Polymer actuator valves toward controlled drug delivery application

Maximizing Performance of a Hybrid MnO2/Ni Electrochemical Actuator through Tailoring Lattice Tunnels and Cation Vacancies

Electrochemical actuators play a key role in converting electrical energy to mechanical energy. However, a low actuation stress and an unsatisfied strain response rate strongly limit the extensive applications of the actuators. Here, we report hybrid manganese dioxide (MnO₂) fabricated by introducing ramsdellite (R-MnO₂) and Mn vacancies into birnessite (δ-MnO₂) nanosheets, which in situ grew on the surface of a nickel (Ni) film, forming a hybrid MnO₂/Ni actuator. The actuator demonstrated a rapid strain response of 0.88% s^-1 (5.3% intrinsic strain in 6 s) and a large actuation stress of 244 MPa owing to the special R-MnO₂ with a high density of sodium ion (Na⁺)-accessible lattice tunnels, Mn vacancies, and also a high Young's modulus of the hybrid MnO₂/Ni composite. Besides, the cyclic stability of the actuator was realized after 1.2 × 10⁴ cycles of electric stimulation under a frequency of 0.05 Hz. The finding of the novel hybrid MnO₂/Ni actuator may provide a new strategy to maximize the actuating performance evidently through tailoring the lattice tunnel structure and introducing cation vacancies into electrochemical electrode materials.

Distributed sensor and actuator networks for closed-loop bioelectronic medicine

Designing implantable bioelectronic systems that continuously monitor physiological functions and simultaneously provide personalized therapeutic solutions for patients remains a persistent challenge across many applications ranging from neural systems to bioelectronic organs. Closed-loop systems typically consist of three functional blocks, namely, sensors, signal processors and actuators. An effective system, that can provide the necessary therapeutics, tailored to individual physiological factors requires a distributed network of sensors and actuators. While significant progress has been made, closed-loop systems still face many challenges before they can truly be considered as long-term solutions for many diseases. In this review, we consider three important criteria where materials play a critical role to enable implantable closed-loop systems: Specificity, Biocompatibility and Connectivity. We look at the progress made in each of these fields with respect to a specific application and outline the challenges in creating bioelectronic technologies for the future.

Electroactive material-based biosensors for detection and drug delivery

Electroactive materials are employed at the interface of biology and electronics due to their advantageous intrinsic properties as soft organic electronics. We examine the most recent literature of electroactive material-based biosensors and their emerging role as theranostic devices for the delivery of therapeutic agents. We consider electroactive materials through the lens of smart drug delivery systems as materials that enable the release of therapeutic cargo in response to specific physiological and external stimuli and discuss the way these mechanisms are integrated into medical devices with examples of the latest advances. Studies that harness features unique to conductive polymers are emphasized; lastly, we highlight new perspectives and future research direction for this emerging technology and the challenges that remain to overcome.

Highly Conductive Collagen by Low-Temperature Atomic Layer Deposition of Platinum

In modern biomaterial-based electronics, conductive and flexible biomaterials are gaining increasing attention for their wide range of applications in biomedical and wearable electronics industries. The ecofriendly, biodegradable, and self-resorbable nature of these materials makes them an excellent choice in fabricating green and transient electronics. Surface functionalization of these biomaterials is required to cater to the need of designing electronics based on these substrate materials. In this work, a low-temperature atomic layer deposition (ALD) process of platinum (Pt) is presented to deposit a conductive thin film on collagen biomaterials, for the first time. Surface characterization revealed that a very thin ALD-deposited seed layer of TiO₂ on the collagen surface prior to Pt deposition is an alternative for achieving a better nucleation and 100% surface coverage of ultrathin Pt on collagen surfaces. The presence of a pure metallic Pt thin film was confirmed from surface chemical characterization. Electrical characterization proved the existence of a continuous and conductive Pt thin film (∼27.8 ± 1.4 nm) on collagen with a resistivity of 295 ± 30 μΩ cm, which occurred because of the virtue of TiO₂. Analysis of its electronic structures showed that the presence of metastable state due to the presence of TiO₂ enables electrons to easily flow from valence into conductive bands. As a result, this turned collagen into a flexible conductive biomaterial.

Conjugated Polymer Actuators and Devices: Progress and Opportunities

Conjugated polymers (CPs), as exemplified by polypyrrole, are intrinsically conducting polymers with potential for development as soft actuators or "artificial muscles" for numerous applications. Significant progress has been made in the understanding of these materials and the actuation mechanisms, aided by the development of physical and electrochemical models. Current research is focused on developing applications utilizing the advantages that CP actuators have (e.g., low driving potential and easy to miniaturize) over other actuating materials and on developing ways of overcoming their inherent limitations. CP actuators are available as films, filaments/yarns, and textiles, operating in liquids as well as in air, ready for use by engineers. Here, the milestones made in understanding these unique materials and their development as actuators are highlighted. The primary focus is on the recent progress, developments, applications, and future opportunities for improvement and exploitation of these materials, which possess a wealth of multifunctional properties.

Electronic Noses in Medical Diagnostics

BACKGROUND

Electronic nose technology is being developed in order to analyse complex mixtures of volatiles in a way parallel to biologic olfaction. When applied in the field of medicine, the use of such devices should enable the identification and discrimination between different diseases. In this review, a comprehensive summary of research in medical diagnostics using electronic noses is presented. A special attention has been paid to the application of these devices and sensor technologies, in response to current trends in medicine.

METHODS

Peer-reviewed research literature pertaining to the subject matter was identified based on a search of bibliographic databases. The quality and relevance of retrieved papers was assessed using standard tools. Their content was critically reviewed and certain information contained therein was compiled in tabularized form.

RESULTS

The majority of reviewed studies show promising results, often surpassing the accuracy and sensitivity of established diagnostic methods. However, only a relatively small number of devices have been field tested. The methods used for sample collection and data processing in various studies were listed in a table, together with electronic nose models used in these investigations.

CONCLUSION

Despite the fact that devices equipped with arrays of chemical sensors are not routinely used in everyday medical practice, their prospective use would solve some established issues in medical diagnostics, as well as lead to developments in prophylactics by facilitating a widespread use of non-invasive screening tests.

Redox- and pH-Responsive Nanoparticles Release Piperlongumine in a Stimuli-Sensitive Manner to Inhibit Pulmonary Metastasis of Colorectal Carcinoma Cells

Redox-responsive nanoparticles having a diselenide linkage were synthesized to target pulmonary metastasis of cancer cells. Methoxy poly(ethylene glycol)-grafted chitosan (ChitoPEG) was crosslinked using selenocystine-acetyl histidine (Ac-histidine) conjugates (ChitoPEGse) for stimuli-responsive delivery of piperlongumine (PL). ChitoPEGse nanoparticles swelled in an acidic environment and became partially disintegrated in the presence of H2O2, resulting in an increase of particle size and in a size distribution having multimodal pattern. PL release increased under acidic conditions and in the presence of H2O2. Uptake of ChitoPEGse nanoparticles by CT26 cells significantly increased in acidic and redox state. PL-incorporated ChitoPEGse nanoparticles (PL NPs) showed similar anticancer activity in vitro against A549 and CT26 cells compared to PL itself. PL NP showed superior anticancer and antimetastatic activity in an in vivo CT26 cell pulmonary metastasis mouse model. Furthermore, an immunofluorescence imaging study demonstrated that PL NP conjugates were specifically delivered to the tumor mass in the lung. Conclusively, ChitoPEGse nanoparticles were able to be delivered to cancer cells with an acidic- or redox state-sensitive manner and then efficiently targeted pulmonary metastasis of cancer cells since ChitoPEGse nanoparticles have dual pH- and redox-responsiveness.

Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology

The electronics surrounding us in our daily lives rely almost exclusively on electrons as the dominant charge carrier. In stark contrast, biological systems rarely use electrons but rather use ions and molecules of varying size. Due to the unique combination of both electronic and ionic/molecular conductivity in conducting and semiconducting organic polymers and small molecules, these materials have emerged in recent decades as excellent tools for translating signals between these two realms and, therefore, providing a means to effectively interface biology with conventional electronics-thus, the field of organic bioelectronics. Today, organic bioelectronics defines a generic platform with unprecedented biological recording and regulation tools and is maturing toward applications ranging from life sciences to the clinic. In this Review, we introduce the field, from its early breakthroughs to its current results and future challenges.

Dipole correlation effects on the local field and the effective dielectric constant in composite dielectrics containing high-k inclusions

Mixing dielectric polymers with high permittivity (high-k) inclusions can affect their electrical properties. In actuation applications of dielectric elastomers, the polarized inclusions generate additional volume polarization-related electrostriction. In energy storage applications, it is possible to store more energy in dielectric composites because of additional polarization of the inclusions and interfaces. However, mixing an electroactive polymer with high-k inclusions also brings several disadvantages. The expulsion of the field from the interior of high-k fillers and the presence of two poles on the filler surface along the applied field direction result in higher local fields EL near the inclusion poles. The resulting field enhancement lowers the breakdown field (Eb) threshold for the material and therefore compromises the actuation and energy storage capabilities of dielectric composites. To mitigate this issue, the dependence of EL on the morphology of inclusion distribution, the field localization effect in chained configurations, and the role of the dipole-dipole correlation effects in the enhancement of the dipolar field of inclusions are analyzed. We show that the dipolar correlation effects are strong in large inclusion composites and their contribution to the inclusion dipole moment μ and to the local fields EL can reach 30-50%. A new method for deriving the composite permittivity from the field EL distribution, based on a caged probe technique, is also presented.

A Review of Patterned Organic Bioelectronic Materials and their Biomedical Applications

Organic electronic materials are rapidly emerging as superior replacements for a number of conventional electronic materials, such as metals and semiconductors. Conducting polymers, carbon nanotubes, graphenes, organic light-emitting diodes, and diamond films fabricated via chemical vapor deposition are the most popular organic bioelectronic materials that are currently under active research and development. Besides the capability to translate biological signals to electrical signals or vice versa, organic bioelectronic materials entail greater biocompatibility and biodegradability compared to conventional electronic materials, which makes them more suitable for biomedical applications. When patterned, these materials bring about numerous capabilities to perform various tasks in a more-sophisticated and high-throughput manner. Here, we provide an overview of the unique properties of organic bioelectronic materials, different strategies applied to pattern these materials, and finally their applications in the field of biomedical engineering, particularly biosensing, cell and tissue engineering, actuators, and drug delivery.

Design of Hydrogels for Biomedical Applications

Hydrogels are considered key tools for the design of biomaterials, such as wound dressings, drug reservoirs, and temporary scaffolds for cells. Despite their potential, conventional hydrogels have limited applicability under wet physiological conditions because they suffer from the uncontrollable temporal change in shape: swelling takes place immediately after the installation. Swollen hydrogels easily fail under mechanical stress. The morphological change may cause not only the slippage from the installation site but also local nerve compression. The design of hydrogels that can retain their original shape and mechanical properties in an aqueous environment is, therefore, of great importance. On the one hand, the controlled degradation of used hydrogels has to be realized in some biomedical applications. This Progress Report provides a brief overview of the recent progress in the development of hydrogels for biomedical applications. Practical approaches to control the swelling properties of hydrogels are discussed. The designs of hydrogels with controlled degradation properties as well as the theoretical models to predict the degradation behavior are also introduced. Moreover, current challenges and limitation toward biomedical applications are discussed, and future directions are offered.

Versatile Method for Producing 2D and 3D Conductive Biomaterial Composites Using Sequential Chemical and Electrochemical Polymerization

Flexible and conductive biocompatible materials are attractive candidates for a wide range of biomedical applications including implantable electrodes, tissue engineering, and controlled drug delivery. Here, we demonstrate that chemical and electrochemical polymerization techniques can be combined to create highly versatile silk-conducting polymer (silk-CP) composites with enhanced conductivity and electrochemical stability. Interpenetrating silk-CP composites were first generated via in situ deposition of polypyrrole during chemical polymerization of pyrrole. These composites were sufficiently conductive to serve as working electrodes for electropolymerization, which allowed an additional layer of CP to be deposited on the surface. This sequential method was applied to both 2D films and 3D sponge-like silk scaffolds, producing conductive materials with biomimetic architectures. Overall, this two-step technique expanded the range of available polymers and dopants suitable for the synthesis of mechanically robust, biocompatible, and highly conductive silk-based materials.

A simulation study of the electrostriction effects in dielectric elastomer composites containing polarizable inclusions with different spatial distributions

Controlled actuation of electroactive polymers with embedded high dielectric nanoparticles is theoretically analyzed.

Recent advances towards the fabrication and biomedical applications of responsive polymeric assemblies and nanoparticle hybrid superstructures

We highlight recent developments, microstructural control, and biomedical applications of stimuli-responsive polymeric assemblies and responsive hybrid superstructures.

Redox cycling for passive modification of polypyrrole surface properties: effects on cell adhesion and proliferation

The surface properties of electrodeposited poly(pyrrole) (Ppy) doped with sodium dodecylbenzenesulphonate (NaDBS) are modified by two methods: addition of poly(ethylene glycol) (PEG) during the electrodeposition and through redox cycling post electrodeposition. X-ray photoelectron spectroscopy (XPS) was used to ascertain PEG incorporation and to analyze the change in the oxidation state of the polymer. Anodic cycling resulted in the formation of micrometer-sized surface cracks which increased the amount of Rhodamine-B dye adsorbed onto the surface, and played a role in decreasing the wettability of the surface. The change in surface wettability caused by these cracks was mitigated by the presence of PEG in the Ppy matrix. Compared to the incorporation of PEG, redox cycling was more effective in passively modulating the adhesion of NIH 3T3 fibroblast cells on the Ppy surface. Based on the attenuation of surface polarity of the Ppy surfaces by the incorporated PEG, a mechanism is proposed to explain the observed cell adhesion behavior.

Electrically switchable polypyrrole film for the tunable release of progesterone

Background: Intrinsically conducting polymers, such as polypyrrole (PPy), have been utilized for drug delivery purposes as drug release rates can be tuned by electrical stimulation. Electrical stimulation can be used to switch the redox state of PPy, subsequently changing the electrostatic charge and volume of the polymer. Most literature to date has focused on the delivery of charged bioactives. This study aimed to prepare a PPy film formulation where the release rate of the uncharged drug progesterone could be electrically tuned. Results & discussion: In this study PPy films loaded with progesterone are described. Drug loading levels were influenced by the concentration of drug during manufacture and polymerization time. The polymer formulation was electrically conductive and electroactive, switchable between oxidized and reduced states. Drug release was influenced by the application of electrical stimulation, the greatest release was observed on application of +0.8 V (to oxidize the polymer). Triggered release was observed in response to a period of electrical stimulation (±0.8 V at 0.5 Hz). Conclusion: This study describes the preparation of a PPy film loaded with the uncharged drug progesterone. The release rate could be tuned with electrical stimulation.

Enzyme-responsive polymeric assemblies, nanoparticles and hydrogels

Being responsive and adaptive to external stimuli is an intrinsic feature characteristic of all living organisms and soft matter. Specifically, responsive polymers can exhibit reversible or irreversible changes in chemical structures and/or physical properties in response to a specific signal input such as pH, temperature, ionic strength, light irradiation, mechanical force, electric and magnetic fields, and analyte of interest (e.g., ions, bioactive molecules, etc.) or an integration of them. The past decade has evidenced tremendous growth in the fundamental research of responsive polymers, and accordingly, diverse applications in fields ranging from drug or gene nanocarriers, imaging, diagnostics, smart actuators, adaptive coatings, to self-healing materials have been explored and suggested. Among a variety of external stimuli that have been utilized for the design of novel responsive polymers, enzymes have recently emerged to be a promising triggering motif. Enzyme-catalyzed reactions are highly selective and efficient toward specific substrates under mild conditions. They are involved in all biological and metabolic processes, serving as the prime protagonists in the chemistry of living organisms at a molecular level. The integration of enzyme-catalyzed reactions with responsive polymers can further broaden the design flexibility and scope of applications by endowing the latter with enhanced triggering specificity and selectivity. In this tutorial review, we describe recent developments concerning enzyme-responsive polymeric assemblies, nanoparticles, and hydrogels by highlighting this research area with selected literature reports. Three different types of systems, namely, enzyme-triggered self-assembly and aggregation of synthetic polymers, enzyme-driven disintegration and structural reorganization of polymeric assemblies and nanoparticles, and enzyme-triggered sol-to-gel and gel-to-sol transitions, are described. Their promising applications in drug controlled release, biocatalysis, imaging, sensing, and diagnostics are also discussed.

Multiplexed and Switchable Release of Distinct Fluids from Microneedle Platforms via Conducting Polymer Nanoactuators for Potential Drug Delivery

We report on the development of a microneedle-based multiplexed drug delivery actuator that enables the controlled delivery of multiple therapeutic agents. Two individually-addressable channels on a single microneedle array, each paired with its own reservoir and conducting polymer nanoactuator, are used to deliver various permutations of two unique chemical species. Upon application of suitable redox potentials to the selected actuator, the conducting polymer is able to undergo reversible volume changes, thereby serving to release a model chemical agent in a controlled fashion through the corresponding microneedle channels. Time-lapse videos offer direct visualization and characterization of the membrane switching capability and, along with calibration investigations, confirm the ability of the device to alternate the delivery of multiple reagents from individual microneedles of the array with higher precision and temporal resolution than conventional drug delivery actuators. Analytical modeling offers prediction of the volumetric flow rate through a single microneedle and accordingly can be used to assist in the design of subsequent microneedle arrays. The robust solid-state design and lack of mechanical components circumvent reliability issues that challenge fragile conventional microelectromechanical drug delivery devices. This proof-of-concept study demonstrates the potential of the drug delivery actuator system to aid in the rapid administration of multiple therapeutic agents and indicates the potential to counteract diverse biomedical conditions.

Advances in electronic-nose technologies developed for biomedical applications

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry.

Spatially controlled amyloid reactions using organic electronics

Abnormal protein aggregates, so called amyloid fibrils, are mainly known as pathological hallmarks of a wide range of diseases, but in addition these robust well-ordered self-assembled natural nanostructures can also be utilized for creating distinct nanomaterials for bioelectronic devices. However, current methods for producing amyloid fibrils in vitro offer no spatial control. Herein, we demonstrate a new way to produce and spatially control the assembly of amyloid-like structures using an organic electronic ion pump (OEIP) to pump distinct cations to a reservoir containing a negatively charged polypeptide. The morphology and kinetics of the created proteinaceous nanomaterials depends on the ion and current used, which we leveraged to create layers incorporating different conjugated thiophene derivatives, one fluorescent (p-FTAA) and one conducting (PEDOT-S). We anticipate that this new application for the OEIP will be useful for both biological studies of amyloid assembly and fibrillogenesis as well as for creating new bioelectronic nanomaterials and devices.

Three-dimensional conductive constructs for nerve regeneration

The unique electrochemical properties of conductive polymers can be utilized to form stand-alone polymeric tubes and arrays of tubes that are suitable for guides to promote peripheral nerve regeneration. Noncomposite, polypyrrole (PPy) tubes ranging in inner diameter from 25 microm to 1.6 mm as well as multichannel tubes were fabricated by electrodeposition. While oxidation of the pyrrole monomer causes growth of the film, brief subsequent reduction allowed mechanical dissociation from the electrode mold, creating a stand-alone, conductive PPy tube. Conductive polymer nerve guides made in this manner were placed in transected rat sciatic nerves and shown to support nerve regeneration over an 8-week time period.

Sponge-like nanostructured conducting polymers for electrically controlled drug release

An electrically controlled drug release (ECDR) system based on sponge-like nanostructured conducting polymer (CP) polypyrrole (PPy) film was developed. The nanostructured PPy film was composed of template-synthesized nanoporous PPy covered with a thin protective PPy layer. The proposed controlled release system can load drug molecules in the polymer backbones and inside the nanoholes respectively. Electrical stimulation can release drugs from both the polymer backbones and the nanoholes, which significantly improves the drug load and release efficiency. Furthermore, with one drug incorporated in the polymer backbone during electrochemical polymerization, the nanoholes inside the polymer can act as containers to store a different drug, and simultaneous electrically triggered release of different drugs can be realized with this system.

Controlled transport of droplets using conducting polymers

The controlled transport and delivery of dichloromethane through platinum mesh coated with dodecylbenzenesulfonate-doped polypyrrole is demonstrated upon in situ electrochemical redox switching. Droplets of dichloromethane were observed to pass freely through the mesh upon reduction of the polymer as a result of the release of the surfactant dopant into the dichloromethane and the change in the surface energy of the polymer. Planar and liquid-filled tube configurations are investigated. These concepts are envisaged to prove useful for fluid control in microfluidic devices, in the preparation of microparticles for drug delivery, and in the development of organic microreactors.

Organic electronics for precise delivery of neurotransmitters to modulate mammalian sensory function

Significant advances have been made in the understanding of the pathophysiology, molecular targets and therapies for the treatment of a variety of nervous-system disorders. Particular therapies involve electrical sensing and stimulation of neural activity, and significant effort has therefore been devoted to the refinement of neural electrodes. However, direct electrical interfacing suffers from some inherent problems, such as the inability to discriminate amongst cell types. Thus, there is a need for novel devices to specifically interface nerve cells. Here, we demonstrate an organic electronic device capable of precisely delivering neurotransmitters in vitro and in vivo. In converting electronic addressing into delivery of neurotransmitters, the device mimics the nerve synapse. Using the peripheral auditory system, we show that out of a diverse population of cells, the device can selectively stimulate nerve cells responding to a specific neurotransmitter. This is achieved by precise electronic control of electrophoretic migration through a polymer film. This mechanism provides several sought-after features for regulation of cell signalling: exact dosage determination through electrochemical relationships, minimally disruptive delivery due to lack of fluid flow, and on-off switching. This technology has great potential as a therapeutic platform and could help accelerate the development of therapeutic strategies for nervous-system disorders.

Polypyrrole actuator with a bioadhesive surface for accumulating bacteria from physiological media

A gold/polypyrrole (Au/PPy) bilayer actuator was fabricated by electrochemical deposition, and its surface was modified with a bioadhesive polymer, polydopamine. The actuator exhibited high performances of actuation in physiological media. Furthermore, the surface of the actuator is sticky in water and thus can seize bacteria from their aqueous solutions. Actuation greatly increased the efficiency of adhering bacteria on the actuator surface, and this technique provides a cheap and convenient approach for accumulating bacteria from physiological media.

On-chip chemical stimulation of neurons by local and controlled release of neurotransmitter

This paper describes the fabrication and in vitro testing of a device capable of chemically stimulating individual neurons. Electrophoretic actuation is used to locally induce the release of the neurotransmitter L-glutamate in a network of hippocampal neurons cultured on top of the device. Cell activation by the neurotransmitter is visualized using calcium imaging. Single-cell stimulation is demonstrated close to the release site after application of a voltage of 500 mV. Such a device could provide a useful tool in both basic and clinical neuroscience. In a broader context, this device can be used to locally release small amounts of chemical compounds in Lab-on-Chip and drug delivery applications.

Stimuli-responsive polymer gels

Stimuli-responsive polymer gels have received considerable attention due to their singular mechanical properties, which make them materials of choice for niche applications. Polymer gels comprising either physical or chemical cross-links can undergo controlled and reversible shape changes in response to an applied field. The stimulus or external field applied may include thermal, electrical, magnetic, pH, UV/visible light, ionic or metallic interactions or combinations thereof. The shape change can manifest itself in two-dimensional actuation, bending motion, or three-dimensional actuation, volume change. This reversible contraction and expansion of polymer gels as well as their mechanical properties are similar to that of biological muscles. This review will describe and critique some of the recent advances in the field of stimuli-responsive polymer gels including the design of new classes of polymeric gels, controlled actuation in response to external stimuli, and ability to tailor material properties for different applications.

Electronic control of Ca2+ signalling in neuronal cells using an organic electronic ion pump

Cells and tissues use finely regulated ion fluxes for their intra- and intercellular communication. Technologies providing spatial and temporal control for studies of such fluxes are however, limited. We have developed an electrophoretic ion pump made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) to mediate electronic control of the ion homeostasis in neurons. Ion delivery from a source reservoir to a receiving electrolyte via a PEDOT:PSS thin-film channel was achieved by electronic addressing. Ions are delivered in high quantities at an associated on/off ratio exceeding 300. This induces physiological signalling events that can be recorded at the single-cell level. Furthermore, miniaturization of the device to a 50-microm-wide channel allows for stimulation of individual cells. As this technology platform allows for electronic control of ion signalling in individual cells with proper spatial and temporal resolution, it will be useful in further studies of communication in biological systems.