Exploiting osmosis for blood cell sorting

Microfluidic pumps for cell sorting

Microfluidic cell sorting has shown promising advantages over traditional bulky cell sorting equipment and has demonstrated wide-reaching applications in biological research and medical diagnostics. The most important characteristics of a microfluidic cell sorter are its throughput, ease of use, and integration of peripheral equipment onto the chip itself. In this review, we discuss the six most common methods for pumping fluid samples in microfluidic cell sorting devices, present their advantages and drawbacks, and discuss notable examples of their use. Syringe pumps are the most commonly used method for fluid actuation in microfluidic devices because they are easily accessible but they are typically too bulky for portable applications, and they may produce unfavorable flow characteristics. Peristaltic pumps, both on- and off-chip, can produce reversible flow but they suffer from pulsatile flow characteristics, which may not be preferable in many scenarios. Gravity-driven pumping, and similarly hydrostatic pumping, require no energy input but generally produce low throughputs. Centrifugal flow is used to sort cells on the basis of size or density but requires a large external rotor to produce centrifugal force. Electroosmotic pumping is appealing because of its compact size but the high voltages required for fluid flow may be incompatible with live cells. Emerging methods with potential for applications in cell sorting are also discussed. In the future, microfluidic cell sorting methods will trend toward highly integrated systems with high throughputs and low sample volume requirements.

Role of ribosomal RNA released from red cells in blood coagulation in zebrafish and humans

Hemolysis releases 5.8S rRNA and activates blood coagulation in human and zebrafish via FXII and Hgfac, respectively.

Only the 3'-end 26 nucleotides of 5.8S rRNA were necessary and sufficient for this activation.

Hemolytic disorders are characterized by hemolysis and are prone to thrombosis. It has previously been shown that the RNA released from damaged blood cells activates clotting. However, the nature of the RNA released from hemolysis is still elusive. We found that after hemolysis, red blood cells from both zebrafish and humans released RNA that contained mostly 5.8S ribosomal RNA (5.8S rRNA), This RNA activated coagulation in zebrafish and human plasmas. By using both natural and synthetic 5.8S rRNA and its truncated fragments, we found that the 3'-end 26-nucleotide-long RNA (3'-26 RNA) and its stem-loop secondary structure were necessary and sufficient for clotting activity. Corn trypsin inhibitor (CTI), a coagulation factor XII (FXII) inhibitor, blocked 3'-26 RNA–mediated coagulation activation in the plasma of both zebrafish and humans. CTI also inhibited zebrafish coagulation in vivo. 5.8S rRNA monoclonal antibody inhibited both 5.8S rRNA– and 3'-26 RNA–mediated zebrafish coagulation activity. Both 5.8S rRNA and 3'-26 RNA activated normal human plasma but did not activate FXII-deficient human plasma. Taken together, these results suggested that the activation of zebrafish plasma is via an FXII-like protein. Because zebrafish have no FXII and because hepatocyte growth factor activator (Hgfac) has sequence similarities to FXII, we knocked down the hgfac in adult zebrafish. We found that plasma from this knockdown fish does not respond to 3'-26 RNA. To summarize, we identified that an rRNA released in hemolysis activates clotting in human and zebrafish plasma. Furthermore, we showed that fish Hgfac plays a role in rRNA-mediated activation of coagulation.

Low-stress Microfluidic Density-gradient Centrifugation for Blood Cell Sorting

Density gradient centrifugation exploits density differences between different blood cells to accomplish separation of peripheral blood mononuclear cells (PBMCs) from polymorphonuclear (PNM) cells, and erythrocytes or red blood cells (RBCs). While density gradient centrifugation offers a label-free alternative avoiding the use of harsh lysis buffers for blood cell isolation, it is a time-consuming and labor-intensive process during which blood cells are subject to high-levels of centrifugal force that can artifactually activate cells. To provide a low-stress alternative to this elegant method, we miniaturized and automated this process using microfluidics to ensure continuous PBMCs isolation from whole blood while avoiding the exposure to high-levels of centrifugal stress in a simple flow-through format. Within this device, a density gradient is established by exploiting laminar flow within microfluidic channels to layer a thin stream of blood over a larger stream of Ficoll. Using this approach we demonstrate successful isolation of PBMCs from whole blood with preservation of monocytes and different lymphocyte subpopulations similar to that seen with conventional density gradient centrifugation. Evaluation of activation status of PBMCs isolated using this technique shows that our approach achieves minimal isolation process induced activation of cells in comparison to conventional lysis or density gradient centrifugation. This simple, automated microfluidic density gradient centrifugation technique can potentially serve as tool for rapid and activation-free technique for isolation of PBMCs from whole blood for point-of-care applications.

Analyzing mitochondrial function in human peripheral blood mononuclear cells

Mitochondrial oxidative phosphorylation (OXPHOS) is responsible for producing most of the adenosine triphosphate required by eukaryotic cells. Lymphocytes make up the majority of the peripheral blood mononuclear cells. Peripheral blood mononuclear cells are readily obtainable, providing an ideal sample to monitor systemic changes and understand molecular signaling mechanisms in disease processes. Mitochondrial energy metabolism of lymphocyte has been used to screen for OXPHOS disorders. While there are increasing studies of lymphocyte OXPHOS, few studies examined activity of electron transport chain of lymphocyte mitochondria. We present an optimal protocol to harvest fresh peripheral blood mononuclear cells from human whole blood, determine integrated mitochondrial function, and analyze electron transport chain complex activity. Analyzing integrated mitochondrial function using OXPHOS provides data to uncover defects in the transport of substrates into the mitochondria, generation of reducing equivalents, the electron transport chain, and coupling to the production of adenosine triphosphate. The optimal conditions to harvest peripheral blood mononuclear cells were using blood anticoagulated with ethylenediaminetetraacetic acid, processed utilizing Lymphoprep™, and washed in phosphate buffered saline, all at room temperature. Using isolated peripheral blood mononuclear cells, integrated mitochondrial function and the activities of electron transport chain were determined.

Using a multivariate model to assess the interactive effects of demographics and lifestyle on the hematological profile

AIM

To assess the extent to which a multivariate approach to modeling interrelated hematological indices provides more informative results than the traditional approach of modeling each index separately.

MATERIALS & METHODS

The effects of demographics and lifestyle on ten hematological indices collected from a Dutch population-based sample (n = 3278) were studied, jointly using multivariate distance matrix regression and separately using linear regression.

RESULTS

The multivariate approach highlighted the main effects of all predictors and several interactions; the traditional approach highlighted only main effects.

CONCLUSION

The multivariate approach provides more power than traditional methods to detect effects on interrelated biomarkers, suggesting that its use in future research may help identify subgroups that benefit from different treatment or prevention measures.

Inertial microfluidics combined with selective cell lysis for high throughput separation of nucleated cells from whole blood

The ability to rapidly analyze blood cells provides a wealth of information about our health. Here, we report on an automated, high-throughput, method that completely removes red blood cells and sort cells into subpopulation for downstream analysis.

A new technique for reversible permeabilization of live cells for intracellular delivery of quantum dots

A major challenge with the use of quantum dots (QDs) for cellular imaging and biomolecular delivery is the attainment of QDs freely dispersed inside the cells. Conventional methods such as endocytosis, lipids based delivery and electroporation are associated with delivery of QDs in vesicles and/or as aggregates that are not monodispersed. In this study, we demonstrate a new technique for reversible permeabilization of cells to enable the introduction of freely dispersed QDs within the cytoplasm. Our approach combines osmosis driven fluid transport into cells achieved by creating a hypotonic environment and reversible permeabilization using low concentrations of cell permeabilization agents like Saponin. Our results confirm that highly efficient endocytosis-free intracellular delivery of QDs can be accomplished using this method. The best results were obtained when the cells were treated with 50 μg ml⁻¹ Saponin in a hypotonic buffer at a 3:2 physiological buffer:DI water ratio for 5 min at 4 °C.