CELL - BASED NANOCOMPOSITES AND BIOMOLECULES FOR BONE TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 548

16.3 TYPES OF MATERIALS FOR BONE APPLICATIONS

It is of paramount importance that material selection should not be overlooked
as the type of material selected plays a pivotal consideration of the success of
bone tissue engineering as illustrated in this section of the chapter.

16.3.1 Bioceramics
Calcium phosphate materials have been used as bone substitutes because they
possess excellent biocompatibility and osteoconduction characteristics. Materials
such as Bioglass®, TCP and HA are some bioactive ceramics used in orthopedic
applications. The bioceramic coatings on total joint replacement prostheses may
also act as bonding agents between the implant and the native tissue. Some issues
pertaining to these materials are inadequacies in bulk properties, lack of mechan-
ical strength especially in load-bearing sites, problems in fi lling up large bony
defects etc. Consequently, there is a medical need for a biomimetic material,
which can solve the above-mentioned concerns, whilst improving bone formation
in vivo .
Some researchers have successfully fabricated ceramic nanofi bers such as
HA and fl uoro-hydroxyapatite (FHA) using an electrospinning technology 46 .
The HA and FHA precusors were employed in sol-gel solutions and the solutions
were subjected to aging and gelation processes. Subsequently, the sol-gel solu-
tions were mixed with polyvinyl butyral (PVB) and used for electrospinning. By
manipulating the sol concentration, the diameter of the fi ber can range from
micrometers to nanometers in size (1.55 m to 240 nm). Other processing factors

which affect the fi ber diameter to a lesser extent are the injection rate and fi eld
strength of the electrospinning parameters. Apatite polycrystallines (approxi-
mately 30 - to - 40 nm) were observed. The FHA nanofi bers exhibited greater
chemical stability than HA nanofi bers 46 and the release of fl uorine ions was
said to be benefi cial in dental restoration applications because fl uorine helped
to prevent the dental caries formation and enhance mineralization and bone
formation 47,48 .
Biphasic calcium phosphate scaffolds comprising of

μ

β - tricalcium phosphate

( -TCP) matrix reinforced with HA nanofi bers were produced by using a gel

casting and polymer sponge techniques to improve material properties 49 . HA
nanofi bers were fi rst synthesized via a biomimetic chemical precipitation method
and incorporated with the

β

-TCP powder to make ceramic slurries. After polym-
erization of the monomers, a polyurethane foam with the desired shapes and
sizes was then immersed into the ceramic slurries and subjected to sintering pro-
cesses for the production of the nanocomposite scaffolds. The compressive
strength and modulus increased as the HA nanofi ber concentration increased.
The HA nanofi bers owing to their high surface energy can be easily diffused in
the grain boundaries of the matrix during sintering. Scaffolds with 5wt% HA
nanofi bers had a compressive strength of 9.8

β

0.3 MPa, comparable to the high
end of the compressive strength of cancellous bone (2-10 MPa) 50 .

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