Abstract:This article is an overview of extensive research efforts in many laboratories in the last two decades in the area of light‐switchable electrochemical systems and modified electrodes. Electrochemical reactions, including electrocatalytic and bioelectrocatalytic processes, have been reversibly activated and inhibited upon irradiation with light at different wavelengths. In order to realize these light activated or inhibited processes, the electrodes or/and reacting molecules were functionalized with photoisomer… Show more
“…Signal‐controlled (bio)electrochemical systems with switchable/tunable activity are essential for assembling bioelectronic, (particularly implantable bioelectronic) systems with adaptable behavior in biological environment. The majority of signal‐controlled electrochemical systems has been based on electrodes chemically modified with stimuli‐responsive materials (usually polymers) sharply changing their properties upon receiving external signals in the form of light irradiation, magnetic field application, temperature change, pH variation, etc. These changes result in activation/inhibition of electrochemical processes at the modified electrode surfaces, predominantly affecting electronic communication between biological molecules (usually enzymes, frequently involving electron‐transfer mediators) and the conducting support, thus switching bioelectrocatalytic processes ON and OFF.…”
Construction of artificial allosteric protein switches is one of the central goals of synthetic biology that holds promise to transform the way we detect and quantify substances in vitro and in vivo. An artificial chimeric fusion protein of pyrroloquinoline quinone‐dependent glucose dehydrogenase with calmodulin (PQQ‐GDH‐CaM) was covalently attached to graphene nanosheets produced electrochemically on a carbon fiber electrode. The chimeric PQQ‐GDH‐CaM represents an artificial allosteric switch activated by association of a calmodulin‐binding peptide with the Ca2+‐bound calmodulin domain. The activity of the immobilized enzyme was switched between active and inactive states by adding/removing the activating peptide. The peptide‐signal switchable features originated from the enzyme 3D‐structural variations induced by the conformational (folding/unfolding) changes in the connected calmodulin unit upon formation/dissociation of its complex with the specific peptide. The peptide‐activated immobilized PQQ‐GDH‐CaM enzyme displayed direct (non‐mediated) electron transfer to the conducting electrode support upon glucose oxidation. On the contrary, in the absence of the peptide, the inactive form of the enzyme demonstrated very low bioelectrocatalytic activity for glucose oxidation. Since the conformational changes of the PQQ‐GDH‐CaM depend on the presence of Ca2+ cations and the calmodulin‐binding peptide, both of them were used as input signals to control the enzyme activity mimicking a Boolean AND logic gate. The switchable behavior of the enzyme‐modified electrode was studied electrochemically and used to assemble a signal‐switchable biofuel cell. The use of the peptide as the signaling messenger enables the design of generalizable bioelectronic systems controlled by native and synthetic biochemical signaling systems.
“…Signal‐controlled (bio)electrochemical systems with switchable/tunable activity are essential for assembling bioelectronic, (particularly implantable bioelectronic) systems with adaptable behavior in biological environment. The majority of signal‐controlled electrochemical systems has been based on electrodes chemically modified with stimuli‐responsive materials (usually polymers) sharply changing their properties upon receiving external signals in the form of light irradiation, magnetic field application, temperature change, pH variation, etc. These changes result in activation/inhibition of electrochemical processes at the modified electrode surfaces, predominantly affecting electronic communication between biological molecules (usually enzymes, frequently involving electron‐transfer mediators) and the conducting support, thus switching bioelectrocatalytic processes ON and OFF.…”
Construction of artificial allosteric protein switches is one of the central goals of synthetic biology that holds promise to transform the way we detect and quantify substances in vitro and in vivo. An artificial chimeric fusion protein of pyrroloquinoline quinone‐dependent glucose dehydrogenase with calmodulin (PQQ‐GDH‐CaM) was covalently attached to graphene nanosheets produced electrochemically on a carbon fiber electrode. The chimeric PQQ‐GDH‐CaM represents an artificial allosteric switch activated by association of a calmodulin‐binding peptide with the Ca2+‐bound calmodulin domain. The activity of the immobilized enzyme was switched between active and inactive states by adding/removing the activating peptide. The peptide‐signal switchable features originated from the enzyme 3D‐structural variations induced by the conformational (folding/unfolding) changes in the connected calmodulin unit upon formation/dissociation of its complex with the specific peptide. The peptide‐activated immobilized PQQ‐GDH‐CaM enzyme displayed direct (non‐mediated) electron transfer to the conducting electrode support upon glucose oxidation. On the contrary, in the absence of the peptide, the inactive form of the enzyme demonstrated very low bioelectrocatalytic activity for glucose oxidation. Since the conformational changes of the PQQ‐GDH‐CaM depend on the presence of Ca2+ cations and the calmodulin‐binding peptide, both of them were used as input signals to control the enzyme activity mimicking a Boolean AND logic gate. The switchable behavior of the enzyme‐modified electrode was studied electrochemically and used to assemble a signal‐switchable biofuel cell. The use of the peptide as the signaling messenger enables the design of generalizable bioelectronic systems controlled by native and synthetic biochemical signaling systems.
“…Anchoring very thin gel layers on the surface of an electrode could increase the possible applications of both materials. Modification of electrode surfaces with environmentally sensitive hydrogel layers could lead to the development of devices such as sensors or biosensors, logic gates, switchable electrochemical systems, electrochemical actuators, or electrochemical valves. − In addition, hydrogel and polymer layers can be used as potentially advanced drug delivery and proteins systems . For instance, Xu et al used a poly( N -isopropylacrylamide- co -acrylic acid) microgel layer on an electrode surface as an electrochemically controlled drug release system.…”
In this study, we
present a thermoresponsive thin hydrogel
layer
based on poly(N-isopropylacrylamide), functionalized
with β-cyclodextrin groups (p(NIPA-βCD)), as a novel electrochemically
controlled release system. This thin hydrogel layer was synthesized
and simultaneously attached to the surface of a Au quartz crystal
microbalance (QCM) electrode using electrochemically induced free
radical polymerization. The process was induced and monitored using
cyclic voltammetry and a quartz crystal microbalance with dissipation
monitoring (QCM-D), respectively. The properties of the thin layer
were investigated by using QCM-D and scanning electron microscopy
(SEM). The incorporation of β-cyclodextrin moieties within the
polymer network allowed rhodamine B dye modified with ferrocene (RdFc),
serving as a model metallodrug, to accumulate in the p(NIPA-βCD)
layer through host–guest inclusion complex formation. The redox
properties of the electroactive p(NIPA-βCD/RdFc) layer and the
dissociation of the host–guest complex triggered by changes
in the oxidation state of the ferrocene groups were investigated.
It was found that oxidation of the ferrocene moieties led to the release
of RdFc. It was crucial to achieve precise control over the release
of RdFc by applying the appropriate electrochemical signal, specifically,
by applying the appropriate potential to the electrode. Importantly,
the electrochemically controlled RdFc release process was performed
at a temperature similar to that of the human body and monitored using
a spectrofluorimetric technique. The presented system appears to be
particularly suitable for transdermal delivery and delivery from intrabody
implants.
“…Regarding the sensing electrode, many recent advances in biomolecular logic systems [18,19] have led to the development of systems capable to mimicking traditional computing logic, such as AND and OR logic gates, through the use of integrated enzyme-biocatalyzed reactions. [20] By utilizing enzymes, a specific and fixed response to a biomolecular biomarker is ensured all while utilizing the incredible selectivity and sensitivity unique to enzymes and their paired substrate. The combining effect of multiple enzymes following one another's reaction allows for a cascading effect that will increase the effectiveness of one enzyme triggering the next.…”
Electrochemically-triggered payload release as a potential method for signal-responsive "smart drug" development has been increasingly utilized in the field of modern pharmaceuticals. Among the various approaches to design electrochemically-triggered payload release systems, the basis of using electrochemical reactions to develop sensing and releasing electrodes allows for increased diversity and adaptability with regards to signal, payload, and release conditions. In this review, an overview of the two main categories (pH-independent and pH-dependent) of electrochemically-triggered release and their most commonly used subsets were summarized. These variations provided the foundational basis from which an electrochemically-triggered payload release system can be designed and adapted to meet the demands of potential treatment requirements. Moreover, different practically demonstrated adaptions of electrochemically-triggered payload release sensing and releasing electrodes were evaluated comprehensively and the advantages and disadvantages were discussed. Finally, some overarching recommendations for optimized use of these electrochemical systems were proposed.
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