pH Monitoring Research Articles

Excellent physicochemical and sensing characteristics of a Re x O y based pH sensor at low post-deposition annealing temperature.

pH monitoring in clinical assessment is pivotal as pH imbalance significantly influences the physiological and extracellular functions of the human body. Metal oxide based pH sensors, a promising alternative to bulky pH electrodes, mostly require complex fabrication, high-temperature post-deposition treatment, and high expenses that inhibit their practical applicability. So, there is still room to develop a straightforward and cost-effective metal oxide based pH sensor comprising high sensitivity and reliability. In this report, a novel solution-processed and low-temperature annealed (220 °C) mixed-valence (vii/vi) oxide of rhenium (RexOy) was applied in an electrolyte–insulator–semiconductor (EIS) structure. The annealing effect on morphological, structural, and compositional properties was scrutinized by physical and chemical characterizations. The post-annealed RexOy exhibited a high pH sensitivity (57.3 mV pH−1, R2 = 0.99), a lower hysteresis (4.7 mV), and a reduced drift rate (1.7 mV h−1) compared to the as-prepared sample for an analytically acceptable pH range (2–12) along with good stability and reproducibility. The magnified sensing performance originated due to the valence state of Re from Re6+ to Re7+ attributed to each electron transfer for a single H+ ion. The device showed high selectivity for H+ ions, which was confirmed by the interference study with other relevant ions. The feasibility of the sensor was verified by measuring the device in real samples. Hence, the ease-of-fabrication and notable sensing performance of the proposed sensor endorsed its implementation for diagnosing pH-related diseases.

Analiza pacijenata sa neerozivnom gastroezofagealnom refluksnom bolešću korišćenjem Bravo® pH sistema za monitoring

Background and aim: Gastroesophageal reflux disease (GERD) is a common disease in the world. GERD is always treated with drugs. The Bravo® wireless pH monitoring system is a good technique. The Bravo® may affect increasing the specificity and sensitivity in the diagnosis of GERD with its 48-hour recording feature. In this study, we aimed to assess the diagnostic performance of the Bravo® pH monitoring system in patients with non-erosive GERD. Materials and Methods: Patients with non-erosive reflux disease (normal endoscopy) whose symptoms persisted after PPI treatment (at least two months) were included in the study. All patients had upper gastrointestinal system endoscopies performed in our clinic between January 2013 and December 2019. All patients had a 48-hour Bravo® wireless pH monitoring record. Results: Twenty-three patients (M: 18 (78.3%; Age: 35.7 ± 11) were included in the study. All patients completed the 2-day recording protocol. During and after the procedure, no patient showed any adverse effects of the Bravo® procedure. We diagnosed GERD in 13 of 23 patients by Bravo® capsule. According to the Bravo® pH-meter recordings; Total time pH < 4 (minute) was 187 ± 190, the total number of refluxes was 90 ± 61, the percentage of time with pH < 4 was 7.1 ± 7.22, the number of long reflux events were 8.1 ± 8, the duration of the longest reflux episode during pH < 4 (minute) was 31 ± 49, the Demeester score was 20.8 ± 19.3 detected. Conclusion: Based on the results of the current study, the Bravo® pH monitoring system is a practical and effective diagnostic technique for non-erosive GERD. Further prospective studies would be useful for comparing the differences between 24-hour and 48-hour pH recording results.

Dietary and lifestyle factors related to gastroesophageal reflux among Saudi population: a questionnaire-based study

Background: Gastroesophageal reflux (GER) differs from gastroesophageal reflux disease (GERD), which causes more severe symptoms and complications. The backflow of stomach acid initiates GER into the esophagus. Therefore, this study aims to identify the lifestyle factors related to GER. Methods: A cross-sectional study was conducted among 1,391 participants using a designed questionnaire (as a Google form) carried out among the targeted population through social media platforms until the target sample size was attained. After that, the data were analyzed using the Statistical Package for the Social Sciences software. Results: The study included 1,391 participants; 67.3% were female and 32.7% were male. Almost half of the participants (53.7%) were aged between 20 and 30 years old. About 43.1% of the participants had a healthy normal BMI, 26.9% were overweight, and 16.2% were obese. The remaining 11.4% were underweight and only 2.4% were morbidly obese. 5.1% of the participants felt heartburns more than thrice a week, 8.4% felt it twice or thrice a week, and 9.6% felt it once a week. 3% of the participants felt food regurgitation more than thrice a week, 6.3% felt it twice or thrice a week, and 6.7% felt it once a week. Only 9% of the participants had undergone Gastrointestinal tract endoscopy before and 4% did a PH monitoring. 19.5% of the participants eat midnight snacks, 30.9% skip breakfast, 31.3% eat quickly, and 20.1% eat beyond fullness. Conclusion: Eating midnight snacks, skipping breakfast, eating quickly, eating beyond fullness, lying down soon after eating, and less than 3 hours between dinner and sleep were the most reported lifestyle elements associated with GERD symptoms.

Real-Time Monitoring of Local Ph and Biofilm Formation Using a Noninvasive Impedance-Based Method

Real-Time Monitoring of Local Ph and Biofilm Formation Using a Noninvasive Impedance-Based Method

Relationship Among Helicobacter Pylori, Lower Esophagus Sphincter Pressure, and Gastroesophageal Reflux: A Single-Center Experience.

ObjectivesThe aim of the study was to evaluate the relationship among lower esophageal sphincter pressure (LESP), Helicobacter pylori (Hp), and gastroesophageal reflux (GER).MethodsThe retrospective study included patients with isolated hypertensive or hypotensive lower esophageal sphincter (LES) who underwent esophageal manometry in our gastroenterology motility laboratory and had normal manometry results. Demographic characteristics, complaints on admission, upper endoscopy findings, 24-h esophageal pH monitoring results, and presence of Hp in gastric biopsy were evaluated.ResultsA total of 1226 patients were included in the study, among whom women comprised 54% of all patients. Mean age was 45.4±13.4 years. Most common presenting complaint was pyrosis (85.4%). Pathological reflux was detected in 61.4% of the patients in 24-h esophageal pH monitoring. Reflux esophagitis was detected in 22.9% and LES laxity was present in 17.4% of the patients. In gastric biopsy, Hp was positive in 40% of the patients. The age of patients with hypertensive LES was significantly higher and female gender and body mass index (BMI) were associated with hypertensive LES. Pyrosis was significantly less prevalent in patients with hypertensive LESP. Esophagitis and LES laxity were significantly more prevalent in patients with hypotensive LES. No significant difference was found among the three groups with regard to reflux and Hp positivity. No significant difference was found between Hp-positive and Hp-negative groups with regard to reflux and reflux esophagitis.ConclusionNo clear relationship was found among LES disorders, GER, and Hp. Moreover, no significant difference was found among LES disorders with regard to GER, while the presence of hypotensive LESP, rather than Hp, was found to be an important factor in the development of reflux esophagitis.

Current advances in the diagnosis and management of gastroesophageal reflux disease.

Gastroesophageal reflux disease (GERD) is very common and defined as troublesome symptoms owing to excessive acid reflux. The spectrum of GERD is broad, including not only erosive esophagitis and Barrett's esophagus but also nonerosive reflux disease (NERD), reflux hypersensitivity, and functional heartburn. Patients with reflux symptoms despite normal endoscopy remain common clinical presentation, can be heterogeneous overlapping with functional gastrointestinal disorders. Ambulatory esophageal pH monitoring with and without impedance helps the diagnosis of NERD. Metrics such as baseline impedance and postreflux swallow induced peristaltic wave enhance diagnostic accuracy in patients with inconclusive diagnoses. The major treatment of all manifestations of GERD is acid suppression with proton pump inhibitors, while other therapies, such as reflux-reducing agents and adjunctive medications, can be individualized where the response to traditional management is incomplete. GERD patients often need long-term treatment due to frequent relapses. Anti-reflux surgery can be effective too. Endoscopic therapies have some promising results, but long-term outcomes remain to be determined.

MANIFESTATIONS OF EXCESSIVE DAYTIME SLEEPINESS AND GHRELIN LEVEL IN CASE OF GASTROESOPHAGEAL REFLUX DISEASE IN PATIENTS WITH UNDIFFERENTIATED CONNECTIVE TISSUE DISEASE

The aim of the study was to discover the interrelation between the severity of gastroesophageal reflux disease (GERD) symptoms, acid exposure time (AET), excessive daytime sleepiness (EDS) and the level of active blood plasma ghrelin in the patients with undifferentiated connective tissue disease (UCTD). Materials and methods: The study included 120 patients with GERD. All the patients were divided in two groups: Group I - GERD was not accompanied by the signs of connective tissue disease (n=45) and Group II - GERD developed on the background of UCTD syndrome (n=75). Daily transnasal pH monitoring was performed to determine the nature of pathological refluxes. EDS was detected by The Epworth Sleepiness Scale. Active ghrelin in blood plasma samples was determined by ELISA. Results: 80% of the patients of Group II and 35.48% of Group I suffered from EDS (p<0.05). The mean daily AET index was 5.48±0.4% in Group II and 6±0.2% in Group I, in the night hours mostly when patients were in the upright position. This phenomenon contributed to a deterioration of sleep quality and the appearance of EDS and was supported by a connection between AET and EDS (r=+0.827 for Group I and r=+0.768 for Group II). The mean De Meester index was higher in the patients of Group II (23.01±2.24 in Group I vs 31.08±2.4 in Group II; p<0.05). Conclusions: GERD manifestations are strongly related to the level to AET and intensity of EDS. The EDS symptoms depend on circulating ghrelin level.

Esophageal Achalasia: From Laparoscopic to Robotic Heller Myotomy and Dor Fundoplication.

Objective:Laparoscopic Heller myotomy and Dor fundoplication has become the gold standard in treating esophageal achalasia and robotic surgical platform represents its natural evolution. The objective of our study was to assess durable long-term clinical outcomes in our cohort.Methods and Procedures:Between June 1, 1999 and June 30, 2019, 111 patients underwent minimally invasive treatment for achalasia (96 laparoscopically and 15 robotically). Fifty-two were males. Mean age was 49 years (20 – 96). Esophageal manometry confirmed the diagnosis. Fifty patients underwent pH monitoring study, with pathologic reflux in 18. Preoperative esophageal dilation was performed in 76 patients and 21 patients received botulin injection. Dysphagia was universally present, and mean duration was 96 months (5 – 480).Results:Median operative time was 144 minutes (90 – 200). One patient required conversion to open approach. Four mucosal perforations occurred in the laparoscopic group and were repaired intraoperatively. Seven patients underwent completion esophageal myotomy and added Dor fundoplication. Upper gastrointestinal series was performed before discharge. Median hospital stay was 39 hours (24 – 312). Median follow up was 157 months (6 – 240), and dysphagia was resolved in 94% of patients. Seven patients required postoperative esophageal dilation.Conclusions:Minimally invasive Heller myotomy and Dor fundoplication are feasible. The operation is challenging, but excellent results hinge on the operative techniques and experience. The high dexterity, three-dimensional view, and the ergonomic movements of robotic surgery allow application of all the technical elements, achieving the best durable outcome for the patient. Robotic surgery is the natural evolution of minimally invasive treatment of esophageal achalasia.

Which is the best algorithm for evaluating a patient’s candidate to sleeve with suspected reflux or hiatal hernia: is manometry or reflux assessment always necessary

Laparoscopic sleeve gastrectomy (SG) has reached wide popularity during the last 15 years, owing to limited morbidity and mortality rates, very successful weight loss results, and impact on comorbidities. However, the postoperative development or worsening of gastroesophageal reflux disease (GERD) is one of the most important drawbacks of this surgical procedure. To date, there is great heterogeneity concerning the definition of GERD, the indication for SG in patients with GERD, and the standardization of pre and postoperative diagnostic pathways. In patients with severe obesity, a strictly symptom-based diagnosis of GERD is unreliable. In fact, a high rate of silent GERD (s-GERD, asymptomatic patients despite objective evidence of GERD) has been reported. Moreover, patients with preoperative s-GERD have a significantly higher risk of experiencing GERD symptoms after SG. For these reasons, the reflux burden and the competence of the anti-reflux barrier should be carefully assessed during the preoperative work-up of patients undergoing SG. Ambulatory pH monitoring (APM) and high-resolution manometry (HRM) are useful diagnostic tools that could provide valuable evidence in the guidance of surgical strategy. In this review, we evaluate the current literature concerning the use of APM and HRM in the diagnostic pathway before SG, as well as their predictive value for the evolution of GERD in the postoperative course. Moreover, we propose a diagnostic algorithm for preoperative GERD assessment, which includes validated symptom questionnaires, upper gastrointestinal endoscopy, APM, and HRM.

Cavity enhanced lab-on-fiber optrode for ultra-sensitive pH monitoring

pH-Responsive microgels placed between two gold films form a Fabry–Perot cavity above an optical fiber tip. The pH variations modulate the cavity length causing a huge wavelength shift of the reflection interference fringes in a wide pH range.

TEMPSENSE: LoRa Enabled Integrated Sensing and Localization Solution for Water Quality Monitoring

With the continuous increase in water pollution, water quality monitoring has become quite essential. Though existing solutions facilitate various features, (e.g., the potential of hydrogen (pH), dissolved oxygen (DO), temperature, electrical conductivity (EC), etc.), they possess numerous limitations; a) most of the existing systems rely on regional wireless systems, e.g., global system for mobile communication (GSM), a global positioning system (GPS), etc., hence their performance varies with local connectivity, b) usually the setup is deployed at remote locations including river site, so the solutions need to be power-optimized and should be able to support self-localization ability, which lacks in the existing solutions. In this context, we have developed a cost-effective functionality integration that brings different sensors, processing units, and Long Range (LoRa) transmission to a single platform, providing a compact, power-efficient, and low-cost Tds (total dissolved solids), Ec, teMperature, pH monitoring SystEm with integrated localizatioN Solution (TEMPSENSE). The proposed TEMPSENSE hardware is equipped with interactive sensing and localization algorithms, that address the above-mentioned concerns and facilitate the real-time location along with the required water quality parameters. Also, the proposed system has been thoroughly investigated by designing the hardware at the institution’s lab. Further, it is shown that the proposed hardware is several times cheaper than the available industrial solutions. Moreover, a number of experiments on different types of solutions have been performed for validation of the proposed design. Furthermore, extensive experiments have been performed for localization in low and high-density scenarios and is found that the proposed algorithm is potentially able to estimate the real-time location of the TEMPSENSE.

3d-Printed Microneedle-Based Potentiometric Sensor for Ph Monitoring in Skin Interstitial Fluid

3d-Printed Microneedle-Based Potentiometric Sensor for Ph Monitoring in Skin Interstitial Fluid

24-HOUR ESOPHAGEAL MULTICHANNEL PH-IMPEDANCE MONITORING IN THE DIAGNOSIS OF GASTROESOPHAGEAL REFLUX DISEASE (CLINICAL CASES)

Background. Gastroesophageal reflux disease (GERD) is an urgent problem of modern gastroenterology as well as the most common pathology of the upper gastrointestinal tract; it is a chronic disease that significantly reduces the patient's quality of life, increases the risk of developing Barrett's esophagus and esophageal adenocarcinoma. Objective. To assess the potentials of multichannel intraluminal pH impedance monitoring in the diagnosis of esophageal diseases. Material and methods. In 3 patients with clinical and endoscopic signs of GERD esophageal multichannel intraluminal pH-impedance monitoring was performed using the diagnostic equipment Digitrapper pH-Z from Given Imaging (USA). Results. 24-hour esophageal pH monitoring enabled to verify the diagnosis of GERD, to reveal a hypersensitive esophagus and manifestations of nocturnal acid breakthrough. Conclusions. Multichannel intraluminal pH-impedance monitoring is the "gold standard" for the diagnosis of esophageal diseases; it significantly expands opportunities of gastroenterologists in the treatment of GERD.

Denitrifying halophilic archaea derived from salt dominate the degradation of nitrite in salted radish during pickling

Salted radish is a popular high-salinity table food in China, and nitrite is always generated during the associated pickling process. However, this nitrite can be naturally degraded, and the underlying mechanism is unknown. Here, we identified the microbial groups that dominate the natural degradation of nitrite in salted radish and clarified the related metabolic mechanism. Based on dynamic monitoring of pH and the concentrations of nitrogen compounds as well as high-throughput sequencing analysis of the structural succession of microbial communities in the tested salted radish, we determined that the halophilic archaea derived from pickling salt dominate the natural degradation of nitrite via denitrification. Based on isolation, identification, nitrite reduction assays, and genome annotation, we further determined that Haloarcula, Halolamina, and Halobacterium were the key genera. These halophilic archaea might cope with high salt stress through the “salt-in” mechanism with the assistance of the accumulation of potassium ions, obtain electrons necessary for “truncated denitrification” from the metabolism of extracellular glucose absorbed from salted radish, and efficiently reduce nitrite to nitrogen, bypassing nitrite generation from nitrate reduction. The present study provides important information for the prevention and control of nitrite hazards in salted vegetables with high salinity, such as salted radish.

In Vivo Monitoring of pH in Subacute PD Mouse Brains with a Ratiometric Electrochemical Microsensor Based on Poly(melamine) Films.

In vivo monitoring of cerebral pH is of great significance because its disturbance is related to some pathological processes such as neurodegenerative diseases, for example, Parkinson's disease (PD). In this study, we developed an electrochemical microsensor based on poly(melamine) (PMel) films for ratiometric monitoring of pH in subacute PD mouse brains. In this microsensor, PMel films were prepared from a simple electropolymerization approach in a melamine-containing solution, serving as the selective pH recognition membrane undergoing a 2H+/2e- process. Meanwhile, electrochemically oxidized graphene oxide (EOGO) produced a built-in correction signal which helped avoid the environmental interference of the complicated brain systems. The potential difference between the peaks generated from EOGO and PMel gradually decreased with the aqueous pH increasing from 4.0 to 9.0, constituting the detection foundation of the ratiometric electrochemical microsensor (REM). The in vitro studies demonstrated that this proposed method exhibited a high sensitivity (a Nernstian response of -61.35 mV/pH) and remarkable selectivity against amino acids, anions, cations, and biochemical and reactive oxygen species coexisting in the brain. Coupled with its excellent stability and reproducibility and good antibiofouling based on short-term detection, the developed REM could serve as a disposable sensor for the determination of cerebral pH in vivo. Its following successful application in the real-time measurement of pH in the striatum, hippocampus, and cortex of rat brains in the events of global cerebral ischemia/reperfusion verified the reliability of this method. Finally, we adopted this robust REM to systematically analyze and compare the average pH in different regions of normal and subacute PD mouse brains.

Simultaneous Monitoring of pH and Chloride (Cl-) in Brain Slices of Transgenic Mice.

Optosensorics is the direction of research possessing the possibility of non-invasive monitoring of the concentration of intracellular ions or activity of intracellular components using specific biosensors. In recent years, genetically encoded proteins have been used as effective optosensory means. These probes possess fluorophore groups capable of changing fluorescence when interacting with certain ions or molecules. For monitoring of intracellular concentrations of chloride ([Cl−]i) and hydrogen ([H+] i) the construct, called ClopHensor, which consists of a H+- and Cl−-sensitive variant of the enhanced green fluorescent protein (E2GFP) fused with a monomeric red fluorescent protein (mDsRed) has been proposed. We recently developed a line of transgenic mice expressing ClopHensor in neurons and obtained the map of its expression in different areas of the brain. The purpose of this study was to examine the effectiveness of transgenic mice expressing ClopHensor for estimation of [H+]i and [Cl−]i concentrations in neurons of brain slices. We performed simultaneous monitoring of [H+]i and [Cl−]i under different experimental conditions including changing of external concentrations of ions (Ca2+, Cl−, K+, Na+) and synaptic stimulation of Shaffer’s collaterals of hippocampal slices. The results obtained illuminate different pathways of regulation of Cl− and pH equilibrium in neurons and demonstrate that transgenic mice expressing ClopHensor represent a reliable tool for non-invasive simultaneous monitoring of intracellular Cl− and pH.

Evaluation of gastrointestinal transit times and pH in healthy cats using a continuous pH monitoring system.

The aim of this study was to characterize gastrointestinal (GI) transit times and pH in healthy cats. GI transit times and pH were measured in six healthy, colony-housed, purpose-bred spayed female cats using a continuous, non-invasive pH monitoring system in a sequential order design. For the first period ('pre-feeding'), food was withheld for 20 h, followed by oral administration of a pH capsule. Five hours post-capsule administration, cats were meal-fed by offering them their daily allowance of food for 1 h. For the second period ('post-feeding'), food was withheld for 24 h and cats were fed for 1 h, after which a pH capsule was orally administered. Studies in both periods were repeated three times. GI transit times and pH were compared between the two periods. The median transit times for the pre- and post-feeding periods, respectively, were: gastric - 94 mins (range 1-4101) and 1068 mins (range 484-5521); intestinal - 1350 mins (range 929-2961) and 1534 mins (range 442-2538); and GI - 1732 mins (range 1105-5451) and 2795 mins (range 926-6563). The median GI pH values for the first and second periods, respectively, were: esophageal - 7.0 (range 3.5-7.8) and 4.5 (range 2.9-6.4); gastric - 2.7 (range 1.7-6.2) and 2.0 (range 1.1-3.3); intestinal - 8.2 (range 7.6-8.7) and 7.8 (range 6.7-8.5); first-hour small intestinal - 8.2 (range 7.4-8.7) and 8.3 (range 7.9-8.6); and last-hour large intestinal - 8.5 (range 7.0-8.9) and 7.8 (range 6.3-8.7). Gastric (P <0.0020) and intestinal pH (P <0.0059) were significantly increased in the pre-feeding period compared with the post-feeding period. Gastric and intestinal pH differed significantly when the capsule was administered 5 h prior to feeding compared with 1 h after feeding. Transit times for both periods showed high degrees of intra- and inter-individual variability.

Ultra-Thin Chips With ISFET Array for Continuous Monitoring of Body Fluids Ph.

This paper presents ISFET array based pH-sensing system-on-ultra-thin-chip (SoUTC) designed and fabricated in 350 nm CMOS technology. The SoUTC with the proposed current-mode active-pixel ISFET circuit array is desined to operate at 2 V and consumes 6.28 μW per-pixel. The presented SoUTC exhibits low sensitivity to process, voltage, temperature and strain-induced (PVTS) variations. The silicon area occupancy of each active-pixel is 44.9 × 33.5 µm2 with an ion-sensing area of 576 µm2. The design of presented ISFET device is analysed with finite element modeling in COMSOL Multiphysics using compact model parameters of MOSFET in 350 nm CMOS technology. Owing to thin (∼30 µm) Si-substrate the presented SoUTC can conform to curvilinear surfaces, allowing intimate contact necessary for reliable data for monitoring of analytes in body fluids such as sweat. Further, it can operate either in a rolling shutter fashion or in a pseudo-random pixel selection mode allowing the simultaneous detection of pH from different skin regions. Finally, the circuits have been tested in aqueous Dulbecco's Modified Eagle Medium (DMEM) culture media with 5-9 pH values, which mimics cellular environments, to demonstrate their potential use for continuous monitoring of body-fluids pH.

Improved stability of a supported liquid membrane process via hydrophobic modification of PVDF support by plasma activation and chemical vapor deposition

• PVDF membrane support was modified by plasma activation and CVD of a silane PFOCTS. • Water contact angle of support increased from 124.3° to ∼ 142.4° after surface fluorination. • Instability of an SLM process was analyzed by electrical impedance spectroscopy (EIS) • Stability of an SLM containing [BMIM]PF 6 was enhanced with a more hydrophobic support. • Results of in-situ EIS monitoring were verified by a macroscopic mass transfer analysis. In this research, hydrophobic modification of a poly(vinylidene fluoride) (PVDF) membrane through plasma activation and chemical vapor deposition with trichloro(1H,1H,2H,2H-perfluorooctyl)silane was investigated. The modified membrane was used as a support to improve the stability of a supported liquid membrane (SLM) process. Various plasma conditions such as power (6.8, 10.5, and 18 W) and treatment time (1, 2.5, 5, 7.5, and 10 min) were explored. Physicochemical properties of the pristine and modified membranes including the morphology, hydrophobicity, and chemical structure were first analyzed. The hydrophobicity of modified membranes increased, due to successful incorporation of a fluorine-containing silane (a reagent for reducing surface free energy) on the outer surface of the membrane and the inner surface of open pores nearby. The impact of hydrophobic modification on the stability of SLMs was real-time explored by a non-destructive technique, electrical impedance spectroscopy (EIS), where phenol and ionic liquid 1-butyl-3-methylimidazole hexafluorophosphate were selected as the model solute and membrane liquid (organic phase). The stability issues of SLMs deduced from EIS analysis were further verified by mass transfer analysis and feed pH monitoring. Results showed that the modified membranes provided more stable and prolonged SLM processes but relatively slower transport. The optimal plasma condition was found to be 18-W power and 5-min treatment time, at which the hydrophobicity of PVDF support was maximized (water contact angle 142.0°) and the most stable SLM was obtained (impedance reduction at 0.5-h time by ca. 60%). The mechanism causing the instability of the present SLM was finally identified. Plasma treatment and chemical vapor deposition with fluorine-containing silanes was an effective approach for enhancing the stability of an SLM and EIS was a powerful technique for real-time monitoring the instability behavior.

Two birds with one stone: A novel dual-functional fluorescent probe for simultaneous monitoring and real-time imaging of alkaline pH and viscosity in living cells

Viscosity and pH are two crucial microenvironment parameters, and their abnormal fluctuations at the cellular level can act as key indicators of various diseases diagnosis. Considering that the traditional viscosity/pH meters cannot work in the cellular environment, developing some viscosity/pH-sensitive fluorescent probes is urgently demanded. Herein, a novel dual-functional camphor-based fluorescent probe PN-SP for viscosity and pH detection was constructed based on spiropyran open/closed-ring switching strategy. PN-SP exhibited an intense green emission in response to alkaline pH while a bright red fluorescence was observed in high-viscosity media, which could avoid some problems caused by the use of multiple probes such as cross-talk spectrum and different localizations. The sensing performances of PN-SP were also demonstrated for monitoring viscosity and pH fluctuations in living HeLa cells by means of different emisson channels. Therefore, we believed that this work will provide guidance for designing some dual-functional fluorescent probes.