Selective detection of circulating tumor cells (CTCs) is of significant clinical importance for the clinical diagnosis and prognosis of cancer metastasis. However, largely due to the extremely low number of CTCs (as low as one in 10 9 hematologic cells) in the blood of patients, effective detection and separation of the rare cells remain a tremendous challenge. Cell rolling is known to play a key role in physiological processes such as recruitment of leukocytes to sites of inflammation and selectin-mediated CTC metastasis. Furthermore, as CTCs typically express epithelial-cell adhesion molecule (EpCAM) on the surface whereas normal hematologic cells do not, substrates with immobilized antibody against EpCAM may specifically interact with CTCs. In this paper, we created biomimetic surfaces functionalized with P-and E-selectin and anti-EpCAM that induce different responses of HL-60 (used as a model of leukocytes in this study) and MCF-7 (a model of CTCs) cells. HL-60 and MCF-7 cells showed different degrees of interaction with P-/E-selectin and antiEpCAM at a shear stress of 0.32 dyn/cm 2 . HL-60 cells exhibited rolling on P-selectin-immobilized substrates at a velocity of 2.26 ± 0.28 μm/sec whereas MCF-7 cells had no interaction with the surface. Both cell lines, however, showed interactions with E-selectin, and the rolling velocity of MCF-7 cells (4.24 ± 0.31 μm/sec) was faster than that of HL-60 cells (2.12 ± 0.15 μm/sec). On the other hand, only MCF-7 cells interacted with anti-EpCAM-coated surfaces, forming stationary binding under flow. More importantly, the combination of the rolling (E-selectin) and stationary binding (antiEpCAM) resulted in substantially enhanced separation capacity and capture efficiency (more than 3-fold enhancement), as compared to a surface functionalized solely with anti-EpCAM which has been commonly used for CTC capture. Our results indicate that cell-specific detection and separation may be achieved through mimicking the biological processes of combined dynamic cell rolling and stationary binding, which will likely lead to a CTC detection device with significantly enhanced specificity and sensitivity without any complex fabrication process.
Tumor cell rolling on the endothelium plays a key role in the initial steps of cancer metastasis, i.e. extravasation of circulating tumor cells (CTCs). Identification of the ligands that induce the rolling of cells is thus critical to understand how cancers metastasize. We have previously demonstrated that MCF-7 cells, human breast cancer cells, exhibit the rolling response selectively on E-selectinimmobilized surfaces. However, the ligand that induces rolling of MCF-7 cells on E-selectin has not yet been identified, as these cells lack commonly known E-selectin ligands. Here we report, for the first time to our knowledge, a set of quantitative and direct evidence demonstrating that CD24 expressed on MCF-7 cell membranes is responsible for rolling of the cells on E-selectin. The binding kinetics between CD24 and E-selectin was directly measured using surface plasmon resonance (SPR), which revealed that CD24 has a binding affinity against E-selectin (K D = 3.4 ± 0.7 nM). The involvement of CD24 in MCF-7 cell rolling was confirmed by the rolling behavior that was completely blocked when cells were treated with anti-CD24. A simulated study by flowing microspheres coated with CD24 onto E-selectin-immobilized surfaces further revealed that the binding is Ca 2+ dependent. Additionally, we have found that actin filaments are involved in the CD24-mediated cell rolling, as observed by the decreased rolling velocities of the MCF-7 cells upon treatment with cytochalasin D (an inhibitor of actin-filament dynamics) and the stationary binding of CD24-coated microspheres (the lack of actins) on the E-selectin-immobilized slides. Given that CD24 is known to be directly related to enhanced invasiveness of cancer cells, our results imply that CD24-based cell rolling on E-selectin mediates, at least partially, cancer cell extravasation, resulting in metastasis.
Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors. To achieve this goal, a novel process was successfully demonstrated on a laboratory scale using a bank of 1.25-cm centrifugal contactors, fabricated by additive manufacturing, and a simulant containing the major fission product elements. Americium and Cm were separated from the lanthanides with over 99.9% completion. The sum of the impurities of the Am/Cm product stream using the simulated raffinate was found to be 3.2 × 10 −3 g/L. The process performance was validated using a genuine high burnup used nuclear fuel raffinate in a batch regime. Separation factors of nearly 100 for 154 Eu over 241 Am were achieved. All these results indicate the process scalability to an engineering scale.
Here we report a new method for multi-component protein patterning in a microchannel and also a technique for improving immunoaffinity-based circulating tumor cell (CTC) capture by patterning regions of alternating adhesive proteins using the new method. The first of two proteins, anti-epithelial cell adhesion molecule (anti-EpCAM), provides the specificity for CTC capture. The second, E-selectin, increases CTC capture under shear. Patterning regions with and without E-selectin allows captured leukocytes, which also bind E-selectin and are unwanted impurities in CTC isolation, to roll a short distance and detach from the capture surface. This reduces leukocyte capture by up to 82%. The patterning is combined with a leukocyte elution step in which a calcium chelating buffer effectively deactivates E-selectin so that leukocytes may be rinsed away 60% more efficiently than with a buffer containing calcium. The alternating patterning of this biomimetic protein combination, used in conjunction with the elution step, reduce capture of leukocytes while maintaining a high tumor capture efficiency that is up to 1.9 times higher than the tumor cell capture efficiency of a surface with only anti-EpCAM. The new patterning technique described here does not require mask alignment and can be used to spatially control the immobilization of any 2 proteins or protein mixtures inside a sealed microfluidic channel.
A new method for studying solvent extraction kinetics has been applied for measuring americium and lanthanide extraction rate constants. This droplet-based microfluidic method uses commercially available components and provides rapid, high throughput and accurate determination of absolute interfacial mass transfer rate constants. Reported for the first time are americium extraction rates relevant to TALSPEAK-type process conditions, including the americium and lanthanide rate dependencies on pH and extractant power.
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