NADH elevation during chronic hypoxia leads to VHL-mediated HIF-1α degradation via SIRT1 inhibition.

BACKGROUND: Under conditions of hypoxia, cancer cells with hypoxia inducible factor-1α (HIF-1α) from heterogeneous tumor cells show greater aggression and progression in an effort to compensate for harsh environmental conditions. Extensive study on the stability of HIF-1α under conditions of acute hypoxia in cancer progression has been conducted, however, understanding of its involvement during the chronic phase is limited. METHODS: In this study, we investigated the effect of SIRT1 on HIF1 stability in a typical chronic hypoxic conditon that maintains cells for 24 h under hypoxia using Western blotting, co-IP, measurement of intracellular NAD + and NADH levels, semi-quantitative RT-PCR analysis, invasion assay, gene knockdown. RESULTS: Here we demonstrated that the high concentration of pyruvate in the medium, which can be easily overlooked, has an effect on the stability of HIF-1α. We also demonstrated that NADH functions as a signal for conveyance of HIF-1α degradation via the SIRT1 and VHL signaling pathway under conditions of chronic hypoxia, which in turn leads to attenuation of hypoxically strengthened invasion and angiogenic activities. A steep increase in the level of NADH occurs during chronic hypoxia, leading to upregulation of acetylation and degradation of HIF-1α via inactivation of SIRT1. Of particular interest, p300-mediated acetylation at lysine 709 of HIF-1α is recogonized by VHL, which leads to degradation of HIF-1α via ubiquitin/proteasome machinary under conditions of chronic hypoxia. In addition, we demonstrated that NADH-elevation-induced acetylation and subsequent degradation of HIF-1α was independent of proline hydroxylation. CONCLUSIONS: Our findings suggest a critical role of SIRT1 as a metabolic sensor in coordination of hypoxic status via regulation of HIF-1α stability. These results also demonstrate the involvement of VHL in degradation of HIF-1α through recognition of PHD-mediated hydroxylation in normoxia and p300-mediated HIF-1α acetylation in hypoxia.

Highly Stretchable Sensor Based on Fluid Dynamics-Assisted Graphene Inks for Real-Time Monitoring of Sweat.

Graphene inks have recently attracted attention for the development of printed wearable and flexible electronics and sensors not only because of their high conductivity and low cost but also because they are suitable for high-speed printing. Although reliable and scalable printing technologies are well established, further improvement in graphene inks in terms of electrical conductivity, stretchability/flexibility, and mass production is necessary for sensors for real-time monitoring. Herein, highly stretchable and conductive graphene inks were prepared by an efficient and scalable fluid dynamics-assisted exfoliation of graphite and a mixing process with elastomeric Ecoflex. After printing inks onto textile substrates, the serpentine-patterned conductors exhibited high conductivity and stable resistance even under a mechanically stretched state (a strain of 150%). Electrochemical sensors that detect sodium ions were fabricated on this conducting platform. These sensors indicated high potentiometric sensing ability under different mechanical deformations. To demonstrate the on-body performance of the developed sensors, real-time monitoring of sodium-ion concentration in the sweat of a human subject was carried out during an indoor stationary cycling exercise.

Phase I Clinical Trial of Prostate-Specific Membrane Antigen-Targeting 68Ga-NGUL PET/CT in Healthy Volunteers and Patients with Prostate Cancer.

OBJECTIVE: 68Ga-NGUL is a novel prostate-specific membrane antigen (PSMA)-targeting tracer based on Glu-Urea-Lys derivatives conjugated to a 1,4,7-triazacyclononane-N, N', N″-triacetic acid (NOTA) chelator via a thiourea-type short linker. This phase I clinical trial of 68Ga-NGUL was conducted to evaluate the safety and radiation dosimetry of 68Ga-NGUL in healthy volunteers and the lesion detection rate of 68Ga-NGUL in patients with prostate cancer. MATERIALS AND METHODS: We designed a prospective, open-label, single-arm clinical trial with two cohorts comprising six healthy adult men and six patients with metastatic prostate cancer. Safety and blood test-based toxicities were monitored throughout the study. PET/CT scans were acquired at multiple time points after administering 68Ga-NGUL (2 MBq/kg; 96-165 MBq). In healthy adults, absorbed organ doses and effective doses were calculated using the OLINDA/EXM software. In patients with prostate cancer, the rates of detecting suspicious lesions by 68Ga-NGUL PET/CT and conventional imaging (CT and bone scintigraphy) during the screening period, within one month after recruitment, were compared. RESULTS: All 12 participants (six healthy adults aged 31-32 years and six prostate cancer patients aged 57-81 years) completed the clinical trial. No drug-related adverse events were observed. In the healthy adult group, 68Ga-NGUL was rapidly distributed, with the highest uptake in the kidneys. The median effective dose coefficient was calculated as 0.025 mSv/MBq, and cumulative activity in the bladder had the highest contribution. In patients with metastatic prostate cancer, 229 suspicious lesions were detected using either 68Ga-NGUL PET/CT or conventional imaging. Among them, 68Ga-NGUL PET/CT detected 199 (86.9%) lesions and CT or bone scintigraphy detected 114 (49.8%) lesions. CONCLUSION: 68Ga-NGUL can be safely applied clinically and has shown a higher detection rate for the localization of metastatic lesions in prostate cancer than conventional imaging. Therefore, 68Ga-NGUL is a valuable option for prostate cancer imaging.

KSNM60: The History of Radiopharmaceutical Sciences in Korea.

A number of researchers in Korea have tried to set-up the production of radionuclides and develop new radiopharmaceuticals for several decades. Thanks to their 60-year endeavor to advance the field of radiopharmaceutical sciences, now we have a lot of research units and facilities in Korea. Still, there are huge number of issues to be solved in radiopharmaceutical sciences; however, our efforts will be continued to develop new radiopharmaceuticals and to apply the new radiopharmaceuticals into nuclear medicine field.

A Prospective Investigation of Tumor Hypoxia Imaging with 68Ga-Nitroimidazole PET/CT in Patients with Carcinoma of the Cervix Uteri and Comparison with 18F-FDG PET/CT: Correlation with Immunohistochemistry.

Hypoxia in cervical cancer has been associated with a poor prognosis. Over the years 68Ga labelled nitroimidazoles have been studied and have shown improved kinetics. We present our initial experience of hypoxia Positron Emission Tomography (PET) imaging in cervical cancer with 68Ga-Nitroimidazole derivative and the correlation with 18F-FDG PET/CT and immunohistochemistry. Twenty women with cervical cancer underwent both 18F-FDG and 68Ga-Nitroimidazole PET/CT imaging. Dual-point imaging was performed for 68Ga-Nitroimidazole PET. Immunohistochemical analysis was performed with hypoxia inducible factor-1α (HIF-1α). We documented SUVmax, SUVmean of the primary lesions as well as tumor to muscle ratio (TMR), tumor to blood (TBR), metabolic tumor volume (MTV) and hypoxic tumor volume (HTV). There was no significant difference in the uptake of 68Ga-Nitroimidazole between early and delayed imaging. Twelve patients had uptake on 68Ga-Nitroimidazole PET. Ten patients demonstrated varying intensities of HIF-1α expression and six of these also had uptake on 68Ga-Nitroimidazole PET. We found a strong negative correlation between HTV and immunohistochemical staining (r = -0.660; p = 0.019). There was no correlation between uptake on PET imaging and immunohistochemical analysis with HIF-1α. Two-thirds of the patients demonstrated hypoxia on 68Ga-Nitroimidazole PET imaging.

Radionuclide imaging of hypoxia: Where are we now? Special attention to cancer of the cervix uteri.

Cancer of the cervix is the fourth commonest malignancy in women worldwide and it also ranks fourth as the cause of cancer related mortality in women. Hypoxia is a common characteristic of solid tumours and cervical cancer is no exception. Hypoxia is associated with increased aggressiveness, risk of invasion and metastasis. Tumour hypoxia also results in resistance to both radiation therapy and chemotherapy leading to a poorer prognosis. In-vivo measurement of tumour hypoxia is vital in oncologic practice because it can predict outcome and identify patients with a worse prognosis. Mapping of tumour hypoxia may also help select patients that may benefit from applicable treatments. While traditional methods of measuring hypoxia such as the Eppendorf probe is considered the gold standard, it is invasive and technically demanding. Non-invasive methods of measuring tumourhypoxia are ideal. Positron emission tomography/computed tomography (PET/CT) imaging with nitro-imidazole-based tracers is a highly sensitive nuclear imaging technique that is suited for non-invasive in vivo monitoring of hypoxia. Over the years various hypoxia specific PET tracers have been investigated in various malignancies including cancer of the cervix. Several fluorine-18 (18F)-based tracers have been studied and although most had small patient numbers, the results are promising and generally demonstrate an associate between the presence of hypoxia and treatment outcome. The need for an onsite cyclotron and specialized radiopharmacy skills make these tracers unattractive and largely unavailable for routine clinical applications. With the increase in availability of the gallium-68 (68Ga) generator this makes the 68Ga-labelled nitroimidazole derivatives attractive because 68Ga is available from a generator with a shelf life of almost a year. The chemistry of 68Ga makes for easy labelling with several peptides and molecules. Pre-clinical work has demonstrated the feasibility of using these tracers for imaging hypoxia and has laid the groundwork for further human studies with these tracers.The aim of this review is to discuss hypoxia and its impact in cancer of the cervix as well as to look into the progress made in hypoxia imaging in cancer of the cervix. This will focus on the tracers studied thus far and some of the challenges of hypoxia imaging.

Highly Concentrated, Conductive, Defect-free Graphene Ink for Screen-Printed Sensor Application.

HIGHLIGHTS: Ultrathin and defect-free graphene ink is prepared through a high-throughput fluid dynamics process, resulting in a high exfoliation yield (53.5%) and a high concentration (47.5 mg mL-1). A screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m-1 and good mechanical flexibility. An electrochemical sodium ion sensor based on graphene ink exhibits an excellent potentiometric sensing performance in a mechanically bent state. Real-time monitoring of sodium ion concentration in sweat is demonstrated. Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices. However, the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions. In this study, a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process. A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL-1 for graphene ink. The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m-1 and maintains high conductivity under mechanical bending, compressing, and fatigue tests. Based on the as-prepared graphene ink, a printed electrochemical sodium ion (Na+) sensor that shows high potentiometric sensing performance was fabricated. Further, by integrating a wireless electronic module, a prototype Na+-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer. The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost, reproducible, and large-scale printing of flexible and wearable electronic devices.

Head-to-Head Comparison of 68Ga-NOTA (68Ga-NGUL) and 68Ga-PSMA-11 in Patients with Metastatic Prostate Cancer: A Prospective Study.

68Ga-NOTA Glu-Urea-Lys (NGUL) is a novel prostate-specific membrane antigen (PSMA)-targeting tracer used for PET/CT imaging. This study aimed to compare performance in the detection of primary and metastatic lesions and to compare biodistribution between 68Ga-NGUL and 68Ga-PSMA-11 in the same patients with prostate cancer. Methods: Eleven patients with metastatic prostate cancer were prospectively recruited. The quantitative tracer uptake was determined in normal organs and in primary and metastatic lesions. Results:68Ga-NGUL showed significantly lower normal-organ uptake and rapid urinary clearance. The number and sites of detected PSMA-positive primary and metastatic lesions were identical, and no significant quantitative uptake difference was observed. 68Ga-NGUL showed a relatively lower tumor-to-background ratio than 68Ga-PSMA-11. Conclusion: In a head-to-head comparison with 68Ga-PSMA-11, 68Ga-NGUL showed lower uptake in normal organs and similar performance in detecting PSMA-avid primary and metastatic lesions. 68Ga-NGUL could be a valuable option for PSMA imaging.

Classification of crystal structures using electron diffraction patterns with a deep convolutional neural network.

Investigations have been made to explore the applicability of an off-the-shelf deep convolutional neural network (DCNN) architecture, residual neural network (ResNet), to the classification of the crystal structure of materials using electron diffraction patterns without prior knowledge of the material systems under consideration. The dataset required for training and validating the ResNet architectures was obtained by the computer simulation of the selected area electron diffraction (SAD) in transmission electron microscopy. Acceleration voltages, zone axes, and camera lengths were used as variables and crystal information format (CIF) files obtained from open crystal data repositories were used as inputs. The cubic crystal system was chosen as a model system and five space groups of 213, 221, 225, 227, and 229 in the cubic system were selected for the test and validation, based on the distinguishability of the SAD patterns. The simulated diffraction patterns were regrouped and labeled from the viewpoint of computer vision, i.e., the way how the neural network recognizes the two-dimensional representation of three-dimensional lattice structure of crystals, for improved training and classification efficiency. Comparison of the various ResNet architectures with varying number of layers demonstrated that the ResNet101 architecture could classify the space groups with the validation accuracy of 92.607%.

Non-oncological applications of RGD-based single-photon emission tomography and positron emission tomography agents.

INTRODUCTION: Non-invasive imaging techniques (especially single-photon emission tomography and positron emission tomography) apply several RGD-based imaging ligands developed during a vast number of preclinical and clinical investigations. The RGD (Arg-Gly-Asp) sequence is a binding moiety for a large selection of adhesive extracellular matrix and cell surface proteins. Since the first identification of this sequence as the shortest sequence required for recognition in fibronectin during the 1980s, fundamental research regarding the molecular mechanisms of integrin action have paved the way for development of several pharmaceuticals and radiopharmaceuticals with clinical applications. Ligands recognizing RGD may be developed for use in the monitoring of these interactions (benign or pathological). Although RGD-based molecular imaging has been actively investigated for oncological purposes, their utilization towards non-oncology applications remains relatively under-exploited. METHODS AND SCOPE: This review highlights the new non-oncologic applications of RGD-based tracers (with the focus on single-photon emission tomography and positron emission tomography). The focus is on the last 10 years of scientific literature (2009-2020). It is proposed that these imaging agents will be used for off-label indications that may provide options for disease monitoring where there are no approved tracers available, for instance Crohn's disease or osteoporosis. Fundamental science investigations have made progress in elucidating the involvement of integrin in various diseases not pertaining to oncology. Furthermore, RGD-based radiopharmaceuticals have been evaluated extensively for safety during clinical evaluations of various natures. CONCLUSION: Clinical translation of non-oncological applications for RGD-based radiopharmaceuticals and other imaging tracers without going through time-consuming extensive development is therefore highly plausible. Graphical abstract.

In vivo gamma-aminobutyric acid-A/benzodiazepine receptor availability and genetic liability in asymptomatic individuals with high genetic loading of schizophrenia: A [11C]flumazenil positron emission tomography study.

OBJECTIVES: Whilst reduced signalling and gene expression related to gamma-aminobutyric acid (GABA) play a role in the presumed pathophysiology of schizophrenia, its origin is unclear. Studying asymptomatic individuals with high genetic liability to schizophrenia (AIs) would provide insights. Therefore, this study aimed to investigate the role of genetic liability in GABAergic dysfunction of schizophrenia by exploring in vivo GABA-A/benzodiazepine receptor (GABAR) availability in AIs. METHODS: A total of 10 AIs with multiple relatives diagnosed as schizophrenia and 11 healthy controls underwent [11C]flumazenil positron emission tomography and neurocognitive function tests. RESULTS: There was no significant difference in [11C]flumazenil availability based on the groups. GABAR availability in caudate nuclei had positive correlations with genetic liability of AIs. GABAR availability in caudate nuclei and verbal memory measures of AIs revealed positive correlations. Only the correlation between right caudate and short-term verbal memory survived multiple-comparison correction (p = 0.030). CONCLUSIONS: This study, for the first time, reports correlations between the genetic liability of schizophrenia and GABAR availability. Correlations between [11C]flumazenil binding in caudate of individuals with high genetic liability to schizophrenia suggests that the GABAergic dysfunction may arise from shared genetic factors and also that it may be responsible for cognitive impairment of AIs.

Imaging Hydrogen Sulfide in Hypoxic Tissue with [99mTc]Tc-Gluconate.

Hydrogen sulfide (H2S) is the third gasotransmitter and is generated endogenously in hypoxic or inflammatory tissues and various cancers. We have recently demonstrated that endogenous H2S can be imaged with [99mTc]Tc-gluconate. In the present study, we detected H2S generated in hypoxic tissue, both in vitro and in vivo, using [99mTc]Tc-gluconate. In vitro uptake of [99mTc]Tc-gluconate was measured under hypoxic and normoxic conditions, using the colon carcinoma cell line CT26, and was higher in hypoxic cells than that in normoxic cells. An acute hindlimb ischemia-reperfusion model was established in BALB/c mice by exposing the animals to 3 h of ischemia and 3 h of reperfusion prior to in vivo imaging. [99mTc]Tc-gluconate (12.5 MBq) was intravenously injected through the tail vein, and uptake in the lower limb was analyzed by single-photon emission computed tomography/computed tomography (SPECT/CT). SPECT/CT images showed five times higher uptake in the ischemic limb than that in the normal limb. The standard uptake value (SUVmean) of the ischemic limb was 0.39 ± 0.03, while that of the normal limb was 0.07 ± 0.01. [99mTc]Tc-gluconate is a novel imaging agent that can be used both in vitro and in vivo for the detection of endogenous H2S generated in hypoxic tissue.

Flexible nanopillar-based immunoelectrochemical biosensor for noninvasive detection of Amyloid beta.

The noninvasive early detection of biomarkers for Alzheimer's disease (AD) is essential for the development of specific treatment strategies. This paper proposes an advanced method for fabricating highly ordered and flexible nanopillar-based electrochemical biosensors by the combination of soft/photolithography and metal evaporation. The nanopillar array (NPA) exhibits high surface area containing 1500 nm height and 500 nm diameter with 3:1 ratio. In regard with physical properties of polyurethane (PU) substrate, the developed NPA is sustainable and durable to external pressure such as bending and twisting. To manipulate the NPA surface to biocompatible, the gold was uniformly deposited on the PU substrate. The thiol chemistry which is stably modified on the gold surface as a form of self-assembled monolayer was employed for fabricating the NPA as a biocompatible chip by covalently immobilize the antibodies. The proposed nanopillar-based immunoelectrochemical biosensor exhibited good and stable electrochemical performance in ß-amyloid (Aß) detection. Moreover, we successfully confirmed the performance of the as-developed sensor using the artificial injection of Aß in human tear, with sensitivity of 0.14 ng/mL and high reproducibility (as a standard deviation below 10%). Our findings show that the developed nanopillar-based sensor exhibits reliable electrochemical characteristics and prove its potential for application as a biosensor platform for testing at the point of care.

Conjugation of arginylglycylaspartic acid to human serum albumin decreases the tumor-targeting effect of albumin by hindering its secreted protein acidic and rich in cysteine-mediated accumulation in tumors.

Human serum albumin (HSA) accumulates in tumors by the enhanced permeability and retention (EPR) effect, which is a passive targeting effect in tumors. A recent study showed that secreted protein acidic and rich in cysteine (SPARC), an albumin-binding protein, mediates albumin accumulation in tumors. Arg-Gly-Asp (RGD) is a peptide targeting integrin αvß3, which is highly expressed during tumor angiogenesis. We investigated whether conjugation of RGD to HSA could synergistically enhance tumor targeting. Accumulation of cRGDyK-HSA in integrin αvß3-expressing SK-OV3 cells was observed by confocal microscopy. In SK-OV3 cells overexpressing the albumin binding protein SPARC, cellular uptake of HSA increased, but uptake of cRGDyK-HSA did not. cRGDyK-HSA showed decreased tumor accumulation compared with HSA by positron emission tomography (PET) scanning and biodistribution studies in an SK-OV3 xenograft mouse model. In SK-OV3 tumors, HSA accumulation colocalized with SPARC expression, while cRGDyK-HSA only accumulated in the outer region of the tumor, even though SPARC and integrin αvß3 were expressed within the tumor core. We speculate that cRGDyK conjugation to HSA changes the characteristics of HSA and hinders its tumor-targeting effect. Therefore, HSA should be modified to preserve its native characteristics and enhance the tumor-targeting effects of HSA conjugates.

Preparation of a multi-modal agent for sentinel lymph node mapping using Evans blue and 99mTc-labeled mannosylated human serum albumin conjugate.

INTRODUCTION: The identification of sentinel lymph nodes (SLNs) is important in deciding the resection range during surgery. 99mTc-labeled mannosylated human serum albumin ([99mTc]Tc-MSA) is a radiopharmaceutical developed for SLN detection by targeting macrophages. Evans blue (EB) is a blue dye binding strongly to albumin and has been used for SLN detection. [99mTc]Tc-MSA-EB conjugate was prepared as a multi-modal imaging agent and tested its performance by visual investigation, fluorescence imaging and SPECT/CT for SLN mapping in mice. METHODS: EB was mixed with various concentration of MSA to prepare MSA-EB conjugates. The binding efficiencies were determined using thin-layer chromatography. The UV-VIS spectra and molar extinction coefficient of the conjugate were obtained. The fluorescence was monitored at the excitation wavelength range 420-780 nm and the emission wavelength range 520-845 nm. The [99mTc]Tc-MSA-EB conjugate and EB were injected into the footpads of normal BALB/c mice to check the lymph node (LN) uptakes. The visible, fluorescence, and SPECT/CT images were obtained after injection. RESULTS: The conjugation of EB with MSA increased by time and was saturated within 10 min. The molar extinction coefficient of the conjugate was 99,259.3/M/cm at 620 nm. The uptake of conjugate into the popliteal LN after injection into the footpads of mice was investigated visually and fluorescence imaging. SPECT/CT images showed that the standardized uptake values of [99mTc]Tc-MSA-EB conjugate in popliteal LN were about 4 times higher than in sciatic LN at all timepoints. It was confirmed by investigating resected LN that the blue color, fluorescence, and radioactivity of the [99mTc]Tc-MSA-EB conjugate were retained only on the LN and did not spread to adjoining tissues. CONCLUSION: [99mTc]Tc-MSA-EB conjugate has a great potential as a multi-modal SLN mapping agent which could be detected by visual investigation, fluorescence imaging, and SPECT/CT.

Assessment of Inflammation in Pulmonary Artery Hypertension by 68Ga-Mannosylated Human Serum Albumin.

Rationale: Diagnosis and monitoring of patients with pulmonary artery hypertension (PAH) is currently difficult.Objectives: We aimed to develop a noninvasive imaging modality for PAH that tracks the infiltration of macrophages into the pulmonary vasculature, using a positron emission tomography (PET) agent, 68Ga-2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) mannosylated human serum albumin (MSA), that targets the mannose receptor (MR).Methods: We induced PAH in rats by monocrotaline injection. Tissue analysis, echocardiography, and 68Ga-NOTA-MSA PET were performed weekly in rats after monocrotaline injection and in those treated with either sildenafil or macitentan. The translational potential of 68Ga-NOTA-MSA PET was explored in patients with PAH.Measurements and Main Results: Gene sets related to macrophages were significantly enriched on whole transcriptome sequencing of the lung tissue in PAH rats. Serial PET images of PAH rats demonstrated increasing uptake of 68Ga-NOTA-MSA in the lung by time that corresponded with the MR-positive macrophage recruitment observed in immunohistochemistry. In sildenafil- or macitentan-treated PAH rats, the infiltration of MR-positive macrophages by histology and the uptake of 68Ga-NOTA-MSA on PET was significantly lower than that of the PAH-only group. The pulmonary uptake of 68Ga-NOTA-MSA was significantly higher in patients with PAH than normal subjects (P = 0.009) or than those with pulmonary hypertension by left heart disease (P = 0.019) (n = 5 per group).Conclusions:68Ga-NOTA-MSA PET can help diagnose PAH and monitor the inflammatory status by imaging the degree of macrophage infiltration into the lung. These observations suggest that 68Ga-NOTA-MSA PET has the potential to be used as a novel noninvasive diagnostic and monitoring tool of PAH.

Preparation of ultrathin defect-free graphene sheets from graphite via fluidic delamination for solid-contact ion-to-electron transducers in potentiometric sensors.

In this study, ultrathin and defect-free graphene (Gr) sheets were prepared through a fluid dynamics-induced shear exfoliation method using graphite. The high hydrophobicity and surface area of Gr make it attractive as a solid-contact ion-to-electron transducer for potentiometric K+ sensors, in which the electrodes are fabricated through a screen-printing process. The electrochemical characterization demonstrates that Gr solid contact results in a high double-layer capacitance, potential stability, and strong resistance against water layer, gases, and light. The Gr-based K+ sensors showed a Nernstian slope of 53.53 mV/log[K+] within a linear concentration range of 10-1-10-4 M, a low detection limit of 10-4.28 M, a fast response time of ~8 s, good repeatability, and excellent long-term stability. Moreover, the Gr-based K+ sensors provided accurate ion concentrations in actual samples of human sweat and sports drinks.

Imaging of the third gasotransmitter hydrogen sulfide using 99mTc-labeled alpha-hydroxy acids.

INTRODUCTION: Hydrogen sulfide (H2S) defined as the third gasotransmitter after nitric oxide (NO) and carbon monoxide (CO) is an important mediator of various physiological functions. Although various H2S-imaging techniques using fluorescence and luminescence have been developed, only one radionuclide imaging using 64Cu-labeled cyclen complex was reported. Thus, we tried to develop 99mTc-labeled H2S imaging agents. METHODS: Various α-hydroxy acids such as glycolate, L-lactate, D-lactate, D-gluconate, D-glucoheptonate, D-glucuronate, D-glucarate, and citrate were labeled with 99mTc in the presence of stannous chloride. The labeled compounds were incubated with 0.2 mM of NaHS, and reactive sulfur species and then analyzed by ITLC/normal saline to detect the formation of insoluble complex. Matrigels containing various concentrations of NaHS were xenografted on the shoulder of normal mice, and an imaging study was performed after intravenous injection of [99mTc]Tc-gluconate. We also obtained autoradiography image of a rat brain with a temporary brain ischemia after intravenous injection of [99mTc]Tc-gluconate. RESULTS: [99mTc]Tc-gluconate showed the highest formation of insoluble complex (87.8 ±â€¯3.6%) after incubation with 0.2 mM NaHS. The other reactive species such as glutathione, cysteine, sulfite, sulfate, thiosulfate, and NO did not form insoluble complex representing the reaction being specific to H2S. The Matrigel containing 2 µmol NaHS showed uptake of [99mTc]Tc-gluconate, which proved the feasibility as the specific H2S imaging agent in vivo. Temporary ischemic lesion of rat brain showed high radioactivity accumulation representing the feasibility as endogenous H2S imaging agents. CONCLUSION: We proved that 99mTc-labeled α-hydroxy acid especially [99mTc]Tc-gluconate is a novel endogenous H2S imaging agent, which might contribute to study and diagnosis of various diseases related with inflammation and hypoxia.