Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Rapid detection of Escherichia coli by nanoparticle bas ed immunomag netic separation and SERS
Burcu Guven 1 , Nese Basaran Akgul 1 , Erhan Temur 2 , Ugur Tamer 2 1 *
1 Department of Food Engineering, Faculty of Engineering, Hacettepe University, Beytepe 06800, Ankara, Turkey
2 Department of Analytical Chemistry, Faculty of Pharmacy, Gazi University, 06330 Ankara, Turkey
Abstract- Detection of microbial pathogen in food is the solution and to the prevention and recognition of problems related to
health and safety. In this study, a method combining immunomagnetic separation (IMS) and surface-enhanced Raman
scattering (SERS) was developed to detect Escherichia coli (E. coli). The ability of the
immunoassay to detect E. coli in real water samples was investigated and the results were compared with the experimental
results from plate-counting methods.
Nanomaterials can be conjugated with different
biomolecules such as nucleic acids 1, peptides and
proteins, antibodies 2, carbohydrates, and antibiotics 3.
One of the most important research field of nanoscience
and nanotechnology is the control and detection of various
microorganisms 4. The major advantage of using
nanomaterials instead of microbeads is the higher capture
efficiency due to the high surface-to-volume ratio. Other
advantages of using nanoparticles include faster reaction
kinetics and minimal sample preparation 5.
Escherichia coli (E. coli), which found in large numbers
among the intestine of humans and other warm-blooded
animals spread abroad in natural environment, is the major
cause of infection outbreaks with serious consequences 6.
More recently, several rapid assays for detecting E. coli
based on different measuring principles, such as
polymerase chain reaction immunoassay, optical assay
etc., have been developed. Although these methods
shortened the detection time varying from several hours to
one day, many of these methods are still time-consuming
and poor in sensitivity. In recent years, due to magnetic
properties, low toxicity and biocompatibility, magnetic
nanoparticles (MNPs) receive considerable attention.
In this study a method combining immunomagnetic
separation (IMS) and surface-enhanced Raman scattering
(SERS) was developed to detect
Escherichia coli (E. coli). Polyclonal antibody specific
for the E. coli antigen was added to gold coated magnetic
nanoparticles to create antibody-coated beads. Then gold
coated nanoparticles which are treated with 5,5 -
0Tdithiobis (2-nitrobenzoic acid (DTNB)) are interacted
with gold coated magnetic nanoparticles and the
calibration curve was obtained in surface-enhanced Raman
scattering. The capturing efficiency was examined in
different E. coli concentrations (10 1- 10 7 ).
The selectivity of the developed sensor was examined
with Enterobacter aerogenes, Enterobacter dissolvens,
which did not produce any significant response (Figure 1).
compared with the experimental results from platecounting
methods. There was no significant difference
between the methods that were compared (p>0.05). This
method is rapid and sensitive to target organisms.
This work was partially supported by TUBITAK under
Grant No. TBA G-107T682.
*Corresponding author: ihb@hacettepe.edu.tr
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SERS Intensity counts/s
4500
4000
3500
3000
2500
2000
1500
1000
500
0
Enterobacter
aerogenes
Enterobacter
di ssol vens
Escherichia coli
Figure 1. The SERS intensities of E. aerogenes, E. dissolvens,
and E. coli at fixed concentration.
The ability of the immunoassay to detect E. coli in real
water samples was investigated and the results were
6th Nanoscience and Nanotechnology Conference, zmir, 2010 229