Four-part differential leukocyte count using μflow cytometer

This paper reports the four-part differential leukocyte count (DLC) of human blood using a MEMS microflow (μflow) cytometer. It is achieved with a two-color laser-induced fluorescence (LIF) detection scheme. Four types of leukocytes including neutrophils, eosinophils, lymphocytes and monocytes are identified in blood samples, which are stained by fluorescein isothiocyanate (FITC) and propidium iodide (PI). The DLC results show good correlation with the count from a commercial hematology analyzer. The whole system is also implemented into a portable instrument for space application

Platinum Black Electroplated Impedance Particle Sensor

We present a micro electrical impedance particle sensor. To solve the problem of large electrode electrolyte interface impedance, we electroplated the electrodes with platinum black. Devices are fabricated with integrated parylene technology. An electrical model for the system is proposed and analytic solutions are obtained. Impedance spectra measurement of the device filled with various media are in excellent agreement with model analysis. Signals from individual 10 µm polystyrene beads passing the sensing electrodes are successfully obtained

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Fluorescent labeling, sensing, and differentiation of leukocytes from undiluted whole blood samples

In this paper, we demonstrated leukocyte labeling, sensing and differentiation from undiluted human whole blood samples with microfabricated devices.A challenging issue in leukocyte sensing from blood samples is the required high-dilution level, which is used mainly to prevent interference from the overwhelmingly outnumbered erythrocytes. Dilution is undesirable for micro hemacytometers. It not only increases sample volume and processing time, but also requires mixing and buffer storage for on-chip implementation. Unlike commercial bulk instruments and previous efforts by other groups, we completely eliminated the requirement for dilution by staining leukocytes specifically with fluorescent dye acridine orange (AO) in undiluted human whole blood and then sensing them in microfluidic devices. Green fluorescent signal centered at 525 nm is used for leukocyte count and red fluorescent signal centered at 650 nm is used for leukocyte differentiation. Throughput of 1000 leukocytes per second was achieved

Analysis of the Spectroscopic Aspects of Cationic Dye Basic Orange 21

Spectroscopic properties of cationic dye basic orange 21 (BO21) in solutions, in solids, and within leukocytes were examined. Results obtained with solutions indicate that influence of variables such as pH, viscosity, salt composition, and various proteins on the absorption spectrum of BO21 is negligible. However, in the presence of heparin, a blue shift (484–465 nm) is observed, which is attributed to the aggregation of BO21 on the polyanion. Applying density functional theory demonstrates that in aqueous solutions (a) the formation of BO21 oligomers is thermodynamically favorable, they are oriented in an antiparallel dipolar arrangement, and their binding energies are lower than those of parallel dipolar arrangements, (b) association between BO21 aggregates and heparin is highly favorable, and (c) the blue shift is due to the mixing of π → π* transitions caused by BO21 molecule stacking. However, when embedded in basophils, the absorption spectra of intracellular BO21 is extremely red-shifted, with two peaks (at 505 and 550 nm) found to be attributed to BO21 and the BO21–heparin complex, respectively, which are intracellularly hosted in nonaqueous environments. Initial evidence of the ability to differentiate between leukocyte types by BO21 is presented