Modeling of C-SNARF-1 pH Fluorescence Properties: Towards Calibration Free Optical Fiber pH Sensing for in Vivo Applications (original) (raw)

pH Measurements Using Simple Fiber-Optic Instrumentation and Luminescence Detection

2005 IEEE Instrumentationand Measurement Technology Conference Proceedings, 2005

Fiber optic sensing for chemical analysis is a growing technology, since it offers several advantages, as analysis can be done "in situ" in real time, the sensing techniques do not disturb the process, so the sample size can be extremely small and the sensing locations can be in remote areas. Fluorescence measurements are particularly well-suited for optical sensing due to their sensitivity when compared to absorption measurements . Here, we describe the electronic design and the performance of a fiber optic fluorescent-based pH sensor. The chemical sensing phase consists of an organic pH indicator (mercurochrome) immobilized in a sol-gel matrix and placed at the end of a fiber optic by means of a steel grid.

Intrinsic Fiber Optic pH Sensor for Measurement of pH Values in the Range of 0.5–6

IEEE Sensors Journal, 2016

The development, design, and evaluation of an intrinsic optical fiber pH sensor for low pH values (in the range of 0.5-6) based on fluorescence from a novel coumarin dye, which is covalently immobilized onto the end surface of an optical fiber is described. The sensor provides a rapid response (of approximately 25 s) over this pH range of 0.5-6.0, showing with very good stability over a period of several months. The sensor has also demonstrated insensitivity to ionic strength and excellent photostability through a series of laboratory tests.

Fibre-optical sensor based on fluorescent indicator for monitoring physiological pH values

Medical & Biological Engineering & Computing, 1995

~A fibre-optical sensor has been developed based on the fluoresecent indicator 8-hydroxyl-l,3,6-pyrene trisulphonic acid trisodiurn salt (HOPSA) for monitoring physiological pH values. Dowex-1 strongly basic anion exchange resin is used as the medium to immobilise the indicator on the end of an optical fibre. Polyurethane is coated on the sensor as the permeable membrane for H +. The properties of HOPSA in solution, as well as when immobilised on the sensor, are studied and found to have the potential for monitoring physiological pH values.

Design of a Low-Cost Optical Instrument for PH Fluorescence Measurements

Instrumentation and …, 2006

This paper describes the electronic design and the performance of a low-cost fiber-optic instrument for pH fluorescent measurements. The chemical sensing phase consists of an organic pH indicator (mercurochrome) immobilized in a sol-gel matrix placed at the end of a fiber optic by means of a steel grid. The active phase was excited by means of a high-intensity blue light-emitting diode. The light signal was modulated to avoid external interference. Fluorescence emission is detected by a low-cost photodiode. To avoid drifts in excitation light emission intensity, a ratiometric measurement was proposed. To perform such measurements, two fiber-optic measurement channels were used. One of them was employed to measure only the pH indicator fluorescent emission intensity. The second channel was employed to measure only the intensity of the excitation light reflected by the sensing phase. The ratio between both signals is only proportional to pH and proved to be independent of excitation light intensity. The sensor is useful over the pH range of 4-8, providing highly reliable results.

Fiber optic pH/Ca2+ fluorescence microsensor based on spectral processing of sensing signals

Analytica Chimica Acta, 1999

In this paper, we describe the fabrication of a dual function pH/Ca 2+ fluorescence microsensor. Dextran conjugates of the fluorescence indicators Oregon Green BAPTA-1, a calcium ion probe, and SNARF (seminaphtorhodafluor)-1, a ratiometric pH probe, are immobilized in a 2-hydroxyethyl methacrylate (PHEMA) matrix support adsorbed to the distal end of an optical fiber. Both dyes are excited at 488 nm. The emission peak maximum of Oregon Green Bapta-1 is at 520 nm, and the emission peak maxima of SNARF-1 are at 584 and 630 nm. The pH and [Ca 2+ ] in the analyte sample are determined by spectral processing of the fluorescence sensing signals. The sensor covers a pH range between pH 6 and pH 8, and calcium ion concentrations between 0.03 and 1.5 M. The response times of the sensor are about 1 s for pH and 5 s for [Ca 2+ ] changes. The sensor is highly reversible and maintains its function for over 10 days of continuous use. The sensor is stored for 3 months in a dry, light tight environment, at room temperature with no significant degradation of its analytical properties.

Optical pH Detection with U-Shaped Fiber-Optic Probes and Absorption Transducers

Conference Papers in Science, 2015

In medicine knowledge of pH values can provide us with information not only about the patients’ status but also about physiological processes in the patient’s body. Measurements of pH in small-sample volumes and online pH monitoring in vivo can be employed to obtain such information. For such measurements we have developed and investigated U-shaped fiber-optic probes with immobilized pH indicators in this paper. U-shaped probes with a diameter of about 2 mm were prepared. Three different pH indicators, methyl red, methyl orange, and bromothymol blue, were immobilized in two types of matrices, namely, porous silica (PS) and ethylcellulose (EC), and applied on the U-shaped probes. Changes in spectra of transmitted power were measured and calibration curves were determined from these spectra. It has been found that a working pH range of prepared probes was from 3.1 to 7.6. The maximum sensitivity was about 0.1 1/pH unit. Effects of structural relaxations of detection layers and indicat...

Fiber-optic pH detection in small volumes of biosamples

Analytical and Bioanalytical Chemistry, 2010

Determining the pH values of microscopic plant samples may help to explain complex processes in plants, so it is an area of interest to botanists. Fiber-optic probes with small dimensions can be used for this purpose. This paper deals with the fiber-optic detection of the pH values of droplets of plant xylem exudate based on ratiometric fluorescence intensity measurements with an internal reference. For this purpose, novel V-taper sensing probes with a minimum diameter of around 8 μm were prepared that enable the delivery of fluorescence signal from the detection site on the taper tip to the detector. The taper tips were coated with pH-sensitive transducer (8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt; HPTS) and a reference [dichlorotris-(1,10-phenanthroline) ruthenium (II) hydrate (Ru-phen dichloride)] immobilized in a xerogel layer of propyltriethoxysilane and (3-glycidoxy)propyl trimethoxysilane. The prepared probes were sensitive to pH values mainly in the range from 6.0 to 9.0. In the pH range 6-9, the results were limited by measurement errors of about 0.2 pH units, and in the pH range 5-6 by measurement errors of about 0.5 pH units. Using the developed V-taper sensing probes, the pH values of in vivo and in vitro samples of small volumes (∼6 μl) of exudate were measured. The results were validated by comparison with conventional electrochemical pH measurements.

Fiber optic pH probe for physiological use

Analytical Chemistry, 1980

  1. Brabec, V.; Kim, M. H.; Christian, S. D.; Dryhurst, G. J. Nectroanal. A flber optic probe has been developed for pH monitoring, based on the use of a dye indicator. Microspheres of polyacrylamlde containing bound phenol red and smaller polystyrene microspheres for light scattering are packed In an envelope of cellulosic dialysis tublng at the end of a pair of plastic optical flbers. The probe measures pH over the physiological pH range of 7.0 to 7.4 to the nearest 0.01 pH unit. It is of flexible construction and is about 0.4 mm in diameter.

Simplifying Ratiometric C-SNARF-1 pH Calibration Procedures with a Simple Post-Processing

2017

A simple and easy to implement numerical method is proposed in order to considerably simplify the experimental calibration procedure of C-SNARF-1 indicator used for ratiometric pH sensing. Usually, calibration is based on the measurement of fluorescence spectra using perfectly calibrated equipment at extreme pH values. The calibration solutions must be extremely well controlled in terms of indicator concentration and path length. Also, the optical equipment used must be well controlled and excitation energy as well as fluorescence collection efficiency must be perfectly constant over the whole calibration procedure. The method we propose is based on the fact that the emission fluorescence energy does not only depend on pH but also on the excitation wavelength. In this paper, we propose a model describing the evolution of the emitted energy as a function of pH and excitation wavelength. We show that the emitted energy evolves linearly with pH and we express this linear evolution as a...