Low-temperature operating ZnO-based NO2 sensors: a review

Owing to its excellent physical and chemical properties, ZnO has been considered to be a promising material for development of NO₂ sensors with high sensitivity, and fast response and recovery. However, due to the low activity of ZnO at low temperature, most of the current work is focused on detecting NO₂ at high operating temperatures (200–500 °C), which will inevitably increase energy consumption and shorten the lifetime of sensors. In order to overcome these problems and improve the practicality of ZnO-based NO₂ sensors, it is necessary to systematically understand the effective strategies and mechanisms of low-temperature NO₂ detection of ZnO sensors. This paper reviews the latest research progress of low-temperature ZnO nanomaterial-based NO₂ gas sensors. Several efficient strategies to achieve low-temperature NO₂ detection (such as morphology modification, noble metal decoration, additive doping, heterostructure sensitization, two-dimensional material composites, and light activation) and corresponding sensing mechanisms (such as depletion layer theory, grain boundary barrier theory, spill-over effects) are also introduced. Finally, the challenges and future development directions of low-temperature ZnO-based NO₂ sensors are outlined.

A comprehensive review on designs and mechanisms of ZnO-based NO₂ gas sensors operated at low temperature.     

Effect of specific surface area on syngas production performance of pure ceria in high-temperature thermochemical redox cycling coupled to methane partial oxidation

Specific surface area is a key parameter determining the rates of thermochemical redox reactions in metal oxides. We have experimentally investigated the effect of specific surface area on syngas production of pure ceria powders under two experiments such as a heating experiment without syngas production and an isothermal thermochemical redox cycling experiment using carbon dioxide splitting and methane partial oxidation. The specific surface area of ceria powders decreased relatively slowly during 50 hours of ceria powder heating without syngas production due to a combination of oriented attachment and grain-boundary diffusion. When cycled thermochemically, the specific surface area of ceria powders rapidly decreased only in the initial 10 minutes of reduction in the 1st cycle due to evaporation and condensation. A significant decrease of specific surface area during the initial stage of thermochemical ceria powder cycling is unavoidable even if temperatures as low as T = 1173 K are used in the reduction reaction coupled to methane partial oxidation.

Specific surface area is a key parameter determining the rates of thermochemical redox reactions in metal oxides.     

Controllable stripping of radiolabeled group in vivo to optimize nuclear imaging via NO-responsive bioorthogonal cleavage reaction

A novel “turn-off” strategy for controllable radionuclide clearance is established. 1,4-dihydropyridine (DHP) is used as a conditional linker to connect a radioisotope labeled moiety and nano-agent. A highly specific, sensitive and effective C–C bond cleavage of DHP happens in vivo when treated with nitric oxide which is provided by glyceryl trinitrate (GTN). The radioactive cut-off part from the nanoparticle is observed to be cleared quickly by microSPECT-CT. 3–5 times decreases of radioactivity in the blood, kidneys, intestine, heart and lungs are observed after GTN treatment in a biodistribution assay. The radioactivity redistribution indicates that the radioactive leaving part is indeed cut off and the radionuclide metabolism accelerated. Organ level internal dose assessment reveals the GTN treated groups carry only ½ the radiation dose of the control group. Collectively, a feasible pathway for controllable radionuclide clearance is for the first time provided for high contrast and low radiation nuclear imaging.

A novel “turn-off” strategy was developed for controllable radionuclide clearance in organisms.

Radiolabeled compounds with biological activity, or radiotracers, have been widely used for nuclear imaging and radiation therapy. Compared with other imaging modalities, a unique problem in radiotracer-based imaging is that the radioactivity cannot be simply “turned off”. As a result, it is impossible to carry out multi-scans of the same organ with different tracers in a short period. For instance, there are three kinds of marker receptors (ER, PR, HER2) expressed in breast cancer. Different type of breast cancer expresses a different combination of these three. Therefore, three kinds of radiotracers that aim to bind the corresponding receptors will be used to distinguish individual breast cancer phenotype. The uptake of a second tracer can''t be quantified accurately before the radioactivity of the first tracer decayed to background level, which may need one or two days depending on the half-life of radionuclide. So, it''s necessary to develop a strategy to “quench” the radioactivity. Furthermore, nonspecific binding is inevitable, and the “noise” or “background” from non-specific binding of radiotracers to non-target proteins cannot be easily differentiated from the specific binding component.Therefore, it''s meaningful to develop a kind of reaction that could strip the radiation by control. To achieve this goal, the metabolism of the radioactive part should be accelerated. The biorthogonal cleavage reaction would perfectly meet the needs, if (1) cleavable reactions could happen by the control in vivo; (2) the cut-off part has a relatively fast metabolism; (3) radionuclide is linked on the cut-off part.¹ One of the key issues that bio-orthogonal reactions resolve is to bind two components into one, and make the different metabolic rate of different components synchronized.² As the reaction in the opposite direction of bio-orthogonal reaction, the bio-orthogonal cleavage reaction can extinguish the radiation by diversifying the metabolism of radionuclides and the slow metabolic targeting components.Dihydropyridine (DHP) and its cleavage-triggering partner nitric oxide (NO) can perfectly meet the three conditions. NO, a hydrophobic signal molecule, could spread without any transmembrane transporter, which means NO could spread quickly and spend little energy.^3–5 Many kinds of NO donor drugs are commercially available, such as glyceryl trinitrate (GTN), sodium nitroprusside, etc. In our previous work,⁶ it was demonstrated that the physiological concentration of NO is high enough to cleave the C–C bond of DHP. Furthermore, NO donor drugs could offer a circumstance with higher NO concentration than normal physiological concentration. Therefore, it is possible for the reaction between DHP and NO from donor drugs to occur in vivo. Herein, a NO-triggerred “turn-off” system to extinguish the radiation by cleaving the radionuclides from nanoparticles is present. Benzyl group substituted 1,4-dihydropyridine can be cleaved through controlled NO stimulation by intraperitoneal injection of GTN.Nanoparticles as the major kind of theranostic agents have been developed quickly over these years.^7–11 During the process of synthesis, nanoparticles with similar shape, scale and dispersion properties would be obtained by manipulating conditions precisely. Therefore, the metabolism of nanoparticles in the living body is more predictable than diverse small molecules. Especially, radionuclides labeled nanoparticles not only play roles in diagnosis but also work well on tumor therapy. Enhanced permeability and retention (EPR) effect make nanoparticles wonderful radiotherapy reagents.^12–15 However, nanoparticles mean to be easily captured by the mononuclear phagocyte system (MPS), which makes the nanoparticles mostly enriched in liver besides in tumor.^16–20 Furthermore, metabolism of nanoparticles are quite slow than most of the small molecules, which means the radionuclides labeled on nanoparticles have similar slow metabolism to their carriers. Unnecessarily loaded radiation from the nanoparticles will also harm normal liver cells where the nanoparticles accumulate heavily.     

Fitness costs in chlorfenapyr-resistant populations of the chive maggot,Bradysia odoriphaga

The chive maggot, Bradysia odoriphaga (Yang and Zhang) is an economically important insect pest, affecting many key vegetables, including Chinese chive, especially in northern China. Chlorfenapyr, a halogenated pyrrole insecticide that interferes with mitochondrial oxidative phosphorylation is widely used against B. odoriphaga. In this study, we evaluated selection-induced resistance to chlorfenapyr and fitness costs in B. odoriphaga. The results showed that B. odoriphaga developed 43.32-fold resistance after continuous exposure to chlorfenapyr for over 10 consecutive generations. The life-history traits of chlorfenapyr-resistant and susceptible strains were compared using age-stage, two-sex life table approach. No significant effects were observed on the longevity and pre-adult period. However, reduction in the total pre-oviposition period (TPOP) and fecundity (eggs/female) were observed in the resistant strain. Moreover, the demographic parameters such as intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase (λ) were also decreased significantly in the resistant strain compared to the susceptible strain. These results showed the potential of B. odoriphaga to develop resistance against chlorfenapyr under continuous selection pressure. Furthermore, there was a fitness cost linked with chlorfenapyr resistance in B. odoriphaga. We conclude that a better knowlegde on the trade-off at play between resistance degree and fitness cost could be crucial for developing further management of B. odoriphaga in China.     

Characterization of Craniocervical Artery Dissection by Simultaneous MR Noncontrast Angiography and Intraplaque Hemorrhage Imaging at 3T

BACKGROUND AND PURPOSE:Craniocervical artery dissection is the most common cause of ischemic stroke identified in young adults. For the diagnosis of craniocervical artery dissection, multisequence MR imaging is recommended but is time-consuming. Recently, investigators proposed a simultaneous noncontrast angiography and intraplaque hemorrhage imaging technique allowing simultaneous noncontrast MRA and vessel wall imaging in a single scan. This study sought to investigate the feasibility of 3D simultaneous noncontrast angiography and intraplaque hemorrhage MR imaging in the characterization of craniocervical artery dissection.MATERIALS AND METHODS:Twenty-four symptomatic patients (mean age, 45.0 ± 16.1 years; 21 men) with suspected craniocervical artery dissection were recruited. The 3D simultaneous noncontrast angiography and intraplaque hemorrhage 3D TOF MRA and black-blood imaging sequences were performed on a 3T MR imaging scanner. The agreement between simultaneous noncontrast angiography and intraplaque hemorrhage imaging and multisequence MR imaging in evaluating arterial dissection was determined.RESULTS:Dissection was found to involve 1 artery in 22 patients and 2 arteries in 2 patients. The intramural hematoma and luminal occlusion were detected in 19 (79.2%) and 11 (45.8%) patients, respectively. In measuring stenosis, the Cohen κ value between 3D TOF MRA and simultaneous noncontrast angiography and intraplaque hemorrhage imaging was 0.82 (P < .001). All intramural hematomas on multisequence imaging were successfully identified by simultaneous noncontrast angiography and intraplaque hemorrhage imaging.CONCLUSIONS:3D simultaneous noncontrast angiography and intraplaque hemorrhage imaging showed excellent agreement with multisequence MR imaging in evaluating luminal stenosis and intramural hematoma in patients with craniocervical artery dissection. The simultaneous noncontrast angiography and intraplaque hemorrhage imaging saved nearly 50% of scanning time compared with multisequence MR imaging. Our findings suggest that 3D simultaneous noncontrast angiography and intraplaque hemorrhage imaging might be an alternative, time-efficient diagnostic tool for craniocervical artery dissection.

Craniocervical artery dissection (CCAD) is the most common cause of stroke identified in young and middle-aged adults.^1,2 Pathophysiologically, arterial dissections occur when a tear develops in ≥1 layer of the vessel wall, allowing blood to enter the wall and split the layers; this condition is characterized by a cavity or intramural hematoma (IMH).³ The increased volume of the IMH may narrow or occlude the lumen, and it can also damage the intima and trigger thrombosis. Because this arterial disorder is strongly associated with acute ischemic events,^4,5 it is clinically preferable to diagnose CCAD at the early stages so that clinicians can properly treat and prevent potential neurologic complications.⁶Angiographic imaging modalities, such as CTA, MRA, and DSA, have been widely used for the diagnosis of CCAD in clinical settings.^7–9 These approaches can only provide the information of luminal narrowing or occlusion but are unable to directly delineate IMH, which is a key sign of CCAD. Some investigators believe that craniocervical arteries with occlusion but without evidence of IMH cannot be diagnosed as dissection unless the dissected wall is completely recanalized.¹⁰ MR vessel wall imaging has been increasingly used for the diagnosis of CCAD due to its capability of directly visualizing IMH in the vessel wall.^11–13 Recently, a multisequence MR imaging protocol, which includes both MRA and MR vessel wall imaging sequences, was recommended for the diagnosis of CCAD.¹⁰ However, this protocol needs independent acquisition of 2 different time-consuming MR imaging sequences.Most recently, a simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) MR imaging technique has been proposed for the evaluation of vulnerable carotid atherosclerotic plaques.¹⁴ The major advantage of the 3D SNAP imaging sequence is acquiring noncontrast MRA and vessel wall images simultaneously in a single scan. The vessel wall images derived from the 3D SNAP sequence carry heavy T1-weighting, which is very sensitive to intraplaque hemorrhage or IMH. The other advantages of SNAP imaging include fast scanning, large longitudinal coverage (up to 250 mm), and isotropic high resolution (0.8 mm³). Those advantages make SNAP an ideal candidate for quick and reliable identification of dissection, particularly for tortuous craniocervical arteries with longer lesions.We hypothesized that the 3D SNAP MR imaging technique is capable of characterizing CCAD by providing both luminal and vessel wall information simultaneously. In this study, we sought to evaluate the feasibility of 3D SNAP MR imaging in the diagnosis of CCAD.     

The incidence of radioepidermitis and the dose-response relationship in parotid gland cancer patients treated with 125I seed brachytherapy

Background

We studied the incidence and dose–response relationship of radioepidermitis in parotid gland carcinoma patients treated with [¹²⁵I] seed brachytherapy in the hopes of designing an optimized pre-implant treatment plan that would reduce the incidence and severity of radioepidermitis in patients receiving this therapy.

Patients and methods

Between January 2007 and May 2010, 100 parotid gland cancer patients were treated postoperatively with [¹²⁵I] seed brachytherapy. The matched peripheral dose (MPD) was 80–140 Gy, and [¹²⁵I] seed activity was 0.7–0.8 mCi. The mean dose delivered to the skin was calculated in the post-implant CT on day 0 following implantation. Grades of acute and late dermatitis were evaluated at 2, 6, 12, and 18 months post-implantation.

Results

Most patients experienced grade 0–2 acute and late skin side effects (86 and 97?%, respectively), though a small subset developed severe complications. Most grade 1–3 effects resolved within 6 months of implantation, though some grade 1–3 effects and all grade 4 effects remained unchanged throughout the 18-month follow-up period. Grade 3 and 4 effects were most prominent (75 and 25?%, respectively) with doses of 110–140 Gy; doses higher than 140 Gy produced only grade 4 effects.

Conclusion

[¹²⁵I] seed brachytherapy produced acceptable levels of acute and late radioepidermitis with a good clinical outcome. A mean dose under 100 Gy delivered to the skin was safe, though doses of 110–140 Gy should be given with caution and extra monitoring; doses greater than 140 Gy are dangerous and likely to produce grade 4–5 effects.

     

Therapeutic effects of transarterial infusion of lipiodol and ethanol in various ratios in a rabbit VX2 tumor model

PUSRPOSE

We aimed to evaluate the therapeutic effect and safety of transcatheter arterial embolization with various volume ratios of lipiodol and ethanol in a rabbit VX2 tumor model to identify the optimal volume ratio.

METHODS

Eighteen adult male New Zealand white rabbits implanted with VX2 tumors in their left liver lobes were randomly divided into six groups based on volume ratios of lipiodol to ethanol: group A, 3:1; group B, 2:1; group C, 1:1; group D, 1:2; group E, 1:3; and group F, 1:4. Pre- and post-treatment unenhanced magnetic resonance imaging was used to detect tumor formation and evaluate tumor growth rates. Liver samples were harvested one week after the procedure, and apoptosis index of tumor tissues was evaluated by pathologic examination and TUNEL assay.

RESULTS

Tumor size decreased in groups B, C, and D, but increased in groups A, E, and F. Tumor growth rates in groups A–F were 0.40±0.03, −0.11±0.21, −0.08±0.09, −0.12±0.07, 0.06±0.12, and 0.05±0.09, respectively. The change in tumor size was significantly different in group A compared with the rest of the groups, but no significant difference was observed among groups B–F. Apoptosis indexes of the six groups were 4.7±2.1%, 6.7±2.1%, 11.7±3.1%, 11.0±2.0%, 10.7±3.2%, and 12±3%, respectively. Apoptosis index was significantly lower in group A compared with groups C–F (P < 0.05). Apoptosis index of group B was significantly lower than groups C and F. There was no significant difference among the other groups.

CONCLUSION

The volume ratios of lipiodol to ethanol ranging from 2:1 to 1:4 were equally effective, the ratios 2:1 and 1:3 had equal safety, and the ratios 1:1 and 1:2 indicated better long-term therapeutic effect. Increasing ethanol in the mixture caused more severe liver injury. Optimal efficacy and safety was achieved with a lipiodol to ethanol volume ratio of 1:1.Hepatocellular carcinoma (HCC) is one of the most common solid malignancies in the world (1). Transarterial chemoembolization (TACE) is widely used to treat HCC patients who are not suitable candidates for curative treatments (2–5). The most common embolic agent used in TACE is lipiodol, which can be mixed with surgical glues (cyanoacrylates) or with ethanol for interventional procedures. Ethanol was confirmed to be effective in occluding the hepatic arterial system, but it can cause perisinusoidal fibrosis (6). Transarterial ethanol ablation (TEA) with a mixture of lipiodol-ethanol has been shown to be an effective treatment for HCC (7). Yu et al. (8) reported that the embolization efficacy and treatment effectiveness of TEA were probably superior to those of TACE for HCC, and a decreased proportion of ethanol (33% by volume) in the mixture was suggested. Lipiodol-ethanol mixtures with reduced ethanol proportions have been shown to be associated with decreased endothelial damage while maintaining effective delivery of the mixtures to tumor vasculature (9). However, the optimal ratio between lipiodol and ethanol that should be used for TEA remains controversial.In the present study, we aimed to determine the efficacy and optimum volume ratio of lipiodol-ethanol mixture in a rabbit VX2 hepatoma model.