Biomedical Engineering Reference
In-Depth Information
the RBF and the apparatus was sonicated for 1 hour. The reactive mixture
should cover the samples in order to obtain a uniform reaction all over the
surface. After 1 hour, the solution in the RBF was syringed out and the
Ti6Al4V surfaces were sonicated three times for 3 minutes by adding an
excess of anhydrous THF to the RBF each time. After this step, 10 mM of
Ciprofloxacin in anhydrous THF was added to the RBF and sonicated for
1 hour. Finally, the Ciprofloxacin solution was syringed out and sonicated
with an excess of anhydrous THF and deionised water (twice for 2 minutes
each) to remove physisorbed molecules. Care should be taken so that the
whole process is conducted in a nitrogen atmosphere to prevent the for-
mation of HCl gas due to the use of SOCl
2
.
Electron spectroscopy for chemical analysis (ESCA) (XPS; Thermo Scien-
tific K-Alpha) was used to study the surface chemistry. Aluminium (Al) Ka
monochromated radiation at 1486.6 eV was used and photoelectrons were
collected at a take-off angle of 901. The probing spot size used to obtain the
measurement was 400 mm. Survey spectra were collected at a pass energy of
100 eV in a constant energy analyser mode. High resolution spectra were
obtained at a pass energy of 20 eV. Peak deconvolution was performed using
Gaussian-Lorentzian curves to determine the different chemical states.
A built-in Thermo Advantage data system was used for data acquisition and
processing. The NIST database and previously reported literature were used
to identify the unknown spectral lines.
Figure 2.10 shows typical XPS spectra obtained for a Ti6Al4V surface be-
fore SAM attachment (a), after SAM attachment (b) and after the attachment
of a drug (Ciprofloxacin). A phosphorus 2P peak would be expected after
SAM coating since the monolayer used was a phosphonate group and an
increase in carbon (C 1s) intensity would be expected due to the presence of
a long alkyl chain. Similarly, the intensity of the base elements (Ti, Al, O)
present on the surface of the sample would have been expected to decrease.
This is because the intensity of photoelectron penetration to the base
elements will be low and this will result in the decrease of base element's
peak intensity after surface coating. After functionalisation, a fluorine peak
(F 1s) would be expected with an increase in the nitrogen composition due to
the presence of these elements in Ciprofloxacin.
It can be observed from the figure that the phosphorus peak was not
observed initially in the control sample whereas after SAM attachment,
introduction of a phosphorus 2P peak at 133.3 eV can be witnessed. An ex-
pected increase in the carbon (C 1s) intensity and decrease in the intensity of
the titanium, aluminium and oxygen after surface modification with SAMs
confirmed their attachment. Figure 2.11 shows the deconvoluted high-
resolution spectra of fluorine 1s obtained using XPS for these control,
SAM coated and drug coated samples. The appearance of fluorine 1s peak at
the energy 687.1
0.2 eV after the surface functionalisation shows the at-
tachment of Ciprofloxacin. The introduction of the fluorine peak is at-
tributed to its presence in the drug. The wettability of the samples before
and after surface modification was studied using static water contact angle
goniometry to confirm the attachment of SAMs and the drug. As can be
d
n
3
r
4
n
g
|
0
.
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