Conventional Probe Research Articles

Electrochemical imaging of contact boundary by using electron-beam addressing of a virtual cathode display

Abstract A scanning electrochemical microscope (SECM) enables surface measurements of electrical properties of various wet samples including living cells, although its probe cannot reach the interface where the samples contact a substrate. This paper reports our innovative method for electrochemical imaging of the contact boundary in wet samples in water solution. We used electron-beam (EB) addressing of a virtual cathode (VC) for an inverted electron beam lithography system, and we carried out imaging of the contact boundaries which cannot be approached by conventional scanning probe microscopes. This VC was formed on the surface of a 100-nm thick silicon nitride (SiN) membrane by low-energy EB irradiation from the lower side of the membrane. The VC appeared at the contact boundary of the wet samples and the membrane; therefore the VC virtually worked at the boundary as the scanning probe of the SECM to observe the wet contact interface. We acquired topographic and electrochemical images of micro polystyrene spheres and a DPPC/TR-DPPE supported lipid bilayer by measuring the probe current in the sample interface. The imaging results suggested spatial resolutions of ∼180 nm width and ∼90 nm depth in a topographical image could be captured using this VC-SECM system.

Towards a Quantitative Single Particle Characterization by Super Resolution Microscopy: From Virus Structures to Antivirals Design.

In the last year the COVID19 pandemic clearly illustrated the potential threat that viruses pose to our society. The characterization of viral structures and the identification of key proteins involved in each step of the cycle of infection are crucial to develop treatments. However, the small size of viruses, invisible under conventional fluorescence microscopy, make it difficult to study the organization of protein clusters within the viral particle. The applications of super-resolution microscopy have skyrocketed in the last years, converting this group into one of the leading techniques to characterize viruses and study the viral infection in cells, breaking the diffraction limit by achieving resolutions up to 10 nm using conventional probes such as fluorescent dyes and proteins. There are several super-resolution methods available and the selection of the right one it is crucial to study in detail all the steps involved in the viral infection, quantifying and creating models of infection for relevant viruses such as HIV-1, Influenza, herpesvirus or SARS-CoV-1. Here we review the use of super-resolution microscopy (SRM) to study all steps involved in the viral infection and antiviral design. In light of the threat of new viruses, these studies could inspire future assays to unveil the viral mechanism of emerging viruses and further develop successful antivirals against them.

Transformable Ultrasonic Array Transducer for Multiscale Imaging and Beamforming

Conventional ultrasound probes have inherent limitations in some application scenarios. Because of their fixed shapes and sizes, they can hardly pass through small orifices to examine the target closely. With the recent development of microelectromechanical systems and flexible electronic technologies, collapsible and self-assembling devices are being considered as a potential approach to address this problem. This article presents an innovative transformable ultrasonic transducer (TUT), which can transform between a one-dimensional (1-D) linear array and a 2-D planar array with the ability of switching between different functions including 2-D/3-D imaging and high-intensity focused ultrasound beamforming. The transforming process is accomplished with a specially designed flexible printed circuit board inspired by a paper-folding mechanism. The electrical and acoustic properties of the developed transducer along with the acoustic field distribution in its different forms have been characterized. The 2-D/3-D imaging performances of the TUT have been also evaluated under 1-D and 2-D configurations, respectively. In addition, the performance of a focused concave transforming mode has been also discussed. The evaluation results suggest that TUT can maintain its performance under different structures with precise transforming control. The TUT device has the potential to considerably expand the applications of industrial and clinical ultrasound.

The Luminescence and optical behavior of Cd1-xWxSe QDs synthesized using microwave assisted hydrothermal approach for bioimaging applications

Semiconducting quantum dots are light-emitting nanocrystals that have been flourished as novel kind of fluorescent label for biomedical diagnostics and biomolecular imaging. In comparison to conventional fluorescence probe, quantum dots have exceptional optoelectronic characteristics, narrow and symmetric emission spectra, size-tunable light emission, and wide absorption spectrum that permit the concurrent excitations of numerous fluorescent colors. Furthermore, quantum dots are substantially bright and have high resistance to photo bleaching compared with fluorescent proteins and organic dye. Here, a new family of quantum dots based on Cd1-xWxSe nanocrystals using microwave assisted hydrothermal route has been developed. The X-ray demonstrated the cubic phase of these nanocrystals and the expansion of their lattice dimensions due to the incorporation of W dopant. The TEM inspected the increase of the sizes of the Cd1-xWxSe QDs from 3.5 nm to 10.8 nm due to the increase of W dopant. The W dopant caused redshift of the absorption spectra and reduction of the bandgap from 2.54 eV to 2.32 eV. The inclusion of W dopant in the CdSe improved the intensity of luminescence emission by 8 times with narrow bandwidth and quantum yield of 89 %. These auspicious properties pave the way to use the Cd1-xWxSe QDs as fluorescent label for biomedical diagnostics and biomolecular imaging.

Epidemiology of molecular probes in Xpert MTB/RIF assay in Khyber Pakhtunkhwa, Pakistan.

Regardless of a plethora of advanced diagnostics, TB and drug resistance remains a principal killer. We proposed gold nanoparticles (AuNPs) attached with probes to enhance the efficiency of GeneXpert MTB/RIF assay instead of conventional dye probes for molecular detection. A total of 15,000 samples were collected from TB suspects and subjected to Xpert MTB/RIF assay, where 6800 (45.3%) were detected as MTB positive, 280 (4.3%) were detected to harbor mutations in the RRDR, while invalid /errors were found in 690 (4.6%) cases. The mutations were detected by probe E, 199 (71.1%), while probes B and D, 30 and 26 (10% and 9%), respectively. In the Xpert MTB/RIF Assay were found mutations picked by probes E and B codons 529-533 (71%) and 512-518 (10%), respectively. The fast-rising works of TB nano-diagnostics, of Xpert probes, may improve by the applications of gold nanoparticle probes.

Optical penetration of surface-enhanced micro-scale spatial offset Raman spectroscopy in turbid gel and biological tissue

The limited penetration of photons in biological tissue restricts the deep-tissue detection and imaging application. The micro-scale spatially offset Raman spectroscopy (micro-SORS) with an optical fiber probe, colleting photons from deeper regions by offsetting the position of laser excitation from the collection optics in a range of hundreds of microns, shows great potential to be integrated with endoscopy for inside-body noninvasive detection by circumventing this restriction, particularly with the combination of surface-enhanced Raman spectroscopy (SERS). However, a detailed tissue penetration study of micro-SORS in combination with SERS is still lacking. Herein, we compared the signal decay of enhanced Raman nanotags through the tissue phantom of agarose gel and the biological tissue of porcine muscle in the near-infrared (NIR) region using a portable Raman spectrometer with a micro-SORS probe (2.1[Formula: see text]mm in diameter) and a conventional hand-held probe (9.7[Formula: see text]mm in diameter). Two kinds of Raman nanotags were prepared from gold nanorods decorated with the nonresonant (4-nitrobenzenethiol) or resonant Raman reporter molecules (IR-780 iodide). The SERS measurements show that the penetration depths of two Raman nanotags are both over 2[Formula: see text]cm in agarose gel and 3[Formula: see text]mm in porcine muscle. The depth could be improved to over 4[Formula: see text]cm in agarose gel and 5[Formula: see text]mm in porcine tissue when using the micro-SORS system. This demonstrates the superiority of optical-fiber micro-SORS system over the conventional Raman detection for the detection of nanotags in deeper layers in the turbid medium and biological tissue, offering the possibility of combining the micro-SORS technique with SERS for noninvasive in vivo endoscopy-integrated clinical application.

Angular dependence measurements of Magnum-PSI plasmas using MAST-U angled-tip Langmuir probes

Abstract Measurements made using flush-mounted Langmuir probes in tokamaks are difficult to interpret when operating at grazing angles of magnetic field incidence due to the effects of sheath expansion on the probe collection area. The Super-X divertor on the upgraded Mega Amp Spherical Tokamak (MAST-U) can have very shallow angles of magnetic field incidence to plasma facing components (1–10 ° ), making the use of conventional flush-mounted probes problematic. A novel probe tip geometry, based on the angled-tip design used successfully on JET and DIII-D, has therefore been used in MAST-U to mitigate sheath expansion effects by increasing the projected probe extent. To verify whether the new design of probe tip allows temperature ( T e ) and density ( n e ) measurements to be performed accurately at low angles of incidence, a 4-probe array based on this design was used on Magnum-PSI. Parameter scans were made on a range of hydrogen plasmas in conditions comparable to those expected in MAST-U. Plasma parameters were extracted from the measured IV characteristics - using a novel fitting approach which minimised a goodness-of-fit parameter ( T e δ T e ) - and compared to Magnum-PSI Thomson scattering measurements. The measured plasma parameters show that the MAST-U angled-tip design seems to successfully mitigate the effects of sheath expansion at low angles of magnetic field incidence. The standard MAST-U Langmuir probe also shows an apparent upper operational limit of θ = 8 ° . This covers the vast majority of expected plasma configurations in MAST-U when running both conventional and Super-X configurations.

A de novo strategy to develop NIR precipitating fluorochrome for long-term in situ cell membrane bioimaging

Cell membrane-targeted bioimaging is a prerequisite for studying the roles of membrane-associated biomolecules in various physiological and pathological processes. However, long-term in situ bioimaging on the cell membrane with conventional fluorescent probes leads to diffusion into cells from the membrane surface. Therefore, we herein proposed a de novo strategy to construct an antidiffusion probe by integrating a fluorochrome characterized by strong hydrophobicity and low lipophilicity, with an enzyme substrate to meet this challenge. This precipitating fluorochrome HYPQ was designed by conjugating the traditionally strong hydrophobic solid-state fluorochrome 6-chloro-2-(2-hydroxyphenyl) quinazolin-4(3H)-one (HPQ) with a 2-(2-methyl-4H-chromen-4-ylidene) malononitrile group to obtain closer stacking to lower lipophilicity and elongate emission to the far-red to near-infrared wavelength. As proof-of-concept, the membrane-associated enzyme γ-glutamyltranspeptidase (GGT) was selected as a model enzyme to design the antidiffusion probe HYPQG. Then, benefiting from the precipitating and stable signal properties of HYPQ, in situ imaging of GGT on the membrane was successfully realized. Moreover, after HYPQG was activated by GGT, the fluorescence signal on the cell membrane remained unchanged, with incubation time even extending to 6 h, which is significant for in situ monitoring of enzymatic activity. In vivo testing subsequently showed that the tumor region could be accurately defined by this probe after long-term in situ imaging of tumor-bearing mice. The excellent performance of HYPQ indicates that it may be an ideal alternative for constructing universal antidiffusion fluorescent probes, potentially providing an efficient tool for accurate imaging-guided surgery in the future.

TSV fault contactless testing method based on group delay

ABSTRACT As through silicon via (TSV) in three-dimensional (3-D) stacked integrated circuit (IC) has become micro-nanosized, the conventional wafer probe technology cannot fulfil the current detection requirements, so new testing techniques are urgently needed. In this paper, we present amethod for TSV contactless testing based on group delay. The group delay-based mixed testing stimulus is applied to the pending testing TSV through acontactless probe, and then output response is obtained by adetector. The crest factor (CF) is measured and calculated, and fault diagnosis is performed according to the CF difference between faultless and faulty TSV. The void fault of the signal-ground-TSV (SG-TSV) is also detected by the contactless testing method, and its fault function is obtained. The result shows that aresistive open circuit fault as small as several ohms can be detected through this approach. Finally, the fault testing resolution is improved by adjusting the modulation mode of the multi-tone signal.

An organelle-directed chemical ligation approach enables dual-color detection of mitophagy

ABSTRACT Dysfunctional organelles and defective turnover of organelles are engaged in multiple human diseases, but are elusive to image with conventional organelle probes. To overcome this, we developed intra-mitochondrial CLICK to assess mitophagy (IMCLAM), using a pair of conventional ΔΨm probes, where each probe alone fails to track dysfunctional mitochondria. The in situ formed optical triad is stably trapped in mitochondria without resorting to ΔΨm. Utilizing an acidity-responsive ΔΨm probe, IMCLAM enabled fluorescence-on detection of mitophagy by sensing pH acidification upon delivery of mitochondria into lysosomes. Moreover, we applied IMCLAM to assay mitophagy induced by pharmacological compounds in living cells and wild-type zebrafish embryos. Thus, IMCLAM offers a simplified tool to study mitochondria and mitophagy and provide a basis for screening mitophagy-inducing compounds. Abbreviations: CCCP, carbonyl cyanide m-chlorophenylhydrazone; IMCLAM, intra-mitochondrial CLICK to assess mitophagy; ROX, X-rhodamine; SPAAC, stain-promoted azide-alkyne Click Chemistry; TPP, triphenylphosphonium.

Lanthanide-Doped Upconversion Nanoparticles for Super-Resolution Microscopy.

Super-resolution microscopy offers a non-invasive and real-time tool for probing the subcellular structures and activities on nanometer precision. Exploring adequate luminescent probes is a great concern for acquiring higher-resolution image. Benefiting from the atomic-like transitions among real energy levels, lanthanide-doped upconversion nanoparticles are featured by unique optical properties including excellent photostability, large anti-Stokes shifts, multicolor narrowband emissions, tunable emission lifetimes, etc. The past few years have witnessed the development of upconversion nanoparticles as probes for super-resolution imaging studies. To date, the optimal resolution reached 28 nm (λ/36) for single nanoparticles and 82 nm (λ/12) for cytoskeleton structures with upconversion nanoparticles. Compared with conventional probes such as organic dyes and quantum dots, upconversion nanoparticle-related super-resolution microscopy is still in the preliminary stage, and both opportunities and challenges exist. In this perspective article, we summarized the recent advances of upconversion nanoparticles for super-resolution microscopy and projected the future directions of this emerging field. This perspective article should be enlightening for designing efficient upconversion nanoprobes for super-resolution imaging and promote the development of upconversion nanoprobes for cell biology applications.

High-efficiency scattering probe design for s-polarized near-field microscopy

In a conventional scattering-type scanning near-field optical microscopy setup, the atomic force microscope probe is unable to effectively couple with s-polarized light, resulting in low signal and limited in-plane sensitivity. This study aims to investigate a high-resolution probe with enhanced responsivity to both s- and p-polarized light. Full-wave electromagnetic method of moments simulations are utilized. Simulated near-field spectra on prototypical materials (SiO2, Si, SrTiO3), as well as simulated raster scans of a gap nanoantenna, indicate a two order of magnitude increase of the scattering signal for s-polarized incident and detection scheme compared to the conventional probe.

Comparative assessment of conventional periodontal probes and CEJ handpiece of electronic probes in the diagnosis and primary care of periodontal disease.

Objectives:Conventional probes (CPs) have been considered acceptable as diagnostic tools to measure probing pocket depth (PPD) and clinical attachment level (CAL) but are affected by multiple variables. Electronic probes (EPs) provide controlled force, digital readout and data storage in computers. The objectives were to compare the reproducibility in the measurement of PPD and CAL by CP and the newly introduced CEJ handpiece of EP and intra-examiner and inter-examiner errors done in two phases.Methods and Material:Selected 720 periodontal sites in 1st molar of 30 persons with chronic periodontitis ≤4 mm and >4 mm pockets were analysed by two trained investigators in two phases at 2 hours difference by CP and CEJ handpiece of EP. Standard deviation, mean difference, correlation coefficient, P value and student 't' test were done to analyse data.Results:The intra- examiner and inter-examiner analyses revealed that Pearson's correlation coefficient was above 0.080 and 0.722 in the ≤4 mm and >4 mm pockets, respectively. Mean difference was not statistically significant in both groups except in the intra- examiner findings in the 2nd phase. Interprobe analysis depicted a standard error of mean of <0.03 in ≤4 mm pockets, whereas it varied from 0.047–0.056 in >4 mm pockets.Conclusion:In conclusion, EP is advantageous for research purposes by providing automatic recording and long-term maintenance of data storage without the need of an assistant and patient education and motivation, whereas CP appears to be more useful in routine periodontal examination.

Recognition of double-stranded DNA using LNA-modified toehold Invader probes.

Development of molecules capable of binding to specific sequences of double-stranded (ds) DNA continues to attract considerable interest, as this may yield useful tools for applications in life science, biotechnology, and medicine. We have previously demonstrated sequence-unrestricted of dsDNA using Invader probes, i.e., DNA duplexes that are energetically activated through incorporation of +1 interstrand zipper arrangements of O2'-intercalator-functionalized RNA monomers. Nonetheless, recognition of extended dsDNA target regions remains challenging due to the high stability of the corresponding probes. To address this, we introduce toehold Invader probes, i.e., Invader probes with 5'-single-stranded overhangs. This design provides access to probes with shortened double-stranded segments, which facilitates probe denaturation. The single-stranded overhangs can, furthermore, be modified with affinity-enhancing modifications like LNA (locked nucleic acid) monomers to additionally increase target affinity. Herein, we report the biophysical and dsDNA-targeting properties of different toehold Invader designs and compare them to conventional Invader probes. LNA-modified toehold Invader probes display promising recognition characteristics, including greatly improved affinity to dsDNA, excellent binding specificity, and fast recognition kinetics, which enabled recognition of chromosomal DNA targets that have proven refractory to recognition by conventional Invader probes. Thus, toehold Invader probes represent another step toward a robust, oligonucleotide-based approach for sequence-unrestricted dsDNA-recognition.

An Ultrawideband Magnetic Probe With High Electric Field Suppression Ratio

In this article, an ultrawideband magnetic probe with high electric field suppression ratio (EFSR) is proposed. The probe has three parts: the loop part, the transmission part, and the head part. Shield metal sheets are designed in the loop part to enhance EFSR. The tapered transmission line in the transmission part and the quasi coaxial transition in the head part are adopted for impedance matching between the induction loop and the grounded coplanar waveguide (GCPW) in the head part. Then, segmented resistance–inductance–capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RLC</i> ) equivalent circuit models of the probe are proposed for magnetic field coupling and electric field coupling, which are suitable for accurate modeling and efficient optimization of the magnetic probe. In addition, the coupling capacitors between the shield metal sheets and the device under test (DUT) are extracted utilizing the conformal transforming method with analytical formulas. Finally, this magnetic probe is fabricated under printed circuit board (PCB) technology and used in measuring the magnetic field distribution. The measurement and simulation results agree well. The probe has a bandwidth of 100 MHz–30 GHz and an EFSR of higher than 21 dB. Compared with the conventional probe with similar bandwidth, the proposed probe can improve the EFSR by 9 dB.

Improving Flaw Detection through Integration of a Novel Eddy Current Probe with Fluxgate Magnetic Sensor

The objective of this study is to improve the detection capability of eddy current testing by developing a novel eddy current probe. The developed probe is composed of six excitation coils made at different areas and suitably aligned with a single-axis sensitive DRV425EVM fluxgate sensor. The distribution of magnetic field intensity and eddy current density of the developed probe were calculated using ANSYS 2019R3 (Maxwell-3D) simulation software. The simulation results revealed that the new probe design enhances the detection capability and the spatial resolution compared to the conventional design that uses a double-D coil. Experiments were carried out using the double-D coil as reference, under the same input parameter to detect flaws with various sizes and locations. The experimental results validated the simulation results and showed that the sensitivity and spatial resolution of the developed sensor are much better than those obtained by the conventional probe.

Phased array probe for the inspection of large steel forgings

Reliable inspection of large steel forgings is a significant problem across multiple industries. When the dimensions of forgings are at least 1000 mm in each direction, ultrasonic phased array inspection becomes difficult because conventional probes are not designed to transmit and focus acoustic energy over such large distances. Using simulations and experiments, this article aims to discuss the possibilities and limitations of phased array imaging of large forged steel ingots. Simulations were used to design a transducer based on the reflected amplitude, as well as the lateral and axial resolutions of defects in a 1000 mm thick block. It was shown that when limiting the aperture to allow easy handling in an industrial inspection setting, the lateral resolution and the reflected amplitude were the main limitations. Increasing the element width maximizes the energy transmitted into the material, but it also moves elements away from each other, thus reducing the lateral resolution. Based on the simulations, an experimental phased array transducer was manufactured with eight elements of 9.25 × 22.5 mm. The probe was used to perform measurements and generate total focusing method images of three different at a depth of 370 mm in a 776 mm forged steel block.

Lanthanide doped luminescence nanothermometers in the biological windows: strategies and applications.

The development of lanthanide-doped non-contact luminescent nanothermometers with accuracy, efficiency and fast diagnostic tools attributed to their versatility, stability and narrow emission band profiles has spurred the replacement of conventional contact thermal probes. The application of lanthanide-doped materials as temperature nanosensors, excited by ultraviolet, visible or near infrared light, and the generation of emissions lying in the biological window regions, I-BW (650 nm-950 nm), II-BW (1000 nm-1350 nm), III-BW (1400 nm-2000 nm) and IV-BW (centered at 2200 nm), are notably growing due to the advantages they present, including reduced phototoxicity and photobleaching, better image contrast and deeper penetration depths into biological tissues. Here, the different mechanisms used in lanthanide ion-doped nanomaterials to sense temperature in these biological windows for biomedical and other applications are summarized, focusing on factors that affect their thermal sensitivity, and consequently their temperature resolution. Comparing the thermometric performance of these nanomaterials in each biological window, we identified the strategies that allow boosting of their sensing properties.

Aggregation induced bright organic luminogens: Design strategies, advanced bio-imaging and theranostic applications.

The concept of aggregation-induced emission (AIE) in purely organic luminescent molecules has drawn wide attention in the last two decades. Despite the many challenges, AIE-probes have opened versatile opportunities in many research fields. In particular, the emerging functional properties of room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) have boosted the unique features of AIE luminogens (AIEgens). Thus, these luminescent materials extended the utility in sensing, imaging, optoelectronics and theranostic applications in biological field over the conventional fluorescent probe. Unlike the sensitivity of triplet state by oxygen and moisture, the long-lived phosphorescence and delayed fluorescence resulting from the enhanced intersystem crossing (ISC) and reverse intersystem crossing (RISC) from excited triplet state (T1) to excited singlet state (S1) in these luminophores gives rise to long lifetimes ranging from nanoseconds to milliseconds even up to seconds. As compared to traditional fluorescence molecules advanced AIE probes show high contrast imaging and deeper penetration depth, which have been demonstrated through near infrared I and II (NIR-I & NIR-II) fluorescence imaging, room temperature after-glow imaging and photoacoustic imaging. This chapter highlights the recent developments and principle of the efficient design of AIE probe with multi-functional properties evolved with new strategies for translational applications via fluorescence imaging, photoacoustic imaging and image-guided photodynamic/photothermal therapy (PDT/PTT) including future opportunities for AIEgens to advance the overall biomedical field.

AIE materials for nucleus imaging.

Emergence of a captivating phenomenon aggregation induced emission (AIE) in the early years of 21st century attracted worldwide researchers. In the last two decades various novel AIE active biocompatible small molecules, macromolecules and polymers have been developed for diverse biomedical applications. Imaging of specific organelle such as mitochondria, ribosomes, nuclei and many others play important in the controlling and successful treatment of various diseases. Conventional luminescent probe molecules used in the imaging at cellular or subcellular level exhibit very weak emission on dispersion or on aggregation in aqueous media. AIE luminogens development is indispensable to overcome the notorious aggregation-caused quenching (ACQ) issue inherited by conventional fluorophores. In the present chapter we mostly highlighted over one decade development of various AIE active luminogens utilized for imaging of cell nucleus, nucleon and nucleic acids. The development of those AIE luminogens exhibits promising results in the early diagnosis of cancer diseases.