Electrochemically Stimulated Molecule Releaseassociated with Interfacial pH Changes

Abstract

Stimuli responsive materials are extremely important in many applications in biomedical and biotechnological field.1 Over past several decades, a large number of materials/systems which respond to the various activating/deactivating signals have been proposed and developed. External stimuli controlled release of therapeutic agents is one among such systems. In this field a large variety of stimuli such as pH, temperature, light, magnetic field and many more have been exploited to achieve signal stimulated release of drugs/biomolecules. Electrochemically triggered release of (bio)molecules is gaining attention due to the simplicity and easy integration of those systems with sophisticated electronic devices. These methods take advantage of some common phenomenon such as formation/cleavage of redox bonds (for example; disulfide linkages), electrostatic association/dissociation2,3, and entrapping/releasing the (bio)molecules from the (bio)polymer gels for achieving immobilization and electrochemically stimulated release. While these methods are powerful, they have their own limitations (for example, reduction of disulfide bonds is significantly complicated in presence of other redox species). Hence to design an universal approach for electrochemically triggered release of (bio)molecules, we investigated the development of a hydrolysable linker at mild basic (pH 8-10) conditions. Herein we report a new linker with a hydrolysable phenolic ester bond at basic pH (~8-10) for electrode modification. Basic pH locally produced at the electrode surface upon electrochemical reduction of oxygen resulted in the hydrolytic cleavage of the phenolic ester bond and release of the immobilized fluorescent dye used as a model compound4.