Dual-Mode Ratiometric Electrochemical and Turn-On Fluorescent Detection of Butyrylcholinesterase Utilizing a Single Probe for the Diagnosis of Alzheimer's Disease.

Biomarkers detection in blood with high accuracy is crucial for the diagnosis and treatment of many diseases. In this study, the proof-of-concept fabrication of a dual-mode sensor based on a single probe (Re-BChE) using a dual-signaling electrochemical ratiometric strategy and a "turn-on" fluorescent method is presented. The probe Re-BChE was synthesized in a single step and demonstrated dual mode response toward butyrylcholinesterase (BChE), a promising biomarker of Alzheimer's disease (AD). Due to the specific hydrolysis reaction, the probe Re-BChE demonstrated a turn-on current response for BChE at -0.28 V, followed by a turn-off current response at -0.18 V, while the fluorescence spectrum demonstrated a turn-on response with an emission wavelength of 600 nm. The developed ratiometric electrochemical sensor and fluorescence detection demonstrated high sensitivity with BChE concentrations with a low detection limit of 0.08 µg mL-1 and 0.05 µg mL-1, respectively. Importantly, the dual-mode sensor presents the following advantages: (1) dual-mode readout can correct the impact of systematic or background error, thereby achieving more accurate results; (2) the responses of dual-mode readout originate from two distinct mechanisms and relatively independent signal transduction, in which there is no interference between two signaling routes. Additionally, compared with the reported single-signal electrochemical assays for BChE, both redox potential signals were detected in the absence of biological interference within a negative potential window. Furthermore, it was discovered that the outcomes of direct dual-mode electrochemical and fluorescence quantifications of the level of BChE in serum were in agreement with those obtained from the use of commercially available assay kits for BChE sensing. This method has the potential to serve as a useful point-of-care tool for the early detection of AD.

Dual-Ligand Near-Infrared Luminescent Lanthanide-Based Metal-Organic Framework Coupled with In Vivo Microdialysis for Highly Sensitive Ratiometric Detection of Zn2+ in a Mouse Model of Alzheimer's Disease.

Zinc, which is the second most abundant trace element in the human central nervous system, is closely associated with Alzheimer's disease (AD). However, attempts to develop highly sensitive and selective sensing systems for Zn2+ in the brain have not been successful. Here, we used a one-step solvothermal method to design and prepare a metal-organic framework (MOF) containing the dual ligands, terephthalic acid (H2BDC) and 2,2':6',2″-terpyridine (TPY), with Eu3+ as a metal node. This MOF is denoted as Eu-MOF/BDC-TPY. Adjustment of the size and morphology of Eu-MOF/BDC-TPY allowed the dual ligands to produce multiple luminescence peaks, which could be interpreted via ratiometric fluorescence to detect Zn2+ using the ratio of Eu3+-based emission, as the internal reference, and ligand-based emission, as the indicator. Thus, Eu-MOF/BDC-TPY not only displayed higher selectivity than other metal cations but also offered a highly accurate, sensitive, wide linear, color change-based technique for detecting Zn2+ at concentrations ranging from 1 nM to 2 µM, with a low limit of detection (0.08 nM). Moreover, Eu-MOF/BDC-TPY maintained structural stability and displayed a fluorescence intensity of at least 95.4% following storage in water for 6 months. More importantly, Eu-MOF/BDC-TPY sensed the presence of Zn2+ markedly rapidly (within 5 s), which was very useful in practical application. Furthermore, the results of our ratiometric luminescent method-based analysis of Zn2+ in AD mouse brains were consistent with those obtained using inductively coupled plasma mass spectrometry.

Novel Self-Calibrating Amperometric and Ratiometric Electrochemical Nanotip Microsensor for pH Measurement in Rat Brain.

Brain pH has been proven to be a key factor in maintaining normal brain function. The relationship between local pH fluctuation and brain disease has not been extensively studied due to lack of the accurate in situ analysis technology. Herein, we have for the first time proposed a voltammetric pH sensor by measuring the ratio of current signals instead of the previously reported potential based on the Nernst equation. Single-walled carbon nanotubes (CNT) were first self-assembled on the electrode surface of a carbon-fiber nanotip electrode (CFNE). Then, poly-o-phenylenediamine (PoPD) molecules were deposited as pH-responsive molecules through in situ electrochemical polymerization. The compact CFNE/CNT/PoPD exhibited a good redox process with the on-off-on ratiometric electrochemical response to pH ranging from 4.5 to 8.2, providing self-correction for in situ pH detection. Thus, the proposed sensor enabled the accurate measurement of pH with excellent selectivity even in the presence of proteins or electroactive species. In addition, the sensor showed high repeatability, reproducibility, and reversibility in measuring pH and even demonstrated good stability when it was exposed to air for 5 months. Finally, we successfully detected the fluctuation of pH in rat brains with cerebral ischemia and rat whole blood. Overall, this research not only provides a good tool for the detection of rat brain pH but also provides a new strategy for further designing nanosensors for intracellular or subcellular pH.

Intensification of electrochemiluminescence of luminol on TiO2 supported Au atomic cluster nano-hybrid modified electrode.

With TiO(2) nanoparticles as carrier, a supported nano-material of Au atomic cluster/TiO(2) nano-hybrid was synthesized. It was then modified onto the surface of indium tin oxide (ITO) by Nafion to act as a working electrode for exciting the electrochemiluminescence (ECL) of luminol. The properties of the nano-hybrid and the modified electrode were characterized by XRD, XPS, electronic microscopy, electrochemistry and spectroscopy. The experimental results demonstrated that the modification of this nano-hybrid onto the ITO electrode efficiently intensified the ECL of luminol. It was also revealed that the ECL intensity of luminol on this modified electrode showed very sensitive responses to oxygen and hydrogen peroxide. The detection limits for dissolved oxygen and hydrogen peroxide were 2 µg L(-1) and 5.5 × 10(-12) M, respectively. Besides the discussion of the intensifying mechanism of this nano-hybrid for ECL of luminol, the developed method was also applied for monitoring dissolved oxygen and evaluating the scavenging efficiency of reactive oxygen species of the Ganoderma lucidum spore.

Advancement in Analytical Techniques for Determining the Activity of ß-Site Amyloid Precursor Protein Cleaving Enzyme 1.

Alzheimer's disease (AD) is a degenerative disease of the central nervous system. The pathogenesis is still not fully clear. One of the main histopathological manifestations is senile plaques formed by ß-amyloid (Aß) accumulation. Aß is generated from the sequential proteolysis of amyloid precursor protein (APP) by ß-secretase [i.e. ß-site APP cleaving enzyme 1 (BACE1)] and γ-secretase, with a rate-limiting step controlled by BACE1 activity. Therefore, inhibiting BACE1 activity has become a potential therapeutic strategy for AD. The development of reliable detection methods for BACE1 activity plays an important role in early diagnosis of AD and evaluation of the therapeutic effect of new drugs for AD. This article has reviewed the recent advances in BACE1 activity detection techniques. The challenges of applying these analysis techniques to early clinical diagnosis of AD and development trends of the detection techniques have been prospected.

Development of a novel ratiometric electrochemical sensor for monitoring ß-galactosidase in Parkinson's disease model mice.

Rapid, simple, accurate and highly sensitive detection of enzymes is essential for early screening and clinical diagnosis of many diseases. In this study, we report the fabrication of a turn-on ratiometric electrochemical sensor for the in situ determination of ß-Galactosidase (ß-Gal) based on surface engineering and the design of a molecular probe (Pygal) specific for ß-Gal recognition. First, Pygal probe was synthesized and characterized, and then co-assembled with the methylene blue (MB) internal reference probe on the surface of single-wall carbon nanotubes (SWCNT)-modified carbon fiber microelectrode (CFME). The resulting CFME/SWCNT/MB + Pygal sensor is activated in the presence of ß-Gal giving one peak at 0.33 V originating from the oxidation of the product of Pygal enzymatic hydrolysis (PyOH). Another oxidation peak attributed to MB appears simultaneously at -0.28 V allowing the construction of a ratiometric electrochemical sensor for ß-Gal detection with improved sensitivity and accuracy. The sensor showed a linear response to ß-Gal in a wide concentration range from 1.5 to 30 U L-1 and a low detection limit of 0.1 U L-1. Moreover, the sensor demonstrated excellent selectivity against several biologically relevant hydrolases and redox-active molecules. Finally, the combination of excellent electrochemical performance and favorable physicochemical properties of CFME allowed the determination of ß-Gal in the whole blood of Parkinson's Disease (PD) model mice. The workflow reported in this study provides a strategy for the design and development of sensors for the in vivo monitoring of other enzymes important for the early diagnosis of different health issues.

[A clinical study on the determination of cuff pressure in artificial airway by minimum air leakage method].

OBJECTIVE: To compare the cuff pressure and leakage volume and the related complications of filling the tracheal tube cuff by minimum air leakage method and cuff pressure manometer method after endotracheal intubation, so as to provide theoretical basis for patients who was intubated to obtain appropriate cuff pressure. METHODS: A prospective randomized controlled study was conducted. 100 patients admitted to the department of critical care medicine of the Fifth Center Hospital in Tianjin from December 2015 to June 2019 were enrolled. According to the random number table method, the patients were divided into the experimental group and control group, with 50 patients in each group. After successful endotracheal intubation, all patients were placed in a supine position with the head of the bed raised by 30 degree angle. The experimental group used the minimum air leakage method, and used the cuff pressure manometer to obtain the cuff pressure. In the control group, cuff pressure was maintained at 25-30 cmH2O (1 cmH2O = 0.098 kPa). Parameters such as cuff pressure and ventilator leakage volume at the beginning and 4 hours, 8 hours after the inflation were compared between the two groups, as well as the incidence of ventilation-associated pneumonia (VAP) and airway complications after extubation. RESULTS: Among the 100 cases, 53 were males and 47 were females. The age ranged from 23 to 87 years old, with an average of (68.53±8.46) years old. The intubation time ranged from 1 to 16 days. (1) At 4 hours and 8 hours after inflation, the cuff pressures of the two groups were lower than that of the first time of inflation, and the air leakage of the ventilator increased gradually with the extension of time. Compared with the control group, cuff pressures at each time point in the experimental group were significantly higher than those in the control group [mmHg (1 mmHg = 0.133 kPa): 33.72±9.14 vs. 25.68±5.26 at 0 hour, 30.54±7.81 vs. 24.35±4.93 at 4 hours, 26.57±5.64 vs. 22.42±4.14 at 8 hours, all P < 0.05], and ventilator leakage volumes were smaller than those in the control group (mL: 25.57±8.51 vs. 34.65±9.47 at 0 hour, 40.54±8.51 vs. 60.34±7.85 at 4 hours, both P < 0.05). (2) The incidence of VAP in the experimental group was significantly lower than that in the control group (4% vs. 10%, P < 0.05). There was no statistically significant difference in the incidence of other airway complications between the experimental group and control group (airway mucosal edema: 14% vs. 12%, ulcer: 8% vs. 6%, tracheal esophageal fistula: 0% vs. 0%, hoarseness: 4% vs. 6%, cough: 30% vs. 34%, sore throat: 28% vs. 32%, tracheal softening: 0% vs. 0%, cuff rupture: 10% vs. 8%, all P > 0.05). CONCLUSIONS: The optimal cuff pressure is very important for preventing VAP and reducing airway complications. The minimum air leakage method makes the clinical obtained endotracheal intubation cuff pressure more accurately, with less air leakage, safe and effective, and it is worthy of clinical promotion.

A coumarin-based fluorescent probe for ratiometric detection of hydrazine and its application in living cells.

A new ratiometric fluorescent probe (1) was developed for the detection of hydrazine. The probe was obtained by incorporating the recognition moiety of acetyl group onto a coumarin fluorophore. Probe 1 displayed a distinct cyan emission in a 100% aqueous phosphate buffer solution. In the presence of hydrazine, probe 1 undergoes a hydrazinolysis process to release the coumarin fluorophore, which exhibited significant hypsochromic shifts in both absorption and emission spectra, and thus achieving a ratiometric response. This ratiometric probe is highly selective and sensitive towards hydrazine detection. The limit of detection (LOD) was calculated to be 34 nM. Moreover, cellular toxicity and imaging experiments suggested that probe 1 is can be used to monitor hydrazine in live cells.

A highly sensitive resonance light scattering probe for Alzheimer's amyloid-ß peptide based on Fe3O4@Au composites.

The fabrication of Fe3O4@Au composites as a novel resonance light scattering (RLS) probe for the sensitive detection of Alzheimer's amyloid-ß peptide (Aß) was demonstrated. Amino groups coated magnetic Fe3O4 nanoparticles were covered with gold shell by the classical Frens method. The resultant colloids were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and UV-visible spectra. The results indicated that the composite particles with core/shell structure and an average diameter of ~ 320 nm were stable and biocompatible. The RLS intensity of Fe3O4@Au composites was significantly enhanced by interacting with Aß. Under optimal conditions, good linear relationship between the ratio of RLS intensity I/I0 at 463.0 nm and the logarithmic value of Aß concentration in the range of 5.0 × 10(-15)-5.56 × 10(-9)M was found. The limit of detection (LOD) was 1.2 × 10(-15)M. The proposed method is simple, sensitive and cost-effective and complementary to other existing methods for protein analysis.

Development of a reagentless electrochemiluminescent electrode for flow injection analysis using copolymerised luminol/aniline on nano-TiO2 functionalised indium-tin oxide glass.

In this study, a nano-structured copolymer of luminol/aniline (PLA) was deposited onto nano-TiO2-functionalised indium tin oxide (ITO)-coated glass by electrochemical polymerisation using cyclic voltammetry (CV). The resulting reagentless electrochemiluminescent (ECL) electrode (ECLode) can be used for flow injection analysis (FIA). The properties of the ECLode were characterised by CV, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The ECLode has high background ECL emission as well as excellent stability and reproducibility, and yielding sensitive response towards target analytes. The ECL emissions of the ECLode were 50 times higher than PLA/ITO, and 500 times higher than polyluminol (PL)/ITO. The ECLode showed sensitive responses to reactive oxygen species (ROSs), permitting its application for determination of antioxidants by quenching. Under optimised conditions, an absolute detection limit of 69.9 pg was obtained for resveratrol, comparable to the highest levels of sensitivity achieved by other methods. Thus, the gross antioxidant content of red wine was determined, with satisfactory recoveries between 87.6% and 108.3%. These results suggest a bright future for the use of the ECLode for single-channel FIA due to its high sensitivity, accuracy and reproducibility.

A luminol-based micro-flow-injection electrochemiluminescent system to determine reactive oxygen species.

A flow injection analysis (FIA) system with electrochemiluminescent (ECL) detection has been established. Based on a specially designed flow-through ECL cell with a very simple structure, the system possesses rapid response and high sensitivity. With luminol as the ECL reagent, the response of hydrogen peroxide (H(2)O(2)) was investigated on the developed FIA-ECL system. After optimizing the experimental conditions, such as the electric parameters, the buffer condition and the flow rate, it was demonstrated that the developed FIA-ECL system works well for quantified assays. Compared with reported works, the present results indicate that the developed FIA-ECL system has the lowest limit of detection (S/N=3) of 3.0×10(-9) mol/L for H(2)O(2), which is equal to the level of chemiluminescence (CL). The developed system was successfully used to monitor the yield of reactive oxygen species (ROSs) in water vapour during the work of an ultrasonic humidifier with H(2)O(2) as index. And the amount of ROSs in some other real samples, including tap water, drinking water and river water was detected with recoveries from 92.0% to 106%.