Ex-Vivo Measurement of the pH in Aqueous Humor Samples by a Tapered Fiber-Optic Sensor

Abstract

A practical demonstration of pH measurement in real biological samples with an in-house developed fiber-optic pH sensor system is presented. The sensor uses 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) fluorescent dye as the opto-chemical transducer. The dye is immobilized in a hybrid sol-gel matrix at the tip of a tapered optical fiber. We used 405 nm and 450 nm laser diodes for the dye excitation and a photomultiplier tube as a detector. The sensor was used for the measurement of pH in human aqueous humor samples during cataract surgery. Two groups of patients were tested, one underwent conventional phacoemulsification removal of the lens while the other was subjected to femtosecond laser assisted cataract surgery (FLACS). The precision of the measurement was ±0.04 pH units. The average pH of the aqueous humor of patients subjected to FLACS and those subjected to phacoemulsification were 7.24 ± 0.17 and 7.31 ± 0.20 respectively.

Real-time and label-free biosensing using moiré pattern generated by bioresponsive hydrogel

“…To investigate the quantitative pH-sensing capability of the proposed system, the time-dependent change of the moiré signal was investigated at three different pH (pH 4, 6, and 7). pH 4 and 6 was chosen considering the pKa value (4.7) of PAA which was used as pH-responsive hydrogel, while pH 7 was chosen considering the pH of aqueous humor in human [ 47 , 48 ]. As shown in Fig.…”

Recent Advances in Biomedical Photonic Sensors: A Focus on Optical-Fibre-Based Sensing

“…Commercial pH sensors measure the potential difference between two glass electrodes with a detection range of 0–14 and a resolution of 0.01 pH [ 73 ], and about 0.003 pH in a more restricted range (5–7 or 6–8 pH) [ 74 ]. The most common methods for pH measurement using optical fibres (monitoring fluorescence, absorption, lifetime) employ dye indicators or fluorophores deposited on the tip of the fibre [ 75 ] or in U-shaped [ 73 ] or tapered optical fibres [ 76 ]. Typically, such sensors combine fluorescence principles with a variation of the evanescent field by tapering the fibres [ 75 ].…”

“…A high-density deposition of the carboxyfluorescein showed an inverse shift in fluorescence in response to pH changes. In 2021, Podrazký et al reported pH measurement by a tapered optical fibre with dye immobilized at the tip by a hybrid sol-gel matrix at the tip of the fibre [76]. The sensor was tested in cataract surgery in two groups of patients and exhibited a precision of the measurement ±0.04 pH units.…”

Optical pH sensor based on fiber interferometer coated with intelligent hydrogel

“…In various fields such as clinical medicine, biochemistry, and industrial manufacturing, accurate and rapid monitoring of pH has important meaning [1][2][3] . Currently, pH measurement is commonly performed using pH test papers and glass electrode method [4,5] .…”