Reagentless enzyme electrode for malate based on modified polymeric membranes

Abstract A series of polymeric membranes have been employed as outer barriers in an amperometric malate dehydrogenase (MDH)/diaphorase (DI) or MDH/DI/NAD + /mediator enzyme electrode for the determination of malate in undiluted neutral or acidic media. MDH/DI were physically entrapped with NAD + and mediator in a mixed ester cellulose membrane. Outer membranes such as non-anionic surfactant-modified cellulose acetate/Tween-80 and unplasticised spin coated PVC/polycarbonate (PC) resin in conjunction with an ascorbate oxidase (AOD) layer were utilised. Mechanical strength, thickness studies and diffusional properties of the membranes were investigated. Hexacyanoferrate(III), 2,4-dichlorophenolindophenol (DCPI) and naphthoquinone (NQ) were tested as mediators for enzymatically produced NADH using cyclic voltammetry. Analytical utility of the sensors is demonstrated

Enantioselective Artificial Receptors Formed by the Spreader-Bar Technique

Chiroselective binding sites have been created on thin gold films by application of the spreader-bar approach. Impedometric techniques and surface plasmon resonance were applied to detect binding. (R)-(+)-1,1′-Binaphthyl-2,2′-diol (R-BNOH) and (S)-(−)-1,1′-binaphthyl-2,2′-diol (S-BNOH) were used as model analytes. The artificial receptors were prepared by co-adsorption of 16-mercaptohexadecane (matrix) with a thiol-modified chiral selector (template). The conjugates of D,L-thioctic acid and (R)-(+)- or (S)-(−)-1,1′-binaphthyl-2,2′-diamine were used as templates. Different concentration ratios of the matrix and template were tested. No chiral selectivity of surfaces formed by either the matrix or the template alone was observed. The use of alkylthiols shorter than 16-mercaptohexadecane led to the formation of surfaces with no chiral selectivity. The gold electrodes coated by the spreader-bar technique displayed an enantioselectivity of up to 4.76 or up to 2.55 as measured by the capacitive and SPR methods, respectively

Palladium nanoparticle-decorated iron nanotubes hosted in a polycarbonate porous membrane: development, characterization, and performance as electrocatalysts of ascorbic acid

One-dimensional iron metallic nanotubes were prepared by electroless deposition within the pores of polycarbonate (PC) membranes. The longitudinal nucleation of the nanotubes along the pore walls was achieved by mounting the PC membrane between two halves of a U-shaped reaction tube. Palladium nanoparticles were post-deposited on the inner wall of the nanotubes. The composition, morphology, and structure of the Pd/Fe nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. A glassy carbon (GC) electrode modified with the free Pd/Fe bimetallic nanotubes (isolated after the dissolution of the host membranes) showed small improvement on the overpotential oxidation of ascorbic acid in comparison to the bare GC electrode. Alternatively, the Pd/Fe-polycarbonate membrane was covered with a sputtered gold thin layer of 10 nm from one side and mounted in a homemade electrochemical cell acting as the working electrode. The potential use of these functional membranes as catalytic surfaces for the electrochemical monitoring of ascorbic acid was investigated by cyclic voltammetry and amperometry. In the presence of a phosphate buffer solution, pH 7, Pd/Fe-polycarbonate membranes showed excellent electrocatalytic properties toward the oxidation of ascorbic acid even at potentials as low as 0 mV versus a Ag/AgCl reference electrode. In addition to the substantial lower overpotential, these electrodes offered selectivity over acetaminophen and uric acid, and a prolonged working stability without the need for maintenance. The electrodes were kept dry between different working days and retained their original activity for more than 1 week. Pd-polycarbonate and Fe-polycarbonate membranes were also developed for comparison purposes

Preorganized composite material of polyaniline–palladium nanoparticles with high electrocatalytic activity to methanol and ethanol oxidation

We report a simple method for the preparation of a stabilized palladium nanoparticle-polyaniline composite by mixing aniline and PdCl42− in aqueous acidic solutions. Pd nanoparticles (Pd NP) were produced by subsequent reduction of the pre-organized material with different concentrations of NaBH4. Under optimum conditions (0.1 M NaBH4 in ethanol for 1 h at 0 °C), Pd NP with a size of 5–10 nm were obtained, as revealed by transmission electron microscopy. The so-formed pre-organized material was also characterized with scanning electron microscopy, X-ray diffraction, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry, nuclear magnetic resonance spectroscopy, and cyclic voltammetry. The developed catalyst exhibited a large electrochemically active surface area (25.2 m2 g−1 catalyst) and remarkable mass activities for the electro-oxidation of methanol (602 A g−1 Pd) and ethanol (433 A g−1 Pd) in alkaline media. The excellent electrocatalytic performance of the developed polyaniline-Pd NP composite material renders it as a promising anode catalyst in alkaline fuel cells. [Display omitted] •Simple electroless approach for the synthesis of Pd NP incorporated in polyaniline.•The preorganization of the material allows for spatial distribution of Pd NP.•The nanocomposite demonstrated high electrocatalytic activity for alcohol oxidation

Traumatic ulcerative granuloma with stromal eosinophilia: Report of a case and literature review

Traumatic eosinophilic granuloma with stromal eosinophilia is a rare entity that affects the oral mucosa and has a controversial etiologic pathogenesis. Histologically, these lesions are characterized by a dense and deeply infiltrative lymphoproliferation showing epitheliotropic characteristics and massive eosinophilia. Frequently, a population of mitotically active, atypical mononuclear cells can be noted. This report describes a case of traumatic eosinophilic granuloma with stromal eosinophilia in the floor of the mouth of an 88-year-old man. The phenotypic and genotypic profiles of the inflammatory infiltrate and large atypical mononuclear cells, using immunohistochemical and polymerase chain reaction-based molecular analysis, were analyzed. © 2012 American Association of Oral and Maxillofacial Surgeons