Cationic interaction with phosphatidylcholine in a lipid cubic phase studied with electrochemical impedance spectroscopy and small angle X-ray scattering.

Hypothesis: Electrochemical Impedance Spectroscopy (EIS) can be used to investigate cationic interaction with the choline headgroup in the ternary system of monoolein/dioleoylphosphatidylcholine/water (MO/DOPC/HO).

Experiments: EIS was used to estimate the resistance and capacitance of a freestanding membrane of a lipid cubic phase (LCP). The membrane was formed in a small cylindrical aperture separating two compartments, containing one Pt electrode each.

Interaction of anions with lipid cubic phase membranes, an electrochemical impedance study.

Hypothesis: Electrochemical impedance spectroscopy is useful to monitor anionic interactions with a Lipid Cubic Phase, as previously demonstrated for cationic interaction (Khani Meynaq et al., 2016). It was expected that the smaller hydrophilic anions, acetate and chloride, would interact differently than the large tryptophan anion with its hydrophobic tail.

Determination of methotrexate in spiked human blood serum using multi-frequency electrochemical immittance spectroscopy and multivariate data analysis.

This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55.

Aspects on mediated glucose oxidation at a supported cubic phase.

A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase.

Investigation of metal ion interaction with a lipid cubic phase using electrochemical impedance spectroscopy.

Hypothesis: Electrochemical impedance spectroscopy, EIS, can be used as a complementary technique to investigate ion interaction with the headgroup region in the aqueous channels of a lipid cubic phase, LCP.

Experiments: A freestanding membrane made of monoolein LCP was formed by filling a small aperture that separates two cell compartments. The cell compartments were filled with electrolyte solutions at two different ionic strengths: i.

Detection of methotrexate in a flow system using electrochemical impedance spectroscopy and multivariate data analysis.

Methotrexate (MTX), a common pharmaceutical drug in cancer therapy and treatment of rheumatic diseases, is known to cause severe adverse side effects at high dose. As the side effect may be life threatening, there is an urgent need for a continuous, bed-side monitoring of the nominal MTX serum level in a patient while the chemical is being administered. This article describes a detection of MTX using a flow system that consists two modified gold electrodes.

Non-invasive identification of melanoma with near-infrared and skin impedance spectroscopy.

Background/purpose: An early diagnosis of cutaneous malignant melanoma is of high importance for good prognosis. An objective, non-invasive instrument could improve the diagnostic accuracy of melanoma and decrease unnecessary biopsies. The aim of this study was to investigate the use of Near-infrared and skin impedance spectroscopy in combination as a tool to distinguish between malignant and benign skin tumours.

NIR and skin impedance spectroscopic measurements for studying the effect of coffee and alcohol on skin, and dysplastic naevi.

Background/purpose: Near infrared and impedance spectroscopy can be used for clinical skin measurements and need to be evaluated for possible confounding factors; (i) are skin conditions of the patient and the subsequent skin measurements influenced by alcohol and/or coffee consumption and (ii) are measurements of dysplastic naevi (DN) reproducible over time and significantly different compared to reference skin.

Methods: Near infrared and skin impedance spectroscopic data were analysed multivariately. In the first study, the skin characteristics of 15 healthy individuals were examined related to body location, gender, individual differences, and consumption of coffee or alcohol.

In vivo skin measurements with a novel probe head for simultaneous skin impedance and near-infrared spectroscopy.

Background/purpose: Near-infrared (NIR) spectroscopy and skin impedance (IMP) measurements are useful techniques for objective diagnostics of various skin diseases. Here, we present a combined probe head for simultaneous, time-saving NIR spectroscopy and skin impedance measurements. The probe also ensures that both measurements are performed under equal conditions and at the same skin location.

Electrochemical impedance spectroscopy in label-free biosensor applications: multivariate data analysis for an objective interpretation.

Electrochemical impedance spectroscopy plays an important role in biosensor science thanks to the possibility of finding specific information from processes with different kinetics at a chosen electrode potential in one experiment. In this paper we briefly discuss label-free impedimetric biosensors described in the literature. A novel method for neutral interpretation of impedance data is presented that includes complex number chemometrics.

Corrosion of dental nickel-aluminum bronze with a minor gold content-mechanism and biological impact.

Objectives: To study corrosion and to evaluate biological effects in vitro of corrosion products of a copper-aluminum-nickel alloy with 2% gold.

Methods: The alloy NPGtrade mark+2 with the nominal composition Cu:77.3; Al:7.

Cubic phases in biosensing systems.

Incorporation of membrane proteins with retained activity in artificial membranes for use in membrane-based sensors has attracted scientists for decades. This review briefly summarises general concepts on relevant cubic phases with and without incorporated proteins and provides some insight into the development of biosensors where bicontinuous cubic phases are used for incorporation of an enzyme. Some new data on impedance characterisation of a supported cubic phase are also shown.

Characterization of healthy skin using near infrared spectroscopy and skin impedance.

Near infrared spectroscopy (NIR) and skin impedance (IMP) spectroscopy are two methods suggested for diagnoses of diseases inducing adverse effects in skin. The reproducibility of these methods and their potential value in non-invasive diagnostics were investigated. Measurements were performed in vivo on healthy skin at five anatomic body sites on eight young women.

An electrochemical study into the interaction between complement-derived peptides and DOPC mono- and bilayers.

Electrochemical methods employing the hanging mercury drop electrode were used to study the interaction between variants of the complement-derived antimicrobial peptide CNY21 (CNYITELRRQH ARASHLGLAR) and dioleoyl phosphatidylcholine (DOPC) monolayers. Capacitance potential and impedance measurements showed that the CNY21 analogues investigated interact with DOPC monolayers coating the mercury drop. Increasing the peptide hydrophobicity by substituting the two histidine residues with leucine resulted in a deeper peptide penetration into the hydrophobic region of the DOPC monolayer, indicated by an increase in the dielectric constant of the lipid monolayer (Deltaepsilon = 2.

Comparison of three instrumental methods for the objective evaluation of radiotherapy induced erythema in breast cancer patients and a study of the effect of skin lotions.

A non-blinded three armed study of the effect of Aloe vera, Essex and no lotion on erythema was performed. The erythema is an effect of radiotherapy treatment in breast cancer patients. The study required testing of objective methods for measuring the erythema.

Complex numbers in chemometrics: examples from multivariate impedance measurements on lipid monolayers.

Electrical impedance gives multivariate complex number data as results. Two examples of multivariate electrical impedance data measured on lipid monolayers in different solutions give rise to matrices (16x50 and 38x50) of complex numbers. Multivariate data analysis by principal component analysis (PCA) or singular value decomposition (SVD) can be used for complex data and the necessary equations are given.

Multivariate data analysis for enhanced interpretation of electrochemical impedance spectra of gramicidin-ion interactions in phospholipid monolayers.

This article describes a multifrequency electrochemical impedance study of phospholipid monolayers on a mercury drop electrode in solutions containing electrolytes and gramicidin derivatives: gramicidin A (gA), gramicidin-BOC (g-BOC), and desformylgramicidin (g-des). The impedance spectra have been studied individually (univariate approach) and also transformed using a multivariate data reduction method (multivariate approach). It was shown that the two approaches are complementary.

Objective measurements of radiotherapy-induced erythema.

Background/aims: The development of acute radiation erythema is a common phenomenon among patients under-going radiotherapy treatment. Because of the absence of reliable objective classification methods, the degree of skin reaction can at present mainly be judged subjectively in the clinic. This has motivated the present preliminary study,concerning the first steps in the development of an objective method for skin reaction classification.

Are biosensor arrays in one membrane possible? A combination of multifrequency impedance measurements and chemometrics.

A novel concept of a membrane-based micro-array biosensor is presented. The methodology is based on a single lipid membrane interrogated with electrochemical impedance techniques followed by multivariate data analysis. A single membrane is designed so that relaxation processes with a range of time constants can be probed at different potentials.

Gramicidin A interaction at a dioleoyl phosphatidylcholine monolayer on a mercury drop electrode.

A biosensor where the sensing surface is a fluid dioleyl phosphatidylcholine monolayer (DOPC) deposited on a mercury drop was used. The lipid monolayer was held in 0.1 M NaCl and a concentration of gramicidin A in the range 0-12 nM was used.