Fast, ultrasensitive virus detection using a Young interferometer sensor.
ABSTRACT We report the application of an integrated optical Young interferometer sensor for ultrasensitive, real-time, direct detection of viruses. We have validated the sensor by detecting herpes simplex virus type 1 (HSV-1), but the principle is generally applicable. Detection of HSV-1 virus particles was performed by applying the virus sample onto a sensor surface coated with a specific antibody against HSV-1. The performance of the sensor was tested by monitoring virus samples at clinically relevant concentrations. We show that the Young interferometer sensor can specifically and sensitively detect HSV-1 at very low concentrations (850 particles/mL). We have further demonstrated that the sensor can specifically detect HSV-1 suspended in serum. Extrapolation of the results indicates that the sensitivity of the sensor approaches the detection of a single virus particle binding, yielding a sensor of unprecedented sensitivity with wide applications for viral diagnostics.
- SourceAvailable from: Aurel Ymeti
Article: Slotted photonic crystal sensors.[show abstract] [hide abstract]
ABSTRACT: Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study.Sensors 01/2013; 13(3):3675-710. · 1.95 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Optical microcavities that confi ne light in high-Q resonance promise all of the capabilities required for a successful next-generation microsystem biodetection technology. Label-free detection down to single molecules as well as operation in aqueous environments can be integrated cost-effectively on microchips, together with other photonic components, as well as electronic ones. We provide a comprehensive review of the sensing mechanisms utilized in this emerging fi eld, their physics, engineering and material science aspects, and their application to nanoparticle analysis and biomolecular detec-tion. We survey the most recent developments such as the use of mode splitting for self-referenced measurements, plas-monic nanoantennas for signal enhancements, the use of opti-cal force for nanoparticle manipulation as well as the design of active devices for ultra-sensitive detection. Furthermore, we provide an outlook on the exciting capabilities of func-tionalized high-Q microcavities in the life sciences.Nanophotonics. 12/2012; 1(1):267-291.
Fast, Ultrasensitive Virus Detection
Using a Young Interferometer Sensor
Aurel Ymeti,*,†Jan Greve,†Paul V. Lambeck,‡Thijs Wink,§
Stephan W.F.M. van Ho 1vell,§,#Tom A.M. Beumer,|Robert R. Wijn,⊥
Rene G. Heideman,⊥Vinod Subramaniam,†and Johannes S. Kanger†
Biophysical Engineering, MESA+Institute for Nanotechnology and Institute for
Biomedical Technology, UniVersity of Twente, PO Box 217, 7500 AE Enschede,
The Netherlands, Integrated Optical Microsystems, MESA+Institute for
Nanotechnology, UniVersity of Twente, PO Box 217, 7500 AE Enschede,
The Netherlands, Paradocs Group BV, PO Box 99, 4000 AB Tiel, The Netherlands,
bioMe ´rieux BV, Boseind 15, 5281 RM Boxtel, The Netherlands, and LioniX BV,
PO Box 456, 7500 AH Enschede, The Netherlands
Received November 6, 2006; Revised Manuscript Received December 13, 2006
We report the application of an integrated optical Young interferometer sensor for ultrasensitive, real-time, direct detection of viruses. We
have validated the sensor by detecting herpes simplex virus type 1 (HSV-1), but the principle is generally applicable. Detection of HSV-1 virus
particles was performed by applying the virus sample onto a sensor surface coated with a specific antibody against HSV-1. The performance
of the sensor was tested by monitoring virus samples at clinically relevant concentrations. We show that the Young interferometer sensor can
specifically and sensitively detect HSV-1 at very low concentrations (850 particles/mL). We have further demonstrated that the sensor can
specifically detect HSV-1 suspended in serum. Extrapolation of the results indicates that the sensitivity of the sensor approaches the detection
of a single virus particle binding, yielding a sensor of unprecedented sensitivity with wide applications for viral diagnostics.
In recent years, there have been several examples of serious
virus outbreaks such as severe acute respiratory syndrome
(SARS) and H5N1 bird flu virus. There are significant fears
that such outbreaks can rapidly spread worldwide to become
pandemics with devastating effects on populations and their
social and economic development. Therefore, fast, on-site,
and sensitive detection of viruses is essential in detecting
the onset of viral epidemics and preventing their spread.
Traditional virus detection methods such as polymerase chain
reaction (PCR)1and branched-chain DNA test (bDNA)2are
not compatible with point-of-care settings as they are time-
consuming, expensive, and require labor-intensive sample
preparation. This has been the motivation behind the
increased interest for the development of alternative virus
detection methods reported in recent literature. One of them,
called rupture event scanning technique,3is based on
measurement of adhesion forces between a surface and virus
particles. This technique is highly sensitive and can detect
virus particles in complex samples such as serum; however,
a lengthy preparation of antibody-coated surfaces (∼20 h)
is required. Several other techniques4-8have demonstrated
the feasibility for virus detection, but further investigation
is required to show their utility in clinical settings and for
the development of point-of-care systems. Here, we describe
and test an alternative detection method that combines the
different advantages of existing techniques in a single device.
The device is extremely sensitive, compact (allows for point-
of-care detection), easy to use, fast, and requires a minimal
pretreatment of the sample. We believe that these properties
make the current method extremely suitable in detecting,
preventing, or controlling viral outbreaks.
We have recently developed a very sensitive antibody-
based sensor for specific detection of, e.g., proteins. The
sensor principle is based on a Young interferometer (YI) and
requires no labeling of analyte molecules.9The sensitivity
of 10-8refractive index units, corresponding to approxi-
mately a protein mass coverage of 20 fg/mm2, is among the
most sensitive sensors reported.10-12This sensitivity is ∼2
orders of magnitude higher than other nonlabeling sensor
techniques such as surface plasmon resonance.13Moreover,
this sensor is simple, easy to use, and compact, offering the
* Corresponding author. E-mail: A.Ymeti@utwente.nl. Telephone:
0031534893870. Fax: 0031534891105.
†Biophysical Engineering, MESA+Institute for Nanotechnology and
Institute for Biomedical Technology.
‡Integrated Optical Microsystems, MESA+Institute for Nanotechnology.
§Paradocs Group BV.
|bioMe ´rieux BV.
Vol. 7, No. 2
10.1021/nl062595n CCC: $37.00
Published on Web 12/29/2006
© 2007 American Chemical Society
possibility for development of portable point-of-care instru-
ments. As such, this sensor is an excellent candidate for fast
and on-site virus detection. Here we explore the use of this
sensor for the detection of herpes simplex virus type 1. This
virus causes recurrent mucosal infections of the eye, mouth,
and genital tract. The detection principle of the sensor can
be extended to any virus that has specific antibodies available
such as human immunodeficiency virus (HIV), SARS,
Hepatitis B and C, or even H5N1 bird flu virus. The
multichannel character of the sensor allows sensing several
(up to three in this configuration) different viruses and/or
other pathogens simultaneously.
The principle of the sensor is schematically shown in
Figure 1. Monochromatic light from a laser source is coupled
to an optical channel waveguide and is guided into four
parallel optical channels by means of Y-junctions. These four
channels include one reference channel and up to three
different measuring channels that can be used to monitor
different analytes by coating the channels with appropriate
antibodies. Upon exiting from these four waveguide channels,
the light interferes on a screen, generating an interference
pattern. Specific analyte binding to the antibody-coated
waveguide surface, which is probed by the evanescent field
of the guided modes, causes a corresponding phase change
that is measured as a change in the interference pattern.
Analysis of the interference pattern thus yields information
on the amount of adsorbed analytes on different channels.
The feasibility of using the YI sensor for virus detection
was explored by monitoring the interaction between anti-
HSV-1 glycoprotein G monoclonal antibody (R-HSV-1gG)
and HSV-1 virus particles (Virusys Corporation, Sykesville,
MD, United States). Figure 2 shows the phase change
measured between channel 1 and reference channel 4 in the
four-channel YI sensor caused by the immobilization of a
R-HSV-1gG layer on the sensing surface of channel 1,
followed by the binding of HSV-1 virus particles to this layer.
Here, a concentration of ∼105HSV-1 virus particles/mL was
used. This test clearly demonstrates the detection of virus
particles by the YI sensor.
Specificity of the YI sensor to HSV-1 was demonstrated
by immobilizing different receptor layers in adjacent measur-
ing channels and monitoring the sensor response to different
analyte solutions. To do so, anti-human serum albumin (R-
HSA; Sigma-Aldrich, St. Louis, MO) was immobilized in
channel 1 by flowing a 200 µg/mL R-HSA solution prepared
in phosphate buffered saline (PBS). In channel 2, R-HSV-1
gG was immobilized. Next, a solution of 50 µg/mL human
serum albumin (HSA; Sigma-Aldrich, St. Louis, MO) in PBS
was simultaneously applied in channels 1 and 2, and after
approximately 30 min, flow was changed back to PBS for
both channels. The observed binding curves are shown in
Figure 3 (graphs A1 and A2, respectively). After achievement
of a stable baseline, a 105particles/mL HSV-1 solution was
flowed in both channels (see B1 and B2 in Figure 3,
respectively). The observation that a response is measured
only for the R-HSA-HSA and R-HSV-1gG-HSV-1 inter-
actions is a clear indication that the signals are caused by
specific interactions and that cross reactivity between coat-
ings is negligible.
To explore the dynamic range of the sensor and its
sensitivity, the sensor was further tested with HSV-1
concentrations that varied from 8.5 × 102to 8.5 × 106
particles/mL, covering the concentration range that corre-
sponds to the classification “very low” to “very high” in
terms of the viral load.14The phase changes that are observed
at these viral concentrations are plotted in Figure 4A and
demonstrate a dynamic range of at least 4 orders of
magnitude. Figure S1 (see the Supporting Information) shows
the excellent signal-to-noise ratio even for the lowest
measured virus concentration.
Next, the sensor was tested using complex samples such
as a virus suspended in serum. Figure 4B shows the response
of the sensor after the application of a 105HSV-1 particles/
mL solution prepared in human serum in the sensing window
of the measuring channel, which was previously coated with
R-HSV-1gG. Note that we first added serum in the measuring
channel. Later, virus-containing serum was added. According
to Figure 4B, there is a clear response of the sensor due to
Figure 1. Representation of the sensor. Schematic of the four-
channel integrated optical YI sensor (not on scale): 1, 2, and 3
indicate the measuring channels, and 4 is the reference channel.
Figure 2. Virus detection test. Sensor signal (phase change)
measured between channel 1 and the reference channel for the
immobilization of anti-HSV-1 glycoprotein G monoclonal antibody
layer on the sensing surface of channel 1 (∆ΦR-HSV-1gG) and the
binding of HSV-1 particles to this layer (∆ΦHSV-1).
Nano Lett., Vol. 7, No. 2, 2007395
the binding of HSV-1 and is in good agreement with the
measurement of HSV-1 in buffer, as indicated in Figure 4A.
To confirm the specificity of HSV-1-R-HSV-1gG interac-
tion, we carried out a control experiment in which no
antibody was immobilized in the measuring channel. No
response was measured when the virus solution in serum
was applied (graph not shown), indicating the specificity of
The results obtained clearly demonstrate the feasibility to
specifically detect capture of virus particles using an
Figure 3. Specific detection of HSV-1. Phase changes ∆Φ14and ∆Φ24in the four-channel YI sensor as a function of time during several
processes. HSA solution was first flowed through channels 1 and 2 simultaneously (A1 and A2). Next, after washing with PBS, HSV-1
solution was flowed in channels 1 and 2 simultaneously (B1 and B2); PBS was continuously flowed in reference channel 4. Thus, the four
graphs show the following interactions: (A1) R-HSA-HSA, (A2) R-HSV-1gG-HSA, (B1) R-HSA-HSV-1, (B2) R-HSV-1gG-HSV-1.
Note that initial phases in A1 and A2 were shifted to 0 for clarity.
Figure 4. Measurement of different HSV-1 concentrations and detection in serum. (A) Phase change measured for different concentrations
of HSV-1 sample solutions in PBS applied in the measuring channel of the YI sensor (2). Solid line is a linear-fit of the experimental data,
(f) represents the phase change measured for HSV-1 diluted in serum (see Figure 4B), dashed line indicates the phase detection limit of
the sensor. (B) Sensor response due to the binding of HSV-1 diluted in serum. Final concentration of HSV-1 was 105particles/mL. The
total signal is estimated to be ∆Φvirus in serum) 0.37 fringes, consistent with results obtained in PBS (see f in Figure 4A).
Nano Lett., Vol. 7, No. 2, 2007
integrated optical Young interferometer-based sensor. More-
over, it demonstrates the possibility to detect such binding
at very low particle concentrations and at a low number of
In the measured, clinically relevant concentration range,14
covering 4 orders of magnitude, a clear relation between the
sensor signal and the viral concentration is found (a linear
fit through the data points in Figure 4A gives a correlation
coefficient of 0.98) that allows virus concentration predictions
given a calibrated sensor. Given the high signal-to-noise ratio
of 2 × 102(at a bandwidth of 0.1 Hz) that was observed at
the lowest virus concentration (850 particles/mL), it is likely
that much lower concentrations can be detected with the
current sensor. An estimation of the number of captured
HSV-1 particles can be made given the size (150-200 nm)15
and the refractive index (∼1.41).16This results in a phase
change of ∼1.1 × 10-4fringes for the binding of a single
virus particle (see the Supporting Information). This means
that, for the lowest measured concentration (see Figure S1
in the Supporting Information), during the course of the
measurements, ∼700 virus particles were detected with an
average binding rate of 1 virus every 4 s. From these
estimations, it can be argued that the detection limit of the
sensor (10-4fringes) can approach that of a single HSV-1
From Figure 3, we conclude that, by using specific
antibody coatings of the different channels, it is possible to
specifically detect various analytes in parallel. This applies
both for virus particles as well as for antigens. Very
importantly, the YI sensor allows specific detection of virus
particles suspended in serum. Although there is a background
due to nonspecific binding of serum proteins, the signal due
to binding of virus particles could be easily detected. This
lends credence to the use of this type of sensor for clinical
applications. Although the background remains a drawback
of this approach, the influence of the background can be
considerably reduced by using differential phase change
information from different measuring channels. Moreover,
attention should be paid to improvement of the measuring
channels coating, which should result in a further reduction
of the background.
Using the results achieved here, we can compare this
sensor to the standard methods for virus detection. The
sensitivity of this sensor is comparable to the most sensitive
methods reported so far such as PCR,1bDNA,2and the more
recently developed methods such as the rupture event
scanning technique.3However, these methods are rather time-
consuming and/or labor-intensive and therefore less suitable
for point-of-care application. Although the measurements
presented here show that it takes approximately 1 h for the
virus to bind to the sensor surface, it is possible to estimate
the concentration of the applied virus suspension by only
measuring the response of the sensor in the first few minutes
(a correlation coefficient of 0.95 was found between the virus
concentration and the measured slope, see Figure S2 in the
Supporting Information). Especially in combination with
microfluidics, as demonstrated in ref 17, the YI sensor
requires small sample volumes (∼µL) and shows a short-
time response (∼s). A miniaturized stand-alone prototype
of this sensor is currently under development.
Considering the extremely high sensitivity, the short-time
response, multiplexing capability, and the prospect to develop
the sensor as a robust handheld device using disposable
precoated sensor chips, it is anticipated that the Young
interferometer-based virus sensor is a strong candidate for a
point-of-care viral diagnostics.
Acknowledgment. This project was financially supported
by the Dutch Technology Foundation STW (grant no.
TTN.4446). This article is dedicated to Stephan W.F.M. van
Supporting Information Available: Additional figures
showing measurement of the lowest virus concentration, fast
estimation of virus concentrations, and a photograph of the
sensor; estimation of phase change of the captured virus
particles, and experimental section. This material is available
free of charge via the Internet at http://pubs.acs.org.
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