Microchimica Acta

Near-infrared photoluminescence is intrinsic only to a minority of carbonaceous nanomaterials. Longwave fluorescence is, however, well suited for bio-sensing and bio-imaging owing to the low autofluorescence and low absorbance by biomatter. The authors describe here sulfur doped carbon quantum dots (S-CQDs) and their derivatives (referred to as 3D carbon nanoflowers; S-CNFs). Their average diameters are 2 and 28.5 nm, respectively. They display two emission peaks, one being purple and peaking at 407 nm, the other in the near-infrared and peaking at 780 nm. Quantum yields are 4% for S-CQDs and 6.4% for S-CNFs. The nanoparticles are shown to be viable fluorescent probes for hydrogen peroxide which acts as a quencher. The 3D structure of the S-CNFs and near-infrared detection result in a better linear relationship and lower detection limits. The detection limits for H2O2 are 1.1 μM for S-CQDs, and 0.6 μM for S-CNFs. The results presented here contribute to an improved understanding on how the nanostructure and selection of wavelengths affect the sensitivity and detection limits of such probes.

Alkaline phosphatase (ALP) is one of the most versatile biomarkers for early detection of several diseases, such as oral carcinomas and periodontitis; therefore, great efforts have been dedicated for developing an ALP biosensor. Multicolor detection of ALP in saliva is ideal for a point-of-care diagnosis; however, this approach is very challenging since spectral responses over wavelengths of several tens of nanometers have thus far remained difficult to achieve. In this work, a colorimetric biosensor for ALP assay has been developed based on ALP affinity to dephosphorylate glucose phosphate into glucose, which has the affinity to deposit Ag nanoshells onto Au nanobipyramids with a multicolor response. This approach provides a blue shift of localized surface plasmon resonance (LSPR) as large as 190 nm corresponding to distinctive color changes, from yellowish brown to red based on the thickness of the formed Ag shell around the Au nanobipyramids. The change in the LSPR has been conducted for highly sensitive quantitative bioassay of ALP with a detectable multicolor change with linear dynamic range of 0.1–20 U/L and low limit of detection (LOD) of 0.085 U/L. Furthermore, the developed multicolor ALP biosensor exhibits high selectivity with high recovery of 98.6% demonstrating  its reliability and suitability for a point-of-care diagnosis.

Die Geschichte lehrt uns, daß sich Gold mitunter in pflanzlichem und tierischem Material vorfindet. Die älteren Forschungen waren jedoch oft zufällig und nicht belegt. Hauptsächlich war die chemische Analyse nicht auf der erforderlichen Höhe.J. Babička, B. Němec undA. Oborský verfolgten durch systematisches Einsammeln von Material und durch zahlreiche täglich durchgeführte Analysen vom Jahre 1934 bis zum Jahre 1939 die Frage des Goldvorkommens in Pflanzen und Tieren. Hierbei wurden sehr interessante Beobachtungen gemacht, und zwar:

A sensitive ion-pair liquid-liquid extraction-spectrophotometric method has been developed for the determination of copper, palladium, iron and cobalt, based on the formation of metal complexes with 1-nitroso-2-naphthol-6-sulphonic acid or 2-nitroso-1-naphthol-6-sulphonic acid as primary ligand, and zephiramine as counter-ion. The coloured metal complexes obtained over different pH ranges are easily and quantitatively extracted into dichloromethane. The method has been tested with samples containing known amounts of copper, palladium, iron and cobalt in ultrapure water. The reagents provide a sensitive spectrophotometric method for determining these metals.

Die quantitative Bestimmung von Ultramikromengen Cadmium durch Titration des Cd(II)-Xylenolorange-Komplexes mit 0,001-m ÄDTA wird vorgeschlagen. Man kann so noch 0,4μg Cd(II) in Anwesenheit der 40fachen Menge Kupfer mit zufriedenstellender Genauigkeit bestimmen. Von sonstigen Metallen wird das Cadmium mit Hilfe der Ringofentechnik abgetrennt.

A glassy carbon electrode modified with organic–inorganic pillared montmorillonite was used for voltammetric detection of mercury(II) in water. High sensitivity is obtained due to the use of the montmorillonites which displays outstanding capability in terms of adsorbing mercury ion due to its high specific surface and the presence of multiple binding sites. The experimental parameters and the effect of a chelating agent were optimized to further enhance sensitivity and selectivity. Linear calibration curves were obtained over the Hg(II) concentration range from 10 to 800 μg L−1 for 5 min accumulation, with a detection limit of 1 μg L−1. Simultaneous determination of Hg(II) and Cu(II) was also studied, and no interference was observed.

A photothermal immunoassay using a thermometer as readout based on polyaniline@Au organic-inorganic nanohybrids was built. Temperature output is acquired due to the photothermal effect of the photothermal nanomaterial. Polyaniline@Au organic-inorganic nanohybrids were synthesized by interfacial reactions with high photothermal conversion efficiency. A sandwich structure of the immunocomplex was prepared on a microplate for determination of carcinoembryonic antigen (CEA) by polyaniline@Au organic-inorganic nanohybrids as nanolabel. The released heat based on light-to-heat conversion from the photothermal nanolabel under NIR irradiation is detectable using the thermometer. The increased temperature is directly proportional to CEA concentration. The linear range of the photothermal immunoassay is 0.20 to 25 ng mL−1 with determination limit of 0.17 ng mL−1.

Electrochemical methods can be used not only for the sensitive analysis of proteins but also for deeper research into their structure, transport functions (transfer of electrons and protons), and sensing their interactions with soft and solid surfaces. Last but not least, electrochemical tools are useful for investigating the effect of an electric field on protein structure, the direct application of electrochemical methods for controlling protein function, or the micromanipulation of supramolecular protein structures. There are many experimental arrangements (modalities), from the classic configuration that works with an electrochemical cell to miniaturized electrochemical sensors and microchip platforms. The support of computational chemistry methods which appropriately complement the interpretation framework of experimental results is also important. This text describes recent directions in electrochemical methods for the determination of proteins and briefly summarizes available methodologies for the selective labeling of proteins using redox-active probes. Attention is also paid to the theoretical aspects of electron transport and the effect of an external electric field on the structure of selected proteins. Instead of providing a comprehensive overview, we aim to highlight areas of interest that have not been summarized recently, but, at the same time, represent current trends in the field.

Ground samples (150μm, 0.5 g) are decomposed in a mixture of HF and HNO3 acids followed by evaporation to dryness, dissolution of the residue in dilute HNO3 acid, and dilution to 50 ml. Spectral interferences of 14 tested elements are negligible for AAS but in some cases (Nb, Ti, Zr) minor spectral corrections must be made for plasma techniques depending on the level of interferent and analyte. Nonspectral (matrix) interferences at the 1000μg/ml interferent level are all less than 3.5% relative for AAS and less than 5% relative for ICP (except for Ca, Li, and Na where the effects are depressions of 7 to 10% relative). Matrix effects for DCP at the same interferent level are generally more pronounced and amount to enhancements of 5 to 15% relative for 11 of the 14 elements tested. Plasma matrix effects, especially alkali effects, can be compensated by the use of an alkali-aluminum buffer medium (1000μg Na/ml plus 500μg Al/ml as used in this study), a procedure which is most useful for the DCP approach. Copper can be determined down to 10 ppm in the original sample. A comparison of results shows AAS and ICP to be in good agreement with the DCP being slightly less accurate, although the differences in results may be of little practical significance. In terms of freedom from spectral and non-spectral interference, AAS was judged to have a slight advantage for copper.