Barbieri Thesis - BioMedical Materials program (BMM)

Chapter 4 – Conntrol
of mechanical
and degraddation
properties s in composites
frameworrk
for bone fo
osteoblasst
adhesion.
mimic bo
mechanic
however
content a
These int
influence
The use
character
However,
lead to b
entrap th
homogen
particular
avoid fille
provoking
breaking
a solvent
size 300–
acetone
resulting
inorganic
evaporati
their agg
fumes ma
[24
one tissue p
cally and biolo
their develop
and distributio
trinsic propert
the character
of increasing
ristics, [241–243]
ormation
, we observed
brittle compos
he inorganic f
neous distrib
rly it favors un
er aggregates
g and support
of the materia
t–based meth
–400 m). In
and added p
composites w
component
on, the fumin
gregation befo
ay create nano
[241] w
41–243] Thus, co
physicochemic
ogically (i.e. os
pment implies
on, the chemis
ies of compos
ristics of the fin
amounts of
can improve
d that an exce
sites because
filler (see Cha
bution of the
niform load tra
because they
ing the format
al. [333] with increasedd
protein adsorption
and enhanced e
ombining polymmers
with calc cium phospha ates could
cally (i.e. coomposition
an nd porous structure), s
steoconductivvity).
Composites
appear promising, p
the control of many para ameters such h as filler
stry and moleecular
weight of the polyme er phase.
sites should bbe
carefully ba alanced as the ey largely
nal biomateriaal.
inorganic filller,
besides giving better biological
the stiffness of the resulting
composite es. [243, 332]
essive filler quuantity,
i.e. hig gher than 50% %wt., may
the organic component is s not sufficien nt to fully
apter 3 of thiss
thesis). Fur rther to the content, c a
e filler is cruccial
for the mechanical m properties,
ansfer along tthe
whole mat terial. It is imp portant to
y are stress ppoints
where loads l may concentrate
tion of internaal
cracks, whic ch later can le ead to the
In a prev vious study (ssee
Chapter 3 of this thesis) ) we used
od to prepare e porous compposites
(poros sity >60%vv. with pore
n that study we suspendeed
nano–size ed apatite pa articles in
poly(D,L–lactid de), a polymeer
fully dissolv vable in acetone.
The
were not unif form and hadd
aggregates s (2 to 6 m m size) of
(see Chapter
3 of this thhesis)
because
during the e solvent
ng of acetone may have shhifted
the apat tite particles le eading to
ore the comp plete polymerr
hardening. Further, such h solvent
o– and/or micro–pores
in thhe
composite matrix m (Figure 1).
Figure 1. SSEM
picture of thhe
surface of a co omposite prepareed
using solvent– –way (i.e. aceton ne) showing
the pores caused,
most likelly,
by the solvent t evaporation. Figgure
(b) is the hig gher magnification
of (a).
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