Abstract
Electrowetting is the effect by which the contact angle of a droplet exposed to a surface charge is modified. Electrowetting-on-dielectric (EWOD) exploits the dielectric properties of thin insulator films to enhance the charge density and hence boost the electrowetting effect. The presence of charges results in an electrically induced spreading of the droplet which permits purposeful manipulation across a hydrophobic surface. Here, we demonstrate EWOD-based protocol for sample processing and detection of four categories of antigens, using an automated surface actuation platform, via two variations of an Enzyme-Linked Immunosorbent Assay (ELISA) methods. The ELISA is performed on magnetic beads with immobilized primary antibodies which can be selected to target a specific antigen. An antibody conjugated to HRP binds to the antigen and is mixed with H2O2/Luminol for quantification of the captured pathogens. Assay completion times of between 6 and 10 min were achieved, whilst minuscule volumes of reagents were utilized.
Highlights
The proposed method aims to facilitate automated sample preparation for Enzyme-Linked Immunosorbent Assay (ELISA) with quantitative detection of antigens using EWOD-based approach with digital microfluidics (DMF) and magnetophoretic separation
We report on using a bespoke, free-standing, fully automated DMF platform for immunoassays, and we elaborate on the protocol for the rapid detection of biomolecules, namely: proteins, vegetative bacteria, bacterial spores and viruses
105 Vrms was chosen as the standard actuation voltage, 120 Vrms was found to work best for the H2O2/Luminol droplet and 165 Vrms was implemented for the extraction laboratory unit operations (LUOs)
Summary
The proposed method aims to facilitate automated sample preparation for ELISA with quantitative detection of antigens using EWOD-based approach with digital microfluidics (DMF) and magnetophoretic separation. Oil-free systems are simple to integrate and have the advantage of providing easy chip-to-chip sample translation For these reasons, the proposed method was developed to provide an EWOD-based immunoassay on DMF which would not require oil, effectively simplifying the device operation. The proposed method was developed to provide an EWOD-based immunoassay on DMF which would not require oil, effectively simplifying the device operation In this contribution, we report on using a bespoke, free-standing, fully automated DMF platform for immunoassays, and we elaborate on the protocol for the rapid detection of biomolecules, namely: proteins, vegetative bacteria, bacterial spores and viruses. The design and realization of the different components constituting the integrated, completely self-contained DMF platform, including the high voltage waveform generator and drive electronics is disclosed elsewhere[6]
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