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The first page of this article is displayed as the abstract.

Electrochemical impedance spectroscopy (EIS) has been used to investigate the effects of a number of metal ions with DNA films on gold surfaces exploiting [Fe(CN)6]3−/4− as a solution-based redox probe. Alkaline earth metal ions Mg2+, Ca2+, trivalent Al3+, La3+ and divalent transition metal ions Ni2+, Cu2+, Cd2+ and Hg2+ have been selected in this study and the results are compared with previous studies on the effects of Zn2+ on the EIS of DNA films. All experimental results were evaluated with the help of equivalent circuits which allowed the extraction of resistive and capacitive components. For all metal ions studied here, addition of the metal ions causes a decrease in the charge transfer resistance. The difference of charge transfer resistance (ΔRct) of ds-DNA films in the presence and absence of the various metal ions is different and particular to any given metal ion. In addition, we studied the EIS of ds-DNA films containing a single A–C mismatch in the presence and absence of Ca2+, Zn2+, Cd2+ and Hg2+. ΔRct values for ds-DNA films with a single A–C mismatch is smaller than those of fully matched ds-DNA films.

An operationally simple colorimetric way for measuring hyaluronidase activity was developed using cysteamine-bound gold nanoparticles. The addition of gold nanoparticles into hyaluronidase-containing solutions resulted in color changes, which could easily be observed with the naked eye or a UV/Vis spectrophotometer.

Micro- and nano-electromechanical systems (MEMS and NEMS) for use as sensors represent one of the most exciting new fields in analytical chemistry today. These systems are advantageous over currently available non-miniaturized sensors, such as quartz crystal microbalances, thickness shear mode resonators, and flexural plate wave oscillators, because of their high sensitivity, low cost and easy integration into automated systems. In this article, we present and discuss the evolution in the use of MEMS and NEMS, which are basically cantilever-type sensors, as good analytical tools for a wide variety of applications. We discuss the analytical features and the practical potential of micro(nano)-cantilever sensors, which combine the synergetic advantages of selectivity, provided by their functionalization, and the high sensitivity, which is attributed largely to the extremely small size of the sensing element. An insight is given into the different types of functionalization and detection strategies and a critical discussion is presented on the existing state of the art concerning the applications reported for mechanical microsensors. New developments and the possibilities for routine work in the near future are also covered.

In this paper, we describe a simple and sensitive method for the selective detection of histidine by combining Tween 20-capped gold nanoparticles (Tween 20-AuNPs) as aminothiol removers and o-phthaldialdehyde (OPA) as the derivatization reagent. We have shown that Tween 20-AuNPs are capable of removing homocysteine (HCys), glutathione (GSH), and γ-glutamylcysteine (Glu-Cys) at low pH conditions, but they are ineffective in the case of removal of histidine. In contrast, at high pH, Tween 20-AuNPs have strong hydrophobic interactions with the unprotonated imidazole group of histidine. It is observed that 48.0 nM Tween 20-AuNPs can remove 95.7% of HCys, 99.7% of GSH, and 99.5% of Glu-Cys from 40 mM phosphate solution at pH 2.0 in the presence of 0.1 mM cetyltrimethylammonium bromide, whereas only 2.1% of histidine was removed under identical conditions. In addition, OPA is a highly selective fluorogenic reagent for GSH, HCys, Glu-Cys, and histidine. Thus, after the centrifugation of a solution containing Tween 20-AuNPs, histidine, HCys GSH, Glu-Cys, and other amino acids, the selectivity of this method is remarkably high for histidine through OPA derivatization. Under optimum derivatization conditions, the lowest detectable concentration of histidine detected with this method was 5.2 nM. This method has been successfully applied to detect the presence of histidine in urine and serum samples.

Vibrational spectroscopy techniques have demonstrated potential to provide non-destructive, rapid, clinically relevant diagnostic information. Early detection is the most important factor in the prevention of cancer. Raman and infrared spectroscopy enable the biochemical signatures from biological tissues to be extracted and analysed. In conjunction with advanced chemometrics such measurements can contribute to the diagnostic assessment of biological material. This paper also illustrates the complementary advantage of using Raman and FTIR spectroscopy technologies together. Clinical requirements are increasingly met by technological developments which show promise to become a clinical reality. This review summarises recent advances in vibrational spectroscopy and their impact on the diagnosis of cancer.

High performance thin layer chromatography (HPTLC) combined with on-spot detection and characterization via easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is applied to the analysis of biodiesel (B100) and biodiesel–petrodiesel blends (BX). HPTLC provides chromatographic resolution of major components whereas EASI-MS allows on-spot characterization performed directly on the HPTLC surface at ambient conditions. Constituents (M) are detected by EASI-MS in a one component–one ion fashion as either [M + Na]+ or [M + H]+. For both B100 and BX samples, typical profiles of fatty acid methyl esters (FAME) detected as [FAME + Na]+ ions allow biodiesel typification. The spectrum of the petrodiesel spot displays a homologous series of protonated alkyl pyridines which are characteristic for petrofuels (natural markers). The spectrum for residual or admixture oil spots is characterized by sodiated triglycerides [TAG + Na]+. The application of HPTLC to analyze B100 and BX samples and its combination with EASI-MS for on-spot characterization and quality control is demonstrated.

A fast, selective and sensitive method is here proposed for the analysis of female steroid hormones as conjugated forms (mainly, glucuronides and sulfates). The method has been applied to female urine samples to assess the metabolism of these compounds. The method implements an enzymatic hydrolysis (β-glucuronidase with sulfatase activity) kinetically enhanced by ultrasonic energy in order to generate the free steroid forms. This enables a drastic shortening of the time required for this step as compared with conventional protocols (from 12–18 hours to 30 min). The reaction kinetics of the ultrasound-enhanced hydrolysis was characterized by comparison to that of the conventional protocol. After hydrolysis, the free steroid hormones were isolated and preconcentrated by automated solid-phase extraction and the eluate was subsequently analysed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The target analytes were confirmed and quantified by multiple reaction monitoring (MRM). The detection and quantification limits were within 0.06–0.8 ng mL−1 and 0.19–2.69 ng mL−1, respectively. The precision of the method, expressed as intra-day and inter-day variability, ranged between 2.1 and 5.2% and between 4.9 and 8.0%, respectively. A complementary study was carried out to assess the storage conditions of urine samples. This study is crucial in those applications involving metabolic processes as the integrity of the sample has to be preserved.

The first page of this article is displayed as the abstract.

A water-soluble complex of a cationic oligopyrene derivative, oligo(N1,N1,N1,N4,N4,N4-hexamethyl-2-(4-(pyren-1-yl) butanoyloxy) butane-1,4-diaminium bromide), and oligothymine has been prepared. The fluorescence sensor based on this complex showed high sensitivity and selectivity toward mercury(II) ions in aqueous media. The transduction mechanism of this sensor is based on the fluorescence self-quenching of oligopyrene in watervia the interchain π-stacking arising from the specific thymine–Hg–thymine complexation. The detection limit of this sensor was measured to be as low as 5 × 10−9 mol L−1. In addition, the fluorescent color change of the complex solution allows naked-eye detection of mercury(II) ions with an extremely low detection limit of 5 × 10−6 mol L−1.