Influenza virus immunosensor with an electro-active optical waveguide under potential modulation

Significance Statement

Influenza has been the main cause of critical respiratory infections over the years. It is caused by a number of strains of various subtypes of the influenza virus. Therefore, quick diagnosis or detection and classification of the influenza in its early stages of development is pivotal for efficient treatment implementing antiviral drugs and in identifying pandemic occurrences. Immunoassay-based detection of the virus implementing antibody-antigen interactions offers a potential means of detection owing to their unique binding affinity and specificity.

Various approaches have been developed for influenza virus detection, for instance, enzyme-linked immunosorbent assay and fluorescence immunosensors. However, the methods have demonstrated a number of insufficiencies in their implementation and use. For example, the immunosorbent assay has slow throughput and results in time consuming protocols. Researchers have however developed spectro-electrochemical alternatives. This is where the wavelength of the probing light is spectrally tuned in order to interrogate optical transition that is linked to the electrochemically driven electro-transfer process of the redox molecules and is optically blind to ions present in the sample.

Researchers led by Professors Sergio B. Mendes (Physics) and Martin O’Toole (Bioengineering) from the University of Louisville developed a novel immunosensor-based approach for direct detection of viral pathogens by using a sandwich bioassay on a single mode electron active integrated optical waveguide platform. In their study, they targeted the hemagglutinin protein for the H5N1 avian influenza A virus in a bid to show the capacity of the waveguide platform device for detection as well as classification of a selected influenza antigen. Their work is published in Optics Letters.

The authors selected an immunoassay with a monoclonal anti-H5 antibody, which was bound to the electro-active integrated optical waveguide gadget to develop an interface that was prepared to detect and capture the target hemagglutinin protein. When the protein antigens were captured on the surface of the gadget, they initiated the immobilization of polyclonal antibody that was marked with methylene blue dye. Methylene blue dye has reversible changes in optical absorption throughout a transition in the oxidation state, therefore, presenting a characteristic optical probe that can be electrically tuned.

Once the researchers determined the optimal angular frequency for modulating the optical signal of the redox process, they applied an AC voltammetric approach at varying DC bias potentials. They then tested virus protein solutions with different concentrations.

When the DC bias potential was detuned from the formal potential, the signal probe decreased towards zero. The optically measured peak intensity of the faradic current density associated with the redox probe was found to be proportional to the concentration of the antigen and provided a direct path for quantifying the virus analyte.

From the experimental data obtained from this study, a 3-sigma limit detection was realized to be 4 ng/mL for the virus antigen. This figure is perhaps the best performance reported so far. It surpasses several technologies deployed in most clinics.

The analytical signal implemented in this study was linked to electrochemical and spectral attributes of a redox probe designed to detect the target antigen. These selective features are critical in minimizing the unwanted signals from interferents in clinical samples. The spectro-electrochemical approach in the single-mode electro-active optical waveguide platform offers a detection protocol for direct detection and quantification of the virus analyte. The results for the influenza A (H5N1) HA protein obtained in this paper, surpassed an outstanding level of detection.

Influenza virus immunosensor with an electro-active optical waveguide under potential modulation- Advances in Engineering

About The Author

Prof. Sergio B. Mendes received his bachelor degree in Physics from the University of São Paulo in Brazil (1982). He was then for 8 years a researcher and technical manager of Funbec, a non-profit organization focused on developing innovative optical technologies in Brazil.  Afterwards he went to the University of Arizona to pursue his Ph.D. in Optical Sciences, a degree which he received in 1997 working under the supervision of Prof. James Burke.  Upon his graduation, he was hired as a faculty member of the College of Optical Sciences at the University of Arizona, a position which he held until joining the University of Louisville in August 2006 as a Professor of Physics.  From 2000 till 2003, he took a leave of absence from his academic duties to become a Director of NP Photonics Inc., a startup company created to develop novel optical fiber amplifiers and fiber lasers.

His current research work at the University of Louisville focuses on integrated optics, guided-waves, and plasmonic technologies toward investigations and applications of biological/chemical molecular films and surface phenomena using several spectroscopic techniques and laser technologies.

Prof. Mendes has been awarded with numerous research grants from several agencies such as the NSF, NIH, and NASA, has published more than 100 research articles, is the co-inventor of 5 licensed patents, has been invited for several talks at international institutions and conferences, has supervised the research project of several post-doctoral fellows, graduate students, and undergraduates, and has served as a Topical Editor for the journal Applied Optics of The Optical Society.

About The Author

Martin O’Toole received Bachelor of Arts Degrees in Chemistry and Biology from the University of Louisville in 1998 and 1999, respectively. He returned to UofL in 2002 to begin graduate studies in Bioinorganic chemistry, earning his Masters and Ph.D. under the tutelage of Dr. Craig Grapperhaus. He then began a series of post-doctoral studies in the departments of Chemical, Electrical, and Bioengineering where he further developed the skills necessary for Biomaterials design.

He currently holds the position of Assistant Professor in the Bioengineering Department at the University of Louisville where he conducts research in hybrid biomaterial, nanoparticle, and sensor development. He has published 18 peer-reviewed publications, raised over $3M to fund his research, and is currently collaborating with several biomedical and clinical researchers.


Jafar H. Ghithan, Monica Moreno, Guilherme Sombrio, Rajat Chauhan, Martin G. O’toole, And Sergio B. Mendes. Influenza virus immunosensor with an electro-active optical waveguide under potential modulation. Vol. 42, No. 7 / April 1 2017 / Optics Letters.

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