Biomedical Engineering Reference
In-Depth Information
1982
). Thus, surface analysis revealed a chemical pa-
rameter about the surface that could be used to predict
long-term biological reactivity of materials in a complex
ex vivo
environment.
Modern static SIMS instrumentation, using amultivariate
statistical analysis of the data, has demonstrated the
ability to distinguish between more than 13 different
proteins adsorbed on surfaces (
Wagner and Castner,
2001
). Also, the limits of detection for adsorbed proteins
on various surfaces were compared by ESCA and SIMS
(
Wagner
et al.
, 2002
).
Contact-angle correlations
The adhesion of a number of cell types, including bacteria,
granulocytes, and erythrocytes, has been shown, under
certain conditions, to correlate with solid-vapor surface
tension as determined from contact-angle measurements.
In addition, immunoglobulinGadsorption is related to
n
sv
(
Neumann
et al.,
1983
).
Poly(glycolic acid) degradation
studied by SIMS
The degradation of an important polymer for tissue en-
gineering, poly(glycolic acid), has been studied by static
SIMS. As well as providing useful information on this
degradation process, the study illustrates the power of
SIMS for characterizing synthetic polymers and their
molecular weight distributions (
Chen
et al.,
2000
).
Contamination of intraocular lenses
Commercial intraocular lenses were examined by ESCA.
The presence of sulfur, sodium, and excess hydrocarbon
at their surfaces suggested contamination by sodium
dodecyl sulfate (SDS) during the manufacture of the
lenses (
Ratner, 1983
). A cleaning protocol was developed
using ESCA to monitor results that produced a lens
surface of clean PMMA.
Conclusions
The instrumentation of surface analysis steadily advances
and newer instruments and techniques can provide in-
valuable information about biomaterials and medical
devices. The information obtained can be used to moni-
tor contamination, ensure surface reproducibility, and
explore fundamental aspects of the interaction of bi-
ological systems with living systems. Considering that
biomedical experiments are typically expensive to per-
form, the costs for surface analysis are modest to ensure
that the surface is as expected, stable and identical from
experiment to experiment. Surface analysis can also
contribute to the understanding of medical device failure
(and success). Myriad applications for surface methods
are found in device optimization, manufacture and
quality control. Predicting biological reaction based on
measured surface structure is a frontier area for surface
analysis.
Titanium
The discoloration sometimes observed on titanium im-
plants after autoclaving was examined by ESCA and
SIMS (
Lausmaa
et al.
, 1985
). The discoloration was
found to be related to accelerated oxide growth, with
oxide thicknesses to 650
˚
. The oxide contained con-
siderable fluorine, along with alkali metals and silicon.
The source of the oxide was the cloth used to wrap the
implant storage box during autoclaving. Since fluorine
strongly affects oxide growth, and since the oxide layer
has been associated with the biocompatibility of titanium
implants, the authors advise avoiding fluorinated mate-
rials during sterilization of samples. A newer paper con-
tains detailed surface characterization of titanium using
a battery of surface methods and addresses surface
preparation, contamination, and cleaning (
Lausmaa,
1996
).
Acknowledgment
Support was received from the UWEB NSF Engineering
Research Center and the NESAC/BIO National
Resource, NIH grant EB-002027, during the preparation
of this work and for some of the studies described
herein.
SIMS for adsorbed protein identification
and quantification
Questions
All proteins are made up of the same 20 amino acids and
thus, on the average, are compositionally similar. Surface
analysis methods have shown the ability to detect and
quantify surface-bound protein, but biological tools have,
until recently, been needed to identify specific proteins.
1.
Scan the table of contents and abstracts from the last
three issues of the
Journal of Biomedical Materials
Research
or
Biomaterials.
List all the surface analysis
