Fluorescent Silicate Materials for the Detection of Paraoxon

Porphyrins are a family of highly conjugated molecules that strongly absorb visible light and fluoresce intensely. These molecules are sensitive to changes in their immediate environment and have been widely described for optical detection applications. Surfactant-templated organosilicate materials have been described for the semi-selective adsorption of small molecule contaminants. These structures offer high surface areas and large pore volumes within an organized framework. The organic bridging groups in the materials can be altered to provide varied binding characteristics. This effort seeks to utilize the tunable binding selectivity, high surface area, and low materials density of these highly ordered pore networks and to combine them with the unique spectrophotometric properties of porphyrins. In the porphyrin-embedded materials (PEMs), the organosilicate scaffold stabilizes the porphyrin and facilitates optimal orientation of porphyrin and target. The materials can be stored under ambient conditions and offer exceptional shelf-life. Here, we report on the design of PEMs with specificity for organophosphates and compounds of similar structure

Development of a phosphotriesterase enzyme assay for determination of organophosphate pesticides

Phosphotriesterase catalyzes the hydrolysis of a wide range of organophosphate insecticides such as paraoxon and parathion and nerve toxins such as soman and sarin. This project resulted in the development of novel phosphotriesterase enzyme assays to measure paraoxon and other representatives of the organophosphate pesticides. The assay is based on a substrate-dependent change in pH at the local vicinity of the enzyme. This enzyme, which was labeled with fluorescein isothiocyanate (FITC), was immobilized on polymethylmethacrylate beads and the pH change is monitored through the pH-sensitive quantum yield of FITC. Analytes were measured using a KinExA fluorescence analyzer. This assay can detect paraoxon concentration down to 11 {dollar}\mu{dollar}M with a dynamic range of 11 {dollar}\mu{dollar}M to 600 {dollar}\mu{dollar}M. In addition to the paraoxon, this assay was also used to measure 9 other insecticides and to determine the concentrations of coumaphos in the biofilter treated cattle dip waste samples

Enzymatic reactions in confined environments

Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems

InP/ZnS Nanocrystals as Fluorescent Probes for the Detection of ATP

This article reports on a study on fluorescence adenosine triphosphate (ATP) detection by InP/ZnS quantum dots (QDs). We present a spectroscopic analysis displaying the effect of enzymatic reactions of glucose oxidase (GOX) and hexokinase (HEX) on the InP/ZnS quantum dots at physiological pH. The InP/ZnS quantum dots act as glucose sensors in the presence of GOX, Glu and ATP, and their luminescence quenches during the release of hydrogen peroxide from the reaction. However, in the presence of adenosine 5’ triphosphate, glucose, and HEX, a significant photobrightening of the InP/ZnS QDs is recorded. This is dependent on the concentration of ATP in the sample. The relationship between the ATP and the emission intensity of InP/ZnS nanocrystals is linear. The present results are the first to report the effect of different by-products released by these enzymatic reactions on the fluorescence of the InP/ZnS QDs

Progress in host–guest macrocycle/pesticide research: Recognition, detection, release and application

Macrocyclic compounds are formed via a series of cyclic oligomers possessing repeating units, and classical examples include cyclodextrins, calix[n]arenes, cucurbit[n]urils and pillar[n]arenes (n represents the number of repeat units). Given their unique host–guest binding ability, macrocycles are often developed as hosts for specific guest molecular assembly systems, adsorption materials, drug delivery carriers, catalysts, and molecular recognition systems. For example, macrocyclic host molecules are widely used to encapsulate hydrophobic drug molecules to improve both the solubility and utilization efficiency of the drug. One type of potential host molecule that has seen increased agricultural use in recent years are pesticides. This includes herbicides, insecticides, and fungicides, and given the increased use, there is need to develop systems that can rapidly and effectively identify and detect such pesticides. In this review, we will discuss the use of cucurbit[n]urils, pillar[n]arenes, calix[n]arenes, cyclodextrins in this area, and their ability to form host–guest species with herbicides, insecticides and fungicides. Particular emphasis is given to the ability of such systems to improve the toxicity and release of the pesticide and the potential for practical application

Porphyrins as Colorimetric Indicators for Detection and Identification of Chemical and Biological Agents

The objective of this study was to design sensor surfaces for rapid, real-time, optical detection of chemical/biological warfare agents and/or environmental pollutants that yield a minimum of false readings. Porphyrins were used as colorimetric indicators for transduction in surfaces using biological recognition elements such as enzymes and as combination recognition element/transducer in other surfaces. Immobilization protocols and assaying procedures were developed for each of the sensor surfaces. As a reversible, competitive inhibitor of enzymes, porphyrins can be used for identification and quantification of the presence of a substrate or another competitive inhibitor of the enzyme. This technique has been useful for development of glass surfaces for the detection of cholinesterase inhibitors such as organophosphate compounds and nerve agent simulants at parts per trillion levels using acetylcholinesterase, butyrylcholinesterase, and organophosphorous hydrolase as recognition elements. Evanescent wave aDepartment of Physic

Development of 2-Dimensional Photonic Crystal Sensors and Pure Protein Organogel Sensing and Biocatalytic Materials

We developed responsive hydrogels, organogels, and ionogels for chemical sensing and catalysis applications. Gels have two components, polymer networks and solvent mobile phases. Hydrogels contain an aqueous mobile phase; organogels an organic solvent; and ionogels an ionic liquid. Different solvent types were required to target different applications, e.g. gas sensing requires solvents that resist evaporation. Colorimetric chemical sensors utilize our 2-Dimensional Photonic Crystals (2DPC) technology. 2DPC are arrays of self-assembled polystyrene nanoparticles that have close-packed, hexagonal crystal structures. 2DPC diffract wavelengths of light into discrete angles according to the 2D Bragg equation. Diffraction depends on 2DPC particle spacing and ordering. 2DPC—embedded into gels that were designed such that analytes actuate polymer volume phase transitions (VPT)—change particle spacing with the VPT, shifting diffraction angles. VPT occur when analytes cause Gibbs free energy changes, ∆G. 2DPC surfactant sensors utilized poly(N-isopropylacrylamide) (PNIPAAm) hydrogels. PNIPAAm hydrogels swell when the hydrophobic tail of ionic surfactants bind to the PNIPAAm isopropyl group. A Donnan potential created by bound charges induces ∆GIonic, causing swelling that red shifts the diffraction. 2DPC gas sensors for humidity and ammonia utilized poly(hydroxyethylmethacrylate)-based polymers in the ionic liquid ethylguanidinium perchlorate (EGP). Ionogels are suitable gas sensors—ionic liquids have negligible vapor pressures, delivering mobile phases that don’t evaporate. ∆GMixing occurs when EGP absorbs water vapor, causing ionogel shrinking that blue shifts the diffraction. Ammonia sensors incorporated acrylic acid into the polymer. Ammonia absorbed by EGP deprotonated the carboxyl groups, causing swelling that red shifts the diffraction. Responsive pure protein organogels were fabricated from protein hydrogels by exchanging water with ethylene glycol. 2DPC albumin organogels swell when the proteins bind ligands, enabling water insoluble analyte detection that utilizes protein selectivity. Organophosphorus Hydrolase organogels catalyze hydrolysis of organophosphate nerve agents ~160 times faster than their monomers in organic solvent. Organic solvents typically denature proteins. Crosslinked organogel proteins mostly retain their native protein reactivity because the proteins are immobilized—i.e. stabilized—during hydrogel polymerization. Protein polymer phase separation that accompanies the solvent exchange irreversibly changes the polymer morphology, however the proteins retain their secondary structure and solvation shell waters in pure ethylene glycol

Carbon-Based Material for Environmental Protection and Remediation

Carbon-Based Material for Environmental Protection and Remediation presents an overview of carbon-based technologies and processes, and examines their usefulness and efficiency for environmental preservation and remediation. Chapters cover topics ranging from pollutants removal to new processes in materials science. Written for interested readers with strong scientific and technological backgrounds, this book will appeal to scientific advisors at private companies, academics, and graduate students