Characterization and forensic identification of a novel cocaine charcoal smuggling matrix.

Every year new and sophisticated drug-smuggling methods are encountered by law enforcement agencies all over the globe. A seized cross-border smuggling attempt was found to contain charcoal. This unexpected smuggling cargo raised doubts as to the real content of the material. Initial testing indicated that the black charcoal-like material contained cocaine. The material was forensically tested for cocaine presence and quantitatively analyzed for cocaine concentration. Initial testing with an illicit substance identification field kit and FTIR revealed that some of the material contained cocaine whereas other pieces were completely free of cocaine. Cocaine-containing material was quantitatively measured and was found to consist of over 50% cocaine. In addition, the morphology and element composition of the suspected matrix were analyzed by SEM and EDX. The results pointed to some structural and composition differences between material loaded with cocaine and charcoal free of the drug. One of the most significant and surprising differences in the element composition measurements was the finding of iron in the cocaine-containing material. Moreover, thermogravimetric analysis was performed on the samples to support the material composition analyses. Although the exhibits did not display a homogenous presence and concentration of cocaine, the porous morphological structure and the high cocaine concentration in some of the samples reveal that the carbon-rich matrix has a potential for high capacity drug uptake. The iron accompanying the cocaine is probably a left over product of the cocaine masking process.

G-Quadruplex-Stimulated Optical and Electrocatalytic DNA Switches.

The K(+) /18-crown-6-(or [2.2.2] cryptand)-stimulated formation and dissociation of G-quadruplex nanostructures lead to the cyclic and switchable photonic and electrocatalytic molecular devices.

Autonomous control of interfacial electron transfer and the activation of DNA machines by an oscillatory pH system.

An oscillatory pH system is implemented to drive oscillatory pH-switchable DNA machines and to control pH-stimulated electron transfer at electrode surfaces. The oscillatory pH system drives the autonomous opening and closure of DNA tweezers and activates a DNA pendulum by the pH-stimulated formation and dissociation of i-motif structures. Also, a sequence-programmed nucleic acid monolayer-functionalized electrode undergoes autonomous oscillatory pH transitions between random coil and i-motif configurations, leading to the control of electron transfer at electrode surfaces.

Metal nanoparticle-functionalized DNA tweezers: from mechanically programmed nanostructures to switchable fluorescence properties.

DNA tweezers are modified with two 10-nm sized Au NPs and one 5-nm sized Au NP. Upon treatment of the tweezers with fuel and antifuel nucleic acid strands, the switchable closure and opening of the tweezers proceed, leading to the control of programmed nanostructures of the tethered NPs. The tweezers are further modified with a single 10-nm sized nanoparticle, and a fluorophore unit (Cy3), positioned at different distinct sites of the tweezers. The reversible and cyclic fluorescence quenching or fluorescence enhancement phenomena, upon the dynamic opening/closure of the different tweezers, are demonstrated.

Amplified detection of DNA through the enzyme-free autonomous assembly of hemin/G-quadruplex DNAzyme nanowires.

An enzyme-free amplified detection platform is described using the horseradish peroxidase (HRP)-mimicking DNAzyme as an amplifying label. Two hairpin structures that include three-fourths and one-fourth of the HRP-mimicking DNAzyme in caged, inactive configurations are used as functional elements for the amplified detection of the target DNA. In the presence of the analyte DNA, one of the hairpins is opened, and this triggers the autonomous cross-opening of the two hairpins using the strand displacement principle. This leads to the formation of nanowires consisting of the HRP-mimicking DNAzyme. The resulting DNA nanowires act as catalytic labels for the colorimetric or chemiluminescent readout of the sensing processes (the term "enzyme-free" refers to a protein-free catalyst). The analytical platform allows the sensing of the analyte DNA with a detection limit corresponding to 1 × 10(-13) M. The optimized system acts as a versatile sensing platform, and by coaddition of a "helper" hairpin structure any DNA sequence may be analyzed by the system. This is exemplified with the detection of the BRCA1 oncogene with a detection limit of 1 × 10(-13) M.

pH-programmable DNAzyme nanostructures.

Two engineered DNA nanostructures consisting of a nucleic acid functional hairpin and a DNA "tweezers" assembly act as pH-switchable devices for the "ON-OFF" activation/deactivation of the horseradish-peroxidase-mimicking DNAzyme.

Ion-induced DNAzyme switches.

The activities of Mg(2+)-dependent DNAzymes are reversibly switched by ion stimuli using the thymine-Hg(2+)-thymine complexes or cytosine-Ag(+)-cytosine complexes.

pH-triggered switchable Mg2+-dependent DNAzymes.

The activities of Mg(2+)-dependent DNAzymes are reversibly switched by pH stimuli using the i-motif as an activating motif.

Aptamer-DNAzyme hairpins for amplified biosensing.

Engineered nucleic acid hairpin structures are used for the amplified analysis of low-molecular-weight substrates (adenosine monophosphate, AMP) or proteins (lysozyme). The hairpin structures consist of the anti-AMP or antilysozyme aptamer units linked to the horseradish peroxidase (HRP)-mimicking DNAzyme sequence. The HRP-mimicking DNAzyme sequence is protected in a "caged", inactive structure in the stem regions of the respective hairpins, whereas the loop regions include a part of the respective aptamer sequence. The opening of the hairpins by the analytes, AMP or lysozyme, through the formation of the respective analyte-aptamer complexes, results in the self-assembly of the active HRP-mimicking DNAzyme. The DNAzyme catalyzes the H(2)O(2)-mediated oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the colored ABTS(*-), thus providing the amplified optical detection of the respective analytes. The engineered aptamer-DNAzyme hairpin structures reveal significantly improved analytical performance, as compared to analogous fluorophore-quencher-labeled hairpins.

Real-time monitoring of transferrin-induced endocytic vesicle formation by mid-infrared surface plasmon resonance.

We report on the application of surface plasmon resonance (SPR), based on Fourier transform infrared spectroscopy in the mid-infrared wavelength range, for real-time and label-free sensing of transferrin-induced endocytic processes in human melanoma cells. The evanescent field of the mid-infrared surface plasmon penetrates deep into the cell, allowing highly sensitive SPR measurements of dynamic processes occurring at significant cellular depths. We monitored in real-time, infrared reflectivity spectra in the SPR regime from living cells exposed to human transferrin (Tfn). We show that although fluorescence microscopy measures primarily Tfn accumulation in recycling endosomes located deep in the cell's cytoplasm, the SPR technique measures mainly Tfn-mediated formation of early endocytic organelles located in close proximity to the plasma membrane. Our SPR and fluorescence data are very well described by a kinetic model of Tfn endocytosis, suggested previously in similar cell systems. Hence, our SPR data provide further support to the rather controversial ability of Tfn to stimulate its own endocytosis. Our analysis also yields what we believe is novel information on the role of membrane cholesterol in modulating the kinetics of endocytic vesicle biogenesis and consumption.

Self-assembly of enzymes on DNA scaffolds: en route to biocatalytic cascades and the synthesis of metallic nanowires.

DNA strands consisting of programmed sequence-specific domains were synthesized by the rolling circle amplification (RCA) process. The spatial positioning of glucose oxidase (GOx) and of horseradish peroxidase (HRP) on the RCA-synthesized DNA template via hybridization enabled the activation of the bienzyme cascade. The GOx-catalyzed oxidation of glucose yielded gluconic acid and H(2)O(2), and the resulting H(2)O(2) oxidized 2,2'-azino-bis[3-ethylbenzthiazoline-6-sulfonic-acid] (ABTS(2-)) in the presence of HRP. The enzyme cascade could not be activated in the absence of the organizing DNA template or in the presence of a foreign DNA. Also, Au NPs-functionalized GOx was hybridized with the RCA-synthesized single-stranded DNA. The biocatalytic growth of the NPs through the oxidation of glucose, in the presence of AuCl(4)(-), enabled the synthesis of 1-5 microm long Au wires, exhibiting a width of ca. 150 nm.