according to the mechanism control-
ling the drug release: dif usion-controlled systems, chemically controlled
systems, solvent-activated systems and modulated-release systems [8]. In
