ABSTRACT
A novel dissolution method that allows for the total solvation of high-concentration, high-molecular-weight polyaniline (PANi) doped with (+)-camphor-10-sulfonic acid (CSA) is reported. Preparation of 12-16 wt % 65,000 Da PANi solutions in N,N-dimethylformamide is achievable using a simple one-pot method. Doped polyaniline solutions in common organic solvents were processed into nanofibers using a convenient single-nozzle electrospinning technique. The electrospinning of PANi-CSA into nanofibrous membranes generated substrates that were subsequently employed in colorimetric gas sensing. These substrates demonstrated linearity of response upon exposure to 50-5500 ppm ammonia at ambient (50 ± 10% RH) and high (80% RH) humidity.
ABSTRACT
Cavity-enhanced spectroscopy is a sensitive optical absorption technique but one where the practical applications have been limited to studying small wavelength ranges. This Letter shows that wideband operation can be achieved by combining techniques usually reserved for the communications community with that of cavity-enhanced spectroscopy, producing a multiplexed real-time cavity-enhanced spectrometer. We use multiple collinear laser sources operating asynchronously and simultaneously while being detected on a single photodetector. This is synonymous with radio frequency (RF) cellular systems in which signals are detected on a single antenna but decoded uniquely. Here, we demonstrate results with spectra of methyl salicylate and show parts-per-billion per root hertz sensitivity measured in real-time.
ABSTRACT
Manganese(III) N,N'-ethylenebis(salicylideneiminato) chloride (Mn-salen chloride) and manganese(III) N,N'-ethylenebis(3-methoxysalicylideneiminato) chloride (Mn-(3,3'-MeO)salen chloride) are in vitro superoxide dismutase and catalase mimetics. They protect against free radical-related disease in animals, but Mn-salen can also be a potent prooxidant, damaging free DNA. Mn-salen protects human fibroblast DNA against hydrogen peroxide damage, however, damage to free DNA was confirmed by the comet assay. The DNA-damaging activity was dramatically reduced by co-administration with glutathione with the combination being less damaging to free DNA than either molecule alone. alpha-Lipoic acid, an antioxidant disulfide commonly used as a dietary supplement, also prevented Mn-salen prooxidant activity. Mn-(3,3'-MeO)salen protected fibroblasts against hydrogen peroxide as efficiently as Mn-salen and showed little damaging activity against free DNA. Protection was invested by both complexes in the presence and in the absence of EDTA, a potential competing chelator. Stabilities of the complexes with respect to decomposition and inactivation were studied by spectroscopic and electrochemical techniques. The complexes' binding to, and cleavage of, DNA was measured using a quartz crystal resonant sensor. Mn-salen was shown to bind strongly to DNA, prior to cleaving it; Mn-(3,3'-MeO)salen bound weakly and left DNA intact. Co-administration of either glutathione or alpha-lipoic acid appears to inhibit binding by Mn-salen thus preventing DNA-cleavage.
Subject(s)
Catalase/metabolism , Ethylenediamines/pharmacology , Glutathione/pharmacology , Organometallic Compounds/pharmacology , Superoxide Dismutase/metabolism , Thioctic Acid/pharmacology , Animals , Antioxidants/chemistry , Antioxidants/pharmacology , Cells, Cultured , Comet Assay , DNA Damage , Electrochemistry , Ethylenediamines/chemistry , Humans , Manganese Compounds/chemistry , Manganese Compounds/pharmacology , Molecular Mimicry , Molecular Structure , Organometallic Compounds/chemistry , Oxidants/metabolismABSTRACT
This study presents a novel auto-gain-control based quartz acoustic sensor technology capable of constant quartz crystal operation when cycled between ambient (22 degrees C) and cryogenic temperatures (-196 degrees C), afforded by direct exposure of crystals to bulk liquid nitrogen. The real-time frequency response profiles due to freeze-thaw cycling on crystals of differing surface finish and two model macromolecular surface coatings were studied in order to determine surface events such as water uptake. The quartz crystal surface finishes used were optically polished or lapped to one of two surface finishes. These were used as control native gold electrodes, and these surfaces were further coated with bovine serum albumin or the tri-block copolymer, poloxamer-188 as model macromolecular surface architectures. Crystals were snap frozen in liquid nitrogen and allowed to return to ambient temperature under controlled conditions. The processes of ice formation, thawing and evaporation were followed in real-time and comparisons were made between the test samples in order to assess the capability of this technique for sensing changes in surface characteristics such as the entrapment of water.
Subject(s)
Biosensing Techniques/instrumentation , Coated Materials, Biocompatible/chemical synthesis , Electrochemistry/instrumentation , Freezing , Online Systems , Quartz/chemistry , Quartz/radiation effects , Transducers , Water/analysis , Biosensing Techniques/methods , Electrochemistry/methods , Equipment Design , Equipment Failure Analysis , Gold , Macromolecular Substances , Reproducibility of Results , Sensitivity and Specificity , Surface PropertiesABSTRACT
Acoustic sensor technologies have a long and prestigious history. However, liquid phase applications based upon thickness shear mode transducers are a relatively recent addition but are nonetheless being rapidly accepted as a broad usage analytical platform upon which to carry out label-free, real-time chemical, biological and pharmaceutical assays. This article discusses the development of thickness shear mode devices, current technologies, with a focus on the breadth of application and the future potential of the technique within the pharmaceutical and biochemical industries.