Magnetic beads retention device for sandwich immunoassay: comparison of off-chip and on-chip antibody incubation

We use magnetic microbeads, which are magnetically self-assembled in chains in a microfluidic chip, as reaction substrates to implement two different sandwich immunoassay protocols for the detection of mouse monoclonal target antibodies. The magnetic chains form when the chip is placed in a magnetic field, and are geometrically trapped and accurately positioned in a microchannel with periodically enlarged cross-sections. In the first immunoassay protocol, capture and target antibodies are incubated off-chip, while exposure to the detection antibody is performed on-chip. In the second protocol, the complete immunoassay is fully executed on-chip. In the ‘off-chip incubation-on-chip detection' protocol, antibodies can be detected down to a concentration of 50ng/mL in a total assay time of 120min, while consuming 1.5mL of target antibody solution. Using the full on-chip protocol, our system is able to detect target antibodies in the range of a few ng/mL in 30min, using only a few tens of nanoliters of target antibody solution and reagents. The ‘off-chip incubation-on-chip detection' protocol is also applied for dosing antibodies obtained from the supernatant of a cell culture mediu

Magnetic beads retention device for sandwich immunoassay: comparison of off-chip and on-chip antibody incubation

We use magnetic microbeads, which are magnetically self-assembled in chains in a microfluidic chip, as reaction substrates to implement two different sandwich immunoassay protocols for the detection of mouse monoclonal target antibodies. The magnetic chains form when the chip is placed in a magnetic field, and are geometrically trapped and accurately positioned in a microchannel with periodically enlarged cross-sections. In the first immunoassay protocol, capture and target antibodies are incubated off-chip, while exposure to the detection antibody is performed on-chip. In the second protocol, the complete immunoassay is fully executed on-chip. In the ‘off-chip incubation–on-chip detection’ protocol, antibodies can be detected down to a concentration of 50 ng/mL in a total assay time of 120 min, while consuming 1.5 mL of target antibody solution. Using the full on-chip protocol, our system is able to detect target antibodies in the range of a few ng/mL in 30 min, using only a few tens of nanoliters of target antibody solution and reagents. The ‘off-chip incubation–on-chip detection’ protocol is also applied for dosing antibodies obtained from the supernatant of a cell culture medium

Pumping of mammalian cells with a nozzle-diffuser micropump

We discuss the successful transport of jurkat cells and 5D10 hybridoma cells using a reciprocating micropump with nozzle-diffuser elements. The effect of the pumping action on cell viability and proliferation, as well as on the damaging of cellular membranes is quantified using four types of well-established biological tests: a trypan blue solution, the tetrazolium salt WST-1 reagent, the LDH cytotoxicity assay and the calcium imaging ATP test. The high viability levels obtained after pumping, even for the most sensitive cells (5D10), indicate that a micropump with nozzle-diffuser elements can be very appropriate for handling living cells in cell-on-a-chip applications

Dipping-Induced Azimuthal Helix Orientation in Langmuir-Blodgett Monolayers of α-Helical Amphiphilic Diblock Copolypeptides

The azimuthal helix orientation of the rigid-rod amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(α-L-glutamic acid) (PLGA) and poly(γ-methyl-L-glutamate-ran-γ-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) in Langmuir-Blodgett (LB) monolayers was investigated using polarized transmission Fourier transform infrared spectroscopy. The relative position of dipping with respect to the previous transfer position can be used to manipulate the azimuthal orientation of the helices parallel to or tilted by an angle of 45° with respect to the dipping direction in the transferred films. The study of the azimuthal order for the LB monolayers of PLGA-b-PMLGSLGs of various block lengths revealed that the observed effect arises mainly from the deformation of the PMLGSLG top brush layer, induced by the flow orientation around the transfer region. In those cases where the PMLGSLG block is tilted by a sufficiently large angle with respect to the surface normal, high azimuthal order parameters of 0.5-0.75 were obtained.

Full on-chip nanoliter immuno-assay by geometrical magnetic trapping of nanoparticle chains

We propose an original concept to perform a complete on-chip sandwich immunoassay on magnetic nanoparticles that are self-assembled in chains in a uniform magnetic field. The magnetic chains are retained over periodically enlarged cross sections of a microfluidic channel. Thereby they strongly interact with the flow and rapidly capture the total of a low number of target molecules from nanoliter sample volumes. As an example, we demonstrate the detection of murine monoclonal antibodies in a noncompetitive sandwich immunoassay with a detection limit of 1 ng mL-1 in nanoliters of hybridoma cell culture medium

Langmuir-Blodgett Film of a New Fluorinated Polyphilic Compound

International audiencePolyphilic surfactants made up of acarboxylic hydrophilic headgroup, a biphenyl rigid core, a flexible hydrocarbonspacer, and a perfluorinated chain are used to build Langmuir-Blodgett multilayers. The films are investigatedby X-ray reflectivity, infrared dichroism, and scanning electron microscopy. At the transfer pressure used, themolecular area is consistent only with molecular long axes orthogonal to the air-water interface. Such asituation is retained for the first transferred monolayer whose thickness is equal to the molecular length in thefully elongated conformation. For thick films however, molecular long axes are tilted toward the dippingdirection. Such a finding involves a rearrangement which does not retain the total number of layers

Sandwich immunoassay on a microfluidic chip using patterns of electrostatically self-assembled streptavidin-coated beads

In this paper, we demonstrate a bead-based microfluidic immunoassay using self-assembled streptavidin-coated bead micropatterns. The beads are assembled on the microfluidic channel surface using electrostatic forces between the negatively-charged streptavidin-coated beads and the positively-charged aminosilane micropatterns. The immunoassay is performed in the stop-flow mode and uses mouse IgG diluted in phosphate buffered saline (PBS) solution as the model target antigen. The total immunoassay takes around 30 min and is able to detect mouse IgG antigen down to a concentration of 15 ng/mL by using only 560 nl of analyte volume