Electrochemically Triggered DNA Release from a Mixed-brush Polymer-modified Electrode

Stimulation-Inhibition of Protein Release from Alginate Hydrogels Using Electrochemically Generated Local pH Changes

The electrochemically controlled release of proteins was studied in a Ca²⁺-cross-linked alginate hydrogel deposited on an electrode surface. The electrochemical oxidation of ascorbate or reduction of O₂ was achieved upon applying electrical potentials +0.6 or -0.8 V (vs Ag/AgCl/KCl 3 M), respectively, resulting in decreasing or increasing pH locally near an electrode surface. The obtained local acidic solution resulted in the protonation of carboxylic groups in the alginate hydrogel and, as a result, the formation of a hydrophobic shrunken hydrogel film. Conversely, the produced alkaline local environment resulted in a hydrophilic swollen hydrogel film. The release of the proteins was effectively inhibited from the shrunk hydrogel and activated from the swollen hydrogel film. Overall, the electrochemically produced local pH changes allowed control over the biomolecule release process. While the release inhibition by applying +0.6 V was always effective and could be maintained as long as the positive potential was applied, the release activation was different depending on the protein molecular size, being more effective for smaller species, and molecule charge, being more effective for negatively charged species. The repetitive change from the inhibited to stimulated state of the biomolecule release process was obtained upon cyclic application of oxidative and reductive potentials (+0.6 V ↔ -0.8 V). The alginate hydrogel film shrinking-swelling as well as the protein release process were studied and visualized using a confocal fluorescent microscope. In order to be observed, an external surface of the alginate film and the loaded protein molecules were labeled with different fluorescent dyes, which then produced colored fluorescent images under a confocal microscope.

pH dependent degradation properties of lactide based 3D microchamber arrays for sustained cargo release

Encapsulation of small water soluble molecules is important in a large variety of applications, ranging from medical substance releasing implants in the field of medicine over release of catalytically active substances in the field of chemical processing to anti-corrosion agents in industry. In this work polylactic acid (PLA) based hollow-structured microchamber (MC) arrays are fabricated via one-step dip coating of a silicone rubber stamp into PLA solution. These PLA MCs are able to retain small water soluble molecules (Rhodamine B) stably entrapped within aqueous environments. It is shown, that degradation of PLA MCs strongly depends on environmental conditions like surrounding pH and follows first order degradation kinetics. This pH dependent PLA MC degradation can be utilized to control the release kinetics of encapsulated cargo.

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.

Electrochemically stimulated molecule release associated with interfacial pH changes

Molecular release was activated with an electrochemical signal, resulting in the hydrolysis of a linker.