Power-free sequential injection for microchip immunoassay toward point-of-care testing

Abstract

This paper presents a simple fluid handling technique for microchip immunoassay. Necessary solutions were sequentially injected into a microchannel by air-evacuated poly(dimethylsiloxane), and were passively regulated by capillary force at the inlet opening. For heterogeneous immunoassay, microchips are potentially useful for reduction of sample consumption and assay time. However, most of the previously reported microchips have limitations in their use because of the needs for external power sources for fluid handling. In this paper, an on-chip heterogeneous immunofluorescence assay without such an external power source is demonstrated. The microchip consisting of poly(dimethylsiloxane) (PDMS) and glass has a simple structure, and therefore is suitable for single-use applications. Necessary solutions were sequentially injected into a microchannel in an autonomous fashion with the power-free pumping technique, which exploits the high solubility and the rapid diffusion of air in PDMS. For deionized water, this method yielded flow rates of 3-5 nL s-1 with reproducibility of 4-10%. The inlet opening of the microchannel functioned as a passive valve to hold the solution when the flow was finished. Rabbit immunoglobulin G (rIgG) and human C-reactive protein (CRP) were detected using the microchannel walls as reaction sites. With the sample consumption of 1 microL and the assay time of approximately 20 min including the antibody immobilization step, the sandwich immunoassay methods for rIgG and CRP exhibited the limits of detection of 0.21 nM (0.21 fmol) and 0.42 nM (0.42 fmol), respectively.

Detection of Methylated DNA on a Power-Free Microfluidic Chip with Laminar Flow-Assisted Dendritic Amplification

“…A piece of adhesive tape was used for the power-free pumping technique. 16 A straight line pattern (100 μm wide) of the capture probe (CP) DNA was made on the glass substrate, which was then covered with the PDMS part having microchannels (100 μm wide and 25 μm deep). Thus, the CP pattern and the microchannels became orthogonal to each other.…”

“…16 The power-free microfluidic chip needs no external pump, and thus simplifies the whole detection setup. We have also invented a signalamplification technology specialized for microfluidic chips: laminar flow-assisted dendritic amplification (LFDA).…”

Towards autonomous lab-on-a-chip devices for cell phone biosensing

“…In this case whole blood is propelled using a self-powered evacuated dead-end microchannel (Hosokawa et al, 2004(Hosokawa et al, , 2006, which needs to be preserved in a vacuum pouch previous to operation, although the principle could be adapted to other forms of self-propulsion (Wang et al, 2010;Kokalj et al, 2014;Zimmermann et al, 2007;Gervais and Delamarche, 2009) or finger pumps (Comina et al, 2015a;Begolo et al, 2014). The deep trench type of separation feature is also very compatible with 3D printed LOC devices (Comina et al, 2014a(Comina et al, , 2015b and minimizes the number of components and fabrication steps.…”

A “place n play” modular pump for portable microfluidic applications

“…Thus, the sample is drawn into the channels owing to this pressure difference. Recently, this passive pumping method has been used in various microfluidic applications, including immunoassays, 30,31 gold nanoparticle-based DNA analysis, 29,32,33 nanoliter-scale protein crystallization, 34 viscosity measuring, 35,36 blood analysis, 37 and cell loading. 38 This on-chip degas-driven pumping method that is capable of running without any external power is simple and convenient for the end user.…”