Accepted Manuscript Title: Multiplexed detection of foodborne pathogens based on magnetic particles Author: Delfina Brand˜ao Susana Li´ebana Mar´ıa Isabel Pividori PII: DOI: Reference:
S1871-6784(15)00053-9 http://dx.doi.org/doi:10.1016/j.nbt.2015.03.011 NBT 776
To appear in: Received date: Revised date: Accepted date:
2-10-2014 16-3-2015 22-3-2015
Please cite this article as: Brand˜ao, D., Li´ebana, S., Pividori, M.I.,Multiplexed detection of foodborne pathogens based on magnetic particles, New Biotechnology (2015), http://dx.doi.org/10.1016/j.nbt.2015.03.011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Multiplexed detection of foodborne pathogens based on magnetic particles
Grup de Sensors i Biosensors, Departament de Química, Universitat Autònoma de
Applied Enzyme Technology Ltd., Gwent Group Ltd., Monmouth House, Mamhilad Park, Pontypool, NP4 OHZ, UK.
Barcelona, 08193 Cerdanyola del Vallès (Bellaterra), Spain
8 9 10
Delfina Brandão1, Susana Liébana2 and María Isabel Pividori1*
* Tel: +34 93 581 4937, Fax: +34 93 581 2473. E-mail address:
*Authors to whom correspondence should be sent: [email protected]
pt Ac ce
Page 1 of 34
This paper addresses the novel approaches for the multiplex detection of food poisoning
bacteria, paying closer attention to three of the most common pathogens involved in
food outbreaks: Salmonella enterica, Escherichia coli O157:H7 and Listeria
monocytogenes. End-point and real-time PCR, classical immunological techniques,
biosensors, microarrays and microfluidic platforms, as well as commercial kits for
multiplex detection of food pathogens will be reviewed, with special focus on the role
of magnetic particles in these approaches. Although the immunomagnetic separation for
capturing single bacteria from contaminating microflora and interfering food
components has demonstrated to improve the performance on these approaches, the
integration of magnetic particles for multiplex detection of bacteria is still in a
preliminary stage and requires further studies.
Keywords: Food safety, simultaneous detection, magnetic particle, electrochemical
biosensor, multiplex PCR, food pathogens.
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Food safety in Europe
Food contamination caused by pathogens is a significant public health concern for
consumers worldwide. Therefore, identification and detection of microorganisms in
food processing play an important role at control programs provided by Food regulatory
agencies, in order to prevent food outbreaks [1, 2]. In 2013, it was reported by the Rapid
Alert System for Food and Feed (RASFF) that pathogenic microorganisms, mycotoxins
and pesticide residues were the main cause of notification in Europe, especially for meat
products, as well as for fruits and vegetables . For instance, the notifications of
pathogens in meat products are shown in Figure 1, being Salmonella, E. coli and L.
monocytogenes the most common reported pathogens.
Preferred position for Figure 1
Hence, food safety standards, such as RASFF were introduced in Europe in order to
prevent foodborne outbreaks and to ensure that marketed products are safe to the
Preventive approaches like Hazard Analysis and Critical Control Point (HACCP) and
the Codex Alimentarius were also successfully implemented, which can considerably
reduce the survival of pathogens during the process of handling, preparation and storage
of food. But there is still a need for the development of new tools and technologies to
prevent problems related to food safety, including rapid approaches for the
identification and quantification of foodborne pathogens [8, 9].
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Traditional methods for the detection of foodborne pathogens
Threshold limits for the presence of certain microorganisms had been set down for some
food products. If the food product contains an amount above the required legislation, it
must be rejected from the market. Therefore, in this section, the traditional methods
commonly used for the single detection of foodborne pathogens will be discussed, with
special focus on their advantages and disadvantages.
Conventional microbiological culture techniques
Conventional microbiological culture techniques are currently the gold standard for
isolation, detection, and identification of microorganisms. These methods are very
simple, consisting in the following steps: pre-enrichment, selective enrichment,
selective plating, biochemical screening and serological confirmation. Although they
are considered to be reliable, they are also time-consuming, laborious and might
introduce sampling and enumeration errors, due to the low concentration of pathogenic
bacteria in food samples [9, 10].
Immunological assays (IAs) relies on the specificity of the antigen-antibody
recognition, being suitable for the detection of whole bacterial cells or specific cellular
components as lipopolysaccharides or other biomolecules present on the bacterial outer
membrane. Enzyme Linked ImmunoSorbent Assays (ELISAs), such as sandwich with
direct and indirect labelling are the most common formats used for the detection of
pathogens. ELISA methods have been approved by regulatory agencies, being
commercially available. The limit of detection (LOD) for pathogens are normally in the
range of 104 and 105 CFU mL-1 and the assay time can take around 48 h, since a pre4
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enrichment step is commonly required in order to achieve the threshold limits for the
presence of the bacteria on food samples [8- 10].
Immunomagnetic separation (IMS) is also an example of an immunoassay commonly
used for bacteria detection. In this technique, superparamagnetic particles modified with
a variety of molecular groups are coated with antibodies specific to the target bacteria.
Therefore, bacteria will be captured and concentrated either from a culture medium or
from complex food matrices. The use of magnetic particles provides several advantages
to IAs such as (i) pre-concentration of the target bacteria into smaller volumes for
further testing (ii) reducing and simplifying the pre-enrichment step (iii) eliminating the
matrix effect of the food components .
Magnetic particles can also be modified with bacteriophages for capturing and pre-
concentration of bacteria, in an ELISA-like format, named as phagomagnetic
immunoassay, decreasing significantly the LOD of a classic immunoassay, up to 19
CFU mL−1 in 2.5 h without any pre-enrichment in milk samples .
Therefore, IAs are advantageous for decreasing the assay reaction time in comparison
with microbiological culturing techniques, providing also the possibility of being easily
integrated in automated equipments, which consists an important advantage for
industrial applications. Nevertheless, the efficiency of an immunoassay is strongly
dependent on the antibodies affinity and specificity towards the target pathogen. The
risk of antibody cross-reactions consists of a disadvantage of immunological assays by
increasing the possibility of false positive results or high background signals [8- 11].
Nucleic acid amplification methods
Nucleic acid amplification methods include end-point polymerase chain reaction (PCR)
and real-time PCR (qPCR) for single or multiplex detection of bacteria. PCR allows the 5
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production of multiple copies of DNA from the amplification of a single copy or a few
copies of a DNA template. Due to its high sensitivity, nucleic acid amplification has
been widely used for the identification and detection of pathogens in food samples,
being considered as an alternative to conventional microbiological culture techniques.
As occurred in the immunological assays, PCR methodologies require an enrichment
step, being able to detect, for instance in the case of Salmonella, few CFUs in 25 g of
food product. The fact that this methodology does not discriminate between live of dead
cells are pointed out as the main limitations [8- 13].
Hence, it was shown that traditional methodologies can be sensitive for food
microbiological control. However, the stricter and increased legislations and controls to
implement public food safety lead mostly to a need for the development of rapid
methodologies. In this context, the development of new methodologies with
multiplexing capabilities becomes an important advantage presenting a cost effective
and time saving strategy.
Immunosensors, DNA biosensors and phagosensors
Over the recent years, a lot of effort has been directed into the study and development of
rapid methods for foodborne pathogens as an alternative methodology to
microbiological culturing, IAs and PCR approaches . Biosensors technology has
been revolutionised research conducted in food safety. These devices are available in a
wide range of readout platforms, such as surface plasmon resonance ,
electrochemical  and various kinds of optical biosensors . Most of the current
developed biosensors for pathogenic bacteria are based on the specific antigen –
antibody binding reactions, where the antibody is immobilised on the sensor platform to
capture the bacteria that are of interest. Then, the bacteria detection is measured through
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biorecognition is also widely used in biosensing, as well as the biorecognition through
bacteriophages. The integration of magnetic particles in immunosensors, genosensors
and phagosensors was reported, for instance, in electrochemical based approaches,
improving the analytical performance in terms of LODs. A magneto immunosensor
with electrochemical readout was reported for the detection of Salmonella in milk
(Figure 2, A). In this approach, the bacteria were captured and pre-concentrated from
milk samples with magnetic micro or nanoparticles through an immunological reaction.
A second polyclonal antibody labelled with peroxidase was used for the electrochemical
detection based on a magneto-electrode [16, 19]. This strategy was able to detect 1x104
CFU mL-1 in 1h. If the sample is pre-enriched for 8 h, as low as 2.7×CFU in 25 g of
milk were detected accordingly with the legislation. Another approach involves the lysis
of the captured bacteria after immuno or phagomagnetic separation, followed by
amplification of the genetic material by PCR with a double-tagging set of primers
(Figure 2, B). Then, the double-tagged amplicon was immobilised on streptavidin-
modified magnetic beads based on a high affinity interaction though the biotin tagging
the 5`end DNA of the amplicon, while the digoxigenin label was used for the enzymatic
reaction. The electrochemical detection was finally achieved by an enzyme marker,
such as anti-digoxigenin horseradish peroxidase (HRP). A LOD of 1 CFU mL-1 was
obtained in 3.5 h without any pre-treatment. If the milk is pre-enriched for 6 h, the
method is able to feasibly detect as low as 1 CFU in 25 g of milk [20, 21]. The
integration of the magnetic particles improved the analytical performance of these
approaches, providing the pre-concentration of the bacteria during the IMS, reducing
the time required for the pre-enrichment step and the LODs, eliminating the matrix
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effect of the food components and PCR inhibitors, and serving also as a platform for the
electrochemical readout based on magneto-actuated electrodes.
153 154 155
Preferred position for Figure 2
Simultaneous detection of pathogenic bacteria
In this section, different methods for the simultaneous detection of pathogenic bacteria
based on multiplex PCR, DNA microarrays and biosensors will be fully reviewed and
summarised in the Tables 1 and 2.
End-point multiplex PCR (mPCR) has been widely used to detect simultaneously
multiple targets in the same amplification reaction. The efficiency of this methodology
is strongly dependent on different factors, such as primers specificity, buffer,
magnesium chloride and Taq DNA polymerase concentration, thermal cycling
conditions and the amount of DNA template.  When applied to the detection of
foodborne pathogenic bacteria, a pre-enrichment step is required in order to enhance
detection of pathogens in samples. Recently, mPCR for the detection of five different
pathogens in artificially contaminated pork samples was reported [23- 24]. In Table 1,
selected studies published in the literature are shown, summarising and highlighting the
most important parameters in terms of the analytical performance, including the food
matrix, the time required for the pre-enrichment step, the total assay time and the LODs.
For instance, the simultaneous detection of E. coli, Salmonella spp. and L.
monocytogenes by end-point multiplex PCR showed a LOD of 10 CFU in 25 g of
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sample within 15 h of pre-enrichment . The detection by end-point mPCR usually
requires the analysis of the PCR final products on an agarose gel or on capillary
electrophoresis-based DNA sequencer, being for this reason more laborious and time
consuming than Real Time PCR (qPCR), which provides the detection and
quantification during the amplification process in each cycle. In this methodology, the
fluorescence intensity of the amplicons is measured by either intercalation of
fluorescent dyes in the double-stranded DNA or with dual-labelled fluorescent
oligonucleotide probes, among others readout strategies . The application of qPCR
for simultaneous detection has been studied for several years and it requires the use
oligonucleotides tagged with different fluorophores specific for the different
microorganisms to be detected. Moreover, in some cases an internal amplification
control (IAC) is recommended to be added into the PCR mixture [26, 27], which
consists on a non-target DNA sequence, in order to avoid false-negative results caused
by inhibitors, such as phenolic compounds, fats and glycogen, that may affect different
steps of the qPCR method. qPCR procedures are in general faster than the related
conventional methodology, with similar sensitivity. Nevertheless, expensive bench top
equipment and high technical requirements are the main limitation of this methodology.
Recently, it has been reported in the literature the combination of magnetic particles
with PCR based methodologies. As an example, a rapid and simultaneous detection of
Salmonella, Shigella, and Staphylococcus aureus in fresh pork was reported, being able
to detect all pathogens at 10 CFU g-1, within 6 h [28, 29]. In this example, the use of
magnetic particles provided a significant decrease of the total assay time, including the
pre-enrichment step. This strategy is already commercially available for single
pathogens detection, proving the potential application of magnetic particles in food
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Microfluidic systems provide several advantages for the simultaneous determination of
multiple foodborne bacterial pathogens, such as portability, lower reagent consumption,
rapidity and possibility for automation. Usually, these systems are combined with
agarose gel electrophoresis for DNA analysis, but they can also be coupled with other
platforms . The risk of cross-contamination in the process of sample loading is
pointed out as one of the main inconvenients of these systems . In the Table 1, some
approaches for the simultaneous detection of pathogens using PCR based microfluidic
systems are presented. For instance, the simultaneous detection of S. enterica, E. coli
and L. monocytogenes was reported within 35 min, with LODs of 399, 314, and 626
DNA copies per μL, respectively .
212 213 214
Preferred position for Table 1
DNA microarrays were reported for the detection and identification of several
pathogens. In these arrays, a DNA probe or oligonucleotide is immobilised at fixed
positions on a substrate and used to capture the target molecule through hybridisation of
the amplified DNA, offering in this way higher capacity for multiplexing, as well as the
possibility of miniaturisation and automation . Several examples of DNA
microarrays for the simultaneous detection of foodborne pathogens are summarised on
the Table 1. In this context, it is emphasised that DNA microarrays provide an
important advantage of bacteria screening in a high number of food samples. The
detection is achieved by measuring the fluorescence intensity, which presents the
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limitation of being expensive and non-portable. Alternatively, colorimetric methods and
biochips combined with chemiluminescent labels can be used. Therefore, a DNA
microarray based on a colorimetric detection was reported using digoxigenin and biotin
labelled on the DNA. The simultaneous detection of Salmonella spp., Shigella spp., L.
monocytogenes, and E. coli was achieved with a LOD of 105 CFU mL-1, without any
enrichment step . A pathogen detection microarray combined with PCR
methodologies with fluorescence readout was developed for the simultaneous detection
of E. coli, S. enterica, L. monocytogenes and Campylobacter jejuni being able to detect
as low as 103 CFU mL-1 of culture medium or food sample .
Combination of DNA microarrays with nanomaterials are also being explored as an
alternative to overcome problems related to photo bleaching caused by fluorescent the
organic dyes. In this context, the identification of twelve bacterial strains, using
quantum dots coated with streptavidin as fluorescent labels was achieved with a LOD of
10 CFU mL-1 in pure culture, without any enrichment step . Furthermore, magnetic
particles can also be integrated on DNA microarrays opening the possibility of final
detection based on a digital camera or a light microscopy . In this context, it was
reported the detection of E. coli, S. enterica, C. jejuni, presenting LODs of 136, 500,
and 1 CFU mL-1, respectively, without any enrichment procedures. 
Nevertheless, the microarray fabrication and also the hybridisation procedure can be
time consuming, presenting the main disadvantage of this methodology.
Over the past years, a new challenge has been attracting researchers in this field, the
design of novel biosensors with multiplexing capabilities, where the integration of
nanomaterials plays an important role. These novel bionanomaterials, including 11
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nanostructured carbon materials, inorganic nanoparticles (i.e., semi-conducting, noble
metal and magnetic nanoparticles), among others, appears to be keys in bacteria
multiplex detection in biosensors, enhancing the biological reactions, providing high
selectivity and improving the LODs [39, 40, 41, 42].
In this section, different biosensor strategies will be discussed. These strategies are
summarised in the Table 2, with special focus on the assay type, detection technique,
food matrix, LODs and assay times, being classified according to the type of
nanomaterial integrated in each approach.
Preferred position for Table 2
Biosensing based on metallic nanomaterials
Metallic nanomaterials, such as gold or silver nanoparticles, as well as gold films are
the most common selection for the immobilisation of biomolecules and/or signal
amplification. In this context, a biosensor for the detection of Salmonella and E. coli
based on Raman spectroscopy was reported, in which gold, silver and core–shell
nanoparticles were coated with a Raman reporter molecule to improve the LOD of the
assay . This strategy was able to detect both bacteria with a LOD of 102 CFU mL-1
in 45 min. A multi-channel SPR biosensor for the simultaneous detection of S.
Typhimurium, L. monocytogenes, C. jejuni, and E. coli based on a sandwich
immunoassay was also reported, presenting LODs of from 3.4×103 to 1.2×105 CFU mL-
in 50 min .
Biosensing based on Quantum Dots 12
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Semiconductor particles as quantum dots (QDs) are also a common choice in the
strategies for multiplexing, either as a support for the target analyte or as a label to
enhance the optical or electrochemical readout. In this context, an electrochemical
immunosensor for the multiplex detection of E. coli, Campylobacter and Salmonella
based on a sandwich immunoassay with QDs modified with three antibodies specific for
each bacterium was reported with a LOD of 400 CFU mL−1 for Salmonella and
Campylobacter and 800 CFU mL−1 for E. coli in 1h . Another strategy was reported
recently using aptamers specific for Vibrio parahaemolyticus and S. Typhimurium
immobilised on quantum dots. The quantification of bacteria was based on dual
fluorescence resonance energy transfer (FRET) between QDs and carbon nanoparticles,
being able to detect 25 and 35 CFU mL-1 of V. parahaemolyticus and S. Typhimurium
respectively within 2h 20 min. 
Biosensing based on Magnetic Particles
Along this review, the integration of magnetic particles, either with micrometer or
nanometer sizes on the strategies for the detection of foodborne pathogenic bacteria has
been emphasised. The possibility of immobilisation of a variety of biomolecules, such
as enzymes, antibodies, oligonucleotides onto the magnetic particles surface, as well as
the possibility of being easily manipulated by an external magnetic field gradient,
provides a selective capture of the target bacteria, offering an attractive application
towards the development of new biosensors and microfluidic devices .
Magnetic particles have also been combined with several biosensors platforms,
especially biosensors with optical readout. In this context, some studies were reported
using both magnetic particles and quantum dots in a sandwich immunoassay. For one
side, IMS of bacteria was achieved with further fluorescence detection, using different
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quantum dots modified with antibodies specific for each bacterium [48, 49]. Recently,
an aptasensor with optical readout for the simultaneous detection of S. aureus, V.
parahemolyticus, and S. Typhimurium was reported, using magnetic particles and
multicolor upconversion nanoparticles (UCNPs), as luminescence labels (Figure 3). In
this strategy, multicolor UCNPs were conjugated with aptamers specific for each
bacterium and hybridised with the complementary DNA sequence, which was coupled
to magnetic particles, these last providing an important advantage of improving the
washing steps. These conjugates are capable of emitting strong visible luminescence
with the excitation of NIR light (typically 980 nm), using a 980 nm laser, giving three
independent peaks at different wavelengths for each of the three bacteria. Upon addition
of the bacteria, these signals are proportionally reduced, since the multicolor UCNPs
conjugated with the aptamers react with their specific bacterial target being then
eliminated as a supernatant after applying a magnetic field, as shown in Figure 3. The
remaining UCNPs-MNPs were then separated and washed three times, and the
luminescence was measured with a 980 nm excitation laser.
The concentration of the three bacteria was related to the corresponding emission peak
of the multicolor UCNPs. The basic principle of the strategy was that aptamers could
form a defined conformation when binding to the targets and were also able to hybridise
to the complementary DNA sequences attached to the MPs to form a duplex structure.
When the targets and the complementary oligonucleotides were introduced, the
aptamers preferentially bound to the targets, resulting in the specific recognition of the
targets. Therefore, < 25 CFU mL-1 of all pathogens were detected in approximately 1h
with this approach .
Preferred position for Figure 3 14
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Electrochemical immuno and genosensors have been extensively explored for food
safety applications due to their high sensitivity, rapidity, low cost and possibility of
being a hand-held platform operated by batteries for field applications. However, the
use of electrochemical biosensors remains in a preliminary stage towards multiplex
detection of bacteria .
The commercialisation of novel devices for the detection of food microorganisms is
based on a set of specific standards in food microbiology, such as quality control of
culture media, preparation of test samples, uncertainty estimation, method validation
and proficiency testing .
Currently, there are an increasing number of kits commercially available for a rapid
simple and reliable detection of pathogenic bacteria in food samples. In Table 3,
selected kits, mostly for single bacteria detection are compared in terms of assay format,
target pathogens, pre-enrichment step time, total assay time and LODs. Commercial kits
are based on different assays formats either immunological assays or PCR
methodologies for the detection of several foodborne pathogens, being able to detect in
general 1 CFU in 25 g of food sample as required for the legislation, after a pre-
enrichment culturing step. Most recent kits make use of a fully automated system,
which reduces the assay time, increasing the number of samples per test until 300
samples in one assay (Atlas® System, Assurance® EIA or GeneQuence). Rapid nucleic
acid amplification and detection technologies have been increasingly applied to
pathogen detection in food industry. In DuPont™ BAX® System, a qPCR methodology
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is used for the detection of several pathogens with LODs of one CFU per food sample
ranged from 25 g to 375 g.
The use of nano-microsized particles on bioassays has been successfully introduced into
food industry. Lateral Flow System has been commercialised by Dupont (DuPontTM
Lateral Flow System) and Biocontrol (VIP® Gold), where food samples are combined
with gold-colloid particles coated with antibodies specific for the target bacteria. The
results are produced in only 10 min, being for this reason a suitable tool for pathogens
Finally, magnetic particles modified with antibodies specific to the target bacteria have
been used for IMS as a pre-concentration tool from food samples, being able to reduce
substantially the time of enrichment step. IMS is usually combined with PCR
methodologies, as occurred in Assurance GDS® MPX and Pathatrix®. Currently, the
commercialisation of kits for the simultaneous detection of foodborne pathogens is
available in a reduced number, being mostly based on PCR methodology (Assurance
Preferred position for Table 3
A considerable progress regarding food safety in EU has been done in terms of rapid
and multiplexed approaches for detecting bacteria outbreaks. However, food
contamination caused by pathogenic bacteria is still a serious threat for the consumers.
The common strategies for the detection of pathogenic microorganisms are consisted of
the gold standard conventional microbiological culturing techniques, IAs and PCR 16
Page 16 of 34
methodologies. The development of novel strategies with multiplexing capabilities is
highlighted as a rapid and cost effective alternative for the detection of bacteria.
Therefore, in this review, it was shown that mPCR based methodologies could detect
below 10 CFU in 25 g of sample after a pre-enrichment step up to 30 h [25, 53]. The
integration of magnetic particles with PCR based methodologies leads to a LOD of less
than 10 CFU g-1 within 6 h . DNA microarrays showed LODs below 500 CFU mL-1
when using magnetic particles, in approximately 3.5 h, without the need of a pre-
enrichment step . Biosensors combined with nanomaterials have led to a significant
improvement of the assay time and LOD. In this context, no significant differences were
noticed between the different nanomaterials, however it was observed that the
integration of magnetic particles allows a significant decrease of the enrichment times,
reducing thus the total assay time [50, 59-60].
To summarise, in food safety applications the integration of magnetic carriers and IMS
step for capturing the bacteria through an immunological reaction from contaminating
microflora and interfering food components introduces advantages on the analytical
performance due to the pre-concentration upon magnetic actuation for further testing or
readout. For instance, the matrix effect is eliminated and the PCR inhibitors are avoided
which leads to a decrease of the background signals. The improvement of the washing
steps and the decrease of the time required for enrichment steps are also other
advantages. Finally, magnetic particles offer an attractive support to be incorporated in
magnetic actuated biosensors, microfluidic platforms or other devices.
Magnetic particles have also been successfully integrated in commercially available kits
for a rapid, simple and reliable detection of single pathogenic bacteria. However, there
are still only a few commercial kits available for simultaneous detection, with integrated
Page 17 of 34
magnetic nanoparticle functionality. As a conclusion the integration of magnetic
particles for the multiplex detection of bacteria is still in a preliminary stage, requiring
further studies due to their promising features.
Financial support from BioMaX “Novel diagnostic bioassays based on magnetic
particles”, Marie Curie Initial Training Networks (FP7-PEOPLE-2010-ITN) and the
Ministry of Economy and Competitiveness (MINECO), Madrid (Project BIO2013-
41242-R) are acknowledged.
Figure 1. Notifications for pathogens found in meat samples in 2012 and 2013.
Figure 2. Integration of magnetic particles in immunosensors and genosensors. After an
immunomagnetic separation step, (A) a magneto immunosensor and (B) a magneto
genosensor with electrochemical readout were reported for the detection of Salmonella
in milk. Adapted from .
Table 1. Strategies for the simultaneous detection of pathogenic bacteria based on
Nucleic acid amplification methods, Multiplex PCR based microfluidic systems and
Table 2. Biosensors platforms based on the integration of nanomaterials for the
simultaneous detection of bacteria.
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Figure 3. Simultaneous detection of S. aureus, V. parahemolyticus, and S.
Typhimurium, using magnetic particles (MNPs) and multicolor upconversion
nanoparticles (UCNPs), as luminescence labels. UCNPs were modified with aptamers
(Apt1-3) specific for the different bacterium. Complementary oligonucleotides (c1-3DNA-
MPs) were immobilised on the MNPs. Reprinted with permission from . Copyright
(2014) American Chemical Society.
Table 3. Commercial kits for the detection of pathogenic bacteria.
Page 19 of 34
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Table 1 Preenrichment
Total assay time
artificially contaminated pork samples
~ 1h 40 min
9-670 CFU mL-1
artificially contaminated meat samples
~ 1h 35 min
10–17 CFU g1 sample
~ 1h 45 min
1h 10 min
qPCR for Salmonella spp., E. coli, L. monocytogenes
qPCR for Salmonella spp., E. coli, L. monocytogenes
Nonaplex qPCR for L. monocytogenes, Campylobacter, Salmonella, enteropathogenic E. coli
IMS-qPCR assay for Salmonella spp., Shigella spp., S. aureus
IMS -mPCR assay for S. Typhimurium, E. coli, L. monocytogenes
agarose gel electrophoresi s and GoldView™ agarose gel stained with GoldView™
Oscillatory-flow multiplex PCR PCR for S. enterica, E. coli, L. monocytogenes
Microchip capillary electrophoresis for V. parahemolyticus, Salmonella, E. coli, Shigella DNA microarray for Salmonella spp., Shigella spp., L. monocytogenes, E. coli
DNA microarray for E. coli, S. enterica, L. monocytogenes, C. jejuni
DNA microarray for 12 different bacterial strains using QDs
1 CFU in 25 g sample
5 CFU in 25 g sample