Photonic Biosensor Assays to Detect and Distinguish Subspecies of Francisella tularensis

Abstract

The application of photonic biosensor assays to diagnose the category-A select agent Francisella tularensis was investigated. Both interferometric and long period fiber grating sensing structures were successfully demonstrated; both these sensors are capable of detecting the optical changes induced by either immunological binding or DNA hybridization. Detection was made possible by the attachment of DNA probes or immunoglobulins (IgG) directly to the fiber surface via layer-by-layer electrostatic self-assembly. An optical fiber biosensor was tested using a standard transmission mode long period fiber grating of length 15 mm and period 260 μm, and coated with the IgG fraction of antiserum to F. tularensis. The IgG was deposited onto the optical fiber surface in a nanostructured film, and the resulting refractive index change was measured using spectroscopic ellipsometry. The presence of F. tularensis was detected from the decrease of peak wavelength caused by binding of specific antigen. Detection and differentiation of F. tularensis subspecies tularensis (type A strain TI0902) and subspecies holarctica (type B strain LVS) was further accomplished using a single-mode multi-cavity fiber Fabry-Perot interferometric sensor. These sensors were prepared by depositing seven polymer bilayers onto the fiber tip followed by attaching one of two DNA probes: (a) a 101-bp probe from the yhhW gene unique to type-A strains, or (b) a 117-bp probe of the lpnA gene, common to both type-A and type-B strains. The yhhW probe was reactive with the type-A, but not the type-B strain. Probe lpnA was reactive with both type-A and type-B strains. Nanogram quantities of the target DNA could be detected, highlighting the sensitivity of this method for DNA detection without the use of PCR. The DNA probe reacted with 100% homologous target DNA, but did not react with sequences containing 2-bp mismatches, indicating the high specificity of the assay. These assays will fill an important void that exists for rapid, culture-free, and field-compatible diagnosis of F. tularensis.

The Application of a Nanomaterial Optical Fiber Biosensor Assay for Identification of Brucella Nomenspecies

“…Nonetheless, the NOFS assay can be modified to detect antibodies to Brucella by coupling the antigen to the fiber, rather than a DNA probe, or alternatively coupling antibodies to the fiber to detect a specific antigen. We have described such an assay using antibody-coupled sensors to detect methicillin-resistant Staphylococcus aureus [21] and Francisella tularensis [37].…”

Technological Development of Antibody Immobilization for Optical Immunoassays: Progress and Prospects

“…This sensor was fabricated by electrodepositing AuNPs (gold nanoparticles) on the glassy carbon electrode surface to promote electron transfer, then L-cysteine and another layer of AuNPs were assembled onto the modified electrode surface to amplify the ECL signal of peroxydisulfate, and the antibody was immobilized through the electrostatic interaction between AuNPs and antibody (Wang et al, 2012). The conjugation of antibody to microparticles and thin-film structures has also been reported in recent years (Cooper et al, 2011;Han et al, 2008). Recently, a fiber-optic localized surface plasmon resonance sensor was fabricated by Jeong et al (2013) using AuNPs on Scheme 6.…”

Current Trends in the Biosensors for Biological Warfare Agents Assay

“…The biosensors can be based on long-period fiber gratings covered with a nanostructured film or membrane. Such an approach was made in the work by Cooper et al for the detection of Francisella tularensis [59]. They prepared an optical interferometic sensor with immobilized probe for Francisella tularensis subspecies tularensis and subspecies holarctica .…”