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A naturally occurring multivalent binding effect is manipulated by engineering cell capture surfaces using dendrimers. The enhanced binding through the multivalent effect significantly improves detection of tumor cells. This improvement can be potentially translated into clinically significant detection of circulating tumor cells from the blood of cancer patients.

The pathophysiology of sickle cell disease is complicated by the multiscale processes that link the molecular genotype to the organismal phenotype: hemoglobin polymerization occurring in milliseconds, microscopic cellular sickling in a few seconds or less [Eaton WA, Hofrichter J (1990) Adv Protein Chem 40:63-279], and macroscopic vessel occlusion over a time scale of minutes, the last of which is necessary for a crisis [Bunn HF (1997) N Engl J Med 337:762-769]. Using a minimal but robust artificial microfluidic environment, we show that it is possible to evoke, control, and inhibit the collective vasoocclusive or jamming event in sickle cell disease. We use a combination of geometric, physical, chemical, and biological means to quantify the phase space for the onset of a jamming event, as well as its dissolution, and find that oxygendependent sickle hemoglobin polymerization and melting alone are sufficient to recreate jamming and rescue. We further show that a key source of the heterogeneity in occlusion arises from the slow collective jamming of a confined, flowing suspension of soft cells that change their morphology and rheology relatively quickly. Finally, we quantify and investigate the effects of small-molecule inhibitors of polymerization and therapeutic red blood cell exchange on this dynamical process. Our experimental study integrates the dynamics of collective processes associated with occlusion at the molecular, polymer, cellular, and tissue level; lays the foundation for a quantitative understanding of the rate-limiting processes; and provides a potential tool for optimizing and individualizing treatment, and identifying new therapies.

Cellular function and behavior are affected by the partial pressure of O2, or oxygen tension, in the microenvironment.

Controlling oxygen concentration at a microscale level can benefit experimental investigations involving oxidative stress, ischemia, and reactive oxygen species (ROS) mediated cellular pathways. Here, we report the application of microfluidic gradient generation in an open-well culture model, in which a gradient of gas is delivered via diffusion through a gas permeable substrate that separates cells from the gas microchannels below. By using diffusion to localize oxygen delivery, microgradients of oxygen concentrations can be rapidly and controllably applied without exposing cells to mechanical stresses or reducing culture volumes inside microfluidic culture chambers. Furthermore, we demonstrate the modulation of intracellular ROS levels in Madin-Darby canine kidney (MDCK) cells by applying these oxygen microgradients. Increases in ROS levels consistent with both oxidative stress and hypoxic exposures were observed in MDCK cells. The measured ROS increases were comparable to 100 μM hydrogen peroxide exposure in a control comparison, which is within the range of standard ROS induction methods. Incubation with 200 μM vitamin C was able to demodulate the ROS response at both hypoxic and hyperoxic exposures. By providing microfluidic controlled gradients, constant ROS exposure, and a shear-free open well design, the devices introduced here greatly improve upon standard oxygen-based culturing methods. Illustration Content List Entry with Summary Sentence The devices presented here can generate complex oxygen gradients over rapid timescales, permitting investigation of a number of difficult-to-model physiological systems.

A microfluidic device to perfuse pancreatic islets while simultaneously characterizing their functionality through fluorescence imaging of the mitochondrial membrane potential and intracellular calcium ([Ca2+]i) in addition to enzyme linked immunosorbent assay (ELISA) quantification of secreted insulin was developed and characterized. This multimodal characterization of islet function will facilitate rapid assessment of tissue quality immediately following isolation from donor pancreas and allow more informed transplantation decisions to be made which may improve transplantation outcomes. The microfluidic perfusion chamber allows flow rates of up to 1 mL/min, without any noticeable perturbation or shear of islets. This multimodal quantification was done on both mouse and human islets. The ability of this simple microfluidic device to detect subtle variations in islet responses in different functional assays performed in short time-periods demonstrates that the microfluidic perfusion chamber device can be used as a new gold standard to perform comprehensive islet analysis and obtain a more meaningful predictive value for islet functionality prior to transplantation into recipients, which is currently difficult to predict using a single functional assay.

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.