A combined microchannel-type erythrocyte deformability test with optical tweezers has been developed especially for more sensitive detection of cancerous diseases. To demonstrate the performance and sensitivity of the microchannel-type method, we measured the transit velocity of individual erythrocytes passing through a specific confinement region and calculated the modified elongation index defined by the ratio of the width of the microchannel to the elongated length of the squeezed erythrocytes. To know exactly the effect of optical tweezers on erythrocytes, we investigated several morphologies of optically deformed erythrocytes and measured the shape recovery time of erythrocytes in a static aqueous solution under various powers (~ 24 mW) of 1064-nm laser by a dual-trap optical tweezers. Finally we combined these two methods by considering the key parameters of erythrocyte deformability. The results show that the ambiguity of the overlapped experimental data from microchannel-type erythrocyte deformability test was conspicuously reduced, and that the subtle change (≈ 100-200 ms) in shape recovery time which is one of mechanical properties of erythrocyte membrane surface was remarkably amplified to readily discriminate the difference (≈ 2-3 s) between normal and cancerous blood. This suggests the combined method is more sensitive enough to pinpoint the minor quantitative differences between individual erythrocytes, especially in the field of cancer and cardiovascular diseases.
Image cytometry is a method for quantitative cellular analysis using images generally captured on slides or microfabricated chips. The flowless nature of data acquisition in image cytometry allows the use of value components, such as light-emitting diode excitation sources or low-cost charge-coupled device detectors. Unlike flow cytometry, the stationary cellular samples can be exposed to lower-intensity light and utilize less sensitive detectors with higher exposure times. Images are acquired and data is processed using recognition software to identify, count and analyze cells. Current image cytometers cannot replicate the quality of the data from flow cytometers or fluorescence microscopes with full functionality and performance components. Yet, the production of inexpensive image cytometers for use in small laboratories and clinics has made a compelling argument. The addition of fluorescence detection to the new generation of image cytometers has opened the field to a broader range of applications. This article will review the technical aspects and application of image cytometers, the recent progress in the field and available commercial devices.
Electroporation, is widely used method that can be directly applied to the field of gene therapy. However, very little is known about the basic mechanisms of DNA transfer and cell response to the electric pulse. As a more convenient and effective tool for the investigation on the mechanisms of electroporation and the enhancement of the functional efficiency, we developed a micro-electroporation chip with polydimethylsiloxane (PDMS). Owing to the transparency of PDMS, we could observe the process of Propidium Iodide (PI) uptake in real-time, which shows promise in visualization of gene activity in living cells. Furthermore, the design of the electroporation chip as a microchannel offers advantages in terms of efficiency in permeabilization of PI into SK-OV-3 cells. We also noticed the geometric effect on the degree of electroporation in microchannels with diverse channel width, which shows that the geometry can be another parameter to be considered for the electroporation when it is performed in microchannels.
Background: We evaluated the analytical performance of a new one-step rapid quantitative sandwich immunoassay for total prostate-specific antigen (tPSA), the FREND™ PSA Plus (FREND PSA) (NanoEnTek Inc., Seoul, Korea).
This paper presents a novel method for an on-chip erythrocyte deformability test under optical pressure, especially to enhance the level of sensitivity with respect to the detection of cancerous diseases. To demonstrate the performance and sensitivity of the combined method, we introduce the concept of transit velocity, a modified elongation index, and shape recovery time of individual erythrocytes in a strictly confined region (2 µm deep, 4 µm wide, and 100 µm long). Finally, we investigate a synergy or convergence effect due to the combination of these parameters for in situ detection of cancerous diseases under optical pressure.
Although AIDS-related mortality has declined since the introduction of antiretroviral therapy (ART), HIV/ AIDS patients are predominantly present in developing countries that lack high-cost diagnostic devices and human expertise.New methods for counting CD4+ cells cost-effectively are needed to replace conventional flow cytometry-based diagnosis.We developed a CD4+ cell analyzer, ADAMII, which is a benchtop fluorescence image-based CD3+/4+ cell counting analyzer. It bears a three-channel light source and performs CD3+/4+ counting assays. The automatic 3D stage captures a maximum of 136 images that are subsequently processed and analyzed using a software integrated into the system.Results obtained using ADAMII were compared with data obtained by conventional methods using a FACSCalibur flow cytometer and the point-of-care PIMA CD4 analyzer. Both comparisons between ADAMII vs. FACS and ADAMII vs. PIMA data yielded a strong correlation with an R2 value of 0.98, which ensures the feasibility of CD4 test by ADAMII.The proposed method using ADAMII can be easily employed in resource-limited areas to replace conventional flow cytometers, which are expensive and require highly trained staff.
We have developed a microchip for polymerase chain reaction (PCR) with polydimethylsiloxane (PDMS). PDMS has good characteristics: it is cheap, transparent, easy to fabricate and biocompatible. But in micro PCR, the porosity of PDMS causes several critical problems such as bubble formation, sample evaporation and protein adsorption. To solve those problems, we coated the micro PCR chips with Parylene film, which has low permeability to moisture and long-term stability. We investigated the influence of low thermal conductivity of PDMS and Parylene on the thermal characteristics of the PCR chips with numerical analysis. The thermal responses of micro PCR chips were compared for three materials: silicon, glass and PDMS. From the results, we identified appropriate thermal responses of the PDMS-based micro PCR chips by heating both the top and bottom sides. We could successfully amplify the angiotensin converting enzyme gene with as small a volume as 2 μl on the PDMS-based micro PCR chips without any additives.
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