Laser desorption/ionization mass spectrometric analysis of small molecules using fullerene‐derivatized silica as energy‐absorbing material

In spite of the growing acceptance of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the analysis of a wide variety of compounds, including polymers and proteins, its use in analyzing low‐molecular‐weight molecules (<1000m/z) is still limited. This is mainly due to the interference of matrix molecules in the low‐mass range. Here the derivatized fullerenes covalently bound to silica particles with different pore sizes are applied as thin layer for laser desorption/ionization (LDI) mass spectrometric analysis. Thus, an interference of intrinsic matrix ions can be eliminated or minimized in comparison with the state‐of‐the‐art weak organic acid matrices. The desorption/ionization ability of the developed fullerene–silica materials depends on the applied laser power, sample preparation and pore size of the silica particles. Thus, fullerene–silica serves as an LDI support for mass spectrometric analysis of molecules (<1500 Da). The performance of the fullerene–silica is demonstrated by the mass analysis of variety of small molecules such as carbohydrates, amino acids, peptides, phospholipids and drugs. Copyright © 2010 John Wiley & Sons, Ltd.     

CE to monitor endotoxins by protein complexation

A new CE method for fast and efficient analysis of bacterial endotoxins (lipopolysaccharides) is described. It is based on the strong interaction between proteins and endotoxins. The UV absorption of the protein component in the complex is used for the detection. The electrophoretic mobility of the complex hemoglobin/endotoxin can be employed for qualitative analysis of the endotoxin. For instance, the structural differences between "smooth" and "rough" lipopolysaccharides from Salmonella minnesota (wild-type), Salmonella minnesota R595 and Shigella sonnei R562H are reflected in the electrophoretic mobilities of their hemoglobin complex.     

Universal method for synthesis of artificial gel antibodies by the imprinting approach combined with a unique electrophoresis technique for detection of minute structural differences of proteins, viruses, and cells (bacteria). III: gel antibodies against cells (bacteria)

Artificial antibodies in the form of gel granules were synthesized from the monomers acrylamide and N,N'-methylenebisacrylamide by the imprinting method in the presence of Echerichia coli bacteria as template. The electrophoretic migration velocities of the gel antibodies (i) saturated with the antigen (Escherichia coli MRE-600), (ii) freed of the antigen, and (iii) resaturated with bacteria, were determinated by electrophoresis in a rotating narrow-bore tube of 245 mm length and the 2.5 and 9.6 mm inner and outer diameters, respectively. Removal of bacteria from the gel antibodies was made by treatment with enzymes, followed by washing with SDS and buffer. Gel granules becoming charged by adsorption of bacteria move in an electrical field. We obtained a significant selectivity of gel antibodies for E. coli MRE-600, since the granules did not interact with Lactococcus lactis; and when E. coli BL21 bacteria were added to the gels selective for E. coli MRE-600, a significant difference in the migration rate of the complexes formed with the two strains was observed indicating the ability of differentiation between the two strains. The gel antibodies can be used repeatedly. The new imprinting method for the synthesis of artificial gel antibodies against bioparticles described herein, and the classical electrophoretic analysis technique employed, thus represent - when combined - a new approach to distinguish between different types and strains of bacteria. The application area can certainly be extended to cover other classes of cells.     

Graphite epoxy composite electrodes modified with bacterial cells

The modification of a graphite-epoxy composite electrode (GECE) with bacterial cells along with an analytical application are presented. Pseudomonas putida DSM 50026 was used as a biological component and the measurement was based on the respiratory activity of the cells. The optimization of working conditions of resulting biosensor (including pH and temperature) was conducted and the limit of detection was calculated as 7 microM phenol based on the signal to noise ratio. Then the system was applied for xenobiotic detection. Resulting sample signals were found to be very similar with the standard solutions having the same concentration while the recoveries of the spiked samples were close to 100%.     

Photoactivatable prodrug for simultaneous release of mertansine and CO along with a BODIPY derivative as a luminescent marker in mitochondria: a proof of concept for NIR image-guided cancer therapy

Controlled and efficient activation is the crucial aspect of designing an effective prodrug. Herein we demonstrate a proof of concept for a light activatable prodrug with desired organelle specificity. Mertansine, a benzoansamacrolide, is an efficient microtubule-targeting compound that binds at or near the vinblastine-binding site in the mitochondrial region to induce mitotic arrest and cell death through apoptosis. Despite its efficacy even in the nanomolar level, this has failed in stage 2 of human clinical trials owing to the lack of drug specificity and the deleterious systemic toxicity. To get around this problem, a recent trend is to develop an antibody-conjugatable maytansinoid with improved tumor/organelle-specificity and lesser systematic toxicity. Endogenous CO is recognized as a regulator of cellular function and for its obligatory role in cell apoptosis. CO blocks the proliferation of cancer cells and effector T cells, and the primary target is reported to be the mitochondria. We report herein a new mitochondria-specific prodrug conjugate (Pro-DC) that undergoes a photocleavage reaction on irradiation with a 400 nm source (1.0 mW cm⁻²) to induce a simultaneous release of the therapeutic components mertansine and CO along with a BODIPY derivative (BODIPY(PPH₃)₂) as a luminescent marker in the mitochondrial matrix. The efficacy of the process is demonstrated using MCF-7 cells and could effectively be visualized by probing the intracellular luminescence of BODIPY(PPH₃)₂. This provides a proof-of-concept for designing a prodrug for image-guided combination therapy for mainstream treatment of cancer.

Simultaneous release of two therapeutic reagents, mertansine and CO through photo-induced cleavage of a mitochondria-specific prodrug with improved drug efficacy.     

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

There has recently been a growing interest in dye sensitized solar cells (DSSCs) based on ruthenium metal, but due to the scarcity and high price of ruthenium, design of better and cheaper light adsorbent dyes based on more abundant metal ions is one of the key issues for future development of the DSSCs. Using density functional theory (DFT) and time-dependent DFT we have studied the properties of new and abundant metal ion-based polypyridyl dyes for p-type DSSCs and compared with ruthenium and other scarce metal ions. Molecular geometries, electronic structures, and optical absorption spectra have been calculated using an implicit solvent corresponding to acetonitrile. The calculated fair light harvesting efficiency, high hole injection efficiency and Gibbs free energy for the hole injection and longer excited state lifetime (important for reflecting the efficiency of solar cells) for the new abundant metal ions (V³⁺ and Cr²⁺) based dyes could provide promising sensitizers for efficient next generation DSSC's for p-SC.     

Centri-voltammetric study with amberlite XAD-7 resin as a carrier system

Centri-voltammetry is a novel method, which allows combining the advantages of centrifugation and voltammetry. The method offers a practical way for application of coprecipitation in trace analysis allowing direct voltammetric scan hence prevents the loss of the analyte, which usually is the case for other preconcentration techniques. The performance of the method was successfully tested using trace amounts of Pb²⁺ ions in aqueous solution in a vessel specially designed to be compatible to both centrifugation and voltammetry. XAD-7 resin was used as the carrier material and the parameters related to the carrier material and medium characteristics as well as the centrifugation settings were investigated. The sensitivity of the method was found comparable to that of stripping techniques and the detection limit for lead ions was calculated as 5.2 × 10⁻⁹ M with mercury coated gold sphere electrode. The precision of the method depends on the configuration of the working electrode and better reproducibility was obtained with mercury coated plate electrodes (R.S.D. 3.3%, n = 6).     

Harnessing Deep Neural Networks to Analyze Multi-Channel Anion Sensing Characteristics of a Ru(II)-Pyrazolyl-Bis(Benzimidazole) Complex

In this work, the anion-responsive conduct of a Ru(II)-bipyridine complex incorporating pyrazolyl-bis (benzimidazole) ligand is thoroughly investigated in acetonitrile and water via absorption and emission spectroscopy as well as by square-wave voltammetry (SWV). Substantial alteration of the photo-redox behavior of the complex is observed in the presence of the selected anions. The free form of the complex exhibits emission indicating the “on-state”, while inclusion of anions leads to quenching of emission and represents the “off-state”. The restoration of the initial state of the complex is feasible in the presence of acid and the process is reversible and can be recycled. In essence, the complex functions as anion- and acid-responsive molecular switches. Additionally, we applied herein neural network based deep learning methodologies, viz. Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS)} for thorough analysis and fully understand the multi-channel anion sensing behavior of the complex.