Biomedical Engineering Reference
In-Depth Information
CSF: 0.3%
saliva: 1.7%
urine: 6.6%
all years:
8925 articles
CSF: 0.5%
last 5 years:
2385 articles
saliva: 4.2%
urine:13.6%
serum: 91.5%
serum: 81.7%
(a)
(b)
Fig. 3 Number of publications on biosensors in combination with different sample matrices, ISI
Web of Knowledge, August 15, 2011. The keyword combination was ''biosensors AND [sample
type]''. The article counts are shown as a percentage of the sum resulting from the four keyword
combinations. a All years (database starts 1926); b last 5 years
3 Biosensors for the Detection of Biomarkers
in Real Samples
3.1 Real Samples for Diagnostic Applications
When it comes to the choice of material for disease diagnosis, human body
fluids instead of tissue are generally preferred, mainly because of the lower
invasiveness. This goes well together with biosensor measurements, which typ-
ically require liquid samples. Provided that the disease markers to be detected
are contained, samples seem the more attractive the easier they can be collected
and processed with minimum time and effort [
1
]. The most commonly used
sample type for biosensors in diagnostic applications is serum, but in the last
5 years other body fluids, such as urine and saliva, have increasingly been
investigated (Fig.
3
), which is because they can also be collected by noninvasive
sampling. Furthermore, they allow a closer investigation of the state of their
origin. Urine samples, for instance, may provide more information about the
current state of kidney and bladder than serum samples [
99
]. Salivary samples,
aside from detection of viruses, drug abuse, and some cancer biomarkers, allow,
in particular, the monitoring of oral diseases [
13
,
100
]. Biosensor measurements
using CSF have also been gaining interest in recent years owing to potential
biomarkers in CSF allowing early detection of neurodegenerative diseases, such
as Alzheimer's disease [
101
]. All the real sample matrices have in common that
they supply a complex protein background which may nonspecifically bind to the
biosensor surface, resulting in false-positive results. For strategies to overcome
this problem, see
Sect. 2.2
.
