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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) Peak shift for a tapered fiber sensor that was HF treated. The anti-IgG concentration was 50 ng/mL; (b) The comparison of the thinner sensor performance with sensors ~10 µm thickness. Each data point represents at least two separate experiments.
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biosensors-05-00158-f006: (a) Peak shift for a tapered fiber sensor that was HF treated. The anti-IgG concentration was 50 ng/mL; (b) The comparison of the thinner sensor performance with sensors ~10 µm thickness. Each data point represents at least two separate experiments.

Mentions: In an effort to enhance the sensitivity of our sensors, so that we can detect anti-IgG concentrations lower than 500 ng/mL, we subjected our U-shaped sensors to HF treatment, as explained in Section 2.1. Our refractive index sensing tests with ethanol-water mixtures showed that the sensors became ~5 times more sensitive in comparison with the non-HF treated ones. Figure 6 displays data for a biosensor that was treated with HF to enhance its sensitivity, as explained in Section 2.1. This sensor was thinner because of the etching by HF. Figure 6a shows the raw data for the peaks shifting to the right as the IgG on the sensor surface binding with anti-IgG. Figure 6b summarizes peak shifts for various concentrations tested. The sensors tested for 0.5, 5.0, 50.0 µg/mL were about 10 µm thickness, whereas the ones tested for 50 ng/mL anti-IgG were treated with HF, and they were thinner. The comparison confirms our expectation that the thinner sensor provided better limit of detection (LOD), and the average peak shift obtained at 50 ng/mL is about the same as that with 500 ng/mL when thicker sensors were used. Also, we have not observed an increase in the frequency of mechanical failure in the HF-etched sensors in comparison with non-etched ones.


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) Peak shift for a tapered fiber sensor that was HF treated. The anti-IgG concentration was 50 ng/mL; (b) The comparison of the thinner sensor performance with sensors ~10 µm thickness. Each data point represents at least two separate experiments.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-05-00158-f006: (a) Peak shift for a tapered fiber sensor that was HF treated. The anti-IgG concentration was 50 ng/mL; (b) The comparison of the thinner sensor performance with sensors ~10 µm thickness. Each data point represents at least two separate experiments.
Mentions: In an effort to enhance the sensitivity of our sensors, so that we can detect anti-IgG concentrations lower than 500 ng/mL, we subjected our U-shaped sensors to HF treatment, as explained in Section 2.1. Our refractive index sensing tests with ethanol-water mixtures showed that the sensors became ~5 times more sensitive in comparison with the non-HF treated ones. Figure 6 displays data for a biosensor that was treated with HF to enhance its sensitivity, as explained in Section 2.1. This sensor was thinner because of the etching by HF. Figure 6a shows the raw data for the peaks shifting to the right as the IgG on the sensor surface binding with anti-IgG. Figure 6b summarizes peak shifts for various concentrations tested. The sensors tested for 0.5, 5.0, 50.0 µg/mL were about 10 µm thickness, whereas the ones tested for 50 ng/mL anti-IgG were treated with HF, and they were thinner. The comparison confirms our expectation that the thinner sensor provided better limit of detection (LOD), and the average peak shift obtained at 50 ng/mL is about the same as that with 500 ng/mL when thicker sensors were used. Also, we have not observed an increase in the frequency of mechanical failure in the HF-etched sensors in comparison with non-etched ones.

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