Interfacing electrogenic cells with 3D nanoelectrodes: position, shape, and size matter

Real-Time and High-Resolution Monitoring of Neuronal Electrical Activity and pH Variations Based on the Co-Integration of Nanoelectrodes and Chem-FinFETs

Developing new approaches amenable to the measurement of neuronal physiology in real-time is a very active field of investigation, as it will offer improved methods to assess the impact of diverse insults on neuronal homeostasis. Here, the development of an in vitro bio platform is reported which can record the electrical activity of cultured primary rat cortical neurons with extreme sensitivity, while simultaneously tracking the localized changes in the pH of the culture medium. This bio platform features passive vertical nanoprobes with ultra-high signal resolution (several mV amplitude ranges) and Chem-FinFETs (pH sensitivity of sub-0.1 pH units), covering an area as little as a neuronal soma. These multi-sensing units are arranged in an array to probe both chemically and electrically an equivalent surface of ≈ 0.5 mm2. A homemade setup is also developed which allows recording of multiplexed data in real-time (10 ps range) from the active chem-sensors and passive electrodes and which is used to operate the platform. Finally, a proof-of-concept is presented for a neuro-relevant application, by investigating the effect on neuronal activity of Amyloid beta oligomers, the main toxic peptide in Alzheimer's Disease, which reveals that exposure to amyloid beta oligomers modify the amplitude, but not the frequency, of neuronal firing, without any detectable changes in pH values along this process.

Micronano Synergetic Three-Dimensional Bioelectronics: A Revolutionary Breakthrough Platform for Cardiac Electrophysiology

Cardiovascular diseases (CVDs) are the leading cause of mortality and therefore pose a significant threat to human health. Cardiac electrophysiology plays a crucial role in the investigation and treatment of CVDs, including arrhythmia. The long-term and accurate detection of electrophysiological activity in cardiomyocytes is essential for advancing cardiology and pharmacology. Regarding the electrophysiological study of cardiac cells, many micronano bioelectric devices and systems have been developed. Such bioelectronic devices possess unique geometric structures of electrodes that enhance quality of electrophysiological signal recording. Though planar multielectrode/multitransistors are widely used for simultaneous multichannel measurement of cell electrophysiological signals, their use for extracellular electrophysiological recording exhibits low signal strength and quality. However, the integration of three-dimensional (3D) multielectrode/multitransistor arrays that use advanced penetration strategies can achieve high-quality intracellular signal recording. This review provides an overview of the manufacturing, geometric structure, and penetration paradigms of 3D micronano devices, as well as their applications for precise drug screening and biomimetic disease modeling. Furthermore, this review also summarizes the current challenges and outlines future directions for the preparation and application of micronano bioelectronic devices, with an aim to promote the development of intracellular electrophysiological platforms and thereby meet the demands of emerging clinical applications.

Silicon microfabrication technologies for biology integrated advance devices and interfaces

Miniaturization is the trend to manufacture ever smaller devices and this process requires knowledge, experience, understanding of materials, manufacturing techniques and scaling laws. The fabrication techniques used in semiconductor industry deliver an exceptionally high yield of devices and provide a well-established platform. Today, these miniaturized devices are manufactured with high reproducibility, design flexibility, scalability and multiplexed features to be used in several applications including micro-, nano-fluidics, implantable chips, diagnostics/biosensors and neural probes. We here provide a review on the microfabricated devices used for biology driven science. We will describe the ubiquity of the use of micro-nanofabrication techniques in biology and biotechnology through the fabrication of high-aspect-ratio devices for cell sensing applications, intracellular devices, probes developed for neuroscience-neurotechnology and biosensing of the certain biomarkers. Recently, the research on micro and nanodevices for biology has been progressing rapidly. While the understanding of the unknown biological fields -such as human brain- has been requiring more research with advanced materials and devices, the development protocols of desired devices has been advancing in parallel, which finally meets with some of the requirements of biological sciences. This is a very exciting field and we aim to highlight the impact of micro-nanotechnologies that can shed light on complex biological questions and needs.

Combining PEDOT:PSS Polymer Coating with Metallic 3D Nanowires Electrodes to Achieve High Electrochemical Performances for Neuronal Interfacing Applications

This study presents a novel approach to improve the performance of microelectrode arrays (MEAs) used for electrophysiological studies of neuronal networks. The integration of 3D nanowires (NWs) with MEAs increases the surface-to-volume ratio, which enables subcellular interactions and high-resolution neuronal signal recording. However, these devices suffer from high initial interface impedance and limited charge transfer capacity due to their small effective area. To overcome these limitations, the integration of conductive polymer coatings, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is investigated as a mean of improving the charge transfer capacity and biocompatibility of MEAs. The study combines platinum silicide-based metallic 3D nanowires electrodes with electrodeposited PEDOT:PSS coatings to deposit ultra-thin (<50 nm) layers of conductive polymer onto metallic electrodes with very high selectivity. The polymer-coated electrodes were fully characterized electrochemically and morphologically to establish a direct relationship between synthesis conditions, morphology, and conductive features. Results show that PEDOT-coated electrodes exhibit thickness-dependent improved stimulation and recording performances, offering new perspectives for neuronal interfacing with optimal cell engulfment to enable the study of neuronal activity with acute spatial and signal resolution at the sub-cellular level.

Optimizing the fabrication of a 3D high-resolution implant for neural stimulation

BACKGROUND

Tissue-integrated micro-electronic devices for neural stimulation hold great potential in restoring the functionality of degenerated organs, specifically, retinal prostheses, which are aimed at vision restoration. The fabrication process of 3D polymer-metal devices with high resolution and a high aspect-ratio (AR) is very complex and faces many challenges that impair its functionality.

APPROACH

Here we describe the optimization of the fabrication process of a bio-functionalized 3D high-resolution 1mm circular subretinal implant composed of SU-8 polymer integrated with dense gold microelectrodes (23μm pitch) passivated with 3D micro-well-like structures (20μm diameter, 3μm resolution). The main challenges were overcome by step-by-step planning and optimization while utilizing a two-step bi-layer lift-off process; bio-functionalization was carried out by N2 plasma treatment and the addition of a bio-adhesion molecule.

MAIN RESULTS

In-vitro and in-vivo investigations, including SEM and FIB cross section examinations, revealed a good structural design, as well as a good long-term integration of the device in the rat sub-retinal space and cell migration into the wells. Moreover, the feasibility of subretinal neural stimulation using the fabricated device was demonstrated in-vitro by electrical activation of rat's retina.

CONCLUSIONS

The reported process and optimization steps described here in detail can aid in designing and fabricating retinal prosthetic devices or similar neural implants.

Aerosol Jet-Printed High-Aspect Ratio Micro-Needle Electrode Arrays Applied for Human Cerebral Organoids and 3D Neurospheroid Networks

The human brain is a complex and poorly accessible organ. Thus, new tools are required for studying the neural function in a controllable environment that preserves multicellular interaction and neuronal wiring. In particular, high-throughput methods that alleviate the need for animal experiments are essential for future studies. Recent developments of induced pluripotent stem cell technologies have enabled in vitro modeling of the human brain by creating three-dimensional brain tissue mimic structures. To leverage these new technologies, a systematic and versatile approach for evaluating neuronal activity at larger tissue depths within the regime of tens to hundreds of micrometers is required. Here, we present an aerosol-jet- and inkjet-printing-based method to fabricate microelectrode arrays, equipped with high-aspect ratio μ-needle electrodes that penetrate 3D neural network assemblies. The arrays have been successfully applied for electrophysiological recordings on interconnected neurospheroids formed on an engineered substrate and on cerebral organoids, both derived from human induced pluripotent stem cells.

3D Printed Hollow Microneedles for Treating Skin Wrinkles Using Different Anti-Wrinkle Agents: A Possible Futuristic Approach

Skin wrinkles are an inevitable phenomenon that is brought about by aging due to the degradation of scleroprotein fibers and significant collagen reduction, which is the fundamental basis of anti-wrinkle technology in use today. Conventional treatments such as lasering and Botulinum toxin have some drawbacks including allergic skin reactions, cumbersome treatment procedures, and inefficient penetration of the anti-wrinkle products into the skin due to the high resistance of stratum corneum. Bearing this in mind, the cosmetic industry has exploited the patient-compliant technology of microneedles (MNs) to treat skin wrinkles, developing several products based on solid and dissolvable MNs incorporated with antiwrinkle formulations. However, drug administration via these MNs is limited by the high molecular weight of the drugs. Hollow MNs (HMNs) can deliver a wider array of active agents, but that is a relatively unexplored area in the context of antiwrinkle technology. To address this gap, we discuss the possibility of bioinspired 3D printed HMNs in treating skin wrinkles in this paper. We compare the previous and current anti-wrinkling treatment options, as well as the techniques and challenges involved with its manufacture and commercialization.

High-Aspect-Ratio Nanoelectrodes Enable Long-Term Recordings of Neuronal Signals with Subthreshold Resolution

The further development of neurochips requires high-density and high-resolution recordings that also allow neuronal signals to be observed over a long period of time. Expanding fields of network neuroscience and neuromorphic engineering demand the multiparallel and direct estimations of synaptic weights, and the key objective is to construct a device that also records subthreshold events. Recently, 3D nanostructures with a high aspect ratio have become a particularly suitable interface between neurons and electronic devices, since the excellent mechanical coupling to the neuronal cell membrane allows very high signal-to-noise ratio recordings. In the light of an increasing demand for a stable, noninvasive and long-term recording at subthreshold resolution, a combination of vertical nanostraws with nanocavities is presented. These structures provide a spontaneous tight coupling with rat cortical neurons, resulting in high amplitude sensitivity and postsynaptic resolution capability, as directly confirmed by combined patch-clamp and microelectrode array measurements.

Expansion Microscopy for Imaging the Cell-Material Interface

Surface topography on the scale of tens of nanometers to several micrometers substantially affects cell adhesion, migration, and differentiation. Recent studies using electron microscopy and super-resolution microscopy provide insight into how cells interact with surface nanotopography; however, the complex sample preparation and expensive imaging equipment required for these methods makes them not easily accessible. Expansion microscopy (ExM) is an affordable approach to image beyond the diffraction limit, but ExM cannot be readily applied to image the cell-material interface as most materials do not expand. Here, we develop a protocol that allows the use of ExM to resolve the cell-material interface with high resolution. We apply the technique to image the interface between U2OS cells and nanostructured substrates as well as the interface between primary osteoblasts with titanium dental implants. The high spatial resolution enabled by ExM reveals that although AP2 and F-actin both accumulate at curved membranes induced by vertical nanostructures, they are spatially segregated. Using ExM, we also reliably image how osteoblasts interact with roughened titanium implant surfaces below the diffraction limit; this is of great interest to understand osseointegration of the implants but has up to now been a significant technical challenge due to the irregular shape, the large volume, and the opacity of the titanium implants that have rendered them incompatible with other super-resolution techniques. We believe that our protocol will enable the use of ExM as a powerful tool for cell-material interface studies.

Advances in Cell-Conductive Polymer Biointerfaces and Role of the Plasma Membrane

The plasma membrane (PM) is often described as a wall, a physical barrier separating the cell cytoplasm from the extracellular matrix (ECM). Yet, this wall is a highly dynamic structure that can stretch, bend, and bud, allowing cells to respond and adapt to their surrounding environment. Inspired by shapes and geometries found in the biological world and exploiting the intrinsic properties of conductive polymers (CPs), several biomimetic strategies based on substrate dimensionality have been tailored in order to optimize the cell-chip coupling. Furthermore, device biofunctionalization through the use of ECM proteins or lipid bilayers have proven successful approaches to further maximize interfacial interactions. As the bio-electronic field aims at narrowing the gap between the electronic and the biological world, the possibility of effectively disguising conductive materials to "trick" cells to recognize artificial devices as part of their biological environment is a promising approach on the road to the seamless platform integration with cells.

Assessing the Feasibility of Developing in vivo Neuroprobes for Parallel Intracellular Recording and Stimulation: A Perspective

Developing novel neuroprobes that enable parallel multisite, long-term intracellular recording and stimulation of neurons in freely behaving animals is a neuroscientist's dream. When fulfilled, it is expected to significantly enhance brain research at fundamental mechanistic levels including that of subthreshold signaling and computations. Here we assess the feasibility of merging the advantages of in vitro vertical nanopillar technologies that support intracellular recordings with contemporary concepts of in vivo extracellular field potential recordings to generate the dream neuroprobes that read the entire electrophysiological signaling repertoire.

Ultrastructural Analysis of Neuroimplant-Parenchyma Interfaces Uncover Remarkable Neuroregeneration Along-With Barriers That Limit the Implant Electrophysiological Functions

Despite increasing use of in vivo multielectrode array (MEA) implants for basic research and medical applications, the critical structural interfaces formed between the implants and the brain parenchyma, remain elusive. Prevailing view assumes that formation of multicellular inflammatory encapsulating-scar around the implants [the foreign body response (FBR)] degrades the implant electrophysiological functions. Using gold mushroom shaped microelectrodes (gMμEs) based perforated polyimide MEA platforms (PPMPs) that in contrast to standard probes can be thin sectioned along with the interfacing parenchyma; we examined here for the first time the interfaces formed between brains parenchyma and implanted 3D vertical microelectrode platforms at the ultrastructural level. Our study demonstrates remarkable regenerative processes including neuritogenesis, axon myelination, synapse formation and capillaries regrowth in contact and around the implant. In parallel, we document that individual microglia adhere tightly and engulf the gMμEs. Modeling of the formed microglia-electrode junctions suggest that this configuration suffice to account for the low and deteriorating recording qualities of in vivo MEA implants. These observations help define the anticipated hurdles to adapting the advantageous 3D in vitro vertical-electrode technologies to in vivo settings, and suggest that improving the recording qualities and durability of planar or 3D in vivo electrode implants will require developing approaches to eliminate the insulating microglia junctions.

Electrolyte-gated transistors for enhanced performance bioelectronics

Electrolyte-gated transistors (EGTs), capable of transducing biological and biochemical inputs into amplified electronic signals and stably operating in aqueous environments, have emerged as fundamental building blocks in bioelectronics. In this Primer, the different EGT architectures are described with the fundamental mechanisms underpinning their functional operation, providing insight into key experiments including necessary data analysis and validation. Several organic and inorganic materials used in the EGT structures and the different fabrication approaches for an optimal experimental design are presented and compared. The functional bio-layers and/or biosystems integrated into or interfaced to EGTs, including self-organization and self-assembly strategies, are reviewed. Relevant and promising applications are discussed, including two-dimensional and three-dimensional cell monitoring, ultra-sensitive biosensors, electrophysiology, synaptic and neuromorphic bio-interfaces, prosthetics and robotics. Advantages, limitations and possible optimizations are also surveyed. Finally, current issues and future directions for further developments and applications are discussed.

Graphene Electric Field Sensor Enables Single Shot Label-Free Imaging of Bioelectric Potentials

The measurement of electrical activity across systems of excitable cells underlies current progress in neuroscience, cardiac pharmacology, and neurotechnology. However, bioelectricity spans orders of magnitude in intensity, space, and time, posing substantial technological challenges. The development of methods permitting network-scale recordings with high spatial resolution remains key to studies of electrogenic cells, emergent networks, and bioelectric computation. Here, we demonstrate single-shot and label-free imaging of extracellular potentials with high resolution across a wide field-of-view. The critically coupled waveguide-amplified graphene electric field (CAGE) sensor leverages the field-sensitive optical transitions in graphene to convert electric potentials into the optical regime. As a proof-of-concept, we use the CAGE sensor to detect native electrical activity from cardiac action potentials with tens-of-microns resolution, simultaneously map the propagation of these potentials at tissue-scale, and monitor their modification by pharmacological agents. This platform is robust, scalable, and compatible with existing microscopy techniques for multimodal correlative imaging.

Nanowire-Enabled Bioelectronics

Bioelectronics explores the use of electronic devices for applications in signal transduction at their interfaces with biological systems. The miniaturization of the bioelectronic systems has enabled seamless integration at these interfaces and is providing new scientific and technological opportunities. In particular, nanowire-based devices can yield smaller sized and unique geometry detectors that are difficult to access with standard techniques, and thereby can provide advantages in sensitivity with reduced invasiveness. In this review, we focus on nanowire-enabled bioelectronics. First, we provide an overview of synthetic studies for designed growth of semiconductor nanowires of which structure and composition are controlled to enable key elements for bioelectronic devices. Second, we review nanowire field-effect transistor sensors for highly sensitive detection of biomolecules, their applications in diagnosis and drug discovery, and methods for sensitivity enhancement. We then turn to recent progress in nanowire-enabled studies of electrogenic cells, including cardiomyocytes and neurons. Representative advances in electrical recording using nanowire electronic devices for single cell measurements, cell network mapping, and three-dimensional recordings of synthetic and natural tissues, and in vivo brain mapping are highlighted. Finally, we overview the key challenges and opportunities of nanowires for fundamental research and translational applications.

Nanostraw-Assisted Cellular Injection of Fluorescent Nanodiamonds via Direct Membrane Opening

Due to their stable fluorescence, biocompatibility, and amenability to functionalization, fluorescent nanodiamonds (FND) are promising materials for long term cell labeling and tracking. However, transporting them to the cytosol remains a major challenge, due to low internalization efficiencies and endosomal entrapment. Here, nanostraws in combination with low voltage electroporation pulses are used to achieve direct delivery of FND to the cytosol. The nanostraw delivery leads to efficient and rapid FND transport into cells compared to when incubating cells in a FND-containing medium. Moreover, whereas all internalized FND delivered by incubation end up in lysosomes, a significantly larger proportion of nanostraw-injected FND are in the cytosol, which opens up for using FND as cellular probes. Furthermore, in order to answer the long-standing question in the field of nano-biology regarding the state of the cell membrane on hollow nanostructures, live cell stimulated emission depletion (STED) microscopy is performed to image directly the state of the membrane on nanostraws. The time-lapse STED images reveal that the cell membrane opens entirely on top of nanostraws upon application of gentle electrical pulses, which supports the hypothesis that many FND are delivered directly to the cytosol, avoiding endocytosis and lysosomal entrapment.

New perspectives on the roles of nanoscale surface topography in modulating intracellular signaling

The physical properties of biomaterials, such as elasticity, stiffness, and surface nanotopography, are mechanical cues that regulate a broad spectrum of cell behaviors, including migration, differentiation, proliferation, and reprogramming. Among them, nanoscale surface topography, i.e. nanotopography, defines the nanoscale shape and spatial arrangement of surface elements, which directly interact with the cell membranes and stimulate changes in the cell signaling pathways. In biological systems, the effects of nanotopography are often entangled with those of other mechanical and biochemical factors. Precise engineering of 2D nanopatterns and 3D nanostructures with well-defined features has provided a powerful means to study the cellular responses to specific topographic features. In this Review, we discuss efforts in the last three years to understand how nanotopography affects membrane receptor activation, curvature-induced cell signaling, and stem cell differentiation.

Electrophysiology Read-Out Tools for Brain-on-Chip Biotechnology

Brain-on-Chip (BoC) biotechnology is emerging as a promising tool for biomedical and pharmaceutical research applied to the neurosciences. At the convergence between lab-on-chip and cell biology, BoC couples in vitro three-dimensional brain-like systems to an engineered microfluidics platform designed to provide an in vivo-like extrinsic microenvironment with the aim of replicating tissue- or organ-level physiological functions. BoC therefore offers the advantage of an in vitro reproduction of brain structures that is more faithful to the native correlate than what is obtained with conventional cell culture techniques. As brain function ultimately results in the generation of electrical signals, electrophysiology techniques are paramount for studying brain activity in health and disease. However, as BoC is still in its infancy, the availability of combined BoC-electrophysiology platforms is still limited. Here, we summarize the available biological substrates for BoC, starting with a historical perspective. We then describe the available tools enabling BoC electrophysiology studies, detailing their fabrication process and technical features, along with their advantages and limitations. We discuss the current and future applications of BoC electrophysiology, also expanding to complementary approaches. We conclude with an evaluation of the potential translational applications and prospective technology developments.

Recent advances in three-dimensional microelectrode array technologies for in vitro and in vivo cardiac and neuronal interfaces

Three-dimensional microelectrode arrays (3D MEAs) have emerged as promising tools to detect electrical activities of tissues or organs in vitro and in vivo, but challenges in achieving fast, accurate, and versatile monitoring have consistently hampered further advances in analyzing cell or tissue behaviors. In this review, we discuss emerging 3D MEA technologies for in vitro recording of cardiac and neural cellular electrophysiology, as well as in vivo applications for heart and brain health diagnosis and therapeutics. We first review various forms of recent 3D MEAs for in vitro studies in context of their geometry, materials, and fabrication processes as well as recent demonstrations of 3D MEAs to monitor electromechanical behaviors of cardiomyocytes and neurons. We then present recent advances in 3D MEAs for in vivo applications to the heart and the brain for monitoring of health conditions and stimulation for therapy. A brief overview of the current challenges and future directions of 3D MEAs are provided to conclude the review.

TFT sensor array for real-time cellular characterization, stimulation, impedance measurement and optical imaging of in-vitro neural cells

Real-time in-vitro multi-modality characterization of neuronal cell ensemble involves highly complex interdependent phenomena and processes. Although a variety of microelectrode arrays (MEAs) have been reported, diagnosis techniques are limited in term of sensing area, optical transparency, resolution and number of modalities. This paper presents an optically transparent thin-film-transistor (TFT) array biosensor chip for neuronal ensemble investigation, in which TFT electrodes are used for six modalities including extracellular voltage recording of both action potential (AP) and local field potential (LFP), current or voltage stimulation, chemical stimulation, electrical impedance measurement, and optical imaging. The sensor incorporates a large sensing area (15.6 mm × 15.6 mm) with a 200 × 150 array of indium-tin-oxide (ITO) electrodes placed at a 50 μm or 100 μm pixel pitch and with 10 ms temporal resolution; these performances are comparable to the state-of-the-art MEA devices. The TFT electrode array is designed based on the switch matrix architecture. The reliability and stability of TFTs are examined by measuring their electrical characteristics. Impedance spectroscopy function is verified by mapping the neuron position and the status (cells alive or dead, contamination) on the electrodes, which facilitates the biochemical studies in electrical domain that adds quantitative views to visual observation of cells through the optical microscopy. An in-vitro neuron culture is studied using electrophysiological, electrochemical, and optical characterization. Detailed signal analysis is demonstrated to prove the capability of bioassay.

Nanovolcano microelectrode arrays: toward long-term on-demand registration of transmembrane action potentials by controlled electroporation

Volcano-shaped microelectrodes (nanovolcanoes) functionalized with nanopatterned self-assembled monolayers have recently been demonstrated to report cardiomyocyte action potentials after gaining spontaneous intracellular access. These nanovolcanoes exhibit recording characteristics similar to those of state-of-the-art micro-nanoelectrode arrays that use electroporation as an insertion mechanism. In this study, we investigated whether the use of electroporation improves the performance of nanovolcano arrays in terms of action potential amplitudes, recording durations, and yield. Experiments with neonatal rat cardiomyocyte monolayers grown on nanovolcano arrays demonstrated that electroporation pulses with characteristics derived from analytical models increased the efficiency of nanovolcano recordings, as they enabled multiple on-demand registration of intracellular action potentials with amplitudes as high as 62 mV and parallel recordings in up to ~76% of the available channels. The performance of nanovolcanoes showed no dependence on the presence of functionalized nanopatterns, indicating that the tip geometry itself is instrumental for establishing a tight seal at the cell-electrode interface, which ultimately determines the quality of recordings. Importantly, the use of electroporation permitted the recording of attenuated cardiomyocyte action potentials during consecutive days at identical sites, indicating that nanovolcano recordings are nondestructive and permit long-term on-demand recordings from excitable cardiac tissues. Apart from demonstrating that less complex manufacturing processes can be used for next-generation nanovolcano arrays, the finding that the devices are suitable for performing on-demand recordings of electrical activity from multiple sites of excitable cardiac tissues over extended periods of time opens the possibility of using the devices not only in basic research but also in the context of comprehensive drug testing.

On the Interaction between 1D Materials and Living Cells

One-dimensional (1D) materials allow for cutting-edge applications in biology, such as single-cell bioelectronics investigations, stimulation of the cellular membrane or the cytosol, cellular capture, tissue regeneration, antibacterial action, traction force investigation, and cellular lysis among others. The extraordinary development of this research field in the last ten years has been promoted by the possibility to engineer new classes of biointerfaces that integrate 1D materials as tools to trigger reconfigurable stimuli/probes at the sub-cellular resolution, mimicking the in vivo protein fibres organization of the extracellular matrix. After a brief overview of the theoretical models relevant for a quantitative description of the 1D material/cell interface, this work offers an unprecedented review of 1D nano- and microscale materials (inorganic, organic, biomolecular) explored so far in this vibrant research field, highlighting their emerging biological applications. The correlation between each 1D material chemistry and the resulting biological response is investigated, allowing to emphasize the advantages and the issues that each class presents. Finally, current challenges and future perspectives are discussed.

High-Aspect-Ratio Nanostructured Surfaces as Biological Metamaterials

Materials patterned with high-aspect-ratio nanostructures have features on similar length scales to cellular components. These surfaces are an extreme topography on the cellular level and have become useful tools for perturbing and sensing the cellular environment. Motivation comes from the ability of high-aspect-ratio nanostructures to deliver cargoes into cells and tissues, access the intracellular environment, and control cell behavior. These structures directly perturb cells' ability to sense and respond to external forces, influencing cell fate, and enabling new mechanistic studies. Through careful design of their nanoscale structure, these systems act as biological metamaterials, eliciting unusual biological responses. While predominantly used to interface eukaryotic cells, there is growing interest in nonanimal and prokaryotic cell interfacing. Both experimental and theoretical studies have attempted to develop a mechanistic understanding for the observed behaviors, predominantly focusing on the cell-nanostructure interface. This review considers how high-aspect-ratio nanostructured surfaces are used to both stimulate and sense biological systems.

Opportunities and dilemmas of in vitro nano neural electrodes

Developing electrophysiological platforms to capture electrical activities of neurons and exert modulatory stimuli lays the foundation for many neuroscience-related disciplines, including the neuron–machine interface, neuroprosthesis, and mapping of brain circuitry.

MEA Recordings and Cell-Substrate Investigations with Plasmonic and Transparent, Tunable Holey Gold

Microelectrode arrays are widely used in different fields such as neurobiology or biomedicine to read out electrical signals from cells or biomolecules. One way to improve microelectrode applications is the development of novel electrode materials with enhanced or additional functionality. In this study, we fabricated macroelectrodes and microelectrode arrays containing gold penetrated by nanohole arrays as a conductive layer. We used this holey gold to optically excite surface plasmon polaritons, which lead to a strong increase in transparency, an effect that is further enhanced by the plasmon's interaction with cell culture medium. By varying the nanohole diameter in finite-difference time domain simulations, we demonstrate that the transmission can be increased to above 70% with its peak at a wavelength depending on the holey gold's lattice constant. Further, we demonstrate that the novel transparent microelectrode arrays are as suitable for recording cellular electrical activity as standard devices. Moreover, we prove using spectral measurements and finite-difference time domain simulations that plasmonically induced transmission peaks of holey gold red-shift upon sensing medium or cells in close vicinity (<30 nm) to the substrate. Thus, we establish plasmonic and transparent holey gold as a tunable material suitable for cellular electrical recordings and biosensing applications.

Sensor-free and Sensor-based Heart-on-a-chip Platform: A Review of Design and Applications

Drug efficacy and toxicity are key factors of drug development. Conventional 2D cell models or animal models have their limitations for the efficacy or toxicity assessment in preclinical assays, which induce the failure of candidate drugs or withdrawal of approved drugs. Human organs-on-chips (OOCs) emerged to present human-specific properties based on their 3D bioinspired structures and functions in the recent decade. In this review, the basic definition and superiority of OOCs will be introduced. Moreover, a specific OOC, heart-on-achip (HOC) will be focused. We introduce HOC modeling in the sensor-free and sensor-based way and illustrate the advantages of sensor-based HOC in detail by taking examples of recent studies. We provide a new perspective on the integration of HOC technology and biosensing to develop a new sensor-based HOC platform.

Membrane Poration Mechanisms at the Cell-Nanostructure Interface

3D vertical nanostructures have become one of the most significant methods for interfacing cells and the nanoscale and for accessing significant intracellular functionalities such as membrane potential. As this intracellular access can be induced by means of diverse cellular membrane poration mechanisms, it is important to investigate in detail the cell condition after membrane rupture for assessing the real effects of the poration techniques on the biological environment. Indeed, differences of the membrane dynamics and reshaping have not been observed yet when the membrane-nanostructure system is locally perturbed by, for instance, diverse membrane breakage events. In this work, new insights are provided into the membrane dynamics in case of two different poration approaches, optoacoustic- and electro-poration, both mediated by the same 3D nanostructures. The experimental results offer a detailed overview on the different poration processes in terms of electrical recordings and membrane conformation.

A nanostructure platform for live-cell manipulation of membrane curvature

Membrane curvatures are involved in essential cellular processes, such as endocytosis and exocytosis, in which they are believed to act as microdomains for protein interactions and intracellular signaling. These membrane curvatures appear and disappear dynamically, and their locations are difficult or impossible to predict. In addition, the size of these curvatures is usually below the diffraction limit of visible light, making it impossible to resolve their values using live-cell imaging. Therefore, precise manipulation of membrane curvature is important to understanding how membrane curvature is involved in intracellular processes. Recent studies show that membrane curvatures can be induced by surface topography when cells are in direct contact with engineered substrates. Here, we present detailed procedures for using nanoscale structures to manipulate membrane curvatures and probe curvature-induced phenomena in live cells. We first describe detailed procedures for the design of nanoscale structures and their fabrication using electron-beam (E-beam) lithography. The fabrication process takes 2 d, but the resultant chips can be cleaned and reused repeatedly over the course of 2 years. Then we describe how to use these nanostructures to manipulate local membrane curvatures and probe intracellular protein responses, discussing surface coating, cell plating, and fluorescence imaging in detail. Finally, we describe a procedure to characterize the nanostructure-cell membrane interface using focused ion beam and scanning electron microscopy (FIB-SEM). Nanotopography-based methods can induce stable membrane curvatures with well-defined curvature values and locations in live cells, which enables the generation of a library of curvatures for probing curvature-related intracellular processes.

Adhesion Stabilized en Masse Intracellular Electrical Recordings from Multicellular Assemblies

Coordinated collective electrochemical signals in multicellular assemblies, such as ion fluxes, membrane potentials, electrical gradients, and steady electric fields, play an important role in cell and tissue spatial organization during many physiological processes like wound healing, inflammatory responses, and hormone release. This mass of electric actions cumulates in an en masse activity within cell collectives which cannot be deduced from considerations at the individual cell level. However, continuously sampling en masse collective electrochemical actions of the global electrochemical activity of large-scale electrically coupled cellular assemblies with intracellular resolution over long time periods has been impeded by a lack of appropriate recording techniques. Here we present a bioelectrical interface consisting of low impedance vertical gold nanoelectrode interfaces able to penetrate the cellular membrane in the course of cellular adhesion, thereby allowing en masse recordings of intracellular electrochemical potentials that transverse electrically coupled NRK fibroblast, C2C12 myotube assemblies, and SH-SY5Y neuronal networks of more than 200,000 cells. We found that the intracellular electrical access of the nanoelectrodes correlates with substrate adhesion dynamics and that penetration, stabilization, and sealing of the electrode-cell interface involves recruitment of surrounding focal adhesion complexes and the anchoring of actin bundles, which form a caulking at the electrode base. Intracellular recordings were stable for several days, and monitoring of both basal activity as well as pharmacologically altered electric signals with high signal-to-noise ratios and excellent electrode coupling was performed.

Optoelectronic control of single cells using organic photocapacitors

Optical control of the electrophysiology of single cells can be a powerful tool for biomedical research and technology. Here, we report organic electrolytic photocapacitors (OEPCs), devices that function as extracellular capacitive electrodes for stimulating cells. OEPCs consist of transparent conductor layers covered with a donor-acceptor bilayer of organic photoconductors. This device produces an open-circuit voltage in a physiological solution of 330 mV upon illumination using light in a tissue transparency window of 630 to 660 nm. We have performed electrophysiological recordings on Xenopus laevis oocytes, finding rapid (time constants, 50 μs to 5 ms) photoinduced transient changes in the range of 20 to 110 mV. We measure photoinduced opening of potassium channels, conclusively proving that the OEPC effectively depolarizes the cell membrane. Our results demonstrate that the OEPC can be a versatile nongenetic technique for optical manipulation of electrophysiology and currently represents one of the simplest and most stable and efficient optical stimulation solutions.

Cost-effective and multifunctional acquisition system for in vitro electrophysiological investigations with multi-electrode arrays

In vitro multi-electrode array (MEA) technology is nowadays involved in a wide range of applications beyond neuroscience, such as cardiac electrophysiology and bio-interface studies. However, the cost of commercially available acquisition systems severely limits its adoption outside specialized laboratories with high budget capabilities. Thus, the availability of low-cost methods to acquire signals from MEAs is important to allow research labs worldwide to exploit this technology for an ever-expanding pool of experiments independently from their economic possibilities. Here, we provide a comprehensive toolset to assemble a multifunctional in vitro MEA acquisition system with a total cost 80% lower than standard commercial solutions. We demonstrate the capabilities of this acquisition system by employing it to i) characterize commercial MEA devices by means of electrical impedance measurements ii) record activity from cultures of HL-1 cells extracellularly, and iii) electroporate HL-1 cells through nanostructured MEAs and record intracellular signals.

Nanowire based bioprobes for electrical monitoring of electrogenic cells

The continuous miniaturization of electronic components and the emergence of nano-biotechnology has opened new perspectives to monitor electrical activities at the single cell level. Here, we describe the creation of very high surface-to-volume ratio passive devices (vertical nanowire probes) using large-scale fabrication process, allowing to follow the electrical activity of mammalian neurons. Based on conventional silicon processing, the silicon nanowires were silicided in platinum in order to improve their electrochemical performances and to guarantee their biocompatibility. Very high signal to noise ratio was achieved (up to 2000) when measuring spontaneous action potentials. Moreover, this bio-platform was used to record the impact of various bio-chemical and electrical stimulations on neuronal activity. To conclude, this study proposes a thorough comparison of the characteristics and performances of these new nanowire-based nanoprobes with the main alternative systems published up to now.

Emerging neurotechnology for antinoceptive mechanisms and therapeutics discovery

The tolerance, abuse, and potential exacerbation associated with classical chronic pain medications such as opioids creates a need for alternative therapeutics. Phenotypic screening provides a complementary approach to traditional target-based drug discovery. Profiling cellular phenotypes enables quantification of physiologically relevant traits central to a disease pathology without prior identification of a specific drug target. For complex disorders such as chronic pain, which likely involves many molecular targets, this approach may identify novel treatments. Sensory neurons, termed nociceptors, are derived from dorsal root ganglia (DRG) and can undergo changes in membrane excitability during chronic pain. In this review, we describe phenotypic screening paradigms that make use of nociceptor electrophysiology. The purpose of this paper is to review the bioelectrical behavior of DRG neurons, signaling complexity in sensory neurons, various sensory neuron models, assays for bioelectrical behavior, and emerging efforts to leverage microfabrication and microfluidics for assay development. We discuss limitations and advantages of these various approaches and offer perspectives on opportunities for future development.

Cells Adhering to 3D Vertical Nanostructures: Cell Membrane Reshaping without Stable Internalization

The dynamic interface between the cellular membrane and 3D nanostructures determines biological processes and guides the design of novel biomedical devices. Despite the fact that recent advancements in the fabrication of artificial biointerfaces have yielded an enhanced understanding of this interface, there remain open questions on how the cellular membrane reacts and behaves in the presence of sharp objects on the nanoscale. Here we provide a multifaceted characterization of the cellular membrane's mechanical stability when closely interacting with high-aspect-ratio 3D vertical nanostructures, providing strong evidence that vertical nanostructures spontaneously penetrate the cellular membrane to form a steady intracellular coupling only in rare cases and under specific conditions. The cell membrane is able to conform tightly over the majority of structures with various shapes while maintaining its integrity.

Electrochemistry at single molecule occupancy in nanopore-confined recessed ring-disk electrode arrays

Electrochemical reactions at nanoscale structures possess unique characteristics, e.g. fast mass transport, high signal-to-noise ratio at low concentration, and insignificant ohmic losses even at low electrolyte concentrations. These properties motivate the fabrication of high density, laterally ordered arrays of nanopores, embedding vertically stacked metal-insulator-metal electrode structures and exhibiting precisely controlled pore size and interpore spacing for use in redox cycling. These nanoscale recessed ring-disk electrode (RRDE) arrays exhibit current amplification factors, AF_RC, as large as 55-fold with Ru(NH₃)₆^2/3+, indicative of capture efficiencies at the top and bottom electrodes, Φ_t,b, exceeding 99%. Finite element simulations performed to investigate the concentration distribution of redox species and to assess operating characteristics are in excellent agreement with experiment. AF_RC increases as the pore diameter, at constant pore spacing, increases in the range 200-500 nm and as the pore spacing, at constant pore diameter, decreases in the range 1000-460 nm. Optimized nanoscale RRDE arrays exhibit a linear current response with concentration ranging from 0.1 μM to 10 mM and a small capacitive current with scan rate up to 100 V s^-1. At the lowest concentrations, the average pore occupancy is 〈n〉 ∼ 0.13 molecule establishing productive electrochemical signals at occupancies at and below the single molecule level in these nanoscale RRDE arrays.

Interfacing Cells with Vertical Nanoscale Devices: Applications and Characterization

Measurements of the intracellular state of mammalian cells often require probes or molecules to breach the tightly regulated cell membrane. Mammalian cells have been shown to grow well on vertical nanoscale structures in vitro, going out of their way to reach and tightly wrap the structures. A great deal of research has taken advantage of this interaction to bring probes close to the interface or deliver molecules with increased efficiency or ease. In turn, techniques have been developed to characterize this interface. Here, we endeavor to survey this research with an emphasis on the interface as driven by cellular mechanisms.

Engineering of Neuron Growth and Enhancing Cell-Chip Communication via Mixed SAMs

The interface between cells and inorganic surfaces represents one of the key elements for bioelectronics experiments and applications ranging from cell cultures and bioelectronics devices to medical implants. In the present paper, we describe a way to tailor the biocompatibility of substrates in terms of cell growth and to significantly improve cell-chip communication, and we also demonstrate the reusability of the substrates for cell experiments. All these improvements are achieved by coating the substrates or chips with a self-assembled monolayer (SAM) consisting of a mixture of organic molecules, (3-aminopropyl)-triethoxysilane and (3-glycidyloxypropyl)-trimethoxysilane. By varying the ratio of these molecules, we are able to tune the cell density and live/dead ratios of rat cortical neurons cultured directly on the mixed SAM as well as neurons cultured on protein-coated SAMs. Furthermore, the use of the SAM leads to a significant improvement in cell-chip communications. Action potential signals of up to 9.4 ± 0.6 mV (signal-to-noise ratio up to 47) are obtained for HL-1 cells on microelectrode arrays. Finally, we demonstrate that the SAMs facilitate a reusability of the samples for all cell experiments with little re-processing.

Self-Aligned Functionalization Approach to Order Neuronal Networks at the Single-Cell Level

Despite significant progress, our knowledge of the functioning of the central nervous system still remains scarce to date. A better understanding of its behavior, in either normal or diseased conditions, goes through an increased knowledge of basic mechanisms involved in neuronal function, including at the single-cell level. This has motivated significant efforts for the development of miniaturized sensing devices to monitor neuronal activity with high spatial and signal resolution. One of the main challenges remaining to be addressed in this domain is, however, the ability to create in vitro spatially ordered neuronal networks at low density with a precise control of the cell location to ensure proper monitoring of the activity of a defined set of neurons. Here, we present a novel self-aligned chemical functionalization method, based on a repellant surface with patterned attractive areas, which permits the elaboration of low-density neuronal network down to individual cells with a high control of the soma location and axonal growth. This approach is compatible with complementary metal-oxide-semiconductor line technology at a wafer scale and allows performing the cell culture on packaged chip outside microelectronics facilities. Rat cortical neurons were cultured on such patterned surfaces for over one month and displayed a very high degree of organization in large networks. Indeed, more than 90% of the network nodes were settled by a soma and 100% of the connecting lines were occupied by a neurite, with a very good selectivity (low parasitic cell connections). After optimization, networks composed of 75% of unicellular nodes were obtained, together with a control at the micron scale of the location of the somas. Finally, we demonstrated that the dendritic neuronal growth was guided by the surface functionalization, even when micrometer scale topologies were encountered and we succeeded to control the extension growth along one-dimensional-aligned nanostructures with sub-micrometrical scale precision. This novel approach now opens the way for precise monitoring of neuronal network activity at the single-cell level.

Direct Electrical Neurostimulation with Organic Pigment Photocapacitors

An efficient nanoscale semiconducting optoelectronic system is reported, which is optimized for neuronal stimulation: the organic electrolytic photocapacitor. The devices comprise a thin (80 nm) trilayer of metal and p-n semiconducting organic nanocrystals. When illuminated in physiological solution, these metal-semiconductor devices charge up, transducing light pulses into localized displacement currents that are strong enough to electrically stimulate neurons with safe light intensities. The devices are freestanding, requiring no wiring or external bias, and are stable in physiological conditions. The semiconductor layers are made using ubiquitous and nontoxic commercial pigments via simple and scalable deposition techniques. It is described how, in physiological media, photovoltage and charging behavior depend on device geometry. To test cell viability and capability of neural stimulation, photostimulation of primary neurons cultured for three weeks on photocapacitor films is shown. Finally, the efficacy of the device is demonstrated by achieving direct optoelectronic stimulation of light-insensitive retinas, proving the potential of this device platform for retinal implant technologies and for stimulation of electrogenic tissues in general. These results substantiate the conclusion that these devices are the first non-Si optoelectronic platform capable of sufficiently large photovoltages and displacement currents to enable true capacitive stimulation of excitable cells.

The Role of Membrane Curvature in Nanoscale Topography-Induced Intracellular Signaling

Over the past decade, there has been growing interest in developing biosensors and devices with nanoscale and vertical topography. Vertical nanostructures induce spontaneous cell engulfment, which enhances the cell-probe coupling efficiency and the sensitivity of biosensors. Although local membranes in contact with the nanostructures are found to be fully fluidic for lipid and membrane protein diffusions, cells appear to actively sense and respond to the surface topography presented by vertical nanostructures. For future development of biodevices, it is important to understand how cells interact with these nanostructures and how their presence modulates cellular function and activities. How cells recognize nanoscale surface topography has been an area of active research for two decades before the recent biosensor works. Extensive studies show that surface topographies in the range of tens to hundreds of nanometers can significantly affect cell functions, behaviors, and ultimately the cell fate. For example, titanium implants having rough surfaces are better for osteoblast attachment and host-implant integration than those with smooth surfaces. At the cellular level, nanoscale surface topography has been shown by a large number of studies to modulate cell attachment, activity, and differentiation. However, a mechanistic understanding of how cells interact and respond to nanoscale topographic features is still lacking. In this Account, we focus on some recent studies that support a new mechanism that local membrane curvature induced by nanoscale topography directly acts as a biochemical signal to induce intracellular signaling, which we refer to as the curvature hypothesis. The curvature hypothesis proposes that some intracellular proteins can recognize membrane curvatures of a certain range at the cell-to-material interface. These proteins then recruit and activate downstream components to modulate cell signaling and behavior. We discuss current technologies allowing the visualization of membrane deformation at the cell membrane-to-substrate interface with nanometer precision and demonstrate that vertical nanostructures induce local curvatures on the plasma membrane. These local curvatures enhance the process of clathrin-mediated endocytosis and affect actin dynamics. We also present evidence that vertical nanostructures can induce significant deformation of the nuclear membrane, which can affect chromatin distribution and gene expression. Finally, we provide a brief perspective on the curvature hypothesis and the challenges and opportunities for the design of nanotopography for manipulating cell behavior.

Multisite Attenuated Intracellular Recordings by Extracellular Multielectrode Arrays, a Perspective

Multielectrode arrays (MEA) are used extensively for basic and applied electrophysiological research of neuronal- and cardiomyocyte-networks. Whereas immense progress has been made in realizing sophisticated MEA platforms of thousands of addressable, high-density, small diameter, low impedance sensors, the quality of the interfaces formed between excitable cells and classical planar sensor has not improved. As a consequence in vitro and in vivo MEA are “blind” to the rich and important “landscape” of sub-threshold synaptic potentials generated by individual neurons. Disregarding this essential fraction of network signaling repertoire has become the standard and almost the “scientific ideology” of MEA users. To overcome the inherent limitations of substrate integrated planar MEA platforms that only record extracellular field potentials, a number of laboratories have developed in vitro MEA for intracellular recordings. Most of these novel devices use vertical nano-rods or nano-wires that penetrate the plasma membrane of cultured cells and record the electrophysiological signaling in a manner similar to sharp intracellular microelectrodes. In parallel, our laboratory began to develop a bioinspired approach in-which cell biological energy resources are harnessed to self-force a cell into intimate contact with extracellular gold mushroom-shaped microelectrodes to record attenuated synaptic- and action-potentials with characteristic features of intracellular recordings. Here we describe some of the experiments that helped evolve the approach and elaborate on the biophysical principles that make it possible to record intracellular potentials by an array of extracellular electrode. We illustrate the qualities and limitations of the method and discuss prospects for further improvement of this technology.

Equivalent Circuit of the Neuro-Electronic Junction for Signal Recordings From Planar and Engulfed Micro-Nano-Electrodes

In the latest years, several attempts to develop extracellular microtransducers to record electrophysiological activity of excitable cells have been done. In particular, many efforts have been oriented to increase the coupling conditions, and, thus, improving the quality of the recorded signal. Gold mushroom-shaped microelectrodes (GMμE) are an example of nano-devices to achieve those requirements. In this study, we developed an equivalent electrical circuit of the neuron-microelectrode system interface to simulate signal recordings from both planar and engulfed micro-nano-electrodes. To this purpose, models of the neuron, planar, gold planar microelectrode, and GMμE, neuro-electronic junction (microelectrode-electrolyte interface, cleft effect, and protein-glycocalyx electric double layer) are presented. Then, neuronal electrical activity is simulated by Hspice software, and analyzed as a function of the most sensitive biophysical models parameters, such as the neuron-microelectrode cleft width, spreading and seal resistances, ion-channel densities, double-layer properties, and microelectrode geometries. Results are referenced to the experimentally recorded electrophysiological neuronal signals reported in the literature.

Bioelectronics goes 3D: new trends in cell–chip interface engineering

Bioelectronic platforms can be used for electrophysiology, monitoring and stimulating specific cellular functions.

Nano- and microparticles at fluid and biological interfaces

Systems with interfaces are abundant in both technological applications and biology. While a fluid interface separates two fluids, membranes separate the inside of vesicles from the outside, the interior of biological cells from the environment, and compartmentalize cells into organelles. The physical properties of interfaces are characterized by interface tension, those of membranes are characterized by bending and stretching elasticity. Amphiphilic molecules like surfactants that are added to a system with two immiscible fluids decrease the interface tension and induce a bending rigidity. Lipid bilayer membranes of vesicles can be stretched or compressed by osmotic pressure; in biological cells, also the presence of a cytoskeleton can induce membrane tension. If the thickness of the interface or the membrane is small compared with its lateral extension, both can be described using two-dimensional mathematical surfaces embedded in three-dimensional space. We review recent work on the interaction of particles with interfaces and membranes. This can be micrometer-sized particles at interfaces that stabilise emulsions or form colloidosomes, as well as typically nanometer-sized particles at membranes, such as viruses, parasites, and engineered drug delivery systems. In both cases, we first discuss the interaction of single particles with interfaces and membranes, e.g. particles in external fields, non-spherical particles, and particles at curved interfaces, followed by interface-mediated interaction between two particles, many-particle interactions, interface and membrane curvature-induced phenomena, and applications.

Revealing the Cell-Material Interface with Nanometer Resolution by Focused Ion Beam/Scanning Electron Microscopy

The interface between cells and nonbiological surfaces regulates cell attachment, chronic tissue responses, and ultimately the success of medical implants or biosensors. Clinical and laboratory studies show that topological features of the surface profoundly influence cellular responses; for example, titanium surfaces with nano- and microtopographical structures enhance osteoblast attachment and host-implant integration as compared to a smooth surface. To understand how cells and tissues respond to different topographical features, it is of critical importance to directly visualize the cell-material interface at the relevant nanometer length scale. Here, we present a method for in situ examination of the cell-to-material interface at any desired location, based on focused ion beam milling and scanning electron microscopy imaging to resolve the cell membrane-to-material interface with 10 nm resolution. By examining how cell membranes interact with topographical features such as nanoscale protrusions or invaginations, we discovered that the cell membrane readily deforms inward and wraps around protruding structures, but hardly deforms outward to contour invaginating structures. This asymmetric membrane response (inward vs outward deformation) causes the cleft width between the cell membrane and the nanostructure surface to vary by more than an order of magnitude. Our results suggest that surface topology is a crucial consideration for the development of medical implants or biosensors whose performances are strongly influenced by the cell-to-material interface. We anticipate that the method can be used to explore the direct interaction of cells/tissue with medical devices such as metal implants in the future.

Soft electroporation for delivering molecules into tightly adherent mammalian cells through 3D hollow nanoelectrodes

Electroporation of in-vitro cultured cells is widely used in biological and medical areas to deliver molecules of interest inside cells. Since very high electric fields are required to electroporate the plasma membrane, depending on the geometry of the electrodes the required voltages can be very high and often critical to cell viability. Furthermore, in traditional electroporation configuration based on planar electrodes there is no a priori certain feedback about which cell has been targeted and delivered and the addition of fluorophores may be needed to gain this information. In this study we present a nanofabricated platform able to perform intracellular delivery of membrane-impermeable molecules by opening transient nanopores into the lipid membrane of adherent cells with high spatial precision and with the application of low voltages (1.5–2 V). This result is obtained by exploiting the tight seal that the cells present with 3D fluidic hollow gold-coated nanostructures that act as nanochannels and nanoelectrodes at the same time. The final soft-electroporation platform provides an accessible approach for controlled and selective drug delivery on ordered arrangements of cells.