Biomedical Engineering Reference
In-Depth Information
200 ng / ml Ricin
100 ng / ml Cholera toxin
7.3x10
6
cfu/ml
F. tularensis LVS
1.4x10
5
cfu / ml killed
B. abortus
7.1x10
4
cfu/ml
B. anthracis Sterne
100 ng / ml SEB
Direction of flow
Fig. 11.9.
Antibody array used to interrogate six samples for six different biothreat
agents. Reprinted from [40] with permission of the Elsevier
The planar geometry provides a surface for depositing arrays of detection
molecules. This makes it ideal for multianalyte detection. An example of such
an array is shown below. In numerous papers reviewed by Sapsford et al.
in [1,2], the limits of detection are typically about an order of magnitude bet-
ter with good array biosensors, based on planar waveguides than for standard
ELISAs using the same reagents. In addition to antibodies and DNA, detec-
tion molecules used with planar waveguide biosensors include siderophores,
carbohydrates, antimicrobial peptides, and gangliosides [2] (Fig. 11.9).
11.7 Critical Issues and Future Opportunities
Fluorescence-based optical biosensors have inherent advantages for discrimi-
nating targets in complex samples and for increasing sensitivity compared with
label-free methods. Limits of detection can be further reduced using amplifi-
cation methods such as enzymes, polymerases, or multifluorophore complexes
(e.g., labeled dendrimers as in [41], or virus particles carrying 60 carefully sep-
arated fluorophores as in Sapsford et al., 2006). However, labeling and ampli-
fication procedures can complicate assay processes, making automation more
di
cult and possibly increasing fluorescence background. Another method
for increasing signal include preconcentration of target prior to analysis using
