Conventional Probe Research Articles

DNA Probes that Store Mechanical Information Reveal Transient Piconewton Forces Applied by T Cells

The advent of molecular tension probes for real-time mapping of piconewton forces in living systems has had a major impact on mechanobiology. For example, DNA-based tension probes have revealed roles for mechanics in platelet, B cell, T cell, and fibroblast function. Nonetheless, imaging short-lived forces transmitted by low-abundance receptors remains a challenge. This is a particular problem for mechanoimmunology where ligand-receptor bindings are short lived, and a few antigens are sufficient for cell triggering. Herein, we present a mechano-selection strategy that uses locking oligonucleotides to preferentially and irreversibly bind DNA probes that are mechanically strained over probes at rest. Thus, infrequent and short-lived mechanical events are tagged. This strategy allows for integration and storage of mechanical information into a map of molecular tension history. Upon addition of unlocking oligonucleotides that drive toehold-mediated strand displacement, the probes reset to the real-time state, thereby erasing stored mechanical information. As a proof of concept, we applied this strategy to study OT-1 T cells, revealing that the T cell receptor (TCR) mechanically samples antigens carrying single amino acid mutations. Such events are not detectable using conventional tension probes. Each mutant peptide ligand displayed a different level of mechanical sampling and spatial scanning by the TCR that strongly correlated with its functional potency. Finally, we show evidence that T cells transmit pN forces through the programmed cell death receptor-1 (PD1), a major target in cancer immunotherapy. We anticipate that mechanical information storage will be broadly useful in studying the mechanobiology of the immune system.

Biodegradable and photostable Nb2C MXene quantum dots as promising nanofluorophores for metal ions sensing and fluorescence imaging

Conventional fluorescent probes are either easily photobleached or non-biodegradable, which often leads to the unstable fluorescence signal output and long-term biological toxicity. Therefore, the development of novel fluorescent materials with both excellent photostability and biodegradability is of great significance for further broadening their application in numerous research fields. In this work, Nb2C quantum dots (Nb2C QDs) with pristine crystallographic structures of Nb2C MXene phases and surface oxygen-containing species are synthesized by an ultrasound assisted physicochemical exfoliation in tetrapropylammonium hydroxide. Detailed analyses indicate that the Nb2C QDs not only possess excellent chemical- and photo-stable fluorescence emission but also achieve successful application in fluorescence sensing of heavy metal ions and fluorescence imaging. More importantly, it is confirmed that the Nb2C QDs present high biocompatibility and unique biodegradation property responsive to human myeloperoxidase, implying the application safety of Nb2C QDs in vivo. Under the background of ever-growing and stringent requirements for biosafety and technical stability, the chemical- and photo-stability, biocompatibility, biodegradability, and most importantly the promising fluorescence sensing/imaging characteristic of the obtained Nb2C QDs may argue well for their future applications in environmental monitoring, biomedical diagnosis, visual display, and anti-counterfeiting.

Contactless determination of doping concentration and resistivity of silicon wafers with cavity ring-down technique

A contactless method for measuring the doping concentration and resistivity of silicon wafers based on cavity ring-down technique was developed and verified experimentally. The doping concentration and resistivity of the silicon wafer in our experiment were calculated to be 1.53 ± 0.47 × 1016 cm−3 and 1.08 ± 0.41 Ω·cm, respectively, by measuring the optical loss caused by the sample, which are consistent with that obtained with conventional four-point probe measurements. The results indicated that the proposed method can be an alternative non-destructive tool for doping concentration and resistivity measurements.

A probing system with a rotatable tip for 3D coordinate nanometrology

Performing coordinate nanometrology of arbitrarily shaped three-dimensional (3D) objects about a micrometer or less in size remains a challenge. In this paper we report a probing system with a rotatable tip for performing coordinate metrology on such objects. An atomically sharp tip is mounted on an active ball-and-socket microjoint, and the two are integrated into a conventional microcantilever probe. The ball-and-socket joint allows the tip to be pointed in any direction, and thereby enables access to any desired 3D feature, while the probe is employed to repeatedly touch the sample surface and extract its corresponding coordinates. The system has been demonstrated to access the surfaces of both horizontally and vertically oriented muscovite mica surfaces and to perform their coordinate nanometrology.

A Novel Screw-Based Probe to Measure Pulse Forming Line Voltage in Tesla-Type Generators

A novel screw-based probe is put forward to measure the pulse forming line (PFL) voltage in Tesla-type generators. This probe utilizes an existing screw as the key part of the conventional probe. Therefore, no extra hole is needed, which simplifies the design of the PFL. The voltage ratio of this probe is not a constant which varies within the pulsewidth with a deviation of ±5%. By analysis, it is found that this deviation is mainly due to the complicated electromagnetic environment on the outer magnetic core of the Tesla transformer where this probe is assembled. The electromagnetic environment can cause perturbation which adds on the main test waveform when the Tesla transformer is charging. Two solutions are proposed for this question. One is to consider the voltage ratio as a time-dependent variable, rather than a constant any more. The other is to redesign the screw-based probe and assemble it where the electromagnetic environment is weak. Both the methods can decrease the deviation of the voltage ratio to a level smaller than 1% and are applied in practical measurements.

Patterns and vertical loads in water shipping in systematic wet dam-break experiments

Water shipping on the deck of structures is a problem in marine environments. Different types of shipping water events can be expected, and systematic experiments are required to better understand their behavior. In this work, systematic experiments were carried out to analyse some patterns of shipping water events and the related vertical loads on the deck of a rectangular fixed structure, using the wet dam-break method to generate the incident waves. The influence of bores generated with different wet dam-break ratios on the resultant water shipping patterns and the trends of vertical loads on the structure was investigated. Conventional wave probes, a force balance and a high-speed camera were synchronized in a controlled environment for the investigation. The results allowed a detailed visualization of different types of shipping water events, mainly differentiated by the formation of different sized cavities at the bow of the structure. Quasi-static vertical loads over the deck generated by the events were presented, including forward and backflow loading. This approach can be useful when performing simplified analyses to investigate the details of shipping water behavior and for acquiring detailed data for model validations.

Advancing Aptamers as Molecular Probes for Cancer Theranostic Applications-The Role of Molecular Dynamics Simulation.

Theranostics cover emerging technologies for cell biomarking for disease diagnosis and targeted introduction of drug ingredients to specific malignant sites. Theranostics development has become a significant biomedical research endeavor for effective diagnosis and treatment of diseases, especially cancer. An efficient biomarking and targeted delivery strategy for theranostic applications requires effective molecular coupling of binding ligands with high affinities to specific receptors on the cancer cell surface. Bioaffinity offers a unique mechanism to bind specific target and receptor molecules from a range of non-targets. The binding efficacy depends on the specificity of the affinity ligand toward the target molecule even at low concentrations. Aptamers are fragments of genetic materials, peptides, or oligonucleotides which possess enhanced specificity in targeting desired cell surface receptor molecules. Aptamer-target binding results from several inter-molecular interactions including hydrogen bond formation, aromatic stacking of flat moieties, hydrophobic interaction, electrostatic, and van der Waals interactions. Advancements in Systematic Evolution of Ligands by Exponential Enrichment (SELEX) assay has created the opportunity to artificially generate aptamers that specifically bind to desired cancer and tumor surface receptors with high affinities. This article discusses the potential application of molecular dynamics (MD) simulation to advance aptamer-mediated receptor targeting in targeted cancer therapy. MD simulation offers real-time analysis of the molecular drivers of the aptamer-receptor binding and generate optimal receptor binding conditions for theranostic applications. The article also provides an overview of different cancer types with focus on receptor biomarking and targeted treatment approaches, conventional molecular probes, and aptamers that have been explored for cancer cells targeting.

Polydiacetylene-based ultrastrong bioorthogonal Raman probes for targeted live-cell Raman imaging

Live-cell Raman imaging based on bioorthogonal Raman probes with distinct signals in the cellular Raman-silent region (1800–2800 cm−1) has attracted great interest in recent years. We report here a class of water-soluble and biocompatible polydiacetylenes with intrinsic ultrastrong alkyne Raman signals that locate in this region for organelle-targeting live-cell Raman imaging. Using a host-guest topochemical polymerization strategy, we have synthesized a water-soluble and functionalizable master polydiacetylene, namely poly(deca-4,6-diynedioic acid) (PDDA), which possesses significantly enhanced (up to ~104 fold) alkyne vibration compared to conventional alkyne Raman probes. In addition, PDDA can be used as a general platform for multi-functional ultrastrong Raman probes. We achieve high quality live-cell stimulated Raman scattering imaging on the basis of modified PDDA. The polydiacetylene-based Raman probes represent ultrastrong intrinsic Raman imaging agents in the Raman-silent region (without any Raman enhancer), and the flexible functionalization of this material holds great promise for its potential diverse applications.

High Resolution and Polarization Independent Microwave Near-Field Imaging Using Planar Resonator Probes

Various near-field microwave imaging probes were developed previously for nondestructive testing of material structures. Sensitivity and resolution are key parameters for quantifying the efficacy of a given imaging probe. For polarized targets like cracks, the sensitivity of conventional aperture probes depends on the relative orientation between the probe's electric-field vector and the target. In practice, target orientation is typically unknown. Furthermore, the imaging resolution of conventional aperture probes is limited to aperture dimensions. Obtaining imaging resolution in the order of few millimeters using conventional aperture probes requires operation at high frequencies, (above 30 GHz). In contrast, planar probes consisting of loops loaded with spiral resonators could provide resolution in the order of few millimeters while working at relatively low frequencies (below 1 GHz). Unlike conventional aperture probes, the radiated near-fields of these probes are characterized by two significant components oriented along orthogonal axes. Therefore, the probe intrinsically provides a polarization-independent response. In this article, the near-field imaging resolution of the planar resonator probe is further enhanced, and its polarization-independent response is demonstrated for the first time. The response of three planar probe prototypes of different dimensions is analyzed based on numerical simulation and experimental results. The performance of the probes is extensively evaluated by acquiring line-scans and 2D-images of metal and dielectric samples. The near-field images of the metal sample obtained using the planar probes working below 1 GHz are compared to the images obtained using aperture probes working at 24 GHz, 33 GHz, and 70 GHz. Furthermore, the probe imaging performance for a polarized target (i.e., narrow cuts) is compared to dual-polarized circular probe working at 24 GHz and open-ended coaxial probe working at 10 GHz. Overall, the proposed probe yielded more than twofold increase in the image signal-to-noise ratio (SNR) compared to all the probes utilized herein.

Люминесцентные наноматериалы, допированные редкоземельными ионами, и перспективы их биомедицинского применения (обзор)

Luminescent nanomaterials doped with rare-earth elements are characterized by such physicochemical properties as long-lived luminescence, large Stokes or anti-Stokes shifts, narrow emission bands, high photostability and low toxicity. These materials can be considered as a new generation of biosensors along with conventional molecular probes, such as organic dyes, quantum dots and chelate-based lanthanide probes. In recent years there has been significant interest in the study of functional nanomaterials based on rare earth elements. The purpose of this paper is to provide an overview of recent advances in the development of luminescent inorganic nanoparticles doped with rare earth elements which could be used for biomedical applications.

Magnetic Nanomotor-Based Maneuverable SERS Probe.

Surface-enhanced Raman spectroscopy (SERS) is a powerful sensing technique capable of capturing ultrasensitive fingerprint signal of analytes with extremely low concentration. However, conventional SERS probes are passive nanoparticles which are usually massively applied for biochemical sensing, lacking controllability and adaptability for precise and targeted sensing at a small scale. Herein, we report a “rod-like” magnetic nanomotor-based SERS probe (MNM-SP) that integrates a mobile and controllable platform of micro-/nanomotors with a SERS sensing technique. The “rod-like” structure is prepared by coating a thin layer of silica onto the self-assembled magnetic nanoparticles. Afterwards, SERS hotspots of silver nanoparticles (AgNPs) are decorated as detecting nanoprobes. The MNM-SPs can be navigated on-demand to avoid obstacles and target sensing sites by the guidance of an external gradient magnetic field. Through applying a rotating magnetic field, the MNM-SPs can actively rotate to efficiently stir and mix surrounding fluid and thus contact with analytes quickly for SERS sensing. Innovatively, we demonstrate the self-cleaning capability of the MNM-SPs which can be used to overcome the contamination problem of traditional single-use SERS probes. Furthermore, the MNM-SPs could precisely approach the targeted single cell and then enter into the cell by endocytosis. It is worth mentioning that by the effective mixing of intracellular biocomponents, much more informative Raman signals with improved signal-to-noise ratio can be captured after active rotation. Therefore, the demonstrated magnetically activated MNM-SPs that are endowed with SERS sensing capability pave way to the future development of smart sensing probes with maneuverability for biochemical analysis at the micro-/nanoscale.

Study on the conductivity model of SCC by using a new eddy current probe

Usually, the stress corrosion crack (SCC) has a complex shape of non-zero conductivity. Its shape is very difficult to reconstruct accurately by using eddy current testing signals. At present, most defaults being dealt with are shallow cracks with a simple shape, which are not consistent with the actual cases. In order to detect the deep SCC in metal materials quantitatively, a new eddy current probe with capability of deep penetrating is proposed in the paper. Based on the research results of current literature, the conductivity model of deep SCC is established. ANSYS software is used to analyze the influence of crack inclination, branching position and branch number on eddy current signals to build the equivalent model of SCC. Simulation results show that the new probe is more sensitive to complex SCC than the conventional pancake probe, and can distinguish whether the SCC having branches or not and what the branching position is. The quantitative results of SCC obtained by using a calibration curve show that the detection signals picked up by the new probe can effectively be used to deduce the depth of branching SCC.

Expanding the analytical applications of nucleic acid hybridization using junction probes.

Nucleic acid hybridization is crucial in target recognition with respect to in vitro and in vivo nucleic acid biosensing. Conventional linear probes and molecular beacons encounter challenges in multiplexing and specific recognition of intractable nucleic acids. Advances in nucleic acid nanotechnologies have resulted in a set of novel structural probes: junction probes (JPs), which make full use of the advantages of specificity, stability, programmability and predictability of Watson-Crick base pairing. In recent years, junction probes have been regularly implemented in constructing systems related to biosensing, synthetic biology and gene regulation. Herein, we summarize the latest advances in JP designs as potential nucleic acid biosensing systems and their expansive applications, and provide some general guidelines for developing JP based sensing strategies for implementation of such systems.

Glutathione-responsive disassembly of disulfide dicyanine for tumor imaging with reduction in background signal intensity.

Near-infrared (NIR) fluorescence imaging has been proved as an effective modality in identifying the tumor border and distinguishing the tumor cells from healthy tissue during the oncological surgery. Developing NIR fluorescent probes with high tumor to background (T/B) signal is essential for the complete debulking of the tumor, which will prolong the survival rate of tumor patients. However, the nonspecific binding and “always-on” properties of the conventional fluorescent probes leads to high background signals and poor specificity.Method: To address this problem, glutathione (GSH)-responsive, two disulfide-bonded dicyanine dyes (ss-diCy5 and ss-diNH800CW) were synthesized. As synthesized dyes are quenched under normal physiological conditions, however, once reached to the tumor site, these dyes are capable of emitting strong fluorescence signals primarily because of the cleavage of the disulfide bond in the tumor microenvironment with high GSH concentration. Besides, the GSH-responsive behavior of these dyes was monitored using the UV-vis and fluorescence spectroscopy. The diagnostic accuracy of the aforementioned dyes was also tested both in tumor cells and 4T1-bearing mice.Results: The fluorescence signal intensity of disulfide dicyanine dyes was quenched up to 89% compared to the mono cyanine dyes, thus providing a very low fluorescence background. However, when the disulfide dicyanine dye reaches the tumor site, the dicyanine is cleaved by GSH into two mono-dyes with high fluorescence strength, thus producing strong fluorescent signals upon excitation. The fluorescent signal of the dicyanine was enhanced by up to 27-fold after interacting with the GSH solution. In vivo xenografts tumor studies further revealed that the fluorescence signals of aforementioned dyes can be quickly recovered in the solid tumor.Conclusion: In summary, the disulfide dicyanines dyes can provide a promising platform for specific tumor-activatable fluorescence imaging with improved T/B value.

Optikai szkenner vizsgálata

The conventional touch probes used to digitizing objects are not applicable in many cases because of accuracy limitations, time of scanning, or merely the fact of touching. In the field of digitizing objects, the touchless methods play more and more roles. It gives dense points and such a way it is more realistic, and the time scanning is shorter.

Impact of non-nucleotidic bulges on recognition of mixed-sequence dsDNA by pyrene-functionalized Invader probes.

Invader probes, i.e., DNA duplexes modified with +1 interstrand zippers of intercalator-functionalized nucleotides like 2'-O-(pyren-1-yl)methyl-RNA monomers, are energetically activated for sequence-unrestricted recognition of double-stranded DNA (dsDNA) as they are engineered to violate the neighbor exclusion principle, while displaying high affinity towards complementary DNA sequences. The impact on Invader-mediated dsDNA-recognition upon additional modification with different non-nucleotidic bulges is studied herein, based on the hypothesis that bulge-containing Invader probes will display additionally disrupted base-stacking, more extensive denaturation, and improved dsDNA-recognition efficiency. Indeed, Invader probes featuring a single central large bulge - e.g., a nonyl (C9) monomer - display improved recognition of model DNA hairpin targets vis-à-vis conventional Invader probes (C50 values ∼1.5 μM vs. ∼3.9 μM). In contrast, probes with two opposing central bulges display less favorable binding characteristics. Remarkably, C9-modified Invader probes display perfect discrimination between fully complementary dsDNA and dsDNA differing in only one of eighteen base-pairs, underscoring the high binding specificity of double-stranded probes. Cy3-labeled bulge-containing Invader probes are demonstrated to signal the presence of gender-specific DNA sequences in fluorescent in situ hybridization assays (FISH) performed under non-denaturing conditions, highlighting one potential application of dsDNA-targeting Invader probes.

Non-Reacting studies on Transverse Injection Upstream of Aft Wall Angled Cavities

Cavity performance in coaxial supersonic jets is investigated experimentally in a supersonic flow facility. The coaxial jets issued from the supersonic nozzle enter into a supersonic combustor in which the cavities are incorporated. The primary jet is maintained at a Mach of 1.32, while secondary jet is designed for Mach of 1.00, 1.11 and 1.45. The open type cavities are axisymmetric. The primary flow is maintained at a temperature of 1050K and the secondary flow is at atmospheric temperature. Static and stagnation pressures are measured by using a conventional pitot probe to analyze the quantitative mixing performance and total pressure loss. Uniform momentum flux distribution is observed in cavity configurations compared with nocavity. A more uniform mixing, as well as minimum stagnation pressure loss, is observed for cavity configuration - 4, L/D = 1.53, than other cavity configurations

Relationship between airborne electrical and total water content measurements in ice clouds

Abstract During the High Altitude Ice Crystal -High Ice Water Content (HAIC-HIWC) project, instrumented aircraft were flown in the vicinity and inside deep tropical convective clouds. Among the probes installed on one of these aircraft, were the Isokinetic Probe (IKP2), to retrieve the cloud total water content (TWC) and the AMPERA (Atmospheric Measurement of Potential and Electric field on Aircraft) system to provide information on the electrostatic state of the atmosphere and the aircraft. AMPERA is an electric field mill network which locally measures the electrostatic field at the aircraft fuselage. The distribution and amplitude of the electrostatic field on the aircraft skin depends on the atmospheric electrostatic field around the aircraft and the net electric charge of the aircraft. This latter parameter depends on the balance between the triboelectric current due to the impact of the cloud particles on the aircraft fuselage, the current due to the charged particles emitted by the engines, and the corona current emitted by the aircraft. Based on the flights of the HAIC-HIWC campaigns, which were conducted almost exclusively in cloud composed of ice particles, a comparison between the total water content recorded by microphysical sensor and the aircraft net charge has highlighted the possibility of deducing an estimate of the TWC from the aircraft electrical potential. In contrast to conventional TWC probes which sample a local area of the atmosphere, the AMPERA system uses the aircraft as a sensor and provides an overall estimation of its net TWC exposure. This study provides the first results of the efficacy of the electrostatic method through comparisons with direct in-situ bulk TWC measurements in ice clouds.

In situ localization of alkaline phosphatase activity in tumor cells by an aggregation-induced emission fluorophore-based probes

In situ detection of certain specific enzyme activities in cells is deeply attached to tumor diagnosis. Conventional enzyme-responsive fluorescent probes have difficulty detecting targeted enzymes in situ in cells due to the low detection accuracy caused by the spread of fluorescence probes. In order to solve this problem, we have designed and synthesized an enzyme-responsive, water-soluble fluorescent probe with AIE characteristics, which could aggregate and precipitate to produce in situ fluorescence when reacting with the targeted enzyme in cells. The AIE fluorophore (TPEQH) was utilized to design the enzyme-responsive, fluorescent probe (TPEQHA) by introducing a phosphate group on to it, which could be specifically decomposed by the targeted enzyme, namely alkaline phosphatase (ALP). In tumor cells, TPEQH was highly produced due to the interaction of phosphate on the TPEQHA and the overexpressed ALP. Water-insoluble TPEQH then precipitated and release fluorescence in situ, thereby successfully detecting the ALP. Furthermore, the expression level of ALP could be determined by the fluorescence intensity of TPEQH with higher accuracy due to the inhibition of TPEQH leak, which demonstrated a potential application of in suit ALP detection in both clinical diagnosis and scientific research of tumor.

Enhancing the local conductivity of Cu films using temperature-assisted agglomerated Cu nanostructures

We investigate the structural and electrical properties of Cu film and reveal their changes as a function of post-annealing temperature. Thermal annealing of a Cu film on a dielectric substrate can improve its crystallinity; however, high-temperature annealing also leads to a morphological transformation that hinders the precise measurement of electrical properties. The enhanced crystallinity of the Cu films is verified with x-ray diffraction as the annealing temperature increases. To examine the electrical properties of the Cu film after the dewetting processes, which promotes the formation of voids and agglomerations, we utilize both conventional micro four-point probe method as well as an advanced four-point probe scanning tunneling microscopy (4P-STM) technique to measure the conductance and evolution of the microscopic structural properties. We could eliminate a deceptive effect of voids with 4P-STM technique, and disclosed a significantly reduced resistivity (1.88 ± 0.07 µΩ·cm) of Cu nanostructure after post-annealing at 700 °C. We unveiled impact of crystallinity and imperfections of Cu nanostructure, and discussed the critical role of the twin grain boundaries of single-crystalline Cu (1 1 1) on an Al2O3 substrate. We anticipate that understanding the evolution of the structures and the enhanced electrical properties of the post-annealed Cu nanostructures would be important for nanoscale devices where Cu is used as an interconnecting material and could provide a new route to control the plasmonic applications.