Electrochemically controlled release of lipid/DNA complexes: a new tool for synthetic gene delivery system

DNA Release from a Modified Electrode Triggered by a Bioelectrocatalytic Process

DNA release from an electrode surface was stimulated by application of a mild electrical potential (0 V vs Ag/AgCl). The release process was activated by interfacial pH increase originating from H⁺ consumption during O₂ reduction bio-electrocatalyzed by bilirubin oxidase immobilized at the electrode surface. The pH increase resulted in a change of the electrical charge from positive to negative at the surface of SiO₂ nanoparticles (200 nm) associated with the electrode surface and functionalized with trigonelline and boronic acid. While the negatively charged DNA molecules were electrostatically bound to the positively charged surface, the negative charge produced upon O₂ reduction resulted in the DNA repulsion and release from the modified interface. The small electrical potential for O₂ reduction resulting in the interface recharge was allowed due to the bio-electrocatalysis using bilirubin oxidase enzyme. While, in the first set of experiments, the potential was applied on the modified electrode from an electrochemical instrument, later it was generated in situ by biocatalytic or photo-biocatalytic processes at a connected electrode. A multistep biocatalytic cascade generating NADH or photosynthetic process in thylakoid membranes was used to produce in situ a small potential to stimulate the DNA release catalyzed by bilirubin oxidase. The designed system can be used for different release processes triggered by various signals (electrical, biomolecular, and light signals, etc.), thus representing a general interfacial platform for the controlled release of different biomolecules and nanosize species.

DNA Computing Systems Activated by Electrochemically-triggered DNA Release from a Polymer-brush-modified Electrode Array

An array of four independently wired indium tin oxide (ITO) electrodes was used for electrochemically stimulated DNA release and activation of DNA-based Identity, AND and XOR logic gates. Single-stranded DNA molecules were loaded on the mixed poly(N,N-di-methylaminoethyl methacrylate) (PDMAEMA)/poly-(methacrylic acid) (PMAA) brush covalently attached to the ITO electrodes. The DNA deposition was performed at pH 5.0 when the polymer brush is positively charged due to protonation of tertiary amino groups in PDMAE-MA, thus resulting in electrostatic attraction of the negatively charged DNA. By applying electrolysis at -1.0 V(vs. Ag/AgCl reference) electrochemical oxygen reduction resulted in the consumption of hydrogen ions and local pH increase near the electrode surface. The process resulted in recharging the polymer brush to the negative state due to dissociation of carboxylic groups of PMAA, thus repulsing the negatively charged DNA and releasing it from the electrode surface. The DNA release was performed in various combinations from different electrodes in the array assembly. The released DNA operated as input signals for activation of the Boolean logic gates. The developed system represents a step forward in DNA computing, combining for the first time DNA chemical processes with electronic input signals.

Dielectrophoretically-assisted electroporation using light-activated virtual microelectrodes for multiple DNA transfection

Gene transfection is an important technology for various biological applications. The exogenous DNA is commonly delivered into cells by using a strong electrical field to form transient pores in cellular membranes. However, the high voltage required in this electroporation process may cause cell damage. In this study, a dielectrophoretically-assisted electroporation was developed by using light-activated virtual microelectrodes in a new microfluidic platform. The DNA electrotransfection used a low applied voltage and an alternating current to enable electroporation and transfection. Single or triple fluorescence-carrying plasmids were effectively transfected into various types of mammalian cells, and the fluorescent proteins were successfully expressed in live transfected cells. Moreover, the multi-triangle optical pattern that was projected onto a photoconductive layer to generate localized non-uniform virtual electric fields was found to have high transfection efficiency. The developed dielectrophoretically-assisted electroporation platform may provide a simpler system for gene transfection and could be widely applied in many biotechnological fields.