Microfluidic inverse phase ELISA via manipulation of magnetic beads

Abstract

We report a new technique for conducting immuno-diagnostics on a microfluidic platform. Rather than handling fluid reagents against a stationary solid phase, the platform manipulates analyte-coated magnetic beads through stationary plugs of fluid reagents to detect an antigenic analyte. These isolated but accessible plugs are preencapsulated in a microchannel by capillary force. We call this platform microfluidic inverse phase enzyme-linked immunosorbent assay (lIPELISA). lIPELISA has distinctive advantages in the family of microfluidic immunoassay. In particular, it avoids pumping and valving fluid reagents during assaying, thus leading to a lab-on-a-chip format that is free of instrumentation for fluid actuation and control. We use lIPELISA to detect digoxigenin-labeled DNA segments amplified from E. coli O157:H7 by polymerase chain reaction (PCR), and compare its detection capability with that of microplate ELISA. For 0.259 ng ll -1 of digoxigenin-labeled amplicon, lIPELISA is as responsive as the microplate ELISA. Also, we simultaneously conduct lIP-ELISA in two parallel microchannels.

Experimental investigations of liquid flow in rib-patterned microchannels with different surface wettability

“…After the experiments for microchannels with hydrophilic surface, the channels were rendered hydrophobic by following procedure which was reported by Chen et al (2010). Solutions of 1H, 1H, 2H, 2H-perfluorooctyl-trichlorosilane (PFO-TCS; 4% v:v) filled the microchannels for 1 h in a closed chamber filled with dry nitrogen gas.…”

Liquid carry-over in an injection moulded all-polymer chip system for immiscible phase magnetic bead-based solid-phase extraction

“…Shikida et al determined an average carry-over of 0.08 nL/mg using 150-600 mg of 32.7 mm MBs in a 10% KCl solution [5]. Chen et al reported 3.62 nL carry-over of water using 5 Â 10 5 MBs having a diameter of 3.12 mm amounting to approximately 0.37 nL/mg [6]. Sur et al used 40-180 mg of 450 nm MBs to estimate the carry-over of Tris buffer in their system amounting to 2.02 nL/mg.…”

“…This is done by transporting the target-MB cluster through an immiscible phase, such as oil [4][5][6], wax [4,7,8], or air [8], often using an external permanent magnet. Such systems have been demonstrated for a number of applications including enzyme linked immunosorbent assays [6,9,10], nucleic acid extraction [4,7,8,[11][12][13][14], protein extraction [8], and cell extraction [15,16].…”

Magnetic droplet actuation on natural (Colocasia leaf) and fluorinated silica nanoparticle superhydrophobic surfaces

“…Extensive and comprehensive analysis of ferrofluidic manipulation on DMF devices has been previously reported therefore here we concentrate on aqueous droplets containing paramagnetic particles only [24,30,31]. Commercial "magnetic particles" for this purpose are based on (super)paramagnetic particles, where an iron oxide core is surrounded by a layer of silica, which can be functionalized as desired for a given application [32][33][34][35]. Many devices using magnetic actuation have been reported, and complex droplet movement has been demonstrated in three dimensions, including actuation of an inverted droplet [20].…”