D. S. Volkov

In vivo multispectral photoacoustic and photothermal flow cytometry with multicolor dyes: a potential for real-time assessment of circulation, dye-cell interaction, and blood volume

Recently, photoacoustic (PA) flow cytometry (PAFC) has been developed for in vivo detection of circulating tumor cells and bacteria targeted by nanoparticles. Here, we propose multispectral PAFC with multiple dyes having distinctive absorption spectra as multicolor PA contrast agents. As a first step of our proof‐of‐concept, we characterized high‐speed PAFC capability to monitor the clearance of three dyes (Indocyanine Green [ICG], Methylene Blue [MB], and Trypan Blue [TB]) in an animal model in vivo and in real time. We observed strong dynamic PA signal fluctuations, which can be associated with interactions of dyes with circulating blood cells and plasma proteins. PAFC demonstrated enumeration of circulating red and white blood cells labeled with ICG and MB, respectively, and detection of rare dead cells uptaking TB directly in bloodstream. The possibility for accurate measurements of various dye concentrations including Crystal Violet and Brilliant Green were verified in vitro using complementary to PAFC photothermal (PT) technique and spectrophotometry under batch and flow conditions. We further analyze the potential of integrated PAFC/PT spectroscopy with multiple dyes for rapid and accurate measurements of circulating blood volume without a priori information on hemoglobin content, which is impossible with existing optical techniques. This is important in many medical conditions including surgery and trauma with extensive blood loss, rapid fluid administration, and transfusion of red blood cells. The potential for developing a robust clinical PAFC prototype that is safe for human, and its applications for studying the liver function are further highlighted.

Improving the dispersity of detonation nanodiamond: differential scanning calorimetry as a new method of controlling the aggregation state of nanodiamond powders

Detonation nanodiamond (ND) is a suitable source material to produce unique samples consisting of almost uniform diamond nanocrystals (d = 3-5 nm). Such samples exist in the form of long stable aqueous dispersions with narrow size distribution of diamond particles. The material is finding ever increasing application in biomedicine. The major problem in producing monodispersed diamond colloids lies in the necessity of deagglomeration of detonation soot and/or removing of clusters formed by already isolated core particles in dry powders. To do this one must have an effective method to monitor the aggregation state or dispersity of powders and gels prior to the preparation of aqueous dispersions. In the absence of dispersity control at various stages of preparation the reproducibility of properties of existing ND materials is poor. In this paper we introduce differential scanning calorimetry (DSC) as a new tool capable to distinguish the state of aggregation in dry and wetted ND materials and to follow changes in this state under different types of treatment. Samples with identical X-ray diffraction patterns (XRD) and high resolution transmission electron microscopy (HRTEM) images gave visibly different DSC traces. Strong correlation was found between dynamic light scattering (DLS) data for colloids and DSC parameters for gels and powders of the same material. Based on DSC data we improved dispersity of existing ND materials and isolated samples with the best possible DSC parameters. These were true monodispersed easily dispersible fractions of ND particles with diameters of ca. 3 nm.

Advances in thermal lens spectrometry

The main examples of the application of thermal lens spectrometry and thermal lens microscopy as highly sensitive power-based thermooptical (photothermal) methods of molecular absorption spectroscopy to photometric, chromatographic, and electromigration methods of analysis and to solving problems related to the use of microfluid chips are considered. The fundamentals and characteristics of the thermooptical methods and instruments and the problems and prospects of their development are discussed. Examples are provided for illustrating the sensitivity and selectivity of combined methods and multidisciplinary studies performed with the aid of thermal lens spectrometry.

Structure and toxicity of aqueous fullerene C60 solutions

In this paper, two types of fullerene C60 solutions are compared with respect to their structural features and toxic properties. The results are discussed in terms of their potential in medical and biological applications. The fullerene cluster state at the nanoscale in these solutions is analyzed by small-angle neutron scattering. Experiments on the cytotoxicity of these systems on Chinese-hamster V-79 cells showed no toxic effects of the solutions.

Quantification of nanodiamonds in aqueous solutions by spectrophotometry and thermal lens spectrometry

Spectrophotometry and thermal lens spectrometry were used to study solutions of several commercial detonation nanodiamonds. It was found that the absorption spectra of solutions of all studied nanodiamond samples obey the Bouger-Lambert-Beer law, which ensures the precise determination of the total mass concentration of unknown nanodiamond solutions using a calibration plot. It was shown that the absorption spectra of nanodiamond solutions exhibit both absorption and scattering components, both significantly affecting signal formation. Conditions were proposed for the spectrophotometric determination of nanodiamonds at 250 nm (l = 1.0 cm). The detection limits were from 60 ng/mL to 2 μg/mL, depending on the nanodiamond type. Limits of detection of SDND nanodiamonds by spectrophotometry and thermal lens spectrometry were calculated for identical conditions of sample preparation and measurements (488 nm, l = 1.0 cm). These were 10 and 0.6 μg/mL for spectrophotometry and thermal lens spectrometry, respectively (power of excitation radiation 150 mW).

Selective Ruthenium Labeling of the Tryptophan Residue in the Bee Venom Peptide Melittin

Melittin is a membrane-active peptide from bee venom with promising antimicrobial and anticancer activity. Herein we report on a simple and selective method for labeling of the tryptophan residue in melittin by the organometallic fragment [(C5 H5 )Ru](+) in aqueous solution and in air. Ruthenium coordination does not disturb the secondary structure of the peptide (as verified by 2D NMR spectroscopy), but changes the pattern of its intermolecular interactions resulting in an 11-fold decrease of hemolytic activity. The high stability of the organometallic conjugate allowed the establishment of the biodistribution of the labeled melittin in mice by inductively coupled plasma MS analysis of ruthenium.

Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons

Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2–5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896–2590 min−1, selectivity 89–98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850–5000 min−1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294–2400 min−1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14–22 min−1, selectivity 7–16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.

Optoacoustic spectroscopy for real-time monitoring of strongly light- absorbing solutions in applications to analytical chemistry §

An optoacoustic technique for solutions of strongly light-absorbing analytes at 0.1–0.01 mol l−1 is proposed. The technique is based on the wide-band forward mode detection of temporal profiles of laser-generated ultrasonic pulses (optoacoustic signals). The leading edge of the signal repeats the distribution of the laser fluence in the medium, which makes it possible to determine its optical absorption and investigate its dynamics during a reaction. The range of light-absorption coefficients starts from 1 to 5 and reaches 104 to 105 cm−1. The determination of iron(II) as ferroin shows the possibility of probing 0.1 mol l−1 of iron(II), which was not previously achieved for this reaction by optical spectroscopy. To further prove the concept, kinetic measurements for ferroin decomposition at the level of 0.1 mol l−1 and at high pHs are performed. The results are compared with spectrophotometry at lower concentrations and show good reproducibility and accuracy of kinetic constants.

Quantification of copolymer composition (methyl acrylate and itaconic acid) in polyacrylonitrile carbon-fiber precursors by FTIR-spectroscopy

Conditions for simple and sensitive FTIR quantitative determination of acrylonitrile, methyl acrylate, and itaconic acid in their copolymer films used as precursor products in carbon-fiber manufacturing are proposed. The measurement mode is IR-spectrophotometry (transmission) with internal spectrum normalization using the peak of acrylonitrile at 2242 cm−1 as the main component and the determination of itaconic acid and methyl acrylate by their overlapping carbonyl peaks at 1740–1700 cm−1. The calculations of comonomer concentrations were made using an external-standard method. The LOQs of itaconic acid and methyl acrylate are 0.5 and 2% w/w, respectively. The RSD of measurements is no higher than 7% rel. for methyl acrylate, 8% rel. for itaconic acid, and 1% rel. for acrylonitrile, which was shown by an example of analysis of PAN fiber samples with known concentrations of the components. The procedure was tested with several thermally unprocessed PAN precursor samples.

The Origins of Specificity in the Microcin-Processing Protease TldD/E.

Summary TldD and TldE proteins are involved in the biosynthesis of microcin B17 (MccB17), an Escherichia coli thiazole/oxazole-modified peptide toxin targeting DNA gyrase. Using a combination of biochemical and crystallographic methods we show that E. coli TldD and TldE interact to form a heterodimeric metalloprotease. TldD/E cleaves the N-terminal leader sequence from the modified MccB17 precursor peptide, to yield mature antibiotic, while it has no effect on the unmodified peptide. Both proteins are essential for the activity; however, only the TldD subunit forms a novel metal-containing active site within the hollow core of the heterodimer. Peptide substrates are bound in a sequence-independent manner through β sheet interactions with TldD and are likely cleaved via a thermolysin-type mechanism. We suggest that TldD/E acts as a “molecular pencil sharpener”: unfolded polypeptides are fed through a narrow channel into the active site and processively truncated through the cleavage of short peptides from the N-terminal end.