Electrochemical Release of Immobilized IgG Protein
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1010-V06-01
Electrochemical Release of Immobilized IgG Protein Tanveer Mahmud1, Wojtek Wlodarski1, Arnan Mitchell1, Sally Gras2, Adrian Trinchi3, and Kourosh Kalantar-zadeh1 1 School of Electrical and Computer Engineering, RMIT University, Melbourne, 3001, Australia 2 Department of Chemical and Biomolecular Engineering, and The Bio21 Molecular Science & Biotechnology, The University of Melbourne, Melbourne, 3004, Australia 3 Manufacturing and Materials Technology, CSIRO, Melbourne, Australia ABSTRACT In this paper, we present the electrochemically programmed release of immobilized IgG protein molecules that have been attached to gold coated surfaces via a thiol-gold linkage. Fluorescence microscopy has been used to image the release of fluorescently tagged IgGs in phosphate buffered saline. In this technique, the reductive desorption of self-assembled monolayers is employed for the release of proteins, which are immobilized on the surface either by non-covalent or covalent interactions. The voltage applied for the release of proteins is in a range of -1.5V to -60V. INTRODUCTION The electrochemical release of biomolecules and biopolymers can be used for the delivery of drugs, proteins, and DNA in both a controlled and programmable fashion. This technique has a number of promising applications in immunosensing, for studies understanding the kinetic performance of biosensors, programmable DNA/protein arrays and micro-reactors, and in the fabrication of devices for controlled drug delivery. The antibody IgG can be immobilized and then electrochemically released from a surface in a controlled manner. An alkanethiol linker has been employed to couple the IgG molecules to a gold surface and facilitate their subsequent release. We describe the properties of alkanethiol coated surfaces before and after the application of an electrical stimulus. We then immobilize proteins via covalent and non-covalent association with the alkanethiol group, and apply fluorescence microscopy to monitor the release of fluorescently tagged IgGs from gold surfaces into a droplet of phosphate buffered saline solution. The process of electrochemical release involves the application of a voltage, followed by a chemical response. In this study, the voltage ranged from -1.5V to -60V and resulted in the reductive desorption of self-assembled monolayers (SAMs). The release of the SAM can be monitored by measuring the change in surface hydrophobicity and change in the contact angle between a water droplet and the surface. The experimental set-up for applying the voltage and determining the contact angle is given in Figure 1. This type of experiment is also known as electrowetting.
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Figure 1. Schematic of an experimental set-up for electrowetting. A difference in surface hydrophobicity and contact angle between a water droplet and the surface is observed after applying an electrical stimulus. Here, θ is the contact angle of the droplet. We first demonstrated the appl
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