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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) Gaussian fitting to the data leads to determination of the peak with better precision; (b) Comparison of the peak wavelength vs. time plot based on Gaussian fit based tracking and that with peak location search based tracking.
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biosensors-05-00158-f003: (a) Gaussian fitting to the data leads to determination of the peak with better precision; (b) Comparison of the peak wavelength vs. time plot based on Gaussian fit based tracking and that with peak location search based tracking.

Mentions: As Figure 1b shows that the sensor spectra involved multiple peaks with about 5–10 nm full width at half maximum (FWHM). To determine the peak shift, we wrote a script in Igor Pro (Wavemetrics, Portland, OR, USA) that finds a peak by a Gaussian fit to the spectra around a local peak. The script first finds the wavelength for the local maximum (λc) and then runs the Gaussian fit between λc − FWHM/2 and λc + FWHM/2 similar to what was reported for Fiber Bragg Gratings [16]. Specifically, we fitted to the following function:(1)T=T0+Aexp[−(λ−λ0w)2]where λ0 represents the peak center wavelength, which is the desired fit parameter. Because of the inherent noise in the system as well as the digitization error of the OSA, Gaussian fitting based tracking proves very useful, as illustrated in Figure 3. In our typical spectra, we have 1000 points, and we typically use 100-nm wavelength range. As shown in Figure 3a, we can determine the peak by maximum searching to the first digit, and have slight unavoidable shifts due to noise. Figure 3b compares peak wavelength data obtained through Gaussian fit based tracking with maximum location search based tracking.


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) Gaussian fitting to the data leads to determination of the peak with better precision; (b) Comparison of the peak wavelength vs. time plot based on Gaussian fit based tracking and that with peak location search based tracking.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-05-00158-f003: (a) Gaussian fitting to the data leads to determination of the peak with better precision; (b) Comparison of the peak wavelength vs. time plot based on Gaussian fit based tracking and that with peak location search based tracking.
Mentions: As Figure 1b shows that the sensor spectra involved multiple peaks with about 5–10 nm full width at half maximum (FWHM). To determine the peak shift, we wrote a script in Igor Pro (Wavemetrics, Portland, OR, USA) that finds a peak by a Gaussian fit to the spectra around a local peak. The script first finds the wavelength for the local maximum (λc) and then runs the Gaussian fit between λc − FWHM/2 and λc + FWHM/2 similar to what was reported for Fiber Bragg Gratings [16]. Specifically, we fitted to the following function:(1)T=T0+Aexp[−(λ−λ0w)2]where λ0 represents the peak center wavelength, which is the desired fit parameter. Because of the inherent noise in the system as well as the digitization error of the OSA, Gaussian fitting based tracking proves very useful, as illustrated in Figure 3. In our typical spectra, we have 1000 points, and we typically use 100-nm wavelength range. As shown in Figure 3a, we can determine the peak by maximum searching to the first digit, and have slight unavoidable shifts due to noise. Figure 3b compares peak wavelength data obtained through Gaussian fit based tracking with maximum location search based tracking.

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