Anaerobic oxidation of methane in landfill and adjacent groundwater environments: Occurrence, mechanisms, and potential applications.

Landfills remain the predominant means of solid waste management worldwide. Widespread distribution and significant stockpiles of waste in landfills make them a significant source of methane emissions, exacerbating climate change. Anaerobic oxidation of methane (AOM) has been shown to play a critical role in mitigating methane emissions on a global scale. The rich methane and electron acceptor environment in landfills provide the necessary reaction conditions for AOM, making it a potentially low-cost and effective strategy for reducing methane emissions in landfills. However, compared to other anaerobic habitats, research on AOM in landfill environments is scarce, and there is a lack of analysis on the potential application of AOM in different zones of landfills. Therefore, this review summarizes the existing knowledge on AOM and its occurrence in landfills, analyzes the possibility of AOM occurrence in different zones of landfills, discusses its potential applications, and explores the challenges and future research directions for AOM in landfill management. The identification of research gaps and future directions outlined in this review encourages further investigation and advancement in the field of AOM, paving the way for more effective waste stabilization, greenhouse gas reduction, and pollutant mitigation strategies in landfills.

Antibiotic resistance genes and heavy metals in landfill: A review.

Landfill is reservoir containing antibiotic resistance genes (ARGs) that pose a threat to human life and health. Heavy metals impose lasting effects on ARGs. This review investigated and analyzed the distribution, composition, and abundance of heavy metals and ARGs in landfill. The abundance ranges of ARGs detected in refuse and leachate were similar. The composition of ARG varied with sampling depth in refuse. ARG in leachate varies with the distribution of ARG in the refuse. The ARG of sulI was associated with 11 metals (Co, Pb, Mn, Zn, Cu, Cr, Ni, Sb, As, Cd, and Al). The effects of the total metal concentration on ARG abundance were masked by many factors. Low heavy metal concentrations showed positive effects on ARG diffusion; conversely, high heavy metal concentrations showed negative effects. Organic matter had a selective pressure effect on microorganisms and could provide energy for the diffusion of ARGs. Complexes of heavy metals and organic matter were common in landfill. Therefore, the hypothesis was proposed that organic matter and heavy metals have combined effects on the horizontal gene transfer (HGT) of ARGs during landfill stabilization. This work provides a new basis to better understand the HGT of ARGs in landfill.

Vehicle emissions of primary air pollutants from 2009 to 2019 and projection for the 14th Five-Year Plan period in Beijing, China.

Over the past decade, the emission standards and fuel standards in Beijing have been upgraded twice, and the vehicle structure has been improved by accelerating the elimination of 2.95 million old vehicles. Through the formulation and implementation of these policies, the emissions of carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NOx), and fine particulate matter (PM2.5) in 2019 were 147.9, 25.3, 43.4, and 0.91 kton in Beijing, respectively. The emission factor method was adopted to better understand the emissions characteristics of primary air pollutants from combustion engine vehicles and to improve pollution control. In combination with the air quality improvement goals and the status of social and economic development during the 14th Five-Year Plan period in Beijing, different vehicle pollution control scenarios were established, and emissions reductions were projected. The results show that the emissions of four air pollutants (CO, VOCs, NOx, and PM2.5) from vehicles in Beijing decreased by an average of 68% in 2019, compared to their levels in 2009. The contribution of NOx emissions from diesel vehicles increased from 35% in 2009 to 56% in 2019, which indicated that clean and energy-saving diesel vehicle fleets should be further improved. Electric vehicle adoption could be an important measure to reduce pollutant emissions. With the further upgrading of vehicle structure and the adoption of electric vehicles, it is expected that the total emissions of the four vehicle pollutants can be reduced by 20%-41% by the end of the 14th Five-Year Plan period.

Spatiotemporal heterogeneous effects of microplastics input on soil dissolved organic matter (DOM) under field conditions.

Microplastics (MPs) as emerging persistent pollutants are ubiquitous in terrestrial environments. The effects of MPs input on soil dissolved organic matter (DOM) yet remain largely unclear, which limits our ability to predict how soil carbon dynamics will respond to the intensifying terrestrial plastic contamination, especially under the context of climate change. Here, a long-term field experiment with MPs addition treatment in soils spanning cold temperate zone to the tropics in China was conducted to evaluate the effects of MPs on DOM composition and to explore the spatial and temporal distribution patterns and relevant mechanistic controls of DOM responses after MPs input. We report that the DOM composition in soils with MPs addition was significantly changed relative to the ambient, in which tryptophan-like substances were decreased and humic-like substances were increased. Moreover, we find more apparent transformations of DOM composition in soils for longer treatment time, suggesting a long-lasting effect of MPs on DOM. The overall impact of MPs on DOM is more pronounced in lower latitudes, and nutrient availability and latitude-related climatic variables are associated with the influence degree of MPs input on soil DOM.

Ten-year emission characteristics of atmospheric pollutants from incineration of sacrificial offerings in China.

The incineration of sacrificial offerings is a significant widely practiced custom that is also a kind of neglected air pollution source in China. Our results showed that the emission factors of particulate matter, SO2, CO, NOx, and VOCs emitted from the incineration of sacrificial offerings with purification systems were reduced by 95%, 19%, 9%, 82%, and 42%, respectively, compared with those without a purification system, revealing a significant effect of the flue gas purification system on reducing particulate matter and gaseous pollutants. The emission level of air pollutants from the incineration of sacrificial offerings remained stable before 2013 and then showed a remarkable decrease after the implementation of China´s Air Pollution Prevention Action Plan in 2013. The emissions of TSP (total suspended particulate), PM10, PM2.5, and NOx in 2009 were 8222, 6106, 5656 and 15,878 ton, respectively, obviously higher than 3434, 2551, 2305 and 8579 ton in 2019. Such trend was affected by both the quantity of incineration and the installation rate of purification systems after the Emission Standard of Air Pollutants for Crematory (GB 13801-2015) issued in China. Distinct spatial distribution of atmospheric pollutants from incineration of sacrificial offerings was found with higher in the east and south of China than the west and north of China, which is proportional to the regional economy and population. The maximum ground-level concentration typically occurred at 0.12-0.2 km from the pollution source, posing potential health risks to people entering and exiting funeral and burial sites and nearby residents.

Highly Enhanced Photoluminescence of Monolayer MoS2 in Plasmonic Hybrids with Double-Layer Stacked Ag Nanoparticles.

In this work, a feasible method was proposed to prepare MoS2-based plasmonic hybrid systems with high photoluminescence (PL) emission enhancement. The enhancement effect of plasmonic hybrids on the PL emission of MoS2 has been systematically studied on MoS2/Ag spherical nanoparticle (SP) hybrid systems with different architectures by changing the stacking position of Ag SPs. It is demonstrated that the sandwich-like hybrid composed of monolayer MoS2 and dielectric Al2O3 layer between two layers of Ag SPs has the highest PL enhancement. Remarkably, after adding an Al2O3 layer under MoS2, the PL intensity enhancement up to 209 times was achieved in the sandwich-like hybrid system. Compared with the hybrid with single-layer SPs, the sandwich-like hybrid system with double-layer Ag SPs exhibited an obvious blue shift as a result of the selective enhancement of the A0 exciton in MoS2. These results demonstrate that MoS2/Ag SP hybrid nanosystems have significant implications for sensing and photoelectronic devices.

Emission Variations of Primary Air Pollutants from Highway Vehicles and Implications during the COVID-19 Pandemic in Beijing, China.

According to the traffic flow variation from January 2019 to August 2020, emissions of primary air pollutants from highway vehicles were calculated based on the emission factor method, which integrated the actual structure of on-road vehicles. The characteristics of on-highway traffic flow and pollution emissions were compared during various progression stages of coronavirus disease (COVID-19). The results showed that the average daily traffic volume decreased by 38.2% in 2020, with a decrease of 62% during the strict lockdown due to the impact of COVID-19. The daily emissions of primary atmospheric pollutants decreased by 29.2% in 2020 compared to the same period in 2019. As for the structure of on-highway vehicle types, the small and medium-sized passenger vehicles predominated, which accounted for 76.3% of traffic, while trucks and large passenger vehicles accounted for 19.7% and 4.0%, but contributed 58.4% and 33.9% of nitrogen oxide (NOx) emissions, respectively. According to the simulation results of the ADMS model, the average concentrations of NOx were reduced by 12.0 µg/m3 compared with the same period in 2019. As for the implication for future pollution control, it is necessary to further optimize the structure of on-highway and the road traffic vehicle types and increase the proportions of new-energy vehicles and vehicles with high emission standards.

On the applicability of the 'humic acids' nomenclature from natural ecosystems to engineering sciences.

•'HA' nomenclature can be undoubtedly applied in engineering sciences.•The real structure of NOM is still a 'black box' in natural ecosystems.•Recognition of 'HA' from natural ecosystems to engineering sciences.•Alkaline extraction on NOM link natural ecosystems to engineering sciences.

Nitrogen addition promotes the transformation of heavy metal speciation from bioavailable to organic bound by increasing the turnover time of organic matter: An analysis on soil aggregate level.

Nitrogen (N) addition can change physicochemical properties and biogeochemical processes in soil, but whether or not these changes further affect the transport and transformation of heavy metal speciation is unknown. Here, a long-term (2004-2016) field experiment was conducted to assess the responses of different heavy metal speciation in three soil aggregate fractions to N additions in a temperate agroecosystem of North China. The organic matter turnover time was quantified based on changes in δ13C following the conversion from C3 (wheat) to C4 crop (corn). Averagely, N addition decreases and increases the heavy metal contents in bioavailable and organic bound fractions by 27.5% and 16.6%, respectively, suggesting N addition promotes the transformation of heavy metal speciation from bioavailable to organic bound, and such a promotion in a small aggregate fraction is more remarkable than that in a large aggregate fraction. The transformations of heavy metal speciation from bioavailable to organic bound in all soil aggregate fractions are largely dependent on the increments in the turnover time of organic matter. The increase in organic matter turnover time induced by N addition may inhibit the desorption of heavy metals from organic matter by prolonging the interaction time between heavy metals and organic matter and enhance the capacity of organic matter to adsorb heavy metals by increasing the humification degree and functional group. Our work can provide insights into the accumulation, migration, and transformation of heavy metals in soils in the context of increasing global soil N input from a microenvironmental perspective.

Biouptake Responses of Trace Metals to Long-Term Irrigation with Diverse Wastewater in the Wheat Rhizosphere Microenvironment.

Wastewater irrigation is widely practiced and may cause serious environmental problems. However, current knowledge on the effects of long-term irrigation with wastewater from different sources on the biouptake of trace metals (TMs) in the rhizosphere zone by plants in farmlands is limited. Here, we analyzed wheat rhizosphere soil and wheat roots collected from a typical wastewater irrigation area in North China to evaluate the influence of wastewater irrigation from different sources on the bioavailability of trace metals in soils. Results showed that irrigation with tanning and domestic wastewater helped enhance the bioavailability of trace metals in rhizosphere soil by increasing the active organic carbon content, soil redox potential, and catalase activity, thus enhancing the proportion of the potentially bioavailable part of trace metal speciation. Conversely, irrigation with pharmaceutical wastewater can reduce the bioavailability of trace metals in rhizosphere soil by increasing total soil antibiotics and thus decreasing the proportions of bioavailable and potentially bioavailable parts of trace metal speciation. These findings can provide insights into the migration and transformation of trace metal speciation in soil rhizosphere microenvironments under the context of wastewater irrigation.

Linking the response of soil microbial community structure in soils to long-term wastewater irrigation and soil depth.

Irrigation with treated wastewater (TWW) has become a prevailing agricultural practice due to the scarcity of fresh water resources, which may have a significant impact on the microbial communities that are critical to many biogeochemical processes in soils. However, it is unclear whether there are links between soil microbial responses to long-term irrigation with different sources of wastewater and soil depth. Here we assess the influence of treated domestic (DTWW), leather industry (LTWW) and pharmaceutical (PTWW) wastewater on microbial communities in vertical soil profiles using high-throughput sequencing based on 16S rRNA and internal transcribed spacer (ITS) gene profiling. We found that microbial α-diversity in the vertical profiles of soils was significantly influenced by TWW irrigation. Bacteria and fungi in different soil depths showed distinct responses to TWW; irrigation with TWW markedly increased abundance of bacterial OTUs and inhibited abundance of fungal OTUs. ß-diversity analysis showed that the effect of TWW irrigation on microbial communities was greater than the effect of soil depth, and microbes in subsurface soil were more sensitive to different sources of irrigation water. We also found that, based on ß-diversity analysis, irrigation with treated industrial wastewater, including LTWW and PTWW, had a greater impact on microbial community structures than DTWW. TWW irrigation significantly affected the composition of indigenous soil microbial communities at different depths and might introduce exogenous microbes into the soil environment. Our work explicitly demonstrates the vertical responses of bacterial and fungal communities in soils to irrigation with TWW from different sources, which can provides insights into the microbial-dominated geochemical processes from the perspective of the entire soil profile under the context of wastewater irrigation.

Soil solid-phase organic matter-mediated microbial reduction of iron minerals increases with land use change sequence from fallow to paddy fields.

The microbial reduction of Fe(III) minerals (MRF) is an important process in paddy soil because it can affect the biogeochemical cycles of many major and trace elements. Natural organic matter (NOM) that mainly exists in the form of solid phase in soil can mediate MRF through electron shuttling functionality. However, whether a link exists between solid-phase NOM-mediated MRF in soil and the age of paddy field since the reclamation on fallow is unclear. Here, we use microbial reduction method to assess the solid-phase NOM-mediated MRF of paddy soils with different reclamation ages. The results show that solid-phase NOM-mediated MRF exhibits a positive response to land use change sequence from fallow to paddy field, indicating that the long-term natural development of paddy field favors the electron shuttling of NOM between cells and Fe(III) minerals. This increase in the electron shuttling of NOM is not due to the increase in the redox functional groups of NOM, but may be attributed to the formation of NOM-mineral complex through the synergistic increases in NOM content and transformation of soil texture from clay loam to loam. The decrease in the redox potential of Fe(III) minerals in soil caused by decreased pH and the increase in Fe content in the organic matter-complexed form may also partly facilitate electron transfer from NOM to Fe(III) minerals. Our work is useful in predicting the role of soil solid-phase NOM in mediating MRF in the context of long-term reclamation of paddy field and provides guidance for the environmental management of paddy fields.

Association Between Pulmonary Vessel-Related Structures and Cryptogenic Fibrosing Alveolitis Using Derived Computed Tomography Among Chinese Patients.

BACKGROUND The aim of this study was to assess the association between pulmonary vessel-related structures and cryptogenic fibrosing alveolitis (CFA) in a drug trial in a Chinese population using derived computed tomography (dCT) to evaluate functional reduction and survival. MATERIAL AND METHODS Discovery and validation cohorts were chosen separately by fulfilment of drug trial entry criteria, and we enrolled 269 and 292 consecutive patients, respectively. CFA patients who had undergone imaging based on volumetric non-contrast CT at our hospital were subjected to pulmonary vessel-related structure (PVS) measures and dCT to forecast mortality and reduction in reduced forced vital capacity of CFA. RESULTS The best forecaster of survival and reduction in terms of reduced forced vital capacity were found to be the dCT-generated outcomes in terms of PVS scores. Patients having less extensive disease highlighted the dCT outcomes through outperformance of CFA measures. When we used the cohort enhancement device, we found reduction in the requisite sample size of a CFA drug trial by 31% with the use of more than 5.0% dCT PVS score. CONCLUSIONS We found an association between CFA and PVS using dCT and it is far better than the results achieved so far by use of criterion standard measures. Additionally, reduction in the restrictive trial costs was also achieved by using cohort enhancement in a CFA drug trial setting, as PVS scores forced us to decrease the size of required CFA drug trial population by 30%. Interestingly, patients who had to take antifibrotic medication for longer periods had longer survival and less decreases forced vital capacity, as identified by PVS scores.

Intercropping wheat and maize increases the uptake of phthalic acid esters by plant roots from soils.

Whether crop intercropping can affect the uptake of phthalic acid esters (PAEs) by plant roots from soils is unclear. In this study, we compare the PAE uptake by plant roots between the wheat/maize intercropping and the wheat and maize monocropping in a field work. We show that the PAE bioconcentration factors of wheat and maize roots are remarkably higher under wheat/maize intercropping than under monocropping, indicating that intercropping may significantly increase the biouptake of PAEs as compared to monocropping. The wheat/maize intercropping can increase the electron transfer capacity (ETC) of water-extractable organic matter (WEOM) in soils by increasing the abundance of redox-active functional groups in WEOM. The ETC-enhanced WEOM may be an important reason for facilitating the reduction of ferric iron [Fe(III)] minerals to soluble ferrous iron [Fe(II)] by acting as electron shuttle, thus leading to the release of the PAEs originally occluded in Fe(III) minerals into soil pore water. The increased bioavailable PAEs distributed in the soil pore water under wheat/maize intercropping eventually result in the increase in the uptake of PAEs by plant roots from soils. The results can provide insights into the link between the uptake of PAEs by crops and the cropping practices in agricultural ecosystems.

Energy saving control strategies for Haliscomenobacter hydrossis filamentous sludge bulking in the A/O process treating real low carbon/nitrogen domestic wastewater.

The control strategies of energy saving for filamentous sludge bulking were investigated in the A/O process under low dissolved oxygen (DO) with low carbon/nitrogen (C/N) ratio, and the dominant filamentous bacteria were identified by using fluorescent in situ hybridization. Initially, the sludge volume index reached nearly 500 mL/g and serious bulking occurred when the DO value was 0.5 mg/L, with Haliscomenobacter hydrossis as the major filamentous bacteria in the bulking sludge. Later on, the compartment number increased in the aerobic zone, increasing by this way DO, to control serious bulking. Increasing DO to 1 mg/L based on the increase of compartment number in the aerobic zone was the favorable controlling method, which solved the sludge loss, improved the effluent quality to the national discharge standard and allowed for energy costs saving. As a result, the effective control method for H. hydrossis filamentous sludge bulking provided the economical, convenient and longstanding method for most municipal wastewater treatment plants treating real low C/N domestic wastewater.

Novel X-Ray Imaging Technology Allows Substantial Patient Radiation Reduction without Image Quality Impairment in Repetitive Transarterial Chemoembolization for Hepatocellular Carcinoma.

RATIONALE AND OBJECTIVES: To assess patient radiation dose reduction and the image quality of a new X-ray imaging technology during repetitive transarterial chemoembolization (TACE) for hepatocellular carcinoma (HCC). METHODS: Fifty HCC patients (36 men; 57 ± 11 years) undergoing repetitive TACE were first randomly assigned to receive a TACE treatment on a reference X-ray system or a low-dose system with advanced real-time image processing. The alternate system was used for a repeated TACE (treatment interval, 0.5-6 months). Fluoroscopy time, number of digital subtraction angiography (DSA), air kerma (AK), and dose area product (DAP) were compared between the two systems and between the two repetitive TACE. Three interventional radiologists independently rated the image quality in blinded offline readings. RESULTS: Fluoroscopy time (8.7 ± 5.9 minutes vs. 8.7 ± 7.9 minutes, P = .981), numbers of DSA runs (6 ± 4 vs. 6 ± 4, P = .735), and exposure images (173 ± 86 vs. 168 ± 91, P = .916) were equivalent between the two systems. No statistical difference in X-ray usage was found between repeated treatments. Compared to the reference system, the technology significantly reduced AK and DAP by 48.6% (0.17 ± 0.13 Gy vs. 0.41 ± 0.36 Gy, P < .0001) and 50.3% (77.3 ± 55.2 Gy cm(2) vs. 195.0 ± 155.5 Gy cm(2), P < .0001), respectively. Image quality was rated comparable between the new system and the reference, with average scores of 3.9 ± 0.3 versus 4.4 ± 0.3 in fluoroscopy and 4.5 ± 0.2 versus 4.3 ± 0.3 in DSA. CONCLUSIONS: Patient radiation exposure can be substantially reduced by a factor of approximately two with the novel X-ray imaging technology while maintaining image quality.

Intrastriatal transplantation of retinal pigment epithelial cells for the treatment of Parkinson disease: in vivo longitudinal molecular imaging with 18F-P3BZA PET/CT.

PURPOSE: To evaluate the performance of N-[2-(diethylamino)ethyl]-(18)F-5-fluoropicolinamide ((18)F-P3BZA) for visualizing porcine retinal pigment epithelium (pRPE) cells transplanted in the striatum for the treatment of Parkinson disease and to monitor the long-term activity of implanted pRPE cells by means of (18)F-P3BZA positron emission tomography (PET)/computed tomography (CT) in vivo. MATERIALS AND METHODS: Animal work was conducted in accordance with the administrative panel on laboratory animal care. In vitro cell uptake of (18)F-P3BZA was determined with incubation of melanotic pRPE or amelanotic ARPE-19 cells with (18)F-P3BZA. To visualize the implanted pRPE cells in vivo, normal rats (four per group) were injected with pRPE or ARPE-19 cells attached to gelatin microcarriers in the left striatum and with control gelatin microcarriers in the right striatum and followed up with small animal PET/CT. Longitudinal PET/CT scans were acquired in 12 rats up to 16 days after surgery. Postmortem analysis, which included autoradiography and hematoxylin-eosin, Fontana-Masson, and immunofluorescence staining, was performed. Data were compared with the Student t test, analysis of variance, and regression analysis. RESULTS: (18)F-P3BZA accumulated in pRPE cells effectively (3.48% of the injected dose [ID] per gram of brain tissue ± 0.58 at 1 hour after injection of the probe at 2 days after surgery in vivo) but not in control ARPE-19 cells (P < .05). Longitudinal PET/CT scans revealed that the activity of implanted pRPE cells decreased over time, as evidenced by a reduction in (18)F-P3BZA uptake (3.39% ID/g ± 0.18, 2.49% ID/g ± 0.41, and 1.20% ID/g ± 0.13 at days 2, 9, and 16, respectively; P < .05). Postmortem analysis helped confirm the results of in vivo imaging. CONCLUSION: (18)F-P3BZA PET/CT is a feasible technique for visualizing and detecting the activity of implanted RPE cells in vivo.

Evaluation of (99) (m)TcN-MPO as a new myocardial perfusion imaging agent in normal dogs and in an acute myocardial infarction canine model: comparison with (99) (m)Tc-sestamibi.

PURPOSE: (99) (m)TcN-MPO ([(99) (m)TcN(mpo)(PNP5)](+): mpo = 2-mercaptopyridine oxide and PNP5 = N-ethoxyethyl-N,N-bis[2-(bis(3-methoxypropyl)phosphino)ethyl]amine) is a cationic (99) (m)Tc-nitrido complex, which has favorable biodistribution and myocardial uptake with rapid liver clearance in Sprague Dawley rats. The objective of this study was to compare the biodistribution and pharmacokinetics of (99) (m)TcN-MPO and (99) (m)Tc-Sestamibi in normal dogs, and to evaluate the potential of (99) (m)TcN-MPO as a myocardial perfusion agent in canines with acute myocardial infarction. METHODS: Five normal mongrel dogs were injected intravenously with (99) (m)TcN-MPO. Venous blood samples were collected via a femoral vein catheter at 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 60, and 90 min post-injection (p.i.). Anterior-posterior planar images were acquired by γ-camera at 10, 20, 30, 60, 90, and 120 min p.i. Regions of interest (ROIs) were drawn around the heart, liver, and lungs. The heart/liver and heart/lung ratios were calculated by dividing the mean counts in heart ROI by the mean counts in the liver and lung ROI, respectively. For comparison, (99) (m)Tc-sestamibi was also evaluated in the same five dogs. The interval period between the two examinations was 1 week to eliminate possible interference between these two radiotracers. In addition, single positron emission computed tomography (SPECT) images in the canine infarct model were collected 24 h after myocardial infarction at 30 and 60 min after the administration of (99) (m)TcN-MPO (n = 4) or (99) (m)Tc-Sestamibi (n = 4). RESULTS: It was found that (99) (m)TcN-MPO and (99) (m)Tc-Sestamibi displayed very similar blood clearance characteristics during the first 90 min p.i. Both (99) (m)TcN-MPO and (99) (m)Tc-Sestamibi had a rapid blood clearance with less than 50% of initial radioactivity remaining at 1 min and less than 5% at 30 min p.i. (99) (m)TcN-MPO and (99) (m)Tc-Sestamibi both showed good heart/lung contrast. The heart/liver ratio of (99) (m)TcN-MPO increased with time (0.53 ± 0.06 at 10 min, 0.90 ± 0.062 at 30 min, and 1.22 ± 0.06 at 60 min p.i.), whereas the heart/liver ratio of (99) (m)Tc-Sestamibi remained low at all time points (0.50 ± 0.03 at 10 min, 0.64 ± 0.03 at 30 min, and 0.60 ± 0.02 at 60 min p.i.). SPECT imaging studies in canines with acute myocardial infarction indicated that good visualization of the left ventricular wall and perfusion defects could be achieved at 30 min after administration of (99) (m)TcN-MPO but not after (99) (m)Tc-Sestamibi. CONCLUSION: The combination of reasonable heart uptake with rapid hepatobiliary excretion makes (99) (m)TcN-MPO a promising new radiotracer for myocardial perfusion imaging.

MR reporter gene imaging of endostatin expression and therapy.

PURPOSE: The aim of this study is to monitor endostatin gene expression and therapy using transferrin receptor (TfR) as reporter gene and transferrin conjugate of ultrasmall supramagnetic iron oxide nanoparticle (Tf-USPIO) as magnetic resonance (MR) reporter probe. PROCEDURE: A retroviral plasmid (pLP-LNCX) encoding mouse endostatin and TfR was constructed, and packaged with a titer of 4 × 10(7)colony-forming units per millimeter. MDA-MB-231 breast tumors were established in BALB/c mice by subcutaneous injection of 2 × 10(6) MDA-MB-231 cells. Mice were intratumorally injected with recombinant retrovirus and imaged with MR using Tf-USPIO. Western blot, Prussian blue, and immunohistochemical staining were performed to validate the magnetic resonance imaging results. The antitumor effect of retro-endostatin (ES)-TfR was also evaluated by intratumoral injection of the viral vector. RESULTS: The expression of both endostatin and TfR genes in MDA-MB-231 cells after retroviral transfection was confirmed by Western blot and flow cytometry. Tf-USPIO conjugate binds specifically to cells stably transfected with retro-ES-TfR. After intravenous injection of the Tf-USPIO conjugate, there was a more pronounced decrease in T2 relaxation time in tumors treated with retro-ES-TfR than in tumors treated with empty retrovirus retro-LNCX. The expression of ES gene significantly delayed the growth of MDA-MB-231 tumor and reduction of microvessel density and VEGF level as compared to those without viral transfection or transfected with empty retro-LNCX vector. CONCLUSIONS: Endostatin therapeutic gene expression was visualized successfully using TfR reporter gene and Tf-USPIO MR reporter probe, which indicates that MR reporter gene imaging may be valuable in gene therapy to evaluate therapeutic gene expression and treatment efficacy.

Characterizing breast cancer xenograft epidermal growth factor receptor expression by using near-infrared optical imaging.

BACKGROUND: Epidermal growth factor receptor (EGFR) overexpression is associated with several key features of cancer development and growth. Therefore, EGFR is a very promising biological target for tumor diagnosis and anticancer therapy. Characterization of EGFR expression is important for clinicians to select patients for EGFR-targeted therapy and evaluate therapeutic effects. PURPOSE: To investigate whether near-infrared (NIR) fluorescent dye Cy5.5-labeled anti-EGFR monoclonal antibody Erbitux can characterize EGFR expression level in MDA-MB-231 and MCF-7 breast cancer xenografts using an in vivo NIR imaging method. MATERIAL AND METHODS: A fluorochrome probe was designed by coupling Cy5.5 to Erbitux through acidylation, and the fluorescence property of the Erbitux-Cy5.5 conjugate was characterized by fluorospectroscopy. Flow cytometry and laser confocal microscopy were used to test the EGFR specificity of the antibody probe in vitro. Erbitux-Cy5.5 was also injected intravenously into immune-deficient mice bearing MDA-MB-231 or MCF-7 tumors. Whole-body and region-of-interest fluorescence images were acquired and analyzed. The EGFR expression was also analyzed and confirmed by immunohistochemical assay. RESULTS: The maximum excitation/emission wavelength for the Erbitux-Cy5.5 probe was 674/697 nm, similar to that of free Cy5.5 (674/712 nm). Confocal microscopy confirmed receptor-specific uptake in MDA-MB-231 and MCF-7 cells. In flow cytometry probe specificity assay, Erbitux-Cy5.5 showed a 9.32-fold higher affinity for MDA-MB-231 than MCF-7 cells. In vivo NIR imaging also indicated specific uptake in EGFR-positive tumors. Probe uptake rate and maximum intake dose in MDA-MB-231 were significantly higher than those in MCF-7 xenografts (P < 0.001). Immunohistochemical staining confirmed the in vivo imaging results, showing differentiated EGFR expression in MDA-MB-231 (+ + +) and MCF-7 (+) tumor tissues. CONCLUSION: Erbitux-Cy5.5 may be used as a specific NIR contrast agent for the noninvasive characterization of EGFR expression level in breast cancer xenografts.