Preformed donor HLA-DP-specific antibodies mediate acute and chronic antibody-mediated rejection following renal transplantation

Donor-specific HLA alloantibodies may cause acute and chronic antibody-mediated rejection (AMR) and significantly compromise allograft survival. The clinical relevance of antibodies directed against some HLA class II antigens, particularly HLA-DP, is less clear with conflicting reports on their pathogenicity. We report two patients with high levels of pretransplant donor-specific HLA-DP antibodies who subsequently developed recurrent acute AMR and graft failure. In both cases, there were no other donor-specific HLA alloantibodies, suggesting that the HLA-DP-specific antibodies may be directly pathogenic.

Programmable large area digital microfluidic array with integrated droplet sensing for bioassays

We describe a new device concept for digital microfluidics, based on an active matrix electrowetting on dielectric (AM-EWOD) device. A conventional EWOD device is limited by the number of electrical connections that can be made practically, which restricts the number and type of droplet operations. In an AM-EWOD, the patterned electrodes of a conventional EWOD device are replaced by a thin film transistor (TFT) array, as found in a liquid crystal display (LCD), facilitating independent control of each electrode. The arrays can have many thousand individually addressable electrodes, are fully reconfigurable and can be programmed to support multiple simultaneous operations. Each element is 210 μm × 210 μm in size and contains a circuit that measures the electrical impedance of the liquid above it. This is used to determine the presence and size of a droplet, a method that can improve assay reliability and accuracy. This sensor provides feedback, error detection and closed loop control of an assay sequence. We describe the design, fabrication and testing of a 64 × 64 format AM-EWOD device with impedance sensor functionality. A colorimetric assay is implemented on the device and used to measure glucose in human blood serum. Results are compared with the same assay performed on a microtitre plate.

Time, action and psychosis: using subjective time to investigate the effects of ketamine on sense of agency

Sense of agency refers to the experience of initiating and controlling actions in order to influence events in the outside world. A disturbed sense of agency is found in certain psychiatric and neurological disorders, most notably schizophrenia. Sense of agency is associated with a subjective compression of time: actions and their outcomes are perceived as bound together in time. This is known as 'intentional binding' and, in healthy adults, depends partly on advance prediction of action outcomes. Notably, this predictive contribution is disrupted in patients with schizophrenia. In the present study we aimed to characterise the psychotomimetic effect of ketamine, a drug model for psychosis, on the predictive contribution to intentional binding. It was shown that ketamine produced a disruption that closely resembled previous data from patients in the early, prodromal, stage of schizophrenic illness. These results are discussed in terms of established models of delusion formation in schizophrenia. The link between time and agency, more generally, is also considered.

Conditional IL-2 Gene Deletion: Consequences for T Cell Proliferation

To explore the role of interleukin-2 (IL-2) in T cell proliferation, and to circumvent the IL-2 deficiency autoimmune syndrome of conventional il2 gene deletion, mice were created to allow conditional il2 gene deletion when treated with the estrogen analog, tamoxifen (TAM) as adults. Splenocytes from four different mouse strains, C57Bl/6 wild type (WT), conventional IL-2(−/−), TAM-treated Cre recombinase-negative (Cre−)/IL2fl/fl, and Cre recombinase-positive (Cre+)/IL2fl/fl, were activated with anti-CD3 and anti-CD28, and monitored for CD4+ and CD8+ T cell lymphocyte blastogenesis, aerobic glycolysis, BrdU incorporation into newly synthesized DNA, and CFSE dye dilution to monitor cell division. IL-2 production was monitored by quantitative ELISA and multiple additional cytokines were monitored by quantitative protein-bead arrays. Splenocytes from conventional IL-2(−/−) and TAM-treated Cre+ mice resulted in undetectable IL-2 production by ELISA, so that both strains were IL-2-deficient. As monitored by flow cytometry, activated CD4+ and CD8+ T cells from WT, Cre+, and Cre− mice all underwent blastogenesis, whereas far fewer cells from conventional IL-2(−/−) mice did so. By comparison, only cells from IL-2 sufficient WT and Cre− mice switched to aerobic glycolysis as evidenced by a drop in media pH. Blastogenesis was mirrored by BrdU incorporation and CFSE dye dilution by CD4+ and CD8+ T cells from WT, Cre+, and Cre− mice, which were all equivalent, while proliferation of cells from conventional IL-2(−/−) mice was compromised. Splenocytes from IL-2 deficient conventional IL-2(−/−) mice produced low or undetectable other γ_c-chain cytokines (IL-4, IL-7, IL-9, IL-13, IL-15, and IL-21), whereas production of these γ_c-chain cytokines from IL-2-deficient conditional IL-2(−/−) Cre+ mice were comparable with WT and Cre− mice. These results indicate that CD4+ and CD8+ T cell blastogenesis cannot be attributable to IL-2 alone, but a switch to aerobic glycolysis was attributable to IL-2, and proliferation after CD3/CD28 activation is dependent on γ_c-chain cytokines, and not CD3/28 triggering per se.

Chemically resistant microfluidic valves from Viton® membranes bonded to COC and PMMA

We present a reliable technique for irreversibly bonding chemically inert Viton® membranes to PMMA and COC substrates to produce microfluidic devices with integrated elastomeric structures. Viton® is widely used in commercially available valves and has several advantages when compared to other elastomeric membranes currently utilised in microfluidic valves (e.g. PDMS), such as high solvent resistance, low porosity and high temperature tolerance. The bond strength was sufficient to withstand a fluid pressure of 400 kPa (PMMA/Viton®) and 310 kPa (COC/Viton®) before leakage or burst failure, which is sufficient for most microfluidic applications. We demonstrate and characterise on-chip pneumatic Viton® microvalves on PMMA and COC substrates. We also provide a detailed method for bonding fluorinated Viton® elastomer, a highly chemically compatible material, to PMMA and COC polymers. This allows the production of microfluidic devices able to handle a wide range of chemically harsh fluids and broadens the scope of the microfluidic platform concept.

Early Osteoblast Attachment, Spreading, and Focal Adhesions on RGD Coated Surfaces

Cells recognize and interact with the extracellular matrix (ECM) through heterodimeric receptors known as integrins. The objective of our work is to immobilize integrin-stimulating peptides to bone-contacting implants in order to control cellular activity and response.

We have previously demonstrated that cysteine (C) containing peptides self-assemble onto gold-coated substrates. Investigations have focused on the RGD (Arg-Gly-Asp) peptide sequence since it is found in several bone ECM proteins. Gold was first coated onto glass coverslips by evaporation and the peptide was applied in a 0.22 mM solution. Contact angle and surface plasmon resonance verified RGDC peptide attachment and formation of a monolayer.

Rat calvarial osteoblasts isolated from six-day-old rat pups were used from passages one to three. Cell attachment at 20 minutes is 100% greater on RGDC than on CG (control peptides) or plain gold surfaces. Cells on RGDC also stain positively for vinculin, a protein which is present in focal adhesions (functional structures into which integrins assemble) whereas surfaces without integrin stimulating peptides do not. Scanning electron micrographs show cells to be more spread and have more processes at 20 minutes, 1, 3, and 24 hours on RGDC. Live video images of these surfaces from zero to three hours after plating confirmed earlier and greater cell spreading on RGDC.

Ongoing in vitro experiments are investigating the long-term response of osteoblasts to RGDC and other immobilized peptides in terms of differentiation, matrix production, and integrin expression.

Electroporation and lysis of marine microalga Karenia brevis for RNA extraction and amplification

We describe here a simple device for dielectrophoretic concentration of marine microalga Karenia brevis non-motile cells, followed by electric field-mediated lysis for RNA extraction. The lysate was purified using magnetic beads and pure RNA extracted. RNA quality was assessed off-chip by nucleic acid sequence-based amplification and the optimum conditions for lysis were determined. This procedure will form part of an integrated microfluidic system that is being developed with sub-systems for performing cell concentration and lysis, RNA extraction/purification and real-time quantitative RNA detection. The integrated system and its components could be used for a large range of applications including in situ harmful algal bloom detection, transcriptomics and point-of-care diagnostics.

Note: Characterization of electrode materials for dielectric spectroscopy

When measuring the dielectric properties of aqueous samples, the impedance of the electrode/sample interface can limit low frequency measurements. The electrode polarization problem can be reduced by increasing the effective surface area of the electrodes. In this work, impedance spectroscopy was used to characterize and compare three different electrode surfaces that can be used to mitigate this effect: platinum black, iridium oxide, and [polypyrrole/poly(styrenesulphonate)] (PPy/PSS) conducting polymer. All three materials were directly compared with a bright platinum electrode. Equivalent circuit models were used to extract the increase in the effective surface area of the electrodes: platinum black, iridium oxide and PPy/PSS increase the effective capacitance of the electrode by factors of approximately 240, 75, and 790, respectively. The practical aspects of all electrode materials are discussed. These results suggest that iridium oxide and PPy/PSS are good alternatives to the commonly used platinum black, which is prone to mechanical damage (scratches) and is potentially toxic to cells.

Group B streptococcus disease in neonates: To screen or not to screen?

An audit was undertaken of the prevention of early-onset Group B streptococcus (EOGBS) disease in neonates. The prevention strategy in use involved offering Intra-partum Antibiotic Prophylaxis (IAP) to mothers with identified risk factors, which include maternal fever in labour > 38 degrees C, previous baby with GBS disease, prolonged rupture of membranes > 18 h, pre-term labour, GBS urinary tract infection and known GBS carriage. The most common risk factor identified was GBS carriage (41%) which was known ante-partum but logistical problems prevented these mothers from receiving adequate prophylaxis 4 h before delivery and so were classified as at risk of GBS disease. We found an incidence of GBS in our unit of 0.55 per 1,000 births over the study period. One neonate developed EOGBS disease and the mother had no identifiable risk factor ante-partum/intra-partum. Recent recommendations from the Royal College of Obstetricians and Gynaecologists (RCOG) could reduce the number of babies having sepsis screens performed as the time interval from beginning IAP to delivery has been shortened to 2 h and routine surface cultures or blood cultures are not recommended in well newborns. The evidence is lacking at this point to recommend universal screening for GBS in all pregnant women but patients are increasingly aware of this option and may request anogenital swabs to assess GBS carriage.

Flow reversal in traveling-wave electrokinetics: an analysis of forces due to ionic concentration gradients

Pumping of electrolytes using ac electric fields from arrays of microelectrodes is a subject of current research. The behavior of fluids at low signal amplitudes (<2-3 V(pp)) is in qualitative agreement with the prediction of the ac electroosmosis theory. At higher voltages, this theory cannot account for the experimental observations. In some cases, net pumping is generated in the direction opposite to that predicted by the theory (flow reversal). In this work, we use fluorescent dyes to study the effect of ionic concentration gradients generated by Faradaic currents. We also evaluate the influence of factors such as the channel height and microelectrode array shape in the pumping of electrolytes with traveling-wave potentials. Induced charge beyond the Debye length is postulated to be responsible for the forces generating the observed flows at higher voltages. Numerical calculations are performed in order to illustrate the mechanisms that might be responsible for generating the flow.

Traveling-wave electrokinetic micropumps: velocity, electrical current, and impedance measurements

An array of microelectrodes covered in an electrolyte and energized by a traveling-wave potential produces net movement of the fluid. Arrays of platinum microelectrodes of two different characteristic sizes have been studied. For both sizes of arrays, at low voltages (<2 V pp) the electrolyte flow is in qualitative agreement with the linear theory of ac electroosmosis. At voltages above a threshold, the direction of fluid flow is reversed. The electrical impedance of the electrode-electrolyte system was measured after the experiments, and changes in the electrical properties of the electrolyte were observed. Measurements of the electrical current during pumping of the electrolyte are also reported. Transient behaviors in both electrical current and fluid velocity were observed. The Faradaic currents probably generate conductivity gradients in the liquid bulk, which in turn give rise to electrical forces. These effects are discussed in relation to the fluid flow observations.

Discrimination and analysis of phytoplankton using a microfluidic cytometer

Identification and analysis of phytoplankton is important for understanding the environmental parameters that are influenced by the oceans, including pollution and climate change. Phytoplanktons are studied at the single cell level using conventional light-field and fluorescence microscopy, but the technique is labour intensive. Flow cytometry enables rapid and quantitative measurements of single cells and is now used as an analytical tool in phytoplankton analysis. However, it has a number of drawbacks, including high cost and portability. We describe the fabrication of a microfluidic (lab-on-a-chip) device for high-speed analysis of single phytoplankton. The device measures fluorescence (at three wavelength ranges) and the electrical impedance of single particles. The system was tested using a mixture of three algae (Isochrysis Galbana, Rhodosorus m., Synechococcus sp.) and the results compared with predictions from theory and measurements using a commercial flow cytometer (BD FACSAria). It is shown that the microfluidic flow cytometer is able to distinguish and characterise these different taxa and that impedance spectroscopy enables measurement of phytoplankton biophysical properties.

Analytical electric field and sensitivity analysis for two microfluidic impedance cytometer designs

Microfabricated impedance cytometers have been developed to measure the electrical impedance of single biological particles at high speed. A general approach to analytically solve the electric field distributions for two different designs of cytometers: parallel facing electrodes and coplanar electrodes, using the Schwarz-Christoffel Mapping method is presented. Compared to previous analytical solutions, our derivations are more systematic and solutions are more straightforward. The solutions have been validated by comparison with numerical simulations performed using the finite element method. The influences on the electric field distribution due to the variations in the geometry of the devices have been discussed. A simple method is used to determine the impedance sensitivity of the system and to compare the two electrode designs. For identical geometrical parameters, we conclude that the parallel electrodes design is more sensitive than the coplanar electrodes.

Global endometrial ablation: a modern day solution to an age-old problem

Menorrhagia remains a significant health issue for women worldwide. Traditionally hysterectomy has been the treatment of choice when excessive menstrual bleeding remains unresolved by hormonal manipulation. In an attempt to provide a less invasive alternative to hysterectomy, traditional techniques such as rollerball endometrial ablation were developed 20 years ago. Although extremely effective, they possessed the potential of significant intra-operative risks and their success depended on high technical proficiency of the surgeon. As surgery and technology evolved, second generation endometrial ablation devices were developed which demonstrated improved safety and efficacy rates that paralleled traditional treatments. Since 1997, the Food and Drug Administration (FDA) has approved five such devices for use in the United States. Each possesses a unique technology profile with supporting level I evidence that allows for the treatment of a wide variety of uterine anatomy.

Renal MALToma: an unusual lymphoma in a patient with lupus

Non-Hodgkin's Lymphomas (NHL) have been reported in association with autoimmune disorders particularly Sjogren's syndrome. We report a case of renal MALToma, an unusual NHL in an 84-year-old Caucasian lady with long-standing, non-aggressive Systemic Lupus Erythematosis with no associated Sjorgen's syndrome and who never received cytotoxics.

Controlled delivery of membrane proteins to artificial lipid bilayers by nystatin-ergosterol modulated vesicle fusion

The study of ion channels and other membrane proteins and their potential use as biosensors and drug screening targets require their reconstitution in an artificial membrane. These applications would greatly benefit from microfabricated devices in which stable artificial lipid bilayers can be rapidly and reliably formed. However, the amount of protein delivered to the bilayer must be carefully controlled. A vesicle fusion technique is investigated where composite ion channels of the polyene antibiotic nystatin and the sterol ergosterol are employed to render protein-carrying vesicles fusogenic. After fusion with an ergosterol-free artificial bilayer, the nystatin-ergosterol channels do not dissociate immediately and thus cause a transient current signal that marks the vesicle fusion event. Experimental pitfalls of this method were identified, the influence of the nystatin and ergosterol concentration on the fusion rate and the shape of the fusion event marker was explored, and the number of different lipid species was reduced. Under these conditions, the -amyloid peptide could be delivered in a controlled manner to a standard planar bilayer. Additionally, electrical recordings were obtained of vesicles fusing with a planar lipid bilayer in a microfabricated device, demonstrating the suitability of nystatin-ergosterol modulated vesicle fusion for protein delivery within microsystems.

On-chip high-speed sorting of micron-sized particles for high-throughput analysis

A new design of particle sorting chip is presented. The device employs a dielectrophoretic gate that deflects particles into one of two microfluidic channels at high speed. The device operates by focussing particles into the central streamline of the main flow channel using dielectrophoretic focussing. At the sorting junction (T- or Y-junction) two sets of electrodes produce a small dielectrophoretic force that pushes the particle into one or other of the outlet channels, where they are carried under the pressure-driven fluid flow to the outlet. For a 40 microm wide and high channel, it is shown that 6 microm diameter particles can be deflected at a rate of 300/s. The principle of a fully automated sorting device is demonstrated by separating fluorescent from non-fluorescent latex beads.