Conventional methods of monitoring and testing water quality involve collection of the sample to be tested and its subsequent analysis in a research laboratory for which some procedures may not be feasible or even accessible under certain field situations. Therefore, next generation sensors are required. Herein, an innovative concept that combines a micromixer and microparticle trap is proposed that should enable more rapid pathogen detection in contaminated water. In it, immunomagnetic separation (a procedure [1,2] that is well practiced in the field of immunochemistry) is scaled down from the benchtop to the microscale. Our design is generic, i.e., design is not limited to the detection of waterborne biological agents, but can be used for other forms of chemical analysis. Testing for waterborne bacteria requires analysis methods that must meet a number of challenging criteria. Time and sensitivity of analysis are the more important limitations. Bacterial detection methods have to be rapid and very sensitive since the presence of even a small pathogenic sample may sometimes constitute an infectious or otherwise harmful dose. Selective detection is also required because small numbers of pathogenic bacteria are often present in a complex biological environment along with many other nonpathogenic organisms. As an example, the infectious dosage of a pathogen such as E. coli O157:H7 or Salmonella is as low as 10 cells and the existing coliform standard for E. coli in water is 4 cells: 100 ml [3].

1.
Olsvik
O.
, et al.
1994
, “
Magnetic Separation Techniques in Diagnostic Microbiology
,”
Clinical Microbiology Reviews
, Vol.
7
, pp.
43
54
.
2.
Ohara
et al.,
2001
, “
Magnetic separation using superconducting magnets
,”
Physica C
,
357–360
, pp.
1272
1280
.
3.
Greenberg, A.R., Trussel, R.R., Clesceri, L.S., Franson, M.A.H. (Eds.), 1992. Standard Methods for the Examination of Water and Wastewater. American Pablic Health Association, Washington, DC.
4.
Madigan, M.T., Martinko, J.M., Parker, J. (Eds.), 1997. Brock Biology of Microorganisms, eight ed. A Viacom Company Upper Saddle River, NJ, 986 pp.
5.
Kawaguchi
H.
, et al,
1996
, “
Modification and functionalization of hydrogel microspheres
,”
Colloids and Surfaces, A: Physicochemical and Engineering Aspects
, Vol.
109
, pp.
147
154
.
6.
Caliceti, P., et al, 2005, “Preparation and characterization of active site protected poly(ethylene glycol)-avidin bioconjugates,” Biochimica et Biophysica Acta, article in press.
7.
Graham
D. L.
,
2003
, “
High sensitivity detection of molecular recognition using magnetically labelled biomolecules and magnetoresistive sensors
,”
Biosensors and Bioelectronics
, Vol.
18
, pp.
483
488
.
8.
Ahn, C. H., Allen, M. G., 1994, “A fully integrated micromachined magnetic particle manipulator and separator,” IEEE 0-7803-1883-1/94.
9.
Hessel
V.
,
Lowe
H.
,
Schonfeld
F.
,
2005
, “
Micromixers-A review on passive and active mixing principles
,”
Chemical Engineering Science
, Vol.
60
, pp.
2479
2501
.
10.
Smistrup
et al.,
2005
, “
Magnetic separation in microfluidic systems using microfabricated electromagnets—experiments and simulations
,”
Journal of Magnetism and Magnetic Materials
Vol.
293
pp.
597
604
11.
Choi
et al.,
2001
, “
An on-chip magnetic bead separator using spiral electromagnets with semi-encapsulated permalloy
,”
Biosensors & Bioelectronics
, Vol.
16
, pp.
409
416
12.
Gillies
G. T. R.
,
Ritter
R. C.
,
Broaddus
W. C.
,
Grady
M. S.
,
Howard
M. A.
,
McNeil
R. G.
,
1994
,
Review of Scientific Instruments
, Vol.
65
,
533
533
.
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