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[Display omitted] • Sulfa drugs work as on–off molecular pH sensors. • pH behaviour of Sulfa drugs at A 240, A 260 and F 344 mimics the IMPLICATION gate. • pH behaviour of Sulfa drugs at A 315 and F 410 mimics the I-INHIBIT gate. • Study suggests the role of sulfa drugs in bio-information technology research. In this study, the absorption and fluorescence characteristics of sulfa drugs, specifically Sulfadiazine (SDZ), Sulfamerazine (SMZ), and Sulfamethazine (STZ), were examined across a pH range of 1–14. The absorption and fluorescence spectra of these sulfa drugs showed significant changes depending on the pH value. Analysis of their pH-dependent absorption and fluorescence properties indicated that these sulfa drugs could used to design molecular logic gates. The absorption and fluorescence behaviors at various wavelength maxima were utilized to design IMPLICATION and Improved-INHIBIT (I-INHIBIT) molecular logic gates. [ABSTRACT FROM AUTHOR]

Abstract Objective Accurate determination of the mixing time in bioreactors is essential for the optimization of the productivity of bioprocesses. The aim of this work was to develop a simple optical method to determine the mixing time in a photobioreactor. The image processing method should be based on freeware tools, should not require programming skills, and thus could be used in education within high schools and in early stages of undergraduate programs. Results An optical method has been established to analyze images from recorded videos of mixing experiments. The steps are: 1. Extraction of a sequence of images from the video file; 2. Cropping of the pictures; 3. Background removal; and 4. Image analysis and mixing time evaluation based on quantification of pixel-to-pixel heterogeneity within a given area of interest. The novel method was generally able to track the dependency between aeration rate and mixing time within the investigated photobioreactor. In direct comparison, a pearson correlation coefficient of rho = 0.99 was obtained. Gas flow rates between 10 L h−1, and 300 L h−1 resulted from mixing times of between 48 and 14 s, respectively. This technique is applicable without programming skills and can be used in education with inexperienced user groups.

Objective: Accurate determination of the mixing time in bioreactors is essential for the optimization of the productivity of bioprocesses. The aim of this work was to develop a simple optical method to determine the mixing time in a photobioreactor. The image processing method should be based on freeware tools, should not require programming skills, and thus could be used in education within high schools and in early stages of undergraduate programs. Results: An optical method has been established to analyze images from recorded videos of mixing experiments. The steps are: 1. Extraction of a sequence of images from the video file; 2. Cropping of the pictures; 3. Background removal; and 4. Image analysis and mixing time evaluation based on quantification of pixel-to-pixel heterogeneity within a given area of interest. The novel method was generally able to track the dependency between aeration rate and mixing time within the investigated photobioreactor. In direct comparison, a pearson correlation coefficient of rho = 0.99 was obtained. Gas flow rates between 10 L h−1, and 300 L h−1 resulted from mixing times of between 48 and 14 s, respectively. This technique is applicable without programming skills and can be used in education with inexperienced user groups. [ABSTRACT FROM AUTHOR]

Intracellular pH has a significant influence on cell metabolism and various physiological activities. Therefore, there is an urgent need for a chemical sensor with excellent performance for intracellular pH-sensitive detection, which is extremely helpful for further understanding of related physiological and pathological processes. In this work, a ratiometric fluorescent probe, (1-(pyren-1-yl)-3-(pyridine-3-yl)-acrylketone (PPAK), was synthesized by the condensation reaction of 1-acetylpyrene and 3-pyridinecarboxaldehyde. PPAK has been used to detect extremely acidic and extremely alkaline pH in aqueous solutions. The recognition mechanism of PPAK depended on the protonation of the pyridine groups under acidic conditions and the attack of hydroxyl toward the carbonyl group to break down the conjugated structure under alkaline conditions, respectively. PPAK also exhibited favorable properties including outstanding photostability, excellent selectivity, rapid response and large stokes shift (166 nm). Finally, the results of E. coli cells imaging demonstrated its applicability in monitoring the pH changes in living cells. [ABSTRACT FROM AUTHOR]

By tactfully structuring a luminescent molecule as an accurate pH probe with aggregation-induced emission (AIE) feature, it is significant to overcome aggregation-caused quenching of emitted light in practice. Herein, we present a simple AIE-active fluorescence probe for pH detection on the basis of intramolecular charge transfer (ICT) with wide response range and high sensitivity reaction. The donor-acceptor-donor (D-A-D) style probe utilized a conjugated structural hybrid of the electron-withdrawing nitrile group and electron-donating hydroxyl as well as dimethylamino groups for fluorescent platform. The AIE-active probe possesses good fluorescence under water fraction up to 90% in mixed MeOH/water system. Furthermore, it can be used in profiling and visualization of pH detection in MeOH/water system at fw = 90% under UV 365 nm lamp. What's more, the probe can be employed to be a broad range test paper of pH detection, paving the way for low-cost practical applications. [ABSTRACT FROM AUTHOR]

A new pH‐dependent fluorescence probe 2,8‐bis((E)‐4‐([2,2′:6′,2″‐terpyridin]‐4′‐yl)styryl)‐6H,12H‐5,11‐methanodibenzo[b,f][1,5]diazocine (TBPTP) based on Tröger's base (TB) bound to terpyridine was designed and synthesized. Photophysical properties and titration experiments of TBPTP were investigated by absorption and fluorescence spectroscopy. TBPTP exhibited high sensitivity in an acidic environment with the working pH range 7.2–2.5, especially having a good liner response to pH changes in the range 2.5–4.3, which suggested that TBPTP is a good candidate for pH monitoring. [ABSTRACT FROM AUTHOR]

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Bone is a highly dynamic organ that is continuously being remodeled by the reciprocal interactions between bone and immune cells. We have originally established an advanced imaging system for visualizing the in vivo behavior of osteoclasts and their precursors in the bone marrow cavity using two-photon microscopy. Using this system, we found that the blood-enriched lipid mediator, sphingosine-1-phosphate, controlled the migratory behavior of osteoclast precursors. We also developed pH-sensing chemical fluorescent probes to detect localized acidification by bone-resorbing osteoclasts on the bone surface in vivo, and identified two distinct functional states of differentiated osteoclasts, “bone-resorptive” and “non-resorptive.” Here, we summarize our studies on the dynamics and functions of bone and immune cells within the bone marrow. We further discuss how our intravital imaging techniques can be applied to evaluate the mechanisms of action of biological agents in inflammatory bone destruction. Our intravital imaging techniques would be beneficial for studying the cellular dynamics in arthritic inflammation and bone destruction in vivo and would also be useful for evaluating novel therapies in animal models of bone-destroying diseases.

It is very important to measure the pH in the cells because abnormal pH in the body can cause many neurological diseases. In this work, a simple emission fluorescent pH probe 2-(benzothiazol-2-yl)-1-((pyren-3-yl) methylene) hydrazine (BMH) was synthesized by connecting pyrene-1-carboxaldehyde and 2-hydrazinobenzothiazole. BMH displayed fluorescence emission characteristics in which the pKa was 3.49 and responded linearly to measure pH range from 4.70 to 3.16. Meanwhile, it possessed high fluorescence quantum yield (64.60%). Moreover, BMH exhibited good stability and highly selectivity which promotes its ability in analytical application and the detection limit of approach was 0.41 μΜ. Simultaneously, it was fully able to image pH fluctuations due to its cell membrane permeability, biocompatibility and no auto-fluorescence effects. [ABSTRACT FROM AUTHOR]

Real-time monitoring of lysosomal pH is critical for understanding lysosome-related biological processes and diseases, but few lysosome probes can achieve this response effectively. Therefore, it is essential to develop pH-sensitive probes with better performance. In this study, we designed and synthesized a lysosome-targeting "buffering fluorogenic probe" (Lyso-BFP) by introducing a salicylamide group to naphthalimide for buffering strategy and a hydroxyethyl piperazine unit to target lysosome as well as specific pH response. Lyso-BFP demonstrated excellent photostability, pH specificity, and responsiveness to lysosomal acidification in living cells, thanks to its well-suit p Ka. Density functional theory calculation revealed that Lyso-BFP's excellent pH sensing performance resulted from the inhibition of the photo-induced electron transfer (PET) process from hydroxyethyl piperazine to the naphthalimide moiety after the piperazine ring's protonation at low pH. Remarkably, Lyso-BFP allowed for wash-free imaging and long-term real-time monitoring of lysosome pH changes based on its off-on fluorescence behavior and buffer strategy. With its superior pH selectivity and real-time pH monitoring capability, Lyso-BFP holds great potential in the diagnosis of lysosome-related disease, and the design concept of this fluorogenic probe provides a new perspective for real-time tracking of cell organelles. [Display omitted] • A pH-dependent buffering fluorogenic probe Lyso-BFP was developed. • Lyso-BFP exhibits high sensitivity and selectivity towards changes in pH. • Lyso-BFP enables wash-free and long-term imaging of lysosomes. • Real-time imaging of lysosomal alkalization was achieved using Lyso-BFP. [ABSTRACT FROM AUTHOR]

Here, we report that a mesoporous silica nanoparticle (MSN) coated with a fluoresceine-labeled bovine serum albumin (F-BSA) hydrogel layer works as a temperature-responsive nanocarrier for tetrakis- N -methylpyridyl porphyrin (TMPyP) and as a fluorescence ratiometric pH probe. F-BSA hydrogel-coated MSN containing TMPyP (F-BSA/MSN/TMPyP) was synthesized by thermal gelation of denatured F-BSA on the external surface of MSN. The F-BSA hydrogel layer was composed of an inner hard corona layer and an outer soft layer and was stable under physiological conditions. F-BSA/MSN/TMPyP exhibited temperature-dependent exponential release of TMPyP. In this release profile, the MSN was found to be a suitable host for stable encapsulation of tetracationic TMPyP by electrostatic interactions, and the F-BSA hydrogel layer mediated the diffusion of TMPyP from the MSN pore interior into the solution phase. Increasing temperature promoted partitioning of TMPyP from the pore interior to the F-BSA hydrogel layer, from where it was spontaneously released into the bulk solution phase by cation exchange. F-BSA/MSN/TMPyP also gave a linear ratiometric fluorescence response (1.3 per pH unit) in the pH range from 6.1 to 8.9.

Abstract High-efficient orange fluorescence nitrogen-doped carbon dots (N-CDs) were facilely prepared from P-phenylenediamine as a precursor via hydrothermal method. The as-prepared N-CDs with an average diameter of 3.65 nm displayed excitation-independent emission at 590 nm. The N-CDs demonstrated a remarkable fluorescence enhancement behavior with the increase of pH. A sigmoidal curve was well fitted using BiDoseResp equation with pK a1 3.57 and pK a2 6.01, which can be ascribed to the unique surface properties of N-CDs. Two-segment linear ranges of 2.6–4.6 and 5.0–6.8 broaden the response range to pH of the orange-emission N-CDs to some extent. The confocal fluorescent microscopic images of SMMC7721 cells were performed successfully, which demonstrating that N-CDs possess exceptional cell membrane permeability and can implement as biosensing platform to monitor pH fluctuations in living cells. Graphical abstract Image 1 Highlights • The long-wavelength fluorescent N-CDs were prepared by one-step hydrothermal method and using water as the reaction solvent. • The N-CDs displayed excitation-independent emission at 590 nm, which can better applied in biosensor and bioimaging. • The N-CDs shown a remarkable fluorescence enhancement behavior with the increase of pH corresponding to double pK a. • The N-CDs possessed favorable biocompatibility, high photostability, ultra-low toxicity and cellular labeling capability. [ABSTRACT FROM AUTHOR]

Graphical abstract Inverse electron demand Diels–Alder reaction in situ generates green fluorescence, which is applied to construct ratiometric fluorescent pH probe for pH measurement in living cells. Highlights • Inverse electron demand Diels–Alder (IEDDA) reaction in situ generates green fluorescence. • Ratiometric fluorescent pH probe is constructed based on IEDDA reaction. • The new pH probe shows linear response in pH change in 3.5–5.0. • Ratiometric fluorescent probe can be used for pH measurement in living cells. Abstract To endow fluorescent functions to the inverse electron demand Diels–Alder (IEDDA) reaction products, introduction of extraneous fluorophores is usually inevitable. However, this strategy is blamed for complex construction and background fluorescence. It is desirable to construct IEDDA fluorescent products in a more convenient manner. In this work, we reported the in-situ generated green fluorescence in IEDDA reaction. The fluorescence intensity of IEDDA products RA-TZ-1 and RA-TZ-2 decreased in reduced pH values (from pH 7.0–3.0). Based on this novel property, we developed a ratiometric fluorescent probe RB–RA-TZ-2 by conjugation with another probe RB-NH 2 (Em = 584 nm) with inverse response toward pH values. By single excitation, the fluorescence intensity ratio (I 584 /I 488) showed a linear response (R = 0.9797) to H+ in pH range of 3.5–5.0. Colocalization imaging with LysoTracker Green indicated the capacity of RB–RA-TZ-2 to detect lysosomal pH (Pearson's coefficient 0.81). Confocal microscopy was applied to measure and image intracellular pH in living cells. [ABSTRACT FROM AUTHOR]

Abstract Two novel benzyl aryl ether light-harvesting antennae accomplishing high effective energy transfer, core and peripherally decorated with fluorescent 1,8-naphthalimide units were successfully synthesized. The peripheral blue-emitting benzyl aryl ether intermediate wedge showed considerable probe potential for determination of water content in organic solvents probably as a result of a TICT process. The core of one of the two light-harvesting antennae was configured on the " fluorophore-spacer-receptor " format. Due to the simultaneous operation of FRET and PET processes that system showed excellent pH sensing characteristics and high potential as a probe for monitoring the pH variations in environmental and biological samples. [ABSTRACT FROM AUTHOR]

On base of the good optical properties of coumarin and fluorescein, we designed and synthesized two coumarin/fluorescein-fused fluorescent dyes ( CF dyes), which enlarged the emission wavelength and increased the Stokes shift of fluorescein moiety. The corresponding optical properties of CF dyes were investigated in detail. CF dyes could easily introduce other groups to design different functional molecules. CF dyes also exhibited rapid and sensitive responses to pH values in the range of 4.0–7.4 through the characterization of absorption and fluorescence spectra in buffer solution. More importantly, CF ethyl ester dye ( CFE dye) not only showed good cell membrane permeability and low cytotoxicity, but also had the ability to rapidly monitor mitochondrial pH changes in living cells. [ABSTRACT FROM AUTHOR]

Objective The objective was to determine if the presence of a nasogastric (NG) feeding tube is associated with increased gastroesophageal reflux (GER) and acid exposure in preterm infants. Study Design This is a retrospective study on preterm infants [gestational age (GA) <37 weeks] who were evaluated by multichannel intraluminal impedance and pH monitoring (MII-pH) between October 2009 and March 2016. Infants were divided into two groups, NG tube present and no feeding tube. GER events per hour and the percent of time with pH <4 during a 24-hour period were then compared. Results Eighty-three infants were included, 41 had an NG tube present and 42 did not. The group without an NG tube had significantly more reflux events per hour (2.3 ± 2.9 vs. 1.3 ± 0.8, p < 0.05) even after adjusting for differences in birth weight, GA, corrected GA, and total fluid intake. There was no significant difference in acidic events per hour and acid exposure time between the two groups. Conclusion The presence of a 5-French NG tube is not associated with an increase in GER or acid exposure in preterm infants. In fact, it appears that infants fed through an NG tube have fewer episodes of GER. [ABSTRACT FROM AUTHOR]

There are as many as 200 cell types in the body, and highly sophisticated and varied life phenomena are carried out by cell migration to appropriate places at appropriate times following the appropriate interactions. Recent advances in optical imaging technology using multi-photon excitation microscopy have enabled visualization inside intact bone tissues in living animals without thin sectioning. Using such advanced techniques, the dynamic behaviors of living bone cells on intact bone tissue structures can be elucidated. Here, we focus on recent findings using intravital multi-photon imaging of dynamic biological systems, e.g., bone homeostasis. This novel approach has proven beneficial for understanding the mechanisms underlying the spatiotemporal nature of bone remodeling systems and for evaluating the specific modes of actions of novel drugs currently in development, which will contribute to a new chapter in bone and mineral research. [ABSTRACT FROM AUTHOR]

The pH fluorescent probe 7-hydroxy-4-methyl-8-(((2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)imino)methyl)-2H-chromen-2-one (PICO) contains a donor–π–acceptor (D–π–A) conjugated system. The 'off−on' probe PICO has a pKa value of 8.01 and its fluorescence intensity is enhanced with increasing pH. [ABSTRACT FROM AUTHOR]

Here, we report a highly water‐soluble colorimetric and fluorescent pH probe that works in the pH range 0.2–3.0. The probe showed a rapid response, high stability, and excellent reversibility to acidity. Moreover, the fluorescence of probe was not influenced by the existence of high concentration of cations. The pKa of probe was calculated to be 2.25 ± 0.06. Furthermore, the pH test papers coated with the probe exhibited a distinct color change in acidic conditions. [ABSTRACT FROM AUTHOR]

Two novel spirobifluorene derivatives containing arylamine groups, SPF-M and SPF-P were synthesized. As the protonation of the aromatic amine N atoms, SPF-M and SPF-P showed significant pH-dependent spectral properties. The pK a values are below 3.0 and they are suitable for extremely acid conditions. Under the UV light, SPF-M permit detection with the “naked eye” which makes it particularly attractive. To our knowledge, SPF-M and SPF-P represent the first examples that two-photon pH sensors were used to measure the extremely acidic pH value. When the pH is higher than 4.0, SPF-M and SPF-P exhibited strong one- and two-photon excited fluorescence and showed no dramatic spectral changes toward pH variations. Thus, the feasibility of SPF-M and SPF-P as multiphoton luminescence bioprobe under physiological conditions is demonstrated by two-photon scanning microscopy imaging experiments on 293T cells. [ABSTRACT FROM AUTHOR]

The compound ( E )-8-hydroxyl-2-[( E )-2-(2, 4-dihydroxyphenyl)vinyl]-quinoline ( 1 ) has been developed as a fluorometric and colorimetric dual-modal probe for pH detection in solution and in vivo . Remarkable changes in the fluorescence intensity with large Stokes shifts and colorimetric responses were observed as a function of pH. The sensing mechanisms involving protonation and deprotonation processes over the acidic and alkaline pH ranges were confirmed by 1 H NMR and IR spectroscopic analysis. Furthermore, the application of probe 1 for the imaging of live PC3 cells was successfully achieved. Test strips based on probe 1 were fabricated, and were found to act as a convenient and efficient pH test kits. [ABSTRACT FROM AUTHOR]

Two rosamine-based pH probes 1a and 1b with pyronine-phenol skeleton were designed and synthesized by a simple one-step reaction. pH titration experiments showed that probes 1a and 1b exhibit near OFF-ON fluorescence responses around 550-750 nm towards the hydrogen ions. The p Ka of the probe 1a is 8.29, while that of the probe 1b increases to 12.1 because of the hydrogen bond inside it. Selective and competitive experiments indicated that both common ions and amino acids did not interfere their emission with hydrogen ions. Moreover, confocal fluorescent imaging showed that the probe 1a could be served as mitochondria biomarker in HeLa and Ges-1 cells. [ABSTRACT FROM AUTHOR]

Rhodamine spirolactams (RSLs) have recently emerged as popular fluorescent pH probes due to their fluorescence turn-on capability and ease of functionalization at the spirolactam nitrogen. Design of RSLs is often driven by biological targeting or compatibility concerns, rather than the pH sensitivity of the probe, and the relationship between RSL structure and p Ka is not well understood. To elucidate the relationship between p Ka values and the properties of substituents attached to the spirolactam nitrogen, a series of 19 aniline-derived RSLs is presented. RSLs derived from di- ortho-substituted anilines exhibit p Ka tunability across the moderately acidic region (ca. pH 4-6). Evaluation of p Ka data using the Fujita-Nishioka model for ortho substituent effects reveals that both steric and electronic substituent properties influence RSL pH responsiveness, with p Ka values increasing as substituent size and electron withdrawing character increase. These trends are attributed to changes in the RSL structure induced by large substituents, and to electronic influences on the protonated spirocyclic reaction intermediate. To demonstrate the practical applicability of these probes in completely aqueous environments, RSL-doped conjugated polymer nanoparticles that exhibit a ratiometric fluorescence response to changing pH levels are presented. [ABSTRACT FROM AUTHOR]

A naphthalimide-indoline hybrid ( 1 ) was developed as a pH-sensitive turn-on fluorescent probe. Probe 1 displays a weak fluorescence intensity in pH span of 2.5–11.0 owing to a photo-induced electron transfer (PET) from the indoline moiety to the naphthalimide. However, the PET process is suppressed under the pH of 2.5, showing a strong fluorescence signal at 430 nm. The turn-on fluorescent change of 1 is selective for the acidity (H + ) over other anions, metal ions, redox species and it displays a good reversibility. Moreover, glass TLC plates coated with probe 1 can readily detect acid vapors at an ambient atmosphere. [ABSTRACT FROM AUTHOR]

This paper describes a novel dual emission N-hydroxy 1,8-naphthalimide (NHN) sensor for selective determination of Bi 3+ ion and pH. This chemosensor displayed a red shift in absorption spectra and fluorescence enhancement towards highly selective Bi 3+ ion in neutral aqueous solution. The binding stoichiometry of NHN with Bi 3+ have been determined to be 1:1 by the job’s plot and the binding constant is calculated by Benesi-Hildebrand relation. The effect of β-cyclodextrin (β-CD) on NHN is also studied at pH ∼ 7. The binding mode of NHN with Bi 3+ through carbonyl and the hydroxyl group of NHN is confirmed by FT-IR spectra. The influence of hydroxyl group in naphthalimide as a function of pH and metal ions was studied by UV–vis and fluorescence spectroscopy. Fluorescence emission of naphthalimide varied in a narrow range of pH (5–9) and was only slightly influenced by the addition of metal ions in aqueous solution. [ABSTRACT FROM AUTHOR]

We report the pH switchable fluorescence and aggregation-deaggregation behaviour of a 2-benzimidazolyl substituted acrylonitrile dye (BIA). From the single molecular entity, three prototropic species (tri-state system) are derived that respectively emit in the red, green and cyan spectral regions. The neutral form is capable of self-assembly in an aqueous environment exhibiting stable red-orange aggregation-induced emission (AIE) at 600 nm in the physiologically relevant pH range. The aggregation and emission are pH switchable and fully-reversible. The molecule is shown to similarly function in the solid state where its emission can be modulated by exposure to acidic and basic vapours. Multicolour and reversibly pH switchable tri-state emission from a single fluorophore containing a biologically active benzimidazole moiety can find application in ratiometric optical chemosensing, bioimaging and functional materials. [ABSTRACT FROM AUTHOR]

The aminoquinoline derivatives, ( R )- and ( S )-2-phenyl-2-(quinolin-6-ylamino)ethan-1-ol ( R -PEO and S -PEO ), were synthesized by a tandem one-pot three-step C N coupling method where Smiles rearrangement was the key procedure. The selected compound R -PEO showed a significant fluorescence enhancement with a turn-on ratio over 98-fold and enabled the real time determination of proton concentration in acidic solution. The fluorescence intensity of R -PEO exhibited strong pH-dependent performance with a large Stokes shift (115 nm) and responded linearly to minor pH change within the range of 3.8–6.0. With the help of 1 H NMR spectrum, we also confirmed the protonation of the quinoline unit should be the proposed reaction. Compared with the conjugated acid of N -hexylquinolin-6-amine ( NQA ), the conjugated acid of R -PEO shows significant planar intramolecular charge transfer (PICT) character. Furthermore, biological imaging proved that R -PEO probe can be used to monitor the pH change of S. cerevisiae in vivo. [ABSTRACT FROM AUTHOR]

Objectives: To analyze the area under the curve (AUC) from 24-hour pharyngeal pH probes and evaluate this parameter as a predictor of disease severity for laryngopharyngeal reflux. Methods: Eighty patients met inclusion criteria of a completed 24-hour pharyngeal pH probe and Reflux Symptom Index (RSI) questionnaire. The AUC was calculated below a pH threshold of 5.5 using the trapezoidal rule. The RSI and RYAN scores were correlated with AUC values, and nonparametric tests were used for comparisons. Results: The median AUC value was 18 007 pH-seconds with an interquartile range (IQR) of 63 156, the median RSI score was 21 (IQR = 16), and the median RYAN score was 15.3 (IQR = 78). There was a Spearman’s correlation of .36 between the RSI scores and AUC values (P = .001) and a moderate correlation between AUC values and RYAN scores (0.58, P < .001). An insignificant correlation of .19 between RYAN scores and RSI scores was observed (P = .09). Conclusions: The AUC may be a useful objective value in establishing the diagnosis of laryngopharyngeal reflux. Prospective studies with larger patient populations are necessary to validate these findings and determine standardized thresholds for symptomatic patients. [ABSTRACT FROM AUTHOR]

A novel type of amino functionalized core-shell fluorescein isothiocyanate-doped silica nanoparticles was synthesized using a simple and effective approach of reverse microemulsion. Isothiocyanate coupled with a silane coupling agent, 3-aminopropyltrimethoxysilane, was incorporated into silica sphere and the dye molecules were bound with silica sphere through hydrolysis and polymerization of tetraethoxysilane and 3-aminopropyl-trimethoxysilane. With the covalent binding between the dye molecules and silica sphere, the leakage of the dye was avoided. With amino groups on the surface, the nanoparticles can be directly conjugated with biological molecules with no need of surface modification. The nanoparticles were pH sensitive, highly fluorescent and highly photostable. The pH response range and pH responsive linear range were 2.8~8.5 and 4.6~8.0, respectively. More interestedly, the nanoparticles could be phagocytosed by murine neural stem cell and could be applied to detect pH value for single alive cell.

In this work, the development of a portable device integrated with electronic circuits, termed PotentioCap, is described for the constant-potential coulometric readout of ion-selective membranes. A range of capacitors (22–220 µF) included in the device can be automatically chosen by the control software. The device was evaluated in standard pH solutions and stabilized seawater samples using a hydrogen-selective electrode placed in series with one capacitor. The transient current and integrated charge over time correlate well with that from capacitive readout using a benchtop potentiostat using an external electronic circuit. The capacitor of 47 µF is sufficient to amplify the current signal of 0.01 pH unit change with slopes of 2.68 µC/decade and 2.49 µC/decade in standard pH solutions and stabilized seawater samples, respectively. Unfortunately, however, instrumental control of the measurement protocol, as opposed to the chemical reconditioning reported earlier, results in an order of magnitude larger measurement error (precision of 0.6 mpH). To understand this the Nernst-Planck equation is used to describe the effects of constant and exponential decay currents with ion-selective membranes. Numerical simulations show that the passage of 0.2 µC of charge across the membrane causes a ∼1 % change in membrane concentration. The resulting phase boundary potential is shown to drift in the same manner as that observed experimentally with current polarized membranes. Furthermore, an improved capacitive model using an RC time constant is proposed by additionally considering the potential change with time. The model results compare favorably with the experimental data. Electric migration is shown not to be a significant contribution to the transient current. We discuss solutions to overcome the observed limitation of potential stability, which currently holds back the realization of ultra-high sensitivity measurements with ion-selective membranes. • A portable instrument is described for constant potential capacitive measurements of membrane electrodes. • It integrates a miniature potentiostat and dedicated capacitive switching circuits. • The portable instrument gives comparable performance to a commercial benchtop potentiostat. • The technique gives transient currents across the sensing membrane, which are described by numerical simulation. • Such currents have a negative impact on the resulting precision and must be minimized or eliminated. [ABSTRACT FROM AUTHOR]

We present a case of neonatal esophageal perforation following routine oral gastric (OG) tube placement in the neonatal intensive care unit. This is a rare complication primarily affecting premature infants and can have significant morbidity and mortality. This case demonstrates the initial radiographic presentation of esophageal perforation and the subsequent imaging to confirm the diagnosis. Clinical management of this condition in the neonatal patient is also discussed. A unique highlight of this case is the difference in radiographic presentation on the initial study as compared to the later study., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Borries et al.)

A fluorescent and colorimetric pH probe based on a rhodamine 6G derivative, RP1 , was designed and synthesized. The probe was based on the pH induced change in the structure between the spirocyclic (non-fluorescent, colorless) and quinoid (fluorescent, pink) forms of rhodamine 6G. The effect of the acid concentration on the fluorescence “off-on” behaviors of RP1 was investigated. RP1 was fluorescent in the pH range of 1.1–3.1 and has a p K a value of 2.08 (±0.07). Thus RP1 should be useful for studies in strongly acidic environments. Possible interferences from fourteen common metal ions were tested and excluded showing the excellent selectivity of the probe. Finally, the probe exhibits an intense color change at pH values lower than 3.1 which makes it useful for naked-eye pH detection. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent pH probe 4-((1E, 3E)-4-(benzo[d]thiazol-2-yl)buta-1, 3-dienyl)- N , N -dimethylbenzenamine ( BTDB ) was synthesized via ethylene bridging of thiazol and cinnamaldehyde for extremely acidic sensing. BTDB exhibits ratiometric fluorescence emission ( I 425 nm / I 595 nm ) characteristics with p K a of 2.34 and a large Stokes shift of 177 nm under acidic conditions. The linear response to pH is in the range of 2.3–4.0. Quantum chemical calculations with the B3LYP exchange functional theory demonstrated that the ratiometric response of the probe to acidic pH was due to H + binding with the N of cinnamaldehyde and the induced decreases of the intramolecular charger transfer (ICT) process. The as-prepared probe displayed excellent cell membrane permeability was further applied successfully to monitor pH fluctuations in live cells with excellent lysosomal targeting ability, and extreme acidity in Escherichia coli cells. [ABSTRACT FROM AUTHOR]

The fluorescent pH probes, 3,11-diamino-7-(4-(diethylamino)-phenyl)- dibenzo[c,h]xanthen-14-ium trifluoromethanesulfonate ( 1a ) and 3,11-bis-(diethylamino)-7-(4-(diethylamino)phenyl)dibenzo[c,h]xanthen-14-ium trifluoromethanesulfonate ( 1b ), were reported as pH probes worked in strong acidic conditions. Probes 1a – b were prepared by one-step condensation with 4-diethylaminobenzaldehyde and aminonaphthalen-1-ol derivatives, their absorption maxima gave slight changes between neutral and acidic conditions, and they exhibited pH-dependent near-infrared OFF–ON emission in the range of pH 2.0–5.0 with increasing fluorescent intensities of 272 and 114 folds, the calculated p K a values were 3.28 and 3.24 for probe 1a and probe 1b , respectively. The probes also showed excellent selectivity toward proton over other interferents in the selectivity and competition assays. The photoinduced electron transfer effect from diethylaminophenyl group to dibenzoxanthenium skeleton was proposed and further verified by theoretical calculation. The work indicates that dibenzoxanthenium would be a near-infrared fluorophore for probe design. [ABSTRACT FROM AUTHOR]

In this paper, the design of a lysosome-targetable pH probe that has a fluorescent OFF (pH = 4) to ON (pH = 5–6) response is described to identify lysosomes in normal cells. The mechanism of photoinduced electron transfer with a fluorophore-based reaction (FBR-PET) was proposed. Benzo[ a ]phenoxazines with electro-donating aryl groups were selected, its (2,5-dimethoxyphenyl)imino-, (2-hydroxyphenyl)imino- and (2-hydroxy-5-methoxyphenyl)- imino-derivatives (probes 1a−c ) were prepared and their optical responses towards pH were evaluated; their fluorescence pH titration experiments gave regularly changes with the increasing electro-donating abilities at the linked aryl groups, the (2-hydroxy-5-methoxyphenyl)iminobenzo[ a ]phenoxazine (probe 1c ) exhibited a nearly OFF−ON response at 580–800 nm. All probes were reversible, and they showed excellent selectivity toward the proton over other competitive species. Fluorescence confocal images were performed with HeLa, KB cancer cells and V79 normal cells, probes 1a−c are all lysosome-targetable pH probes, and benzo[ a ]phenoxazine with (2-hydroxy-5-methoxyphenyl)imino-group (probe 1c ) has potential applications in selective differentiation of normal cells from cancer cells. [ABSTRACT FROM AUTHOR]

In the otolaryngology practice, there is a rising concern with the current diagnosis and management of laryngopharyngeal reflux (LPR). The implication of LPR in many common head and neck symptoms, along with the rising cost of empiric therapy and no overall improvement in patient symptoms, has established a need to review what are indeed laryngopharyngeal complaints secondary to reflux and what are not. This article reviews the otolaryngologist’s approach to LPR, the various ways diagnosis is made, and the guidelines that inform the current trends in otolaryngology management of LPR. The goal of this article is to recognize that reflux can be the cause of a variety of laryngopharyngeal complaints seen within an otolaryngology practice, but when empiric therapy does not improve symptoms, consideration should be given to other non-reflux causes. [ABSTRACT FROM AUTHOR]