Integrated systems for rapid point of care (PoC) blood cell analysis

Counting the different subpopulations of cells in a fingerprick of human blood is important for a number of clinical point-of-care (PoC) applications. It is a challenge to demonstrate the integration of sample preparation and detection techniques in a single platform. In this paper we demonstrate a generic microfluidic platform that combines sample processing and characterisation and enumeration in a single, integrated system. Results of microfluidic 3-part differential leukocyte (granulocyte, lymphocyte and monocyte) counts, together with erythrocyte and thrombocyte (platelet) counts, in human blood are shown and corroborated with results from hospital clinical laboratory analysis

Digital signal processing methods for impedance microfluidic cytometry

Impedance microfluidic cytometry is a noninvasive, label-free technology that can characterize the dielectric properties of single particles (beads/cells) at high speed. In this paper we show how digital signal processing methods are applied to the impedance signals for noise removal and signal recovery in an impedance microfluidic cytometry. Two methods are used; correlation to identify typical signals from a particle and for a noisier environment, an adaptive filter is used to remove noise. The benefits of adaptive filtering are demonstrated quantitatively from the correlation coefficient and signal-to-noise ratio. Finally, the adaptive filtering method is compared to the Savitzky–Golay filtering method

Comparison of venous and capillary differential leukocyte counts using a standard hematology analyzer and a novel microfluidic impedance cytometer

Capillary blood sampling has been identified as a potentially suitable technique for use in diagnostic testing of the full blood count (FBC) at the point-of-care (POC), for which a recent need has been highlighted. In this study we assess the accuracy of capillary blood counts and evaluate the potential of a miniaturized cytometer developed for POC testing. Differential leukocyte counts in the normal clinical range from fingerprick (capillary) and venous blood samples were measured and compared using a standard hematology analyzer. The accuracy of our novel microfluidic impedance cytometer (MIC) was then tested by comparing same-site measurements to those obtained with the standard analyzer. The concordance between measurements of fingerprick and venous blood samples using the standard hematology analyzer was high, with no clinically relevant differences observed between the mean differential leukocyte counts. Concordance data between the MIC and the standard analyzer on same-site measurements presented significantly lower leukocyte counts determined by the MIC. This systematic undercount was consistent across the measured (normal) concentration range, suggesting that an internal correction factor could be applied. Differential leukocyte counts obtained from fingerprick samples accurately reflect those from venous blood, which confirms the potential of capillary blood sampling for POC testing of the FBC. Furthermore, the MIC device demonstrated here presents a realistic technology for the future development of FBC and related tests for use at the site of patient car

An Iterative Method for Electrostatic Object Reconstruction in a Half Space

Sensing electrodes arranged in or around a display can provide input function for interactive displays. Commercially this is interesting because the sensing electrodes and electronics can be made in the same manufacturing process as that of the display itself thus reducing cost. In engineering terms the electrodes measure capacitance changes resulting from the presence and movement of objects such as hands and fingers in front of the display. At the quasi static frequencies used (100kHz) the human body is conductive and the hands or fingers provide a screen between the capacitive electrodes. There is no need to touch the actual display and the overall system constitutes a touchless gesture input system. Determining the shape of the hand or fingers is a boundary condition reconstruction problem of finding the boundary of an earthed conductive object D from electrostatic measurements. This is the ill-posed problem of recovering the zero-surface of a solution to Laplace s equation from Cauchy data on part of the boundary of a domain. The problem has similarities with object reconstruction in EIT or inverse scattering but is complicated because only a partial Dirichelet-Neumannn map is available as experimental data. We suggest an algorithm where at each iteration we have an approximation on which we calculate approximate Cauchy data by solving a Tikhonov regularized linear system. This data is used to modify the approximation by extrapolation towards the zero-surface giving the next approximation. We implemented the algorithm in two and three space dimensions using the Boundary Element Method for discretization. Numerical results using simulated data with added noise show that simply connected but not necessarily convex objects can be reconstructed with reasonable positional accuracy and approximate shape, but as might be expected the shape is more accurately determined near the plane of measurements

Substrate specificity of flavin-dependent vanillyl-alcohol oxidase from Penicillium simplicissimum.Evidence for the production of 4-hydroxycinnamyl alcohols from 4-allylphenols

The substrate specificity of the flavoprotein vanillyl-alcohol oxidase from Penicillium simplicissimum was investigated. Vanillyl-alcohol oxidase catalyzes besides the oxidation of 4-hydroxybenzyl alcohols, the oxidative deamination of 4-hydroxybenzylamines and the oxidative demethylation of 4-(methoxymethyl)phenols. During the conversion of vanillylamine to vanillin, a transient intermediate, most probably vanillylimine, is observed. Vanillyl-alcohol oxidase weakly interacts with 4-hydroxyphenylglycols and a series of catecholamines. These compounds are converted to the corresponding ketones. Both enantiomers of (nor)epinephrine are substrates for vanillyl-alcohol oxidase, but the R isomer is preferred. Vanillyl-alcohol oxidase is most active with chavicol and eugenol. These 4-allylphenols are converted to coumaryl alcohol and coniferyl alcohol, respectively. Isotopic labeling experiments show that the oxygen atom inserted at the Cγ atom of the side chain is derived from water. The 4-hydroxycinnamyl alcohol products and the substrate analog isoeugenol are competitive inhibitors of vanillyl alcohol oxidation. The binding of isoeugenol to the oxidized enzyme perturbs the optical spectrum of protein-bound FAD. pH-dependent binding studies suggest that vanillyl-alcohol oxidase preferentially binds the phenolate form of isoeugenol (pKa<6, 25°C). From this and the high pH optimum for turnover, a hydride transfer mechanism involving a p-quinone methide intermediate is proposed for the vanillyl-alcohol-oxidase-catalyzed conversion of 4-allylphenols.