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Biconically tapered fiber optic probes for rapid label-free immunoassays.

Miller J, Castaneda A, Lee KH, Sanchez M, Ortiz A, Almaz E, Almaz ZT, Murinda S, Lin WJ, Salik E - Biosensors (Basel) (2015)

Bottom Line: Hydrofluoric acid treatment makes the sensitive region thinner to enhance sensitivity, which we confirmed by experiments and simulations.The limit of detection for the sensor was estimated to be less than 50 ng/mL.Utilization of the rate of the sensor peak shift within the first few minutes of the antibody-antigen reaction is proposed as a rapid protein detection method.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of California, Los Angeles, 475 Portola Plaza, Los Angeles, CA 90095, USA. johnmiller@physics.ucla.edu.

ABSTRACT
We report use of U-shaped biconically tapered optical fibers (BTOF) as probes for label-free immunoassays. The tapered regions of the sensors were functionalized by immobilization of immunoglobulin-G (Ig-G) and tested for detection of anti-IgG at concentrations of 50 ng/mL to 50 µg/mL. Antibody-antigen reaction creates a biological nanolayer modifying the waveguide structure leading to a change in the sensor signal, which allows real-time monitoring. The kinetics of the antibody (mouse Ig-G)-antigen (rabbit anti-mouse IgG) reactions was studied. Hydrofluoric acid treatment makes the sensitive region thinner to enhance sensitivity, which we confirmed by experiments and simulations. The limit of detection for the sensor was estimated to be less than 50 ng/mL. Utilization of the rate of the sensor peak shift within the first few minutes of the antibody-antigen reaction is proposed as a rapid protein detection method.

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(a) A schematic representation of a biconically tapered fiber sensor with antibodies on the surface; (b) Interference of the two modes (typically HE11 and HE12) excited in the tapered region gives rise to a transmission spectrum with trackable peaks; (c) Photo of a biconically tapered fiber sensor formed into a U-shape. The inset shows a magnified version of the thin region; (d) The biosensor dipped in a solution within a test tube.
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biosensors-05-00158-f001: (a) A schematic representation of a biconically tapered fiber sensor with antibodies on the surface; (b) Interference of the two modes (typically HE11 and HE12) excited in the tapered region gives rise to a transmission spectrum with trackable peaks; (c) Photo of a biconically tapered fiber sensor formed into a U-shape. The inset shows a magnified version of the thin region; (d) The biosensor dipped in a solution within a test tube.

Mentions: A biconically tapered optical fiber (BTOF) is a simple and cost-effective refractive index (RI) sensor based on modal Mach-Zehnder interferometry [1,2,3,4]. For biosensing applications, the surface of the taper is typically functionalized with antibodies specific to an antigen to be detected (Figure 1a). The antibody-antigen reactions create a biological nanolayer on the surface of the tapered region that modifies the waveguide structure, which in turn affects the phase difference between the propagation modes. Because the two of the lowest order HE modes are excited, we observe a sinusoidal pattern for the transmission spectrum. (Figure 1b) Spectral shifts due to modifications in the vicinity of the sensor are measured. Unlike biosensors that work based on fluorescent labels, the data can be recorded in real-time enabling the study of the kinetics of antibody–antigen binding. BTOFs in different schemes were demonstrated for detection of bacteria [5], toxins [6], proteins [7,8,9,10], and nucleic acids [11].


Biconically tapered fiber optic probes for rapid label-free immunoassays.

Miller J, Castaneda A, Lee KH, Sanchez M, Ortiz A, Almaz E, Almaz ZT, Murinda S, Lin WJ, Salik E - Biosensors (Basel) (2015)

(a) A schematic representation of a biconically tapered fiber sensor with antibodies on the surface; (b) Interference of the two modes (typically HE11 and HE12) excited in the tapered region gives rise to a transmission spectrum with trackable peaks; (c) Photo of a biconically tapered fiber sensor formed into a U-shape. The inset shows a magnified version of the thin region; (d) The biosensor dipped in a solution within a test tube.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493543&req=5

biosensors-05-00158-f001: (a) A schematic representation of a biconically tapered fiber sensor with antibodies on the surface; (b) Interference of the two modes (typically HE11 and HE12) excited in the tapered region gives rise to a transmission spectrum with trackable peaks; (c) Photo of a biconically tapered fiber sensor formed into a U-shape. The inset shows a magnified version of the thin region; (d) The biosensor dipped in a solution within a test tube.
Mentions: A biconically tapered optical fiber (BTOF) is a simple and cost-effective refractive index (RI) sensor based on modal Mach-Zehnder interferometry [1,2,3,4]. For biosensing applications, the surface of the taper is typically functionalized with antibodies specific to an antigen to be detected (Figure 1a). The antibody-antigen reactions create a biological nanolayer on the surface of the tapered region that modifies the waveguide structure, which in turn affects the phase difference between the propagation modes. Because the two of the lowest order HE modes are excited, we observe a sinusoidal pattern for the transmission spectrum. (Figure 1b) Spectral shifts due to modifications in the vicinity of the sensor are measured. Unlike biosensors that work based on fluorescent labels, the data can be recorded in real-time enabling the study of the kinetics of antibody–antigen binding. BTOFs in different schemes were demonstrated for detection of bacteria [5], toxins [6], proteins [7,8,9,10], and nucleic acids [11].

Bottom Line: Hydrofluoric acid treatment makes the sensitive region thinner to enhance sensitivity, which we confirmed by experiments and simulations.The limit of detection for the sensor was estimated to be less than 50 ng/mL.Utilization of the rate of the sensor peak shift within the first few minutes of the antibody-antigen reaction is proposed as a rapid protein detection method.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of California, Los Angeles, 475 Portola Plaza, Los Angeles, CA 90095, USA. johnmiller@physics.ucla.edu.

ABSTRACT
We report use of U-shaped biconically tapered optical fibers (BTOF) as probes for label-free immunoassays. The tapered regions of the sensors were functionalized by immobilization of immunoglobulin-G (Ig-G) and tested for detection of anti-IgG at concentrations of 50 ng/mL to 50 µg/mL. Antibody-antigen reaction creates a biological nanolayer modifying the waveguide structure leading to a change in the sensor signal, which allows real-time monitoring. The kinetics of the antibody (mouse Ig-G)-antigen (rabbit anti-mouse IgG) reactions was studied. Hydrofluoric acid treatment makes the sensitive region thinner to enhance sensitivity, which we confirmed by experiments and simulations. The limit of detection for the sensor was estimated to be less than 50 ng/mL. Utilization of the rate of the sensor peak shift within the first few minutes of the antibody-antigen reaction is proposed as a rapid protein detection method.

Show MeSH
Related in: MedlinePlus