Analytical Sciences最新文献

We have developed an N-terminated carbon film electrode that allows accurate determination of the diffusion coefficient of electroactive molecules dissolved in a highly concentrated serum protein solution. The carbon film electrode was formed by the unbalanced magnetron sputtering (UBM) method. Then, nitrogen functional groups were introduced by employing NH₃ or H₂O plasma treatment. Cyclic voltammetry measurements with ferricyanide ion ([Fe(CN)₆]^3-) showed that the N-terminated carbon film electrode exhibited great anti-fouling property against simulated serum proteins (50 mg/mL human serum albumin and 15 mg/mL γ-globulin dissolved in 1 M KCl solution). In contrast, glassy carbon, H₂O plasma-treated, and especially untreated carbon film electrodes were subject to severe electrode fouling, making it difficult to electrochemically determine the diffusion coefficient of the [Fe(CN)₆]^3- ion. The control experiment using less adsorptive ethylene glycol as a viscosity modifier showed that the increase in viscosity is a main factor of the decrease in diffusion coefficient for nitrogen plasma treated electrode, which is not significantly affected by the possible interaction between [Fe(CN)₆]^3- ions and serum proteins. Finally, we applied the electrode for the electrochemical analysis of acetaminophen dissolved in phosphate buffer (0.1 M, pH = 7.0), which suggests that NH₃ plasma-treated carbon film exhibits the lowest ΔE increase when we compare ΔE with and without proteins and also a more stable peak current in continuous voltametric measurements compared with other carbon electrodes.

Electrochemiluminescence (ECL) is a chemiluminescence phenomenon triggered by electrochemical reactions and is widely used for (bio)chemical analyses and electrochemical bioimaging. Compared to fluorescence sensing, ECL sensing reduces background noise by eliminating autofluorescence associated with excitation light. In addition, compared with conventional electrochemical imaging with scanning electrochemical microscopes, ECL imaging is faster as it requires no scanning. Furthermore, unlike electrode arrays, ECL devices can function without complex wiring, simplifying their construction. These characteristics render ECL sensing a useful analytical tool. Recently, ECL sensing has been widely used for in vitro cell analysis due to high demand for biochips in regenerative medicine, drug screening, and microphysiological systems. This review focuses on recent advancements in ECL-based cell analysis with applications for the detection of H₂O₂, respiration activity, cell adhesion, lipid membranes, and bipolar electrochemistry-based devices.

The electrochemical behavior of catecholamines involves an electron transfer-chemical reaction-electron transfer (ECE) mechanism, characterized by two reversible redox reactions interspersed with an irreversible chemical reaction. Previously, we reported ECE studies on dopamine and norepinephrine. In this work, we extend our study to catecholamine drugs including dobutamine, isoprenaline, droxidopa, and methyldopa, using a carbon nanotube electrode. These drugs exhibit significantly faster intramolecular cyclization rates compared to dopamine and norepinephrine. This accelerated cyclization is attributed to (1) the presence of more complex substituents in these drugs and (2) the fact that dobutamine and isoprenaline are secondary amines, while dopamine and norepinephrine are primary amines. This study enhances the understanding of catecholamines and offers valuable insights for the development of novel electrochemical sensing strategies for catecholamine drugs.

Selective bacterial recognition and early diagnosis are urgently required to address the growing problem of antimicrobial resistance and are crucial for achieving sustainable development goals (SDGs). Saccharide recognition is a promising solution because bacterial surfaces are composed of specific polysaccharides. In this study, we summarize our investigations into the use of boronic acid analogs for bacterial recognition, which shows potential for broad applications in various bacterial detection methods using nanoprobes. Methods were developed for the convenient, sensitive, and selective recognition of bacteria using spherical poly(amidoamine) dendrimers functionalized with boronic acids. We evaluated various measurement protocols (turbidity and fluorescence), interactions with bacterial surfaces (electrostatic and hydrophobic), recognition targets, and the further development of ditopic and benzoxaborole-based probes. As these methods require less than ten min, boronic acid-based recognition could serve as a powerful tool for rapid and simple clinical applications in the future. We believe that our study makes a significant contribution to the field, as the findings can be effectively applied to other studies involving boronic acid compounds or targeting bacterial surface saccharides.

Due to its toxicity, contamination with arsenic, a Group 1 carcinogen, is a significant environmental and public health issue. The toxicity of arsenic varies with its chemical form. For example, inorganic species like arsenite (AsO₃^3-) and arsenate (AsO₄^3-) are generally more toxic than organoarsenic compounds. However, some organoarsenic species exhibit higher toxicity than inorganic species. Therefore, the precise quantification and speciation of arsenic is necessary. Chromatographic techniques, particularly liquid chromatography coupled with inductively coupled plasma mass spectrometry (LC-ICP-MS), are widely used for arsenic speciation owing to their high sensitivity and accuracy. Gas chromatography-mass spectrometry (GC-MS) is another effective technique for detecting arsenic species after derivatization. In addition to chromatographic methods, more straightforward and cost-effective techniques are available for inorganic arsenic speciation. These include adsorption techniques, colorimetric assays such as the molybdenum blue method, hydride generation reactions, and voltammetry. Emerging technologies, such as microfluidic and electrochemical devices, enable rapid and portable analysis, facilitating in situ detection of arsenite and arsenate in environmental samples. While LC-ICP-MS remains the gold standard for comprehensive arsenic speciation, other advanced technologies provide a practical, rapid, and cost-effective approach.

Magnesium phosphate grains, minor accessory minerals found on the primitive meteorite Yamato 980115 (Y 980115), were investigated by Raman microspectroscopy. All magnesium phosphate grains found in the present study can be assigned to farringtonite, dehydrated magnesium phosphate Mg₃(PO₄)₂-I. Since the Mg₃(PO₄)₂-I is generally formed via the irreversible thermal transition from the polymorphs of Mg₃(PO₄)₂-II and -III at above 750-800 degree Celsius, we can infer that the parent body of the Y 980115 meteorites experienced thermal alteration with such a high temperature. This result is in good accordance with the previous studies and the proposals on the alteration history of Y 980115 by the electron-beam microscope and X-ray diffraction analyses. Furthermore, the hydrated form of the magnesium phosphates of Mg₃(PO₄)₂·4H₂O, Mg₃(PO₄)₂·8H₂O, and Mg₃(PO₄)₂·22H₂O was not found in the present research, also suggesting that the extensive vaporization of the hydrated water molecules with magnesium phosphate occurred by such high-temperature thermal alteration. Since Y 980115 has been historically categorized to heavily aqueously altered CI (Ivuna-type) carbonaceous chondrites but has distinct characteristic to CI meteorites, the present result would provide further evidence to the complexed alteration history of the parent body of Y 980115 meteorite.

The physiological and pathological processes in lungs indicated that ONOO^- acted as an informative indicator for pulmonary functioning status with the corresponding dynamics, especially in permissive hypercapnia. Herein, for the peroxynitrite (ONOO^-) detection and imaging in living lung cells, an imidazo-pyridin derived fluorescent probe IDPD-ONOO was developed. IDPD-ONOO recognized ONOO^- to exhibit a corresponding fluorescence response at 490 nm with the excitation wavelength at 355 nm. The advantages of the developed probe included practical linear range (0-100 μM), high sensitivity (Limit of Detection 0.005 μM), rapid response (within 15 min), pH tolerance (7.0-9.0), high selectivity, and low cyto-toxicity. Furthermore, IDPD-ONOO achieved the pulmonary intracellular imaging of both the exogenous and endogenous ONOO^- level, which was meaningful for the research on the pulmonary physiological and pathological mechanism with optimized optical implements.

A simple method for determining elemental sulfur in environmental water was developed and applied to seawater samples collected immediately after the occurrence of blue tides in Tokyo Bay. To investigate the concentration and extraction methods, artificial elemental sulfur was quantitatively produced by oxidizing a sulfide solution with an iodine solution, then used as a standard reagent in the experiments. To concentrate the elemental sulfur in the water sample, glass filter paper (GF/F) was used to filter and collect the elemental sulfur. The elemental sulfur was then extracted using n-hexane, the main component of petroleum ether; however, the recovery of elemental sulfur from the wet glass filter paper was low, and remained so even when the glass filter paper was dried. We, therefore, used a mixture of n-hexane and an acetone solvent, which is a hydrophilic organic solvent, for extraction and succeeded in recovering more than 90% of the elemental sulfur from the wet glass filter paper. Using this solvent mixture, we extracted and quantified elemental sulfur from seawater samples collected after the occurrence of blue tide, and detected 0.36-0.38 mgS L^-1 of elemental sulfur in the near-surface layer. We also found that the elemental sulfur concentrations were higher in the surface layer than in the bottom layer. Therefore, we demonstrated that the quantification of elemental sulfur is important to better understand the blue tide phenomenon.

Cartilage is a connective tissue composed of mainly water, collagen (COL) and proteoglycans (PGs) including chondroitin sulfate (CS). Near-infrared (NIR) spectroscopy is adequate for examination of soft and hard tissues with large amount of water non-destructively and non-invasively. We measured tablets containing CS and COL using NIR spectroscopy to develop an evaluation method for PGs in cartilage non-destructively and non-invasively. Calibration curves were constructed using the NIR spectra of the tablets that show the quantitative linear relationship between the concentration and height of the second derivative at 4260 cm^-1 for COL and at 5800 cm^-1 for COL and CS. An equation to calculate the CS-to-COL ratio was derived from the calibrated slopes at 5800 and 4260 cm^-1, and the utility of the equation was demonstrated by the evaluation of tablets. Moreover, we conducted an evaluation of the CS-to-COL ratio in the aqueous nucleus pulposus and annulus fibrosus, and the results were consistent with the glycosaminoglycans (GAGs)-to-COL ratios obtained through Raman spectroscopy of the same specimens. Thus, this method is adequate for evaluating PGs with large amount of water non-destructively, non-invasively and with less damage.