Molecular Release Associated with Interfacial pH Change Stimulated by a Small Electrical Potential Applied

Abstract

Electrochemically stimulated molecular release from a modified electrode surface has been studied. The system was based on a buckypaper electrode modified with a molecular layer, which included a linker with a hydrolyzable phenolic ester bond connecting a fluorescent dye to the electrode surface, and with bilirubin oxidase catalyzing O2 reduction. The O2 reduction resulted in the local pH increase, which resulted in hydrolytic cleavage of the linker and release of the dye. The source of electrons for the reduction process can be electronic (potentiostat) or chemical (NADH). The potential applied on the modified electrode (0 V vs. Ag/AgCl) or generated in situ in the presence of NADH was very small, thus allowing the electrochemical process without complications of any side reaction. While the fluorescent dye released from the electrode represents a convenient model, various (bio)molecular species (e. g., drugs) can be released in the similar process. The designed signal‐controlled release system represents a general platform for various (bio)molecular delivering processes.

Electrochemically produced local pH changes stimulating (bio)molecule release from pH-switchable electrode-immobilized avidin–biotin systems

“…26 The local (interfacial) pH change has been already used to control electrochemically activity of surface-immobilized enzymes 27 and to release molecular loads bound to an electrode surface, 28 particularly with pH-degradable covalent bonds. 29 The present paper reports on the use of electrode-surface immobilized nitro-avidin or avidin in combination with biotinylated or iminobiotinylated substances, respectively, with the local pH changes produced electrochemically. Fig.…”

Electrochemically Generated Interfacial pH Change: Application to Signal‐Triggered Molecule Release

“…Many control experiments confirmed the mechanism of the release process based on hydrolyzes of the chemical bond unstable at the basic pH generated at the interface due to the biocatalytic O 2 reduction. [78] It should be noted that almost the same mechanism has been realized with a similarly modified electrode, but without co-immobilized BOx, thus operating at more negative potential (À 0.5 V) needed for a non-catalytic O 2 reduction. [79] The (bio)molecule release processes performed upon biocatalytic O 2 reduction at a very low potential applied allow another way for activating the process.…”

“…[77] Another concept of the signal-triggered molecule release has been combined with the O 2 reduction catalyzed by BOx to yield local interfacial pH change at a low potential applied. [78] In this system, the target molecule was covalently bound to the interface through a linker with a phenolic ester bond hydrolyzable at basic pH values, Figure 17A. The co-immobilized BOx catalyzed the O 2 reduction resulting in the local pH increase upon applying 0 V (vs. Ag j AgCl reference), then hydrolyzing the phenolic ester bond and releasing the target molecule represented with a model fluorescent dye, Figure 17B.…”

“…The conductive electrode support made of buckypaper composed of compressed carbon nanotubes (CNTs) allowed easy immobilization of the linker with the connected dye and BOx, both bound via pyrene anchor group attached to the CNT walls due to π-π stacking. [78] The biocatalytic O 2 reduction was started at ca. 0.55 V as shown in the cyclic voltammograms in Figure 18A.…”

“…B) The fluorescent dye release to the bulk solution after the electrochemically induced cleavage of the linker and its fluorescent analysis in solution. Adapted from Ref [78]. with permission.…”