A combination tapered fiber-optic biosensor (CTFOB) dip probe for rapid and cost-effective quantification of proteins in serum samples has been developed. This device relies on diode laser excitation and a charged-coupled device spectrometer and functions on a technique of sandwich immunoassay. As a proof of principle, this technique was applied in a quantitative estimation of interleukin IL-6. The probes detected IL-6 at picomolar levels in serum samples obtained from a patient with lupus, an autoimmune disease, and a patient with lymphoma. The estimated concentration of IL-6 in the lupus sample was 5.9 ± 0.6 pM, and in the lymphoma sample, it was below the detection limit. These concentrations were verified by a procedure involving bead-based xMAP technology. A similar trend in the concentrations was observed. The specificity of the CTFOB dip probes was assessed by analysis with receiver operating characteristics. This analysis suggests that the dip probes can detect 5-pM or higher concentration of IL-6 in these samples with specificities of 100%. The results provide information for guiding further studies in the utilization of these probes to quantify other analytes in body fluids with high specificity and sensitivity.
A rapid and cost-effective combination tapered fiber-optic biosensor (CTFOB) dip-probe was used for quantitative
estimation of interleukin (IL)-6 in serum/plasma samples. Sandwich immunoassay was used as the detection technique.
Probes could successfully detect presence of IL-6 in two serum samples, non-neoplastic autoimmune patient (lupus)
sample and lymphoma patient sample. The estimated amount of IL-6 in lupus patient sample was 4.8 ± 0.9 pM and in
lymphoma patient sample was 2 ± 1 pM. It is demonstrated that the developed CTFOB dip-probe is capable of
quantitative estimation of proteins in serum/plasma samples with high specificity.
This document reports a novel method of measuring association rate constant (ka) for antibody-antigen interaction using
evanescent wave-based combination tapered fiber-optic biosensor (CTFOB) dip-probes. The method was demonstrated
by measuring association rate constant for bovine serum albumin (BSA) and anti-BSA antibody interaction. "Direct
method" was used for detection; goat anti-BSA "capture" antibodies were immobilized on the probe surfaces while the
antigen (BSA) was directly labeled with Alexa 488 dye. The probes were subsequently submerged in 3nM Labeled BSA
in egg albumin (1 mg/ml). The fluorescence signal recorded was proportional to BSA anti-BSA conjugates and
continuous signal was acquired suing a fiber optic spectrometer (Ocean Optics, Inc.). A 476 nm diode laser was use as
an excitation source. Association constant was estimated from a plot of signal as a function of time. Measured
association rate constant ka for the binding of BSA with anti-BSA at room temperature is (8.33 ± 0.01) x 104M-1s-1.
We are reporting detection of IL-8 in a mixed protein solution, using combination tapered fiber-optic biosensor
(CTFOB) dip-probe. Sandwich immunoassay was used as the detection technique. The specificity of the sensor was
established by using two types of negative control probes. It is demonstrated that with the help of these CTFOB dipprobe
we could successfully detect IL-8 with high specificity in protein mixture. The lowest detected concentration of
IL-8 was 150 pM.
The document reports a novel method of measuring dissociation constant (kD) of antibody-antigen interaction using
evanescent wave based combination tapered fiber-optic biosensor (CTFOB) dip-probes. The method was demonstrated by
measuring the dissociation constant of human Interleukin-6 (IL-6) and anti-IL-6 interaction. Sandwich immunoassay was
used to generate fluorescence signal proportional to antigen-antibody conjugate pairs. A portable CCD based spectrometer
setup was used to record spectral profile of the fluorescence signal. The measured value of dissociation constant kD for IL-6 and capture anti-IL-6 (clone MQ2-13A5) antibodies at room temperature is588 ±19 pM .
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