Developments in nanoparticles for use in biosensors to assess food safety and quality

The following will provide an overview on how advances in nanoparticle technology have contributed towards developing biosensors to screen for safety and quality markers associated with foods. The novel properties of nanoparticles will be described and how such characteristics have been exploited in sensor design will be provided. All the biosensor formats were initially developed for the health care sector to meet the demand for point-of-care diagnostics. As a consequence, research has been directed towards miniaturization thereby reducing the sample volume to nanolitres. However, the needs of the food sector are very different which may ultimately limit commercial application of nanoparticle based nanosensors. © 2014 Elsevier Ltd

Development of methods based on voltammetry for the characterisation of liquids

The growing interest into multi-sensor systems able to determine general attributes of a process under monitoring, has recently involved the qualitative analysis of liquids; various methodologies to develop taste sensors, often referred to as “e-tongues” have been presented in the literature. The common concept in the different approaches, lies in the combination of signals originated by poorly specific sensors for the characterization of liquids. The fundamental idea of this PhD work is to investigate how an adequate signal processing approach, applied to a mature and affordable sensor technique (voltammetry), can address the issue of extracting an aggregate chemical information, useful to characterize the liquid under measurement. In this Thesis, a general description of electronic taste sensor systems is given, followed by a description of the working principles of e-tongues based on voltammetry. Then, the methodology that represents the core of this PhD Thesis work is introduced: the sensor device, the control software and the data processing approach are described in this sequence. Finally, a few case studies are shown, selected according to their relevancy with respect to the peculiarities of the approach described in this Thesis

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing

Rapid and innovative instrumental approaches for quality and authenticity of olive oils

The quality of virgin olive oils is assessed through the determination of several analytical parameters, whose values must be within the ranges established by the different institutions involved. In addition to official methods, there is a strong need for simple, rapid, and environmentally friendly techniques for the quality control of virgin olive oils and for addressing the challenging task of determining geographical origin and detecting adulterants. Toward this purpose, some of the most interesting applications based on optical spectroscopic techniques, on the measurement of electrical characteristics and on the use of instruments equipped with electronic chemical sensors, including also other promising techniques are herein discussed. These techniques, adequately coupled with an appropriate statistical approach, appear to be promising for assessment of several quality-related parameters. The prediction of sensory attributes and of the oxidative status of virgin olive oils have also been reviewed by adopting these selected techniques, which are also considered to be potentially appropriate solutions for identification of the geographical origin of virgin olive oils and to assess their adulteration with cheaper oils. Overall, the techniques discussed are promising and cutting-edge approaches for the establishment of useful portable instruments for in situ monitoring of the quality of virgin olive oils. Practical applications: The simple, rapid, and environmentally friendly analytical approaches discussed herein represent promising analytical tools for assuring the authenticity and monitoring the quality of virgin olive oils. Such innovative techniques and tools need to be ring-tested and validated. Some innovative reviewed approaches will permit to develop useful portable instruments able to perform in situ appropriate controls also by small laboratories or olive oil mills with limited technical facilities. These equipments will be potentially usable also by trained \u201cnon-professional analytical skilled\u201d people. Some other approaches, rapid but more expensive, will be applicable mainly by quality control labs and will increase the number of samples analyzed per day, thus fostering laboratory proficiency and an effective fighting against olive oil fraud

Novel Synthesis and Structures of Tris-Annelated Benzene Donors for the Electron-Density Elucidation of the Classical Mills−Nixon Effect

A versatile method for the high-yield synthesis of various tris-, bis-, and mono-annelated benzenes (as well as cyclooctatetraene) is based on the Pd-catalyzed coupling of three (or four) ethylenic units comprised of α,β-dibromoalkenes and α‘-alkenyl Grignard reagentsall carried out in a single pot. The particular application to tris(bicyclopentyl)-annelated benzene yields the syn isomer 1s in high purity; X-ray diffraction analysis confirms the aromatic bond alternation relevant to the Mills−Nixon effect. Most importantly, the efficient synthesis of 1s crystals of extraordinary quality allows us (for the first time) to make precise electron-density measurements of the “banana-type” distortion and the ellipticity (π-character) of the various aromatic C−C bondssufficient to identify the electronic origin of the classical Mills−Nixon effect. The unique electron-donor properties of tris-annelated benzenes also relate to their highly reversible one-electron oxidation potentials even in nonpolar solvents

Recent Trends in Monitoring of European Water Framework Directive Priority Substances Using Micro-Sensors: A 2007–2009 Review

This review discusses from a critical perspective the development of new sensors for the measurement of priority pollutants targeted in the E.U. Water Framework Directive. Significant advances are reported in the paper and their advantages and limitations are also discussed. Future perspectives in this area are also pointed out in the conclusions. This review covers publications appeared since December 2006 (the publication date of the Swift report). Among priority substances, sensors for monitoring the four WFD metals represent 81% of published papers. None of analyzed publications present a micro-sensor totally validated in laboratory, ready for tests under real conditions in the field. The researches are mainly focused on the sensing part of the micro-sensors. Nevertheless, the main factor limiting micro-sensor applications in the environment is the ruggedness of the receptor towards environmental conditions. This point constitutes the first technological obstacle to be overcome for any long-term field tests

Electroanalysis of neutral precursors in protic ionic liquids and synthesis of high-ionicity ionic liquids

Protic ionic liquids (PILs) are ionic liquids that are formed by transferring protons from Brønsted acids to Brønsted bases. While they nominally consist entirely of ions, PILs can often behave as though they contain a significant amount of neutral species (either molecules or ion clusters), and there is currently a lot of interest in determining the degree of “ionicity” of PILs. In this contribution, we describe a simple electroanalytical method for detecting and quantifying residual excess acids in a series of ammonium-based PILs (diethylmethylammonium triflate, [dema][TfO], dimethylethylammonium triflate, [dmea][TfO], triethylammonium trifluoroacetate, [tea][TfAc], and dimethylbutylammonium triflate [dmba][TfO]). Ultramicroelectrode voltammetry reveals that some of the accepted methods for synthesising PILs can readily result in the formation of non-stoichiometric PILs containing up to 230 mM excess acid. In addition, vacuum purification of PILs is of limited use in cases where non-stoichiometric PILs are formed. While excess bases can be readily removed from PILs, even under ambient conditions, excess acids cannot, even under high vacuum. The effects of excess acid on the electrocatalytic oxygen reduction reaction (ORR) in PILs have been studied, and the onset potential of the ORR in [dema][TfO] increases by 0.8 V upon addition of excess acid to PIL. Based on the results of our analyses, we provide some recommendations for the synthesis of highly-ionic PILs

Electrochemical detection of fentanyl using screen-printed carbon electrodes with confirmatory analysis of fentanyl and its analogs in oral fluid using liquid chromatography-tandem mass spectrometry

Utilizing screen-printed carbon electrodes (SPCEs), a fast, simple, and sensitive approach toward the detection, identification, and quasi-quantitation of fentanyl was achieved both in an electrochemical cell and as a drop on the electrode surface. Electro-oxidation of fentanyl at the electrode was demonstrated using adsorptive stripping square-wave voltammetry between -0.5 V and +1.6 V with 100 mM Tris-HCl buffer at pH 8.5 as supporting electrolyte. Parameter optimization was conducted during method development to include supporting electrolyte and pH, electrochemical technique, pre-treatment and equilibration time, and various surface modifications. The simplest method utilizing an unmodified SPCE was determined to be appropriate for the identification of fentanyl. Electro-oxidation of the fentanyl compound was observed to occur as an irreversible process due to both diffusion to the electrode surface and oxidation of adsorbed species on the working electrode. The resulting voltammograms demonstrated the presence of two oxidation peaks at 750 mV (peak I) and 880 mV (peak II) versus a pseudo-Ag/AgCl reference. Fentanyl oxidation was observed at concentrations of ~76 ng/mL in cell and ~300 ng/mL in a 100 mL drop. Statistical limits of detection were determined to be slightly above the observable oxidation peaks with limits of detection of 145 ng/mL for the cell method and 530 ng/mL for the drop method. Reproducibility between electrodes, assessed as the average relative standard deviation (RSD), for peak I and peak II in the cell was 12% and 18%, respectively. RSD in the drop was 13% and 15% for peaks I and II. Accuracy of the detection method was determined in the cell by analyzing single-blind samples prepared in the laboratory and demonstrated better accuracy in lower concentrations of fentanyl versus higher concentrations. The effects of interfering compounds were considered due to the likelihood of fentanyl being found in mixtures. Quinine and cocaine were found to interfere with peak II, while peak I remained identifiable except when present with large concentrations of interferent. Methamphetamine was observed to have a similar effect although drastically reduced in comparison to both quinine and cocaine. Acetaminophen and caffeine did not produce interfering signals. Analysis at various ratios of the compounds demonstrated that the identification of fentanyl could still be achieved through the presence of peak I. The oxidative mechanism of fentanyl was proposed based on the literature available for the oxidation of amines and voltammetric data present for fentanyl and related compounds. The proposed mechanism rejects some previously hypothesized oxidation mechanisms of tertiary amines where the presence of two peaks was observed. It was suggested that a two-step oxidation process of the tertiary amine followed by the oxidation of the newly formed secondary amine product resulted in the two observable peaks. However, this work agrees with literature supporting the effect of adsorption of the tertiary diamine to the electrode surface. This mechanism is presented herein, whereby the observed oxidation peaks result from the adsorbed species and the diffusion of the species to the electrode surface, owing to the difference in peak potentials for peak I and peak II. A confirmatory LC/MS/MS method for the analysis of fentanyl and fentanyl analogs in oral fluid was developed and validated. Optimization of fragmentor voltage, collision energy, and fragmentation ions was achieved and used in the construction of a dynamic multiple reaction monitoring (dMRM) method. Chromatographic separation demonstrated resolution between 13 fentanyl-related compounds along with 7 internal standards. The calibration model used was linear with a weighting of 1/x between the range of 0.1 ng/mL to 50 ng/mL. The limit of detection for the majority of drugs was determined to be 0.01 ng/mL with the limit of quantitation at the lowest calibrator of 0.1 ng/mL with correlation coefficients between 0.9992-0.9999. Bias, precision, matrix effects, recovery, and process efficiency were assessed and were within the guideline range for acceptability for the majority of analytes assessed using a solid-phase extraction procedure with spiked oral fluid. Twelve commonly encountered illicit drugs were used to assess selectivity. No interferences were found for fentanyl or its analogs. Stability was assessed for processed samples kept at room temperature in auto-sampler and the freezer, as well as, for freeze/thaw stability. The majority of analytes were considered stable under all conditions for up to 72 hours. Together these two methods demonstrate the identification and quasi-quantitation of fentanyl through electrochemical oxidation and confirmatory analysis via liquid chromatography-tandem mass spectrometry (LC/MS/MS). The combined use of these techniques seeks to emulate the SWGDRUG requirement, although electrochemistry has, to this point, not been included in the list of acceptable techniques. Other work contained herein demonstrates assessment of various electrode modification techniques to improve the signal of fentanyl, attempts at enzymatic detection of codeine and fentanyl utilizing cytochrome P450 isozymes 2D6 and 3A4, and electrochemical detection of the synthetic cannabinoid PB-22