Ratiometric Fluorescent Biosensors for Glucose and Lactate Using an Oxygen-Sensing Membrane.

In this study, ratiometric fluorescent glucose and lactate biosensors were developed using a ratiometric fluorescent oxygen-sensing membrane immobilized with glucose oxidase (GOD) or lactate oxidase (LOX). Herein, the ratiometric fluorescent oxygen-sensing membrane was fabricated with the ratio of two emission wavelengths of platinum meso-tetra (pentafluorophenyl) porphyrin (PtP) doped in polystyrene particles and coumarin 6 (C6) captured into silica particles. The operation mechanism of the sensing membranes was based on (i) the fluorescence quenching effect of the PtP dye by oxygen molecules, and (ii) the consumption of oxygen levels in the glucose or lactate oxidation reactions under the catalysis of GOD or LOX.

Development of a Ratiometric Fluorescent Glucose Sensor Using an Oxygen-Sensing Membrane Immobilized with Glucose Oxidase for the Detection of Glucose in Tears.

Glucose concentration is an important parameter in biomedicine since glucose is involved in many metabolic pathways in organisms. Many methods for glucose detection have been developed for use in various applications, particularly in the field of healthcare in diabetics. In this study, ratiometric fluorescent glucose-sensing membranes were fabricated based on the oxygen levels consumed in the glucose oxidation reaction under the catalysis of glucose oxidase (GOD).

Development of novel optical pH sensors based on coumarin 6 and nile blue A encapsulated in resin particles and specific support materials.

Inspired by traditional pH papers, two types of ratiometric fluorescent pH sensors for neutral and alkaline pH ranges were developed in this study by using two fluorescent dyes, coumarin 6 (C6) and nile blue A (NB). These dyes were encapsulated into melamine-formaldehyde (MF) resin particles, which were then incorporated with polymer Nafion (Nf) or polyurethane hydrogel (PU) to prepare pH-sensing membranes. MF-C6 particles immobilized into polymer Nafion (i.

Development of Ratiometric Fluorescence Sensors Based on CdSe/ZnS Quantum Dots for the Detection of Hydrogen Peroxide.

In this study, carboxyl group functionalized-CdSe/ZnS quantum dots (QDs) and aminofluorescein (AF)-encapsulated polymer particles were synthesized and immobilized to a sol-gel mixture of glycidoxypropyl trimethoxysilane (GPTMS) and aminopropyl trimethoxysilane (APTMS) for the fabrication of a hydrogen peroxide-sensing membrane. CdSe/ZnS QDs were used for the redox reaction of hydrogen peroxide (HO) via a reductive pathway by transferring electrons to the acceptor that led to fluorescence quenching of QDs, while AF was used as a reference dye. Herein, the ratiometric fluorescence intensity of CdSe/ZnS QDs and AF was proportional to the concentration of hydrogen peroxide.

Development of Colorimetric and Ratiometric Fluorescence Membranes for Detection of Nitrate in the Presence of Aluminum-Containing Compounds.

In this study, a quantitative analysis of nitrate in aqueous solution was performed through the combination of an oxazine170 perchlorate⁻ethyl cellulose (O17-EC) membrane with aluminum-containing compounds. Aluminum of Devarda's alloy (DA) or a clay hydrotalcite (HT) was employed for the reduction of nitrate to produce ammonia, and the produced ammonia was detected by the O17-EC membrane. The method of combining the O17-EC membrane with aluminum compounds has showed a broad detection range of nitrate.

Effects of CdSe and CdSe/ZnS Core/Shell Quantum Dots on Singlet Oxygen Production and Cell Toxicity.

Four types of quantum dots (QDs) with varying emission wavelengths were synthesized in this study. The dots included CdSe and CdSe/ZnS core/shell QDs with short emission wavelengths of 540 nm and 560 nm, respectively, as well as CdSe and CdSe/ZnS core/shell QDs with longer emission wavelengths of 585 nm and 595 nm, respectively. The ligands on the QD surfaces were exchanged with mercaptopropionic acid (MPA) to make them water-soluble.

Development of a Sequential Injection Analysis System for the Determination of Saccharin.

Saccharin is a powerfully sweet nonnutritive sweetener that has been approved for food-processing applications within the range of 100-1200 mg/kg. A simple, rapid, and cost-effective sequential injection analysis (SIA) technique was developed to determine the saccharin level. This method is based on the reaction of saccharin with p-chloranil in an ethanol medium with a hydrogen peroxide (H₂O₂) acceleration, and the resultant violet-red compound was detected using a UV-Vis spectrophotometer at λ = 420 nm.

Development of Ratiometric Fluorescent Biosensors for the Determination of Creatine and Creatinine in Urine.

In this study, the oxazine 170 perchlorate (O17)-ethylcellulose (EC) membrane was successfully exploited for the fabrication of creatine- and creatinine-sensing membranes. The sensing membrane exhibited a double layer of O17-EC membrane and a layer of enzyme(s) entrapped in the EC and polyurethane hydrogel (PU) matrix. The sensing principle of the membranes was based on the hydrolytic catalysis of urea, creatine, and creatinine by the enzymes.

Ratiometric fluorescent l-arginine and l-asparagine biosensors based on the oxazine 170 perchlorate-ethyl cellulose membrane.

Ratiometric fluorescent l-arginine (Arg) and l-asparagine (Asn) biosensors were developed using an oxazine 170 perchlorate (O17) ethyl cellulose (EC) membrane and the enzymes entrapped into the matrix of EC and hydrogel polyurethane. The sensing principles were based on the hydrolysis reactions of urea and l-Arg under the catalysis of the urease and arginase to produce ammonia in the case of an l-Arg-sensing membrane and also on the hydrolysis reaction of l-Asn under the catalysis of asparaginase in the case of an l-Asn-sensing membrane. The O17-EC membrane reacted with the ammonia produced from the hydrolysis reactions and changed the fluorescence intensities at = 565 and 625 nm.

CdSe/ZnS Core/Shell Quantum Dots in Cooperation with Other Materials for Direct and Indirect Production of Reactive Oxygen Species.

In this present work, CdSe/ZnS core/shell quantum dots (QDs) were exploited in the oxidation reactions of 5-aminolevulinic acid (ALA) and glutamate (GLU) for the production of reactive oxygen species (ROS). Fast and highly efficient oxidation reactions of ALA to produce the hydroxyl radicals (HO*) and of GLU to produce the superoxide anion (O2*-) were observed in the cooperation of mercaptopropionic acid (MPA) capped-CdSe/ZnS QDs (MPA-QDs) under LED irradiation. Whereas, binding between MPA-QDs and coumarin-derived dendrimer (CdD)-captured silica particles (SiCdDs) through sol-gel GA enhanced singlet oxygen production under LED irradiation by about 80% as compared to that achieved using QDs only.

Simple and sensitive progesterone detection in human serum using a CdSe/ZnS quantum dot-based direct binding assay.

In this study, we developed a CdSe/ZnS quantum dot (QD)-based immunoassay for use in determining the presence of progesterone (P4) in human serum. Hydrophilic QDs were conjugated to anti-progesterone antibody (P4Ab) via ethyl-3-(dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as coupling reagents. After purification, the P4Ab-QD conjugates were immobilized onto the wells of a 96-well microtiter plate, and a direct-binding immunoassay based on the binding of P4 to immobilized P4Ab-QD conjugates had a detection limit of 0.

Development of a ratiometric fluorescent urea biosensor based on the urease immobilized onto the oxazine 170 perchlorate-ethyl cellulose membrane.

In this work, the oxazine 170 perchlorate (O17)-ethyl cellulose (EC) membrane was successfully applied in the fabrication of a urea-sensing membrane. The urea-sensing membrane was a double layer consisting of the O17-EC membrane and a layer of the enzyme urease entrapped into EC matrix. The sensing principle of urea was based on the hydrolysis reaction of urea under the catalysis of the urease to produce ammonia in water and also on the binding of ammonia with the dye O17 to create the shift in the emission wavelength from λ(em)=630 nm to λ(em)=565 nm.

Optimization of extracellular production of recombinant human bone morphogenetic protein-7 (rhBMP-7) with Bacillus subtilis.

Extracellular production of recombinant human bone morphogenetic protein-7 (rhBMP-7) was carried out through the fermentation of Bacillus subtilis. Three significant fermentation conditions and medium components were selected and optimized to enhance the rhBMP-7 production by using the response surface methodology (RSM). The optimum values of the three variables for the maximum extracellular production of rhBMP-7 were found to be 2.

Sequential injection immunoassay for human bone morphogenic protein-7 using an immunoreactor immobilized with anti-human bone morphogenic protein-7 antibody--CdSe/ZnS quantum dot conjugates.

The detection of human bone morphogenic protein-7 (BMP-7) was achieved using a sequential injection immunoassay (SIIA) system. The SIIA system is based on the binding between BMP-7 and anti-human BMP-7 (AbBMP7)-CdSe/ZnS quantum dot (QD) conjugates immobilized onto a glass disk or an optical fiber, using fluorescence detection at excitation and emission wavelengths of 470 nm and 580 nm, respectively. The AbBMP7-QD conjugates were prepared by conjugating anti-human BMP-7 antibody (AbBMP7) to hydrophilic CdSe/ZnS core/shell quantum dots (QDs).

Sequential injection analysis system for on-line monitoring of l-cysteine concentration in biological processes.

A sequential injection analysis (SIA) system was developed to monitor the concentration of l-cysteine in biological processes on-line. It is based on the redox reaction of l-cysteine with iron(III) in the presence of 1,10-phenanthroline (phen) and the detection of the red-iron(II)-phen complex with a spectrophotometry. The system was fully automated using software written in the LabVIEWtrade mark development environment.

Flow injection analysis system for monitoring of succinic acid in biotechnological processes.

In this study, a flow injection analysis (FIA) system using a cartridge of immobilized isocitrate lyase (ICL) and isocitrate dehydrogenase (ICDH) was developed to monitor the concentrations of succinic acid in biotechnological processes. The ICL and ICDH immobilized on VA-Epoxy Biosynth E3-carrier had a good operational lifetime (up to 24h) and storage stability (up to 30 days). The FIA system with the immobilized ICL/ICDH cartridge was characterized with respect to the factors affecting the activity of the immobilized enzymes, such as pH of carrier solution, temperature, sample matrix, etc.

Encapsulation of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) complex linked with dendrons in sol-gels: Stable optical sensing membranes for dissolved oxygen.

To circumvent the leaching problem of optical sensing membranes used for dissolved oxygen (DO) measurements, the encapsulation of Ru(II) complexes linked with bulky dendron(s) in a sol-gel matrix was investigated. A dendron, readily formed via chemical transformations such as amidation and catalytic reduction, was covalently incorporated into tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) complex, leading to an increase in the size and lipophilicity of dye molecules. Sol-gel-based sensing membranes encapsulating these Ru(II) complexes displayed a strong luminescence emission at 590 nm induced by radiation at 480 nm, and showed excellent DO sensing properties and stability for repeated measurements in aqueous solution.

Use of CdSe/ZnS luminescent quantum dots incorporated within sol-gel matrix for urea detection.

In this work, urea detection techniques based on the pH sensitivity of CdSe/ZnS QDs were developed using three types of sol-gel membranes: a QD-entrapped membrane, urease-immobilized membrane and double layer consisting of a QD-entrapped membrane and urease-immobilized membrane. The surface morphology of the sol-gel membranes deposited on the wells in a 24-well microtiter plate was investigated. The linear detection range of urea was in the range of 0-10mM with the three types of sol-gel membranes.

Use of CdSe/ZnS core-shell quantum dots as energy transfer donors in sensing glucose.

In the present work, CdSe/ZnS core-shell quantum dots were synthesized and conjugated with enzymes, glucose oxidase (GOD) and horseradish peroxidase (HRP). The complex of enzyme-conjugated QDs was used as QD-FRET-based probes to sense glucose. The QDs were used as an electron donor, whereas GOD and HRP were used as acceptors for the oxidation/reduction reactions involved in oxidizing glucose to gluconic acid.

Preparation and characterization of sensing membranes for the detection of glucose, lactate and tyramine in microtiter plates.

In this work, sensing membranes for the detection of glucose, lactate and tyramine were successfully prepared by immobilizing enzymes and fluorophore on sol-gels. The membranes were fabricated on the bottom of the wells in a microtiter plate. Glucose oxidase (GOD), lactate oxidase (LOD) and tyramine oxidase (TOD) were immobilized on individual sol-gels or a mixture of different sol-gels (3-glycidoxypropyl-trimethoxysilane (GPTMS), methyl-triethoxysilane (MTES), aminopropyl-trimethoxysilane (APTMS)).

High-level expression of recombinant phospholipase C from Bacillus cereus in Pichia pastoris and its characterization.

The phospholipase c (plc) gene from Bacillus cereus was cloned into the pPICZC vector and integrated into the genome of Pichia pastoris. The phospholipase C (PLC) when expressed in P. pastoris was fused to the alpha-factor secretion signal peptide of Saccharomyces cerevisiae and secreted into a culture medium.