Diagnostic Probes Research Articles

Nanosized Fluorescent Diagnostic Probes Consisting of Single-domain Antibodies Conjugated with Quantum Dots

In state-of-the-art nanoprobes, monoclonal antibodies (mAbs) used as capture molecules are often too large for nanoparticle targeting and are randomly orientated relative to the nanoparticle surface due to the inherent characteristics of the procedure for their fabrication. Here, we are reviewing our recent publications on the smallest known nanoprobes consisting of quantum dots (QDs) and single-domain antibodies (sdAbs), low-molecular-weight fragments of llama immunoglobulins produced in E. coli and attached to the QDs in a strictly specified orientation. The nanoprobe developed has a hydrodynamic diameter smaller than 12nm and consists of four sdAbs and a QD. They are sensitive and specific enough to accurately estimate even a small number of cells with target biomarkers by means of flow cytometry. The small size of the probes enables immunohistochemical staining much deeper areas of tissue samples as compared to standard probes. Tests with clinical biopsies have shown that sdAb–QD probes provide the same or higher quality of biomarker detection compared to the gold-standard histochemical approach. The nanoprobes developed have many implications for quick multiplexed diagnosis and FRET-based detection platforms.

Current–voltage characteristics of a flat probe in a rarified plasma flow

Mathematical and numerical models of a collision-free plasma flow about the flat probe are developed. The current–voltage characteristics of flat probes located along and transverse across the flow, as well as the distributions of the current density over the probe width, are obtained. The numerical simulation results might be applied in probe diagnostics of plasma flows.

High-current impulse magnetron discharge with liquid target

Abstract Impulse magnetron with a liquid cathode operated in copper vapour without the working gas has been experimentally investigated. Stable discharge regimes were obtained through applying the high-current pulses over a 1.5 kW direct current magnetron discharge operated on a liquid copper target. The current–voltage characteristic of the discharge as well as the temporal evolution of the impulse current–voltage relations have been acquired for a constant magnetic field value on the target's surface. The pulsed Langmuir probe diagnostics has been utilized to measure the plasma parameters along the symmetry axis. The pulsed probe diagnostics revealed strong dependences of electron temperature and plasma density on the distance to the target's surface. Electron temperature measured 5 cm away from the target did not exceed 2 eV, and reduced down to 1 eV at longer distances. The maximum value of plasma density along the target's centerline was 2 × 1013 cm− 3, as measured at a distance of 5 cm.

Comparative analyses of plasma probe diagnostics techniques

The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much as an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.

Molecular Imaging of Pancreatic Cancer with Antibodies

Development of novel imaging probes for cancer diagnostics remains critical for early detection of disease, yet most imaging agents are hindered by suboptimal tumor accumulation. To overcome these limitations, researchers have adapted antibodies for imaging purposes. As cancerous malignancies express atypical patterns of cell surface proteins in comparison to noncancerous tissues, novel antibody-based imaging agents can be constructed to target individual cancer cells or surrounding vasculature. Using molecular imaging techniques, these agents may be utilized for detection of malignancies and monitoring of therapeutic response. Currently, there are several imaging modalities commonly employed for molecular imaging. These imaging modalities include positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance (MR) imaging, optical imaging (fluorescence and bioluminescence), and photoacoustic (PA) imaging. While antibody-based imaging agents may be employed for a broad range of diseases, this review focuses on the molecular imaging of pancreatic cancer, as there are limited resources for imaging and treatment of pancreatic malignancies. Additionally, pancreatic cancer remains the most lethal cancer with an overall 5-year survival rate of approximately 7%, despite significant advances in the imaging and treatment of many other cancers. In this review, we discuss recent advances in molecular imaging of pancreatic cancer using antibody-based imaging agents. This task is accomplished by summarizing the current progress in each type of molecular imaging modality described above. Also, several considerations for designing and synthesizing novel antibody-based imaging agents are discussed. Lastly, the future directions of antibody-based imaging agents are discussed, emphasizing the potential applications for personalized medicine.

Recent Advances in the Development and Application of Radiolabeled Kinase Inhibitors for PET Imaging.

Over the last 20 years, intensive investigation and multiple clinical successes targeting protein kinases, mostly for cancer treatment, have identified small molecule kinase inhibitors as a prominent therapeutic class. In the course of those investigations, radiolabeled kinase inhibitors for positron emission tomography (PET) imaging have been synthesized and evaluated as diagnostic imaging probes for cancer characterization. Given that inhibitor coverage of the kinome is continuously expanding, in vivo PET imaging will likely find increasing applications for therapy monitoring and receptor density studies both in- and outside of oncological conditions. Early investigated radiolabeled inhibitors, which are mostly based on clinically approved tyrosine kinase inhibitor (TKI) isotopologues, have now entered clinical trials. Novel radioligands for cancer and PET neuroimaging originating from novel but relevant target kinases are currently being explored in preclinical studies. This article reviews the literature involving radiotracer design, radiochemistry approaches, biological tracer evaluation and nuclear imaging results of radiolabeled kinase inhibitors for PET reported between 2010 and mid-2015. Aspects regarding the usefulness of pursuing selective vs. promiscuous inhibitor scaffolds and the inherent challenges associated with intracellular enzyme imaging will be discussed.

From the Macro to the Micro: Gel Mapping to Differentiate between Sporozoites of Two Immunologically Distinct Strains of Eimeria maxima (Strains M6 and Guelph)

Two immunologically distinct strains of E. maxima were examined in this study: the M6 strain and the Guelph strain. The differential expression between the sporozoites of the two strains of E. maxima was determined by image analysis of 100 μg of protein from each strain separated by standard one- and conventional two-dimensional polyacrylamide gel electrophoresis. In addition to differences in both molecular weight and the electrophoretic mobility, differences in the intensity of polypeptide bands for example, GS 136.4 and M6 169 were explored. Pooled gels were prepared from each strain. A representative 2D-PAGE gel spanning a non-linear pH range of 3–10 of E. maxima strain M6 consisted of approximately 694 polypeptide spots with about 67 (9.6%) of the polypeptide spots being unique relative to the other strain. E. maxima strain GS had about 696 discernable polypeptide spots with 69 spots (9.9%) that differed from those of the M6 strain. In-depth characterization of the variable polypeptide spots; unique polypeptide spots (absence or presence) and shared polypeptide spots with modifications may lead to novel vaccine target in the form of multi-component, multi-stage, multi-immunovariant strains, multi-species subunit vaccine, and diagnostic probe for E. maxima.

Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

Quantitative assessments of glycolysis from single cells.

The most common positron emission tomography (PET) radio-labeled probe for molecular diagnostics in patient care and research is the glucose analog, 2-deoxy-2-[F-18]fluoro-D-glucose (18F-FDG). We report on an integrated microfluidics-chip/beta particle imaging system for in vitro18F-FDG radioassays of glycolysis with single cell resolution. We investigated the kinetic responses of single glioblastoma cancer cells to targeted inhibitors of receptor tyrosine kinase signaling. Further, we find a weak positive correlation between cell size and rate of glycolysis.

Study of the feasibility of distributed cathodic arc as a plasma source for development of the technology for plasma separation of SNF and radioactive wastes

One of the key problems in the development of plasma separation technology is designing a plasma source which uses condensed spent nuclear fuel (SNF) or nuclear wastes as a raw material. This paper covers the experimental study of the evaporation and ionization of model materials (gadolinium, niobium oxide, and titanium oxide). For these purposes, a vacuum arc with a heated cathode on the studied material was initiated and its parameters in different regimes were studied. During the experiment, the cathode temperature, arc current, arc voltage, and plasma radiation spectra were measured, and also probe measurements were carried out. It was found that the increase in the cathode heating power leads to the decrease in the arc voltage (to 3 V). This fact makes it possible to reduce the electron energy and achieve singly ionized plasma with a high degree of ionization to fulfill one of the requirements for plasma separation of SNF. This finding is supported by the analysis of the plasma radiation spectrum and the results of the probe diagnostics.

Study of ablation and implosion stages in wire arrays using coupled ultraviolet and X-ray probing diagnostics

Star and cylindrical wire arrays were studied using laser probing and X-ray radiography at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. The Leopard laser provided backlighting, producing a laser plasma from a Si target which emitted an X-ray probing pulse at the wavelength of 6.65 Å. A spherically bent quartz crystal imaged the backlit wires onto X-ray film. Laser probing diagnostics at the wavelength of 266 nm included a 3-channel polarimeter for Faraday rotation diagnostic and two-frame laser interferometry with two shearing interferometers to study the evolution of the plasma electron density at the ablation and implosion stages. Dynamics of the plasma density profile in Al wire arrays at the ablation stage were directly studied with interferometry, and expansion of wire cores was measured with X-ray radiography. The magnetic field in the imploding plasma was measured with the Faraday rotation diagnostic, and current was reconstructed.

High-current channel characteristics in high-pressure gas

Research results for discharge initiated by wire explosion in hydrogen at initial pressures up to 30 MPa and current amplitudes up to 1 MA are presented. Measurements of channel radius oscillation amplitude by magnetic probe diagnostics were made to calculate channel plasma parameters. The amplitude of channel radius oscillations was observed to decrease with growth of initial gas pressure and to increase with growth of current amplitude.

진단용 초음파 Probe 및 Mode 변화에 따른 초음파 주사빈도가 콩나물 발아 과정에 미치는 영향

진단용 초음파 Probe 및 Mode 변화에 따른 초음파 주사빈도가 콩나물 발아 과정에 미치는 영향

Single element of the matrix source of negative hydrogen ions: Measurements of the extracted currents combined with diagnostics.

Combining measurements of the extracted currents with probe and laser-photodetachment diagnostics, the study is an extension of recent tests of factors and gas-discharge conditions stimulating the extraction of volume produced negative ions. The experiment is in a single element of a rf source with the design of a matrix of small-radius inductively driven discharges. The results are for the electron and negative-ion densities, for the plasma potential and for the electronegativity in the vicinity of the plasma electrode as well as for the currents of the extracted negative ions and electrons. The plasma-electrode bias and the rf power have been varied. Necessity of a high bias to the plasma electrode and stable linear increase of the extracted currents with the rf power are the main conclusions.

99mTc-phytate as a diagnostic probe for assessing inflammatory reaction in malignant tumors.

Once administered intravenously, technetium-99m (99mTc)-labeled phytate binds to calcium in the serum and behaves as a nanoparticle. On the basis of the high permeability of the tumor vasculature, 99mTc-phytate is expected to leak and accumulate specifically in inflammatory cells. The aim of this study was to evaluate the potential of 99mTc-phytate in assessing the degree of inflammation in Ehrlich solid tumors in mice. 99mTc-phytate was prepared by adding pertechnetate to a solution containing phytic acid and stannous chloride. The blood half-life of this particle following intravenous injection was determined using blood samples from healthy animals, whereas its size was measured by photon correlation spectroscopy. Scintigraphic imaging and biodistribution studies were carried out in tumor-bearing mice at 30 min and 2 h after injection. The average size of the particles was in the range of 200 nm, suggesting that they are capable of passively passing through fenestrations in tumor vessels, which are 200-2000 nm in size. The blood half-life for 99mTc-phytate was found to be 2.1 min, a result that is in agreement with previous studies. Data from tumor-bearing mice showed high tumor uptake at 2 h after 99mTc-phytate administration. As a result, a high tumor-to-muscle ratio was achieved (T/M = 25.9 ± 7.54). These findings indicate that 99mTc-sodium phytate has promising properties for identifying the type of tumor. This approach will have significant implications for characterizing tumor biology and treatment of malignant lesions.

Application of Si and SiO2 Etching Mechanisms in CF4/C4F8/Ar Inductively Coupled Plasmas for Nanoscale Patterns.

An investigation of the etching characteristics and mechanism for both Si and SiO2 in CF4/C4F8/Ar inductively coupled plasmas under a constant gas pressure (4 mTorr), total gas flow rate (40 sccm), input power (800 W), and bias power (150 W) was performed. It was found that the variations in the CF4/C4F8 mixing ratio in the range of 0-50% at a constant Ar fraction of 50% resulted in slightly non-monotonic Si and SiO2 etching rates in CF4-rich plasmas and greatly decreasing etching rates in C4F8-rich plasmas. The zero-dimensional plasma model, Langmuir probe diagnostics, and optical emission spectroscopy provided information regarding the formation-decay kinetics for the plasma active species, along with their densities and fluxes. The model-based analysis of the etching kinetics indicated that the non-monotonic etching rates were caused not by the similar behavior of the fluorine atom density but rather by the opposite changes of the fluorine atom flux and ion energy flux. It was also determined that the great decrease in both the Si and SiO2 etching rates during the transition from the CF4/Ar to C4F8/Ar gas system was due to the deposition of the fluorocarbon polymer film.

GMC COLLISIONS AS TRIGGERS OF STAR FORMATION. I. PARAMETER SPACE EXPLORATION WITH 2D SIMULATIONS

We utilize magnetohydrodynamic (MHD) simulations to develop a numerical model for GMC-GMC collisions between nearly magnetically critical clouds. The goal is to determine if, and under what circumstances, cloud collisions can cause pre-existing magnetically subcritical clumps to become supercritical and undergo gravitational collapse. We first develop and implement new photodissociation region (PDR) based heating and cooling functions that span the atomic to molecular transition, creating a multiphase ISM and allowing modeling of non-equilibrium temperature structures. Then in 2D and with ideal MHD, we explore a wide parameter space of magnetic field strength, magnetic field geometry, collision velocity, and impact parameter, and compare isolated versus colliding clouds. We find factors of ~2-3 increase in mean clump density from typical collisions, with strong dependence on collision velocity and magnetic field strength, but ultimately limited by flux-freezing in 2D geometries. For geometries enabling flow along magnetic field lines, greater degrees of collapse are seen. We discuss observational diagnostics of cloud collisions, focussing on 13CO(J=2-1), 13CO(J=3-2), and 12CO(J=8-7) integrated intensity maps and spectra, which we synthesize from our simulation outputs. We find the ratio of J=8-7 to lower-J emission is a powerful diagnostic probe of GMC collisions.

Extracellular Nucleic Acids in Urine: Sources, Structure, Diagnostic Potential

Cell-free nucleic acids (cfNA) may reach the urine through cell necrosis or apoptosis, active secretion of nucleic acids by healthy and tumor cells of the urinary tract, and transport of circulating nucleic acids (cir- NA) from the blood into primary urine. Even though urinary DNA and RNA are fragmented, they can be used to detect marker sequences. MicroRNAs are also of interest as diagnostic probes. The stability of cfNA in the urine is determined by their structure and packaging into supramolecular complexes and by nuclease activity in the urine. This review summarizes current data on the sources of urinary cfNA, their structural features, diagnostic potential and factors affecting their stability.

Plasma probe characteristics in low density hydrogen pulsed plasmas

Probe theories are only applicable in the regime where the probe’s perturbation of the plasma can be neglected. However, it is not always possible to know, a priori, that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas on a similarly short time scale as investigated here. Indeed, in the case studied here, probe measurements would lead to, either a large overestimate, or underestimate of the plasma density, depending on the chosen probe theory. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements. However, limiting cases of probe theories can be used to estimate upper and lower bounds on plasma densities. These theories include and neglect orbital motion, respectively, with different collisional terms leading to intermediate estimates.

Characterization of medical ultrasound fields using modeling with a boundary condition obtained from measurements

Numerical modeling is becoming an important metrological tool for accurate characterization of ultrasound fields generated by medical transducers in water and in situ. While acoustic propagation equations are well established, setting a boundary condition relevant to the experiment still remains a critical problem. Two methods differing in complexity are described to address this problem. The first method comprises 3D simulations of the Westervelt equation with a boundary condition determined from acoustic holography measurements. The second, simpler method utilizes simulations based either on the KZK or Westervelt equation with an equivalent source boundary condition obtained by matching linear simulations to low-amplitude beam profiles along and transverse to the axis of the source. Calculations with both methods are compared to fiber optic hydrophone measurements of 2D phased therapeutic arrays, a 128-element diagnostic probe, and strongly focused single-element transducers. It is shown that the 3D Westervelt model with holographic boundary condition can accurately simulate the entire nonlinear ultrasound field. The simplified methods based on an equivalent source are shown to give accurate results in the focal zone of the transducers, even when shocks are present in the focal waveform. [Work supported by NIH EB7643, EB016118, DK043881, and RSF 14-12-00974.]