Biomedical Engineering Reference
In-Depth Information
CH
3
H
CH
3
CH
2
CH
2
CH
2
stat
stat
stat
COOCH
3
COOH
SO
3
Na
11.2
Schematic representation of functionalized PMMA-based
random terpolymer of methyl methacrylate (MMA), comethacrylic
acid (MA) and cosodium styrene sulfonate (NaSS).
and two anionic monomers, methacrylic acid (MA) and sodium styrene
sulfonate (NaSS), by varying the ratio R = [COO
-
]/[COO
-
+ So
3
-
] from
0 to 1 and keeping the ionic monomer molar content below 15% to avoid
polymer solubilization in the physiologic medium.
Adsorption of fibronectin onto PMMA was shown dramatically to promote
bacterial adherence, whereas strong inhibition of bacteria adherence (up to
90%) was observed onto functionalized terpolymers containing both carboxylate
and sulfonate groups with R at around 0.5-0.6. When terpolymers were
predominantly functionalized by a carboxylate group, bacteria adherence
was favoured and reached values close to PMMa.
22
These results have
been related to the radical copolymerization process of the three monomers,
allowing the creation of active sites responsible for specific interactions with
fibronectin and inducing modifications of its conformation. The conformation
of the adsorbed adhesive protein was then suggested to have an influence on
the availability of its interaction sites with bacteria adhesins and therefore
on modulation of bacteria adherence. inhibition of
S. aureus
adherence by
functionalized PMMa-based terpolymers was shown to be of great interest
in the field of biomedical implants.
The bioactive polymer exhibiting the highest inhibiting properties against
S. aureus
has been covalently grafted onto silicon implants
34
and bacteria
adhesion was assessed
in vivo
on rabbits for 24 hours
21
following the 'model
of infection' developed by Crémieux and co-workers.
20
results evidenced
the maintainence of the inhibiting properties of the bioactive polymer grafted
surfaces in comparison to the non-grafted one under physiological
in vivo
conditions. The observed difference in bacteria adhesion was attributed to
differences in the composition of the protein layer adsorbed onto the surfaces
during the experiment. Indeed, controlling the host response using bioactive
surfaces is generated by controlling the adsorption of proteins; proteins
adsorbed onto bioactive surfaces exposed domains favourable, or not, to
further interactions with cells and bacteria. By varying the chemistry of the
surface - introducing precise functional groups - it is possible to modulate
