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Updated: Jul 11, 2026
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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Detection of bacteria in suspension by using a superconducting quantum interference device
H L Grossman1, W R Myers, V J Vreeland
1Department of Physics, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA.
Summary
This study introduces a novel method for detecting Listeria monocytogenes using magnetic nanoparticles and a sensitive superconducting quantum interference device. The technique allows for rapid quantification of bacteria and measurement of binding rates without sample pre-treatment.
Area of Science:
- Biotechnology
- Microbiology
- Physics
Background:
- Accurate and sensitive detection of bacterial pathogens like Listeria monocytogenes is crucial for public health.
- Existing methods often require extensive sample preparation, including immobilization and washing steps, which can be time-consuming and introduce errors.
- Superconducting quantum interference devices (SQUIDs) offer unparalleled sensitivity for detecting minute magnetic signals.
Purpose of the Study:
- To develop a sensitive and rapid assay for detecting Listeria monocytogenes.
- To quantify the binding rate between antibody-functionalized magnetic nanoparticles and bacteria.
- To establish a method that avoids sample immobilization and washing steps.
Main Methods:
- Utilizing 50-nm superparamagnetic magnetite nanoparticles coated with antibodies specific to Listeria monocytogenes.
- Applying a pulsed magnetic field to align magnetic dipole moments of the nanoparticles.
- Measuring the magnetic relaxation signal using a high-transition temperature superconducting quantum interference device (SQUID) after the field is removed.
- Analyzing the Néel relaxation process of bound versus unbound magnetic particles.
Main Results:
- A detection limit of (5.6 +/- 1.1) x 10^6 Listeria monocytogenes cells in 20 microliters was achieved.
- The assay demonstrated the potential for improved detection limits down to 230 +/- 40 cells in 1 nL.
- Time-resolved measurements enabled the determination of the binding rate between magnetic nanoparticles and bacteria.
- Unbound particles were distinguished from bacteria-bound particles by their rapid Brownian rotation versus slower Néel relaxation.
Conclusions:
- The developed technique offers a sensitive and specific method for detecting Listeria monocytogenes.
- The assay's ability to quantify bacteria and binding rates without immobilization or washing represents a significant advancement.
- This SQUID-based magnetic detection method holds promise for rapid pathogen screening in various sample types.
