Increased Capture Efficiency Research Articles

Rare isotope-containing diamond colour centres for fundamental symmetry tests.

Detecting a non-zero electric dipole moment in a particle would unambiguously signify physics beyond the Standard Model. A potential pathway towards this is the detection of a nuclear Schiff moment, the magnitude of which is enhanced by the presence of nuclear octupole deformation. However, due to the low production rate of isotopes featuring such 'pear-shaped' nuclei, capturing, detecting and manipulating them efficiently is a crucial prerequisite. Incorporating them into synthetic diamond optical crystals can produce defects with defined, molecule-like structures and isolated electronic states within the diamond band gap, increasing capture efficiency, enabling repeated probing of even a single atom and producing narrow optical linewidths. In this study, we used density functional theory to investigate the formation, structure and electronic properties of crystal defects in diamond containing [Formula: see text], a rare isotope that is predicted to have an exceptionally strong nuclear octupole deformation. In addition, we identified and studied stable lanthanide-containing defects with similar electronic structures as non-radioactive proxies to aid in experimental methods. Our findings hold promise for the existence of such defects and can contribute to the development of a quantum information processing-inspired toolbox of techniques for studying rare isotopes. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'.

Long cruising aptamer-albumin nanobots intelligently capture and restrain circulating tumor cells

Circulating tumor cells (CTC) are the root cause of life-threatening cancer metastases. The rare CTC cannot be specifically killed by anti-cancer agents without producing any side effects, nor be targeted-and-eradicated by antibody or aptamer complexes because of the complexes’ limited circulating half-life in the blood owing to metabolism and immune clearance. Here, we build the biosafe and biostable aptamer-albumin nanobots that can cruise in the blood much long together with the CTC, resulting in the increased capture efficiency and specificity of the nanobots targeting CTC. The intelligent-recognizing unit of the novel nanobots is composed of three EpCAM-targeting aptamers (AP) that can specifically target breast CTC, and their sticky ends are completely closed to form the biostable circular trivalent aptamers (CTA). The binding energy, specificity and stability of the circular three arms CTA are significantly superior to their linear AP. After conjugating CTA to human serum albumin (CTA-HSA) by amination reaction, the blood circulation time of CTA-HSA in mice was significantly prolonged by 3 folds, resulting in the enhanced collision probability and increased capture efficiency of CTA-HSA to CTC. CTA-HSA can escape the immune clearance and inhibit adhesion/invasion and cell cycle of CTC, resulting in CTC apoptosis. This proof-of-concept study provides a promising nanobiomaterial for CTC-induced cancer metastases.

High-throughput extraction on a dynamic solid phase for low-abundance biomarker isolation from biological samples

Liquid biopsy, in particular circulating tumor DNA (ctDNA) analysis, has paved the way for a new noninvasive approach to cancer diagnosis, treatment selection and follow-up. As a crucial step in the analysis, the extraction of the genetic material from a complex matrix needs to meet specific requirements such as high specificity and low loss of target. Here, we developed a new generation of microfluidic fluidized beds (FBs) that enable the efficient extraction and preconcentration of specific ctDNA sequences from human serum with flow rates up to 15 µL/min. We first demonstrated that implementation of a vibration system inducing flow rate fluctuations combined with a mixture of different bead sizes significantly enhanced bead homogeneity, thereby increasing capture efficiency. Taking advantage of this new generation of high-throughput magnetic FBs, we then developed a new method to selectively capture a double-stranded (dsDNA) BRAF mutated DNA sequence in complex matrices such as patient serum. Finally, as proof of concept, ligation chain reaction (LCR) assays were performed to specifically amplify a mutated BRAF sequence, allowing the detection of concentrations as low as 6 × 104 copies/µL of the mutated DNA sequence in serum.

Parametric study on the flight envelope of a radio-frequency ion thruster based atmosphere-breathing electric propulsion system

The atmosphere-breathing electric propulsion (ABEP) system utilizes atmospheric species as propellants to generate thrust for drag compensation of a satellite in very-low-Earth-orbit (VLEO). A parametric approach is used to assess the impact of different parameters on the flight envelope of a sample VLEO satellite with an ABEP system based on a radio-frequency ion thruster (RIT). The considered parameters include capture efficiency, maximum input power, solar activity, and atomic oxygen recombination factor. The NRLMSIS 2.0 atmosphere model is used to determine the flow conditions at VLEO, at a target altitude of 150–300 km with high, moderate, and low solar activity levels. DSMC method is employed to calculate the drag of the sample satellite with the ABEP system. The 0-D model of the RIT discharge chamber is used to predict the thrust of the RIT-based ABEP system. The flight envelope of a sample RIT-based ABEP system shows that drag can be compensated at altitudes between 196 km and 248 km. Increasing capture efficiency and maximum input power expands the feasible range for drag compensation to higher and lower altitudes, respectively. Also, the flight envelope shifts to higher altitudes with increasing solar activity levels. However, the atomic oxygen recombination factor of the intake device has minimal effects on the flight envelope.

Profiling of amines in biological samples using polythioester-functionalized magnetic nanoprobe.

Introduction: The metabolic balance of amines is closely related to human health. It remains a great challenge to analyze amines with high-throughput and high-coverage. Methods: Polythioester-functionalized magnetic nanoprobes (PMPs) have been prepared under mild conditions and applied in chemoselective capture of amides. With the introduction of polythioester, PMPs demonstrate remarkably increased capture efficiency, leading to the dramatically improved sensitivity of mass spectrometry detection. Results: The analysis method with PMPs treatment has been applied in rapid detection of more than 100 amines in lung adenocarcinoma cell lines, mouse organ tissues, and 103 human serum samples with high-throughput and high-coverage. Statistical analysis shows that arginine biosynthesis differed between lung adenocarcinoma cell lines. Discussion: Phenylalanine, tyrosine and tryptophan biosynthesis differed between tissues. The combination indicators demonstrate a great diagnostic accuracy for distinguishing between health and lung disease subjects as well as differentiating the patients with benign lung disease and lung cancer. With powerful capture ability, low-cost preparation, and convenient separation, the PMPs demonstrate promising application in the intensive study of metabolic pathways and early diagnosis of disease.high-throughput and high-coverage. Here, polythioester-functionalized magnetic nanoprobes (PMPs) have been prepared under mild conditions and applied in chemoselective capture of amides. With the introduction of polythioester, PMPs demonstrate remarkably increased capture efficiency, leading to the dramatically improved sensitivity of mass spectrometry detection. The analysis method with PMPs treatment has been applied in rapid detection of more than 100 amines in lung adenocarcinoma cell lines, mouse organ tissues, and 103 human serum samples with high-throughput and high-coverage. Statistical analysis shows that arginine biosynthesis differed between lung adenocarcinoma cell lines. Phenylalanine, tyrosine and tryptophan biosynthesis differed between tissues. The combination indicators demonstrate a great diagnostic accuracy for distinguishing between health and lung disease subjects as well as differentiating the patients with benign lung disease and lung cancer. With powerful capture ability, low-cost preparation, and convenient separation, the PMPs demonstrate promising application in the intensive study of metabolic pathways and early diagnosis of disease.

Polyhedral Particles with Controlled Concavity by Indentation Templating.

Current methods for fabricating microparticles offer limited control over size and shape. Here, we demonstrate a droplet microfluidic method to form polyhedral microparticles with controlled concavity. By manipulating Laplace pressure, buoyancy, and particle rheology, we generate microparticles with diverse shapes and curvatures. Additionally, we demonstrate the particles provide increased capture efficiency when used for particle-templated emulsification. Our approach enables microparticles with enhanced chemical and biological functionality.

Attomolar Sensitivity in Single Biomarker Counting upon Aqueous Two-Phase Surface Enrichment.

From longstanding techniques like enzyme-linked immunosorbent assay (ELISA) to modern next-generation sequencing, many of the most sensitive and specific biomarker detection assays require capture of the analyte at a surface. While surface-based assays provide advantages, including the ability to reduce background by washing away excess reagents and/or increase specificity through analyte-specific capture probes, the limited efficiency of capture from dilute solution often restricts assay sensitivity to the femtomolar-to-nanomolar range. Although assays for many nucleic acid analytes can decrease limits of detection (LODs) to the subfemtomolar range using polymerase chain reaction, such amplification may introduce biases, errors, and an increased risk of sample cross-contamination. Furthermore, many analytes cannot be amplified easily, including short nucleic acid fragments, epigenetic modifications, and proteins. To address the challenge of achieving subfemtomolar LODs in surface-based assays without amplification, we exploit an aqueous two-phase system (ATPS) to concentrate target molecules in a smaller-volume phase near the assay surface, thus increasing capture efficiency compared to passive diffusion from the original solution. We demonstrate the utility of ATPS-enhanced capture via single molecule recognition through equilibrium Poisson sampling (SiMREPS), a microscopy technique previously shown to possess >99.9999% detection specificity for DNA mutations but an LOD of only ∼1-5 fM. By combining ATPS-enhanced capture with a Förster resonance energy transfer (FRET)-based probe design for rapid data acquisition over many fields of view, we improve the LOD ∼ 300-fold to <10 aM for an EGFR exon 19 deletion mutation. We further validate this ATPS-assisted FRET-SiMREPS assay by detecting endogenous exon 19 deletion molecules in cancer patient blood plasma.

Foraging Ecology of White-Bellied Heron (Ardea insignis) in the Fast-Flowing Rivers of Namdapha Tiger Reserve, Arunachal Pradesh, India

The critically endangered White-bellied Heron (Ardea insignis) is a piscivorous visual forager that prefers to forage in fast-flowing freshwater rivers. This study highlights White-bellied Heron foraging behavior in the fast-flowing rivers of Namdapha Tiger Reserve during 2013–2017. The herons spent significantly more time and also made more foraging attempts while foraging in shallow water (foraging time: 61.45 ± 15.55%; strike rate: 1.70 strikes/hr). Herons were more successful in catching fishes when they foraged facing upstream (capture rate: 0.62 fishes caught/hr) with increased capture efficiency (44.62%). White-bellied Herons caught the majority (60.98%) of small sized fishes (≤ 9 cm) while facing upstream and the majority (60.92%) of large sized fishes (> 18 cm) while facing downstream. These findings shed light on the manner in which this rare and critically endangered bird is adapted to life on fast-flowing rivers and the importance of these unique places for its conservation.

Efficient Detection and Single-Cell Extraction of Circulating Tumor Cells in Peripheral Blood.

Circulating tumor cells (CTCs) play an important role in cancer biology studies. To further elucidate the role of single CTCs in tumor metastasis and prognosis, effective methods must be developed to isolate and encapsulate single CTCs. In this work, a single CTC capture and encapsulation platform based on ZnO nanofibers and surface acoustic waves was constructed. We also demonstrated that this platform can capture and encapsulate single CTCs efficiently. We first validated that the dense ZnO nanofibers provide additional binding sites, resulting in an increased capture efficiency of up to 93.3%. We then demonstrated that the release efficiency was increased to 100% by dissolving the substrate with ultralow concentration (25 mM) phosphoric acid, and the activity of the released cells was not affected. Furthermore, the released cells were suspended in alginate solution and encapsulated single CTCs via droplet-based surface acoustic wave devices. The encapsulating rate of a single cell is up to 13% under a pulse width duration of 520 μs. Few technology based on nanofibers and acoustic tweezers for single-cell encapsulation via acoustic droplet vaporization has been reported. It has a wide range of potential applications to acquire single target cells, which may facilitate further early clinical diagnosis and treatment of cancer patients.

New Insights into the Role of Surface Nanobubbles in Bubble-Particle Detachment.

It is well recognized that an improved flotation recovery can be achieved by introducing nanobubbles to common flotation practice due to the increased capture efficiency between bubbles and particles. However, the specific role of nanobubbles in bubble-particle interactions (collision, attachment, and detachment) is not well understood. In the present study, we explore the role of surface nanobubbles in bubble-particle detachment. Surface nanobubbles were introduced via ethanol-water exchange and their presence was confirmed using laser scanning confocal microscopy (LSCM). The effect of surface nanobubbles on bubble-particle detachment behavior was then investigated using an oscillating bubble apparatus. Bubble-particle aggregate stability was evaluated using critical detachment amplitude. Further, bubble-particle detachment forces in the absence and presence of nanobubbles were measured directly using a micro-nano mechanical testing system. Using LSCM, numerous surface nanobubbles were observed on a glass surface after ethanol-water exchange, regardless of wettability. The number and lateral dimensions of generated nanobubbles on the hydrophilic surface were significantly smaller than that on the hydrophobic surface. Surface nanobubbles increased the stability of bubble-particle aggregates. Macroscopic air bubbles coalesce with the nanobubbles on the particle surface, increasing the pinning effect of the three-phase contact line and advancing contact angle. As a result, the capillary force between bubbles and particles increased in the presence of surface nanobubbles.

3D printed microfluidic devices for circulating tumor cells (CTCs) isolation

Isolation of circulating tumor cells (CTCs) from blood samples has important prognostic and therapeutic implications for cancer treatments, but the process is very challenging due to the low concentration of CTCs. In this study, we report a novel 3D printed microfluidic device functionalized with anti-EpCAM (epithelial cell adhesion molecule) antibodies to isolate CTCs from human blood samples. A 3D printing technology was utilized with specially designed interior structures to fabricate a microfluidic device with high surface area and fluid flow manipulation, increasing capture efficiency of tumor cells. These devices with the optimal flow rate (1 mL/h) and channel length (2 cm) were demonstrated to test three kinds of EpCAM positive cancer cell lines (MCF-7 breast cancer, SW480 colon cancer, and PC3 prostate cancer), and one kind of EpCAM negative cancer cell line (293T kidney cancer). Experimentally, the capture efficiency higher than 90% has been achieved, and the isolation of MCF-7 tumor cells from spiked human blood samples has also been demonstrated. Combined with DNA-based detection (e.g. polymerase chain reaction or DNA sequencing), the detection and analysis of released DNAs from captured tumor cells could be another future direction for clinical diagnosis and cancer treatment.

A Miniature Gas Sampling Interface with Open Microfluidic Channels: Characterization of Gas-to-Liquid Extraction Efficiency of Volatile Organic Compounds.

Chemosensory protein based olfactory biosensors are expected to play a significant role in next-generation volatile organic compound (VOC) detection systems due to their ultra-high sensitivity and selectivity. As these biosensors can perform most efficiently in aqueous environments, the detection systems need to incorporate a gas sampling interface for gas-to-liquid extraction. This interface should extract the VOCs from the gas phase with high efficiency and transfer them into the liquid containing biosensors to enable subsequent detection. To design such a transfer interface, an understanding of the key parameters influencing the gas-to-liquid extraction efficiency of target VOCs is crucial. This paper reports a gas sampling interface system based on a microfluidic open-channel device for gas-to-liquid extraction. By using this device as a model platform, the key parameters dictating the VOC extraction efficiency were identified. When loaded with 30 μL of capture liquid, the microfluidic device generates a gas-liquid interface area of 3 cm2 without using an interfacial membrane. The pumpless operation based on capillary flow was demonstrated for capture liquid loading and collection. Gas samples spiked with lipophilic model volatiles (hexanal and allyl methyl sulfide) were used for characterization of the VOC extraction efficiency. Decreasing the sampling temperature to 15 °C had a significant impact on increasing capture efficiency, while variation in the gas sampling flow rate had no significant impact in the range between 40–120 mL min−1. This study found more than a 10-fold increase in capture efficiency by chemical modification of the capture liquid with alpha-cyclodextrin. The highest capture efficiency of 30% was demonstrated with gas samples spiked with hexanal to a concentration of 16 ppm (molar proportion). The approach in this study should be useful for further optimisation of miniaturised gas-to-liquid extraction systems and contribute to the design of chemosensory protein-based VOC detection systems.

Carbon Dioxide Capture for Geological Sequestration - The Issues and Decision Parameters for T&amp;amp;T's Petrochemical and Power Generation CO2 Sources

Since there is a growing emphasis on Carbon Dioxide (CO2) sequestration as a carbon management strategy coupled with the acceptance that geological sequestration is perhaps one of the most promising carbon management techniques, the need to capture CO2 at sources in a cost effective and safe manner is gaining widespread attention. This is justified as CO2 capture is often one of the more expensive components of any geological sequestration capture, transportation and storage chain. As such, much emphasis is currently being placed in the advancement of processes such as increasing capture efficiency and reducing capture cost which are demonstrated by the many pilot plants being built worldwide. Carbon capture essentially produces a concentrated stream of CO2 at high pressure, rendering it to be readily transported to appropriate storage sites. Although theoretically the entire gas can be transported using the various transportation modes, the cost associated with doing this often deems this option impractical. Extracting the CO2 in a more concentrated form and elevating it to the required high pressure is therefore an important component of the Carbon Capture and Storage (CCS) chain. For Trinidad and Tobago (T&T), post combustion capture is most desirous as the targeted CO2 sources emanate from existing plants. This is so because physical space at these plants is limited and does not readily allow for precombustion technologies. While oxyfuel combustion may be applicable to some of the existing plants, since the sources being evaluated in this paper are related emissions from Ammonia Synthesis and Power Generation, the concentration of CO2 in these streams is either already high and commensurate with that of oxyfuel carbon capture (as it the case with Ammonia) or the plants cannot be easily retrofitted for oxyfuel capture (as with the Power Generation). Interestingly, most of T&T’s emissions (over 50%) emanate from the petrochemical sector and in particular from Ammonia production processes. There are eleven (11) Ammonia plants in T&T which contributes to the nation being the number one exporter of this commodity globally. During the synthesis of Ammonia, a relatively pure stream of CO2 is produced in the process typically consisting of over 90% CO2 with some mostly water vapour as the other impurity. One can therefore argue that to an extent the CO2 is already captured. Further purification of the CO2 stream via water vapour, oxygen separation and pressurization is all that is needed for engagement in CCS projects. This paper investigates CO2 capture from Ammonia Plants and compares it with CO2 capture from Power Plants in TT Ammonia and Power). These simulations were then used as the primary tool to estimate CO2 capture cost for T&T from Ammonia synthesis and Power Generation. Of particular interest for T&T, this study illustrates an estimate of the costs for capturing up to 8 Mt/yr of CO2. It is expected that this information can be critical in evaluating the overall CCS economics for T&T and can contribute towards a suitable pilot project.

Novel Spray Tower for CO2 Capture Using Uniform Spray of Monosized Absorbent Droplets

Conventional spray towers emit absorbent droplets that are nonuniform in size and spatial distribution; as a result, capture efficiency is degraded. This paper presents the design and evaluation of a novel spray tower for capturing CO2 with much increased capture efficiency. The tower uses a multinozzle plate, and can spray sorbent drops of almost the same size vertically and quite uniformly across the flow cross section. Uniform size and spatial distribution of droplets greatly increased the capture efficiency η, although much bigger drops were used, achieving η ∼ 95%, which has rarely been reported to date for CO2 capture by a spray tower. Experimental results were compared with the predictions by numerical simulations in excellent agreement. The new spray tower has a number of strong points that are favorable for scaling up of diameter and length.

A Refined Electrofishing Technique for Collecting Silver Carp: Implications for Management

AbstractDetecting nuisance species at low abundance or in newly established areas is critical to developing pest management strategies. Due to their sensitivity to disturbance and erratic jumping behavior, Silver Carp Hypophthalmichthys molitrix can be difficult to collect with traditional sampling methods. We compared catch per unit effort (CPUE) of all species from a Long Term Resource Monitoring (LTRM) electrofishing protocol to an experimental electrofishing technique designed to minimize Silver Carp evasion through tactical boat maneuvering and selective application of power. Differences in CPUE between electrofishing methods were detected for 2 of 41 species collected across 2 years of sampling at 20 sites along the Illinois River. The mean catch rate of Silver Carp using the experimental technique was 2.2 times the mean catch rate of the LTRM electrofishing technique; the increased capture efficiency at low relative abundance emphasizes the utility of this method for early detection. The experimental electrofishing also collected slightly larger Silver Carp (mean: 510.7 mm TL versus 495.2 mm TL), and nearly four times as many Silver Carp independently jumped into the boat during experimental transects. Novel sampling approaches, such as the experimental electrofishing technique used in this study, should be considered to increase probability of detection for aquatic nuisance species.Received June 9, 2016; accepted September 19, 2016 Published online January 3, 2017

Performance of Inlet Filtration System in Relation to the Uncaptured Particles Causing Fouling in the Gas Turbine Compressor

Accounting for the impact of uncaptured particles that cause compressor fouling and subsequently performance degradation when a filter system is in place is often ignored when evaluating the performance of filtration systems. Too often, the emphasis is on capture efficiency and the corresponding differential pressure loss, which are important aspects, however only constitutes a part of the overall impact on the engine performance. The main aim of this study is a first step to quantify the loss that is attributed to compressor fouling by the uncaptured particles, identify a threshold point for which further increase in pressure losses (increasing capture efficiency) no longer yields further increases in fouling levels, and subsequently investigate these respective losses and total losses in a reference high efficiency system (HES) and a hypothetical low efficiency system. Corrected operational data from a 268 MW gas turbine engine were used to evaluate the levels of degradation in the engine at different power settings. With the measured filter media pressure loss during operation and turbomatch (an in-house gas turbine performance simulation software), the impact of power reduction due to pressure loss of the filter was accounted for in the total estimated losses due to engine degradation. That of fouling was calculated based on applicable assumptions, while deducting the loss due to filtration systems from the total loss due to degradation. The study shows the inverse relationship between fouling effects and filter pressure losses as expected. More importantly, it indicates that the higher efficiency system performs better than the low efficiency system, notwithstanding the more dominant impact of higher differential pressure losses. It was also observed that the threshold where fouling effects are zero or negligible is around 800 Pa at high power setting and 600 Pa at lower power setting. In general, for all forms of the degradation using the engine data and simulation software, it is observed that at lower power settings, the impact on the engine is a lot more severe in a single-shaft constant speed operation.

Increasing capture efficiency of pallid sturgeon Scaphirhynchus albus (Forbes and Richardson, 1905) and the reliability of catch rate estimates

This study evaluated the effects of environmental parameters on the probability of capturing endangered pallid sturgeon (Scaphirhynchus albus) using trotlines in the lower Mississippi River. Pallid sturgeon were sampled by trotlines year round from 2008 to 2011. A logistic regression model indicated water temperature (T; P < 0.01) and depth (D; P = 0.03) had significant effects on capture probability (Y = −1.75 − 0.06T + 0.10D). Habitat type, surface current velocity, river stage, stage change and non-sturgeon bycatch were not significant predictors (P = 0.26–0.63). Although pallid sturgeon were caught throughout the year, the model predicted that sampling should focus on times when the water temperature is less than 12°C and in deeper water to maximize capture probability; these water temperature conditions commonly occur during November to March in the lower Mississippi River. Further, the significant effect of water temperature which varies widely over time, as well as water depth indicate that any efforts to use the catch rate to infer population trends will require the consideration of temperature and depth in standardized sampling efforts or adjustment of estimates.

Automated microfluidically controlled electrochemical biosensor for the rapid and highly sensitive detection of Francisella tularensis

Tularemia is a highly infectious zoonotic disease caused by a Gram-negative coccoid rod bacterium, Francisella tularensis. Tularemia is considered as a life-threatening potential biological warfare agent due to its high virulence, transmission, mortality and simplicity of cultivation. In the work reported here, different electrochemical immunosensor formats for the detection of whole F. tularensis bacteria were developed and their performance compared. An anti-Francisella antibody (FB11) was used for the detection that recognises the lipopolysaccharide found in the outer membrane of the bacteria. In the first approach, gold-supported self-assembled monolayers of a carboxyl terminated bipodal alkanethiol were used to covalently cross-link with the FB11 antibody. In an alternative second approach F(ab) fragments of the FB11 antibody were generated and directly chemisorbed onto the gold electrode surface. The second approach resulted in an increased capture efficiency and higher sensitivity. Detection limits of 4.5ng/mL for the lipopolysaccharide antigen and 31 bacteria/mL for the F. tularensis bacteria were achieved. Having demonstrated the functionality of the immunosensor, an electrode array was functionalised with the antibody fragment and integrated with microfluidics and housed in a tester set-up that facilitated complete automation of the assay. The only end-user intervention is sample addition, requiring less than one-minute hands-on time. The use of the automated microfluidic set-up not only required much lower reagent volumes but also the required incubation time was considerably reduced and a notable increase of 3-fold in assay sensitivity was achieved with a total assay time from sample addition to read-out of less than 20min.

Local trophic specialisation in a cosmopolitan spider (Araneae)

Trophic specialisation can be observed in species with long-term constant exploitation of a certain prey in all populations or in a population of a species with short-term exploitation of a certain prey. While in the former case the species would evolve stereotyped or specialised trophic adaptations, the trophic traits of the latter should be versatile or generalised. Here, we studied the predatory behavioural adaptations of a presumed myrmecophagous spider, Oecobius navus. We chose two distinct populations, one in Portugal and the other in Uruguay. We analysed the actual prey of both populations and found that the Portuguese population feeds mainly on dipterans, while the Uruguayan population feeds mainly on ants. Indeed, dipterans and springtails in Portugal, and ants in Uruguay were the most abundant potential prey. In laboratory trials O. navus spiders recognised and captured a wide variety of prey. The capture efficiency of the Portuguese population measured as components of the handling time was higher for flies than for ants, while that of the Uruguayan population was higher for ants. We found phenotypic plasticity in behavioural traits that lead to increased capture efficiency with respect to the locally abundant prey, but it remains to be determined whether the traits of the two populations are genetically fixed. We conclude that O. navus is a euryphagous generalist predator which shows local specialisation on the locally abundant prey.

Affinity and size capture of circulating tumor cells: A platform for increased sensitivity

Abstract Background: The potential clinical value of evaluating circulating tumor cells (CTCs) from blood is clear. CTC analysis can aid in cancer diagnosis, prognosis, and treatment prediction. However, since CTCs are rare, current analysis is limited by low efficiencies. Variability of expression of cell surface antigens by CTCs make capture mechanisms based on antibody affinity less than ideal. We report here data from a CTC platform that combines affinity capture with size filtration capture. Methods: A spiked cell model was used, involving whole EDTA blood spiked with SKBR-3 human breast cancer cells. Two microfluidic chips were analyzed, a standard chip (T7) with constant gap size between posts, and a gradient chip (MA3) with a gap-size gradient between posts starting at 40 μ and decreasing to 12 μ. Chips were coated with either an anti-EpCAM monoclonal antibody or with no Ab. An anti-cytokeratin (CK) Ab in combination with a nuclear specific fluorescent stain on an automated cell imaging platform was used to identify CTCs. Results: 45% of cells were captured by size alone (MA3 with no Ab), 16% of cells were captured by affinity alone (T7 with MAb), and 65% of cells were captured by a combination of antibody affinity and size gradient (MA3 with MAb). This increased capture efficiency has been confirmed in clinical samples from patients with metastatic breast cancer, with a greater than 40% increase in capture efficiency utilizing both mechanisms. Whole blood from healthy donors run through either chip type yielded virtually no CTCs. FACS analysis showed that 75% of cultured SKBR-3 cells express high levels of EpCAM. This expression level will vary, as will, presumably, the relative contributions of the antibody capture mechanism and the size capture mechanism. A “heat map” analysis can demonstrate visually the relative contributions of each and these will be presented. Conclusions: The MA3 microfluidic chip captures CTCs using a combination of affinity and size filtration. This allows for the capture of CTCs with varying expression levels of EpCAM by exploiting the size differential between these CTCs and other blood elements. This dual-capture mechanism may allow for more efficient capture than affinity alone. Further work evaluating this platform in late-stage breast cancer patients is ongoing.