Spatially, Temporally, and Quantitatively Controlled Delivery of Broad Range of Molecules into Selected Cells through Plasmonic Nanotubes

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.

Nanoinjection: A Platform for Innovation in Ex Vivo Cell Engineering

ConspectusIn human cells, intracellular access and therapeutic cargo transport, including gene-editing tools (e.g., CRISPR-Cas9 and transposons), nucleic acids (e.g., DNA, mRNA, and siRNA), peptides, and proteins (e.g., enzymes and antibodies), are tightly constrained to ensure healthy cell function and behavior. This principle is exemplified in the delivery mechanisms of chimeric antigen receptor (CAR)-T cells for ex-vivo immunotherapy. In particular, the clinical success of CAR-T cells has established a new standard of care by curing previously incurable blood cancers. The approach involves the delivery, typically via the use of electroporation (EP) and lentivirus, of therapeutic CAR genes into a patient's own T cells, which are then engineered to express CARs that target and combat their blood cancer. But the key difficulty lies in genetically manipulating these cells without causing irreversible damage or loss of function─all the while minimizing complexities of manufacturing, safety concerns, and costs, and ensuring the efficacy of the final CAR-T cell product.Nanoinjection─the process of intracellular delivery using nanoneedles (NNs)─is an emerging physical delivery route that efficiently negotiates the plasma membrane of many cell types, including primary human T cells. It occurs with minimal perturbation, invasiveness, and toxicity, with high efficiency and throughput at high spatial and temporal resolutions. Nanoinjection promises greatly improved delivery of a broad range of therapeutic cargos with little or no damage to those cargos. A nanoinjection platform allows these cargos to function in the intracellular space as desired. The adaptability of nanoinjection platforms is now bringing major advantages in immunomodulation, mechanotransduction, sampling of cell states (nanobiopsy), controlled intracellular interrogation, and the primary focus of this account─intracellular delivery and its applications in ex vivo cell engineering.Mechanical nanoinjection typically exerts direct mechanical force on the cell membrane, offering a straightforward route to improve membrane perturbation by the NNs and subsequent transport of genetic cargo into targeted cell type (adherent or suspension cells). By contrast, electroactive nanoinjection is controlled by coupling NNs with an electric field─a new route for activating electroporation (EP) at the nanoscale─allowing a dramatic reduction of the applied voltage to a cell and so minimizing post-EP damage to cells and cargo, and overcoming many of the limitations of conventional bulk EP. Nanoinjection transcends mere technique; it is an approach to cell engineering ex vivo, offering the potential to endow cells with new, powerful features such as generating chimeric antigen receptor (CAR)-T cells for future CAR-T cell technologies.We first discuss the manufacturing of NN devices (Section 2), then delve into nanoinjection-mediated cell engineering (Section 3), nanoinjection mechanisms and interfacing methodologies (Section 4), and emerging applications in using nanoinjection to create functional CAR-T cells (Section 5).

Coupling of nanostraws with diverse physicochemical perforation strategies for intracellular DNA delivery

Effective intracellular DNA transfection is imperative for cell-based therapy and gene therapy. Conventional gene transfection methods, including biochemical carriers, physical electroporation and microinjection, face challenges such as cell type dependency, low efficiency, safety concerns, and technical complexity. Nanoneedle arrays have emerged as a promising avenue for improving cellular nucleic acid delivery through direct penetration of the cell membrane, bypassing endocytosis and endosome escape processes. Nanostraws (NS), characterized by their hollow tubular structure, offer the advantage of flexible solution delivery compared to solid nanoneedles. However, NS struggle to stably self-penetrate the cell membrane, resulting in limited delivery efficiency. Coupling with extra physiochemical perforation strategies is a viable approach to improve their performance. This study systematically compared the efficiency of NS coupled with polyethylenimine (PEI) chemical modification, mechanical force, photothermal effect, and electric field on cell membrane perforation and DNA transfection. The results indicate that coupling NS with PEI modification, mechanical force, photothermal effects provide limited enhancement effects. In contrast, NS-electric field coupling significantly improves intracellular DNA transfection efficiency. This work demonstrates that NS serve as a versatile platform capable of integrating various physicochemical strategies, while electric field coupling stands out as a form worthy of primary consideration for efficient DNA transfection.

Universal Strategy of Efficient Intracellular Macromolecule Directional Delivery Using Photothermal Pump Patch

The development of a highly efficient, nondestructive, and in vitro/vivo-applicable universal delivery strategy of therapeutic macromolecules into desired cells and tissues is very challenging. Photothermal methods have advantages in intracellular delivery, particularly in in vivo manipulation. However, the inability of directional transmission of exogenous molecules limits their delivery efficiency. Here, a photothermal pump (PTP) patch with numerous "exogenous molecular reservoirs" is reported. Under a laser, the cell membrane ruptures, while "exogenous molecular reservoirs" shrink, resulting in a directional exogenous molecule delivery into cells for a high-efficient intracellular delivery. The PTP patches are considered a universal structure for a highly efficient, nondestructive, and in-vitro/vivo-applicable intracellular macromolecule delivery. Under in vivo transdermal intracellular delivery conditions, the target genes are efficiently and noninvasively delivered into epidermal and dermal cells through the PTP patch and exosomes produced by the epidermal cells, respectively. The PTP patch provides a new strategy for a high-efficiency, nondestructive, and in-vitro/vivo-applicable macromolecule delivery.

Nanopore Electroporation Device for DNA Transfection into Various Spreading and Nonadherent Cell Types

Cell transfection plays a crucial role in the study of gene function and regulation of gene expression. The existing gene transfection methods, such as chemical carriers, viruses, electroporation, and microinjection, suffer from limitations, including cell type dependence, reliance on cellular endocytosis, low efficiency, safety concerns, and technical complexity. Nanopore-coupled electroporation offers a promising approach to localizing electric fields for efficient cell membrane perforation and nucleic acid transfection. However, the applicability of nanopore electroporation technology across different cell types lacks a systematic investigation. In this study, we explore the potential of nanopore electroporation for transfecting DNA plasmids into various cell types. Our nanopore electroporation device employs track-etched membranes as the core component. We find that nanopore electroporation efficiently transfects adherent cells, including well-spreading epithelial-like HeLa cells, cardiomyocyte-like HL-1 cells, and dendritic-cell-like DC2.4 cells. However, it shows a limited transfection efficiency in weakly spreading macrophages (RAW264.7) and suspension cells (Jurkat). To gain insights into these observations, we develop a COMSOL model, revealing that nanopore electroporation better localizes the electric field on adherent and well-spreading cells, promoting favorable membrane poration conditions. Our findings provide valuable references for advancing nanopore electroporation as a high-throughput, safe, and efficient gene transfection platform.

Electroactive nanoinjection platform for intracellular delivery and gene silencing

BACKGROUND

Nanoinjection-the process of intracellular delivery using vertically configured nanostructures-is a physical route that efficiently negotiates the plasma membrane, with minimal perturbation and toxicity to the cells. Nanoinjection, as a physical membrane-disruption-mediated approach, overcomes challenges associated with conventional carrier-mediated approaches such as safety issues (with viral carriers), genotoxicity, limited packaging capacity, low levels of endosomal escape, and poor versatility for cell and cargo types. Yet, despite the implementation of nanoinjection tools and their assisted analogues in diverse cellular manipulations, there are still substantial challenges in harnessing these platforms to gain access into cell interiors with much greater precision without damaging the cell's intricate structure. Here, we propose a non-viral, low-voltage, and reusable electroactive nanoinjection (ENI) platform based on vertically configured conductive nanotubes (NTs) that allows for rapid influx of targeted biomolecular cargos into the intracellular environment, and for successful gene silencing. The localization of electric fields at the tight interface between conductive NTs and the cell membrane drastically lowers the voltage required for cargo delivery into the cells, from kilovolts (for bulk electroporation) to only ≤ 10 V; this enhances the fine control over membrane disruption and mitigates the problem of high cell mortality experienced by conventional electroporation.

RESULTS

Through both theoretical simulations and experiments, we demonstrate the capability of the ENI platform to locally perforate GPE-86 mouse fibroblast cells and efficiently inject a diverse range of membrane-impermeable biomolecules with efficacy of 62.5% (antibody), 55.5% (mRNA), and 51.8% (plasmid DNA), with minimal impact on cells' viability post nanoscale-EP (> 90%). We also show gene silencing through the delivery of siRNA that targets TRIOBP, yielding gene knockdown efficiency of 41.3%.

CONCLUSIONS

We anticipate that our non-viral and low-voltage ENI platform is set to offer a new safe path to intracellular delivery with broader selection of cargo and cell types, and will open opportunities for advanced ex vivo cell engineering and gene silencing.

Photoallosteric Polymersomes toward On-Demand Drug Delivery and Multimodal Cancer Immunotherapy

Allosteric transitions can modulate the self-assembly and biological function of proteins. It remains, however, tremendously challenging to design synthetic allosteric polymeric assemblies with spatiotemporally switchable hierarchical structures and functionalities. Here, a photoallosteric polymersome is constructed that undergoes a rapid conformational transition from β-sheet to α-helix upon exposure to near-infrared light irradiation. In addition to improving nanoparticle cell penetration and lysosome escape, photoinduced allosteric behavior reconstructs the vesicular membrane structure, which stimulates the release of hydrophilic cytolytic peptide melittin and hydrophobic kinase inhibitor sorafenib. Combining on-demand delivery of multiple therapeutics with phototherapy results in apoptosis and immunogenic death of tumor cells, remold the immune microenvironment and achieve an excellent synergistic anticancer efficacy in vivo without tumor recurrence and metastasis. Such a light-modulated allosteric transition in non-photosensitive polymers provides new insight into the development of smart nanomaterials for biosensing and drug delivery applications.

The influence of dysfunctional actin on polystyrene-nanotube-mediated mRNA nanoinjection into mammalian cells

The advancement of nanofabrication technologies has transformed the landscape of engineered nano-bio interfaces, especially with vertically aligned nanoneedles (NNs). This enables scientists to venture into new territories, widening NN applications into increasingly more complex cellular manipulation and interrogation. Specifically, for intracellular delivery application, NNs have been shown to mediate the delivery of various bioactive cargos into a wide range of cells-a physical method termed "nanoinjection". Silicon (Si) nanostructures demonstrated great potential in nanoinjection, whereas the use of polymeric NNs for nanoinjection has rarely been explored. Furthermore, the underlying mechanism of interaction at the cell-NN interface is subtle and multifaceted, and not fully understood-underpinned by the design versatility of the NN biointerface. Recent studies have suggested that actin dynamic plays a pivotal role influencing the delivery efficacy. In this study, we fabricated a new class of NNs-a programmable polymeric nanotubes (NTs)-from polystyrene (PS) cell cultureware, designed to facilitate mRNA delivery into mouse embryonic fibroblast GPE86 cells. The PSNT delivery platform was able to mediate mRNA delivery with high delivery efficiency (∼83%). We also investigated the role of actin cytoskeleton in PSNTs mediated intracellular delivery by introducing two actin inhibitors-cytochalasin D (Cyto D) and jasplakinolide (Jas)-to cause dysfunctional cytoskeleton, via inhibiting actin polymerization and depolymerization, respectively (before and after the establishment of cell-PSNT interface). By inhibiting actin dynamics 12 h before cell-PSNT interfacing (pre-interface treatment), the mRNA delivery efficiencies were significantly reduced to ∼3% for Cyto D-treated samples and ∼1% for Jas-treated sample, as compared to their post-interface (2 h after cell-PSNT interfacing) counterpart (∼46% and ∼68%, respectively). The added flexibility of PSNTs have shown to help withstand mechanical breakage stemming from cytoskeletal forces in contrast to the SiNTs. Such findings will step-change our capacity to use programmable polymeric NTs in fundamental cellular processes related to intracellular delivery.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Long-term in vitro recording of cardiac action potentials on microelectrode arrays for chronic cardiotoxicity assessment

The reliable identification of chronic cardiotoxic effects in in vitro screenings is fundamental for filtering out toxic molecular entities before in vivo animal experimentation and clinical trials. Present techniques such as patch-clamp, voltage indicators, and standard microelectrode arrays do not offer at the same time high sensitivity for measuring transmembrane ion currents and low-invasiveness for monitoring cells over long time. Here, we show that optoporation applied to microelectrode arrays enables measuring action potentials from human-derived cardiac syncytia for more than 1 continuous month and provides reliable data on chronic cardiotoxic effects caused by known compounds such as pentamidine. The technique has high potential for detecting chronic cardiotoxicity in the early phases of drug development.

Nanomaterial-mediated photoporation for intracellular delivery

Translocation of extrinsic molecules into living cells is becoming increasingly crucial in biological studies ranging from cell engineering to biomedical applications. The concerns regarding biosafety and immunogenicity for conventional vectors and physical methods yet challenge effective intracellular delivery. Here, we begin with an overview of approaches for trans-membrane delivery up to now. These methods are featured with a relatively mature application but usually encounter low cell survival. Our review then proposes an advanced application for nanomaterial-sensitized photoporation triggered with a laser. We cover the mechanisms, procedures, and outcomes of photoporation-induced intracellular delivery with a highlight on its versatility to different living cells. We hope the review discussed here encourages researchers to further improvement and applications for photoporation-induced intracellular delivery. STATEMENT OF SIGNIFICANCE.

Role of actin cytoskeleton in cargo delivery mediated by vertically aligned silicon nanotubes

Nanofabrication technologies have been recently applied to the development of engineered nano–bio interfaces for manipulating complex cellular processes. In particular, vertically configurated nanostructures such as nanoneedles (NNs) have been adopted for a variety of biological applications such as mechanotransduction, biosensing, and intracellular delivery. Despite their success in delivering a diverse range of biomolecules into cells, the mechanisms for NN-mediated cargo transport remain to be elucidated. Recent studies have suggested that cytoskeletal elements are involved in generating a tight and functional cell–NN interface that can influence cargo delivery. In this study, by inhibiting actin dynamics using two drugs—cytochalasin D (Cyto D) and jasplakinolide (Jas), we demonstrate that the actin cytoskeleton plays an important role in mRNA delivery mediated by silicon nanotubes (SiNTs). Specifically, actin inhibition 12 h before SiNT-cellular interfacing (pre-interface treatment) significantly dampens mRNA delivery (with efficiencies dropping to 17.2% for Cyto D and 33.1% for Jas) into mouse fibroblast GPE86 cells, compared to that of untreated controls (86.9%). However, actin inhibition initiated 2 h after the establishment of GPE86 cell–SiNT interface (post-interface treatment), has negligible impact on mRNA transfection, maintaining > 80% efficiency for both Cyto D and Jas treatment groups. The results contribute to understanding potential mechanisms involved in NN-mediated intracellular delivery, providing insights into strategic design of cell–nano interfacing under temporal control for improved effectiveness.

Semi-Implantable Bioelectronics

Developing techniques to effectively and real-time monitor and regulate the interior environment of biological objects is significantly important for many biomedical engineering and scientific applications, including drug delivery, electrophysiological recording and regulation of intracellular activities. Semi-implantable bioelectronics is currently a hot spot in biomedical engineering research area, because it not only meets the increasing technical demands for precise detection or regulation of biological activities, but also provides a desirable platform for externally incorporating complex functionalities and electronic integration. Although there is less definition and summary to distinguish it from the well-reviewed non-invasive bioelectronics and fully implantable bioelectronics, semi-implantable bioelectronics have emerged as highly unique technology to boost the development of biochips and smart wearable device. Here, we reviewed the recent progress in this field and raised the concept of "Semi-implantable bioelectronics", summarizing the principle and strategies of semi-implantable device for cell applications and in vivo applications, discussing the typical methodologies to access to intracellular environment or in vivo environment, biosafety aspects and typical applications. This review is meaningful for understanding in-depth the design principles, materials fabrication techniques, device integration processes, cell/tissue penetration methodologies, biosafety aspects, and applications strategies that are essential to the development of future minimally invasive bioelectronics.

Cellular nanointerface of vertical nanostructure arrays and its applications

Vertically standing nanostructures with various morphologies have been developed with the emergence of the micro-/nanofabrication technology. When cells are cultured on them, various bio-nano interfaces between cells and vertical nanostructures would impact the cellular activities, depending on the shape, density, and height of nanostructures. Many cellular pathway activation processes involving a series of intracellular molecules (proteins, RNA, DNA, enzymes, etc.) would be triggered by the cell morphological changes induced by nanostructures, affecting the cell proliferation, apoptosis, differentiation, immune activation, cell adhesion, cell migration, and other behaviors. In addition, the highly localized cellular nanointerface enhances coupled stimulation on cells. Therefore, understanding the mechanism of the cellular nanointerface can not only provide innovative tools for regulating specific cell functions but also offers new aspects to understand the fundamental cellular activities that could facilitate the precise monitoring and treatment of diseases in the future. This review mainly describes the fabrication technology of vertical nanostructures, analyzing the formation of cellular nanointerfaces and the effects of cellular nanointerfaces on cells' fates and functions. At last, the applications of cellular nanointerfaces based on various nanostructures are summarized.

Photothermal scaffolds/surfaces for regulation of cell behaviors

Regulation of cell behaviors and even cell fates is of great significance in diverse biomedical applications such as cancer treatment, cell-based therapy, and tissue engineering. During the past decades, diverse methods have been developed to regulate cell behaviors such as applying external stimuli, delivering exogenous molecules into cell interior and changing the physicochemical properties of the substrates where cells adhere. Photothermal scaffolds/surfaces refer to a kind of materials embedded or coated with photothermal agents that can absorb light with proper wavelength (usually in near infrared region) and convert light energy to heat; the generated heat shows great potential for regulation of cell behaviors in different ways. In the current review, we summarize the recent research progress, especially over the past decade, of using photothermal scaffolds/surfaces to regulate cell behaviors, which could be further categorized into three types: (i) killing the tumor cells via hyperthermia or thermal ablation, (ii) engineering cells by intracellular delivery of exogenous molecules via photothermal poration of cell membranes, and (iii) releasing a single cell or an intact cell sheet via modulation of surface physicochemical properties in response to heat. In the end, challenges and perspectives in these areas are commented.

Microfluidic mechanoporation for cellular delivery and analysis

Highly efficient intracellular delivery strategies are essential for developing therapeutic, diagnostic, biological, and various biomedical applications. The recent advancement of micro/nanotechnology has focused numerous researches towards developing microfluidic device-based strategies due to the associated high throughput delivery, cost-effectiveness, robustness, and biocompatible nature. The delivery strategies can be carrier-mediated or membrane disruption-based, where membrane disruption methods find popularity due to reduced toxicity, enhanced delivery efficiency, and cell viability. Among all of the membrane disruption techniques, the mechanoporation strategies are advantageous because of no external energy source required for membrane deformation, thereby achieving high delivery efficiencies and increased cell viability into different cell types with negligible toxicity. The past two decades have consequently seen a tremendous boost in mechanoporation-based research for intracellular delivery and cellular analysis. This article provides a brief review of the most recent developments on microfluidic-based mechanoporation strategies such as microinjection, nanoneedle arrays, cell-squeezing, and hydroporation techniques with their working principle, device fabrication, cellular delivery, and analysis. Moreover, a brief discussion of the different mechanoporation strategies integrated with other delivery methods has also been provided. Finally, the advantages, limitations, and future prospects of this technique are discussed compared to other intracellular delivery techniques.

Considerations and recent advances in nanoscale interfaces with neuronal and cardiac networks

Nanoscale interfaces with biological tissue, principally made with nanowires (NWs), are envisioned as minimally destructive to the tissue and as scalable tools to directly transduce the electrochemical activity of a neuron at its finest resolution. This review lays the foundations for understanding the material and device considerations required to interrogate neuronal activity at the nanoscale. We first discuss the electrochemical nanoelectrode-neuron interfaces and then present new results concerning the electrochemical impedance and charge injection capacities of millimeter, micrometer, and nanometer scale wires with Pt, PEDOT:PSS, Si, Ti, ITO, IrO x , Ag, and AgCl materials. Using established circuit models for NW-neuron interfaces, we discuss the impact of having multiple NWs interfacing with a single neuron on the amplitude and temporal characteristics of the recorded potentials. We review state of the art advances in nanoelectrode-neuron interfaces, the standard control experiments to investigate their electrophysiological behavior, and present recent high fidelity recordings of intracellular potentials obtained with ultrasharp NWs developed in our laboratory that naturally permeate neuronal cell bodies. Recordings from arrays and individually addressable electrically shorted NWs are presented, and the long-term stability of intracellular recording is discussed and put in the context of established techniques. Finally, a perspective on future research directions and applications is presented.

All-Optical and Label-Free Stimulation of Action Potentials in Neurons and Cardiomyocytes by Plasmonic Porous Metamaterials

Optical stimulation technologies are gaining great consideration in cardiology, neuroscience studies, and drug discovery pathways by providing control over cell activity with high spatio-temporal resolution. However, this high precision requires manipulation of biological processes at genetic level concealing its development from broad scale application. Therefore, translating these technologies into tools for medical or pharmacological applications remains a challenge. Here, an all-optical nongenetic method for the modulation of electrogenic cells is introduced. It is demonstrated that plasmonic metamaterials can be used to elicit action potentials by converting near infrared laser pulses into stimulatory currents. The suggested approach allows for the stimulation of cardiomyocytes and neurons directly on commercial complementary metal-oxide semiconductor microelectrode arrays coupled with ultrafast pulsed laser, providing both stimulation and network-level recordings on the same device.

Tutorial: using nanoneedles for intracellular delivery

Intracellular delivery of advanced therapeutics, including biologicals and supramolecular agents, is complex because of the natural biological barriers that have evolved to protect the cell. Efficient delivery of therapeutic nucleic acids, proteins, peptides and nanoparticles is crucial for clinical adoption of emerging technologies that can benefit disease treatment through gene and cell therapy. Nanoneedles are arrays of vertical high-aspect-ratio nanostructures that can precisely manipulate complex processes at the cell interface, enabling effective intracellular delivery. This emerging technology has already enabled the development of efficient and non-destructive routes for direct access to intracellular environments and delivery of cell-impermeant payloads. However, successful implementation of this technology requires knowledge of several scientific fields, making it complex to access and adopt by researchers who are not directly involved in developing nanoneedle platforms. This presents an obstacle to the widespread adoption of nanoneedle technologies for drug delivery. This tutorial aims to equip researchers with the knowledge required to develop a nanoinjection workflow. It discusses the selection of nanoneedle devices, approaches for cargo loading and strategies for interfacing to biological systems and summarises an array of bioassays that can be used to evaluate the efficacy of intracellular delivery.

Biomaterials-based approaches to model embryogenesis

Understanding, reproducing, and regulating the cellular and molecular processes underlying human embryogenesis is critical to improve our ability to recapitulate tissues with proper architecture and function, and to address the dysregulation of embryonic programs that underlies birth defects and cancer. The rapid emergence of stem cell technologies is enabling enormous progress in understanding embryogenesis using simple, powerful, and accessible in vitro models. Biomaterials are playing a central role in providing the spatiotemporal organisation of biophysical and biochemical signalling necessary to mimic, regulate and dissect the evolving embryonic niche in vitro. This contribution is rapidly improving our understanding of the mechanisms underlying embryonic patterning, in turn enabling the development of more effective clinical interventions for regenerative medicine and oncology. Here we highlight how key biomaterial approaches contribute to organise signalling in human embryogenesis models, and we summarise the biological insights gained from these contributions. Importantly, we highlight how nanotechnology approaches have remained largely untapped in this space, and we identify their key potential contributions.

Advances in Multidimensional Cardiac Biosensing Technologies: From Electrophysiology to Mechanical Motion and Contractile Force

Cardiovascular disease is currently a leading killer to human, while drug-induced cardiotoxicity remains the main cause of the withdrawal and attrition of drugs. Taking clinical correlation and throughput into account, cardiomyocyte is perfect as in vitro cardiac model for heart disease modeling, drug discovery, and cardiotoxicity assessment by accurately measuring the physiological multiparameters of cardiomyocytes. Remarkably, cardiomyocytes present both electrophysiological and biomechanical characteristics due to the unique excitation-contraction coupling, which plays a significant role in studying the cardiomyocytes. This review mainly focuses on the recent advances of biosensing technologies for the 2D and 3D cardiac models with three special properties: electrophysiology, mechanical motion, and contractile force. These high-performance multidimensional cardiac models are popular and effective to rebuild and mimic the heart in vitro. To help understand the high-quality and accurate physiologies, related detection techniques are highly demanded, from microtechnology to nanotechnology, from extracellular to intracellular recording, from multiple cells to single cell, and from planar to 3D models. Furthermore, the characteristics, advantages, limitations, and applications of these cardiac biosensing technologies, as well as the future development prospects should contribute to the systematization and expansion of knowledge.

Single-cell transfection technologies for cell therapies and gene editing

Advances in gene editing and cell therapies have recently led to outstanding clinical successes. However, the lack of a cost-effective manufacturing process prevents the democratization of these innovative medical tools. Due to the common use of viral vectors, the step of transfection in which cells are engineered to gain new functions, is a major bottleneck in making safe and affordable cell products. A promising opportunity lies in Single-Cell Transfection Technologies (SCTTs). SCTTs have demonstrated higher efficiency, safety and scalability than conventional transfection methods. They can also feature unique abilities such as substantial dosage control over the cargo delivery, single-cell addressability and integration in microdevices comprising multiple monitoring modalities. Unfortunately, the potential of SCTTs is not fully appreciated: they are most often restricted to research settings with little adoption in clinical settings. To encourage their adoption, we review and compare recent developments in SCTTs, and how they can enable selected clinical applications. To help bridge the gap between fundamental research and its translation to the clinic, we also describe how Good Manufacturing Practices (GMP) can be integrated in the design of SCTTs.

Emerging Roles of 1D Vertical Nanostructures in Orchestrating Immune Cell Functions

Engineered nano-bio cellular interfaces driven by 1D vertical nanostructures (1D-VNS) are set to prompt radical progress in modulating cellular processes at the nanoscale. Here, tuneable cell-VNS interfacial interactions are probed and assessed, highlighting the use of 1D-VNS in immunomodulation, and intracellular delivery into immune cells-both crucial in fundamental and translational biomedical research. With programmable topography and adaptable surface functionalization, 1D-VNS provide unique biophysical and biochemical cues to orchestrate innate and adaptive immunity, both ex vivo and in vivo. The intimate nanoscale cell-VNS interface leads to membrane penetration and cellular deformation, facilitating efficient intracellular delivery of diverse bioactive cargoes into hard-to-transfect immune cells. The unsettled interfacial mechanisms reported to be involved in VNS-mediated intracellular delivery are discussed. By identifying up-to-date progress and fundamental challenges of current 1D-VNS technology in immune-cell manipulation, it is hoped that this report gives timely insights for further advances in developing 1D-VNS as a safe, universal, and highly scalable platform for cell engineering and enrichment in advanced cancer immunotherapy such as chimeric antigen receptor-T therapy.

Spacer-Defined Intrinsic Multiple Patterning

Periodic nanotube arrays render enhanced functional properties through their interaction with light and matter, but to reach optimal performance for technologically prominent applications, such as wettability or photonics, structural fine-tuning is essential. Nonetheless, a universal and scalable method providing independent dimension control, high aspect ratios, and the prospect of further structural complexity remains unachieved. Here, we answer this need through an atomic layer deposition (ALD)-enabled multiple patterning. Unlike previous methods, the ALD-deposited spacer is applied directly on the prepatterned target substrate material, serving as an etching mask to generate a multitude of tailored nanotubes. By concept iteration, we further realize concentric and/or binary nanoarrays in a number of industrially important materials such as silicon, glass, and polymers. To demonstrate the achieved quality and applicability of the structures, we probe how nanotube fine-tuning induces broadband antireflection and present a surface boasting extremely low reflectance of <1% across the wavelength range of 300-1050 nm.

Surface-Mediated Intracellular Delivery by Physical Membrane Disruption

Effective and nondestructive intracellular delivery of exogenous molecules and other functional materials into living cells is of importance for diverse biological fundamental research and therapeutic applications, such as gene editing and cell-based therapies. However, for most exogenous molecules, the cell plasma membrane is effectively impermeable and thus remains the greatest barrier to intracellular delivery. In recent years, methods based on surface-mediated physical membrane disruption have attracted considerable attention. These methods exploit the physical properties of the surface to transiently increase the membrane permeability of cells come in contact thereto, thereby facilitating the efficient intracellular delivery of molecules regardless of molecule or target cell type. In this Review, we focus on recent progress, particularly over the past decade, on these surface-mediated membrane disruption-based delivery systems. According to the membrane disruption mechanism, three categories can be recognized: (i) mechanical penetration, (ii) electroporation, and (iii) photothermal poration. Each of these is discussed in turn and a brief perspective on future developments in this promising area is presented.

Intracellular Labeling with Extrinsic Probes: Delivery Strategies and Applications

Extrinsic probes have outstanding properties for intracellular labeling to visualize dynamic processes in and of living cells, both in vitro and in vivo. Since extrinsic probes are in many cases cell-impermeable, different biochemical, and physical approaches have been used to break the cell membrane barrier for direct delivery into the cytoplasm. In this Review, these intracellular delivery strategies are discussed, briefly explaining the mechanisms and how they are used for live-cell labeling applications. Methods that are discussed include three biochemical agents that are used for this purpose-purpose-different nanocarriers, cell penetrating peptides and the pore-foraming bacterial toxin streptolysin O. Most successful intracellular label delivery methods are, however, based on physical principles to permeabilize the membrane and include electroporation, laser-induced photoporation, micro- and nanoinjection, nanoneedles or nanostraws, microfluidics, and nanomachines. The strengths and weaknesses of each strategy are discussed with a systematic comparison provided. Finally, the extrinsic probes that are reported for intracellular labeling so-far are summarized, together with the delivery strategies that are used and their performance. This combined information should provide for a useful guide for choosing the most suitable delivery method for the desired probes.

Two-state switchable plasmonic tweezers for dynamic manipulation of nano-objects

In this work, we present a plasmonic platform capable of trapping nano-objects in two different spatial configurations. The switch between the two trapping states, localized on the tip and on the outer wall of a vertical gold nanochannel, can be activated by varying the focusing position of the excitation laser along the main axis of the nanotube. We show that the switching of the trapping site is induced by changes in the distribution of the electromagnetic field and of the trapping force. The "inner" and "outer" trapping states are characterized by a static and a dynamic behavior respectively, and their stiffness is measured by analyzing the positions of the trapped specimens as a function of time. In addition, we demonstrate that the stiffness of the static state is high enough to trap particles with diameter as small as 40 nm. These results show a simple, controllable way to generate a switchable two-state trapping regime, which could be used as a model for the study of dynamic trapping or as a mechanism for the development of nanofluidic devices.

A review of emerging physical transfection methods for CRISPR/Cas9-mediated gene editing

Gene editing is a versatile technique in biomedicine that promotes fundamental research as well as clinical therapy. The development of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) as a genome editing machinery has accelerated the application of gene editing. However, the delivery of CRISPR components often suffers when using conventional transfection methods, such as viral transduction and chemical vectors, due to limited packaging size and inefficiency toward certain cell types. In this review, we discuss physical transfection methods for CRISPR gene editing which can overcome these limitations. We outline different types of physical transfection methods, highlight novel techniques to deliver CRISPR components, and emphasize the role of micro and nanotechnology to improve transfection performance. We present our perspectives on the limitations of current technology and provide insights on the future developments of physical transfection methods.

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.

Photothermally Activated Electrospun Nanofiber Mats for High-Efficiency Surface-Mediated Gene Transfection

Although electrospun nanofibers have been used to deliver functional genes into cells attached to the surface of the nanofibers, the controllable release of genes from nanofibers and the subsequent gene transfection with high efficiency remain challenging. Herein, photothermally activated electrospun hybrid nanofibers are developed for high-efficiency surface-mediated gene transfection. Nanofibers with a core-sheath structure are fabricated using coaxial electrospinning. Plasmid DNA (pDNA) encoding basic fibroblast growth factor is encapsulated in the fiber core, and gold nanorods with photothermal properties are embedded in the fiber sheath composed of poly(l-lactic acid) and gelatin. The nanofiber mats show excellent and controllable photothermal response under near-infrared irradiation. The permeability of the nanofibers is thereby enhanced to allow the rapid release of pDNA. In addition, transient holes are formed in the membranes of NIH-3T3 fibroblasts attached to the mat, thus facilitating delivery and transfection with pDNA and leading to increased proliferation and migration of the transfected cells in vitro. This work offers a facile and reliable method for the regulation of cell function and cell behavior via localized gene transfection, showing great potential for application in tissue engineering and cell-based therapy.

Intracellular Recording of Human Cardiac Action Potentials on Market-Available Multielectrode Array Platforms

High quality attenuated intracellular action potentials from large cell networks can be recorded on multi-electrode arrays by means of 3D vertical nanopillars using electrical pulses. However, most of the techniques require complex 3D nanostructures that prevent the straightforward translation into marketable products and the wide adoption in the scientific community. Moreover, 3D nanostructures are often delicate objects that cannot sustain several harsh use/cleaning cycles. On the contrary, laser optoacoustic poration allows the recording of action potentials on planar nanoporous electrodes made of noble metals. However, these constraints of the electrode material and morphology may also hinder the full exploitation of this methodology. Here, we show that optoacoustic poration is also very effective for porating cells on a large family of MEA electrode configurations, including robust electrodes made of nanoporous titanium nitride or disordered fractal-like gold nanostructures. This enables the recording of high quality cardiac action potentials in combination with optoacoustic poration, providing thus attenuated intracellular recordings on various already commercial devices used by a significant part of the research and industrial communities.

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.

Intracellular Delivery and Sensing System Based on Electroplated Conductive Nanostraw Arrays

One-dimensional nanoneedle-like arrays have emerged as an attractive tool for penetrating the cell membrane to achieve intracellular applications including drug delivery, electrical recording, and biochemical detection. Hollow nanoneedles, also called nanostraws (NSs), combined with nanoelectroporation have been demonstrated as a powerful platform for intracellular drug delivery and extraction of intracellular contents. However, the fabrication technique of nanostraws still requires complicated and expensive atomic layer deposition and etching processes and fails to produce conductive nanostraws. Herein, we developed a commonly accessible and versatile electrodeposition approach to controllably fabricate conductive nanostraw arrays based on various types of metal or conductive polymer materials. Representatively, Pt nanostraws (Pt NSs) with 400 nm diameter were further integrated with a low-voltage nanoelectroporation system to achieve cell detection, intracellular drug delivery, and sensing of intracellular enzymes. Both theoretical simulations and experimental results revealed that the conductive nanostraws in direct contact with cells could induce high-efficiency cell electroporation at relatively low voltage (∼5 V). Efficient delivery of reagents into live cells with spatial control and repeated extraction of intracellular enzymes (e.g., caspase-3) for temporal monitoring from the same set of cells were demonstrated. This work not only pioneers a new avenue for universal production of conductive nanostraws on a large scale but also presents great potential for developing nanodevices to achieve a variety of biomedical applications including cell re-engineering, cell-based therapy, and signaling pathway monitoring.

Intracellular Photothermal Delivery for Suspension Cells Using Sharp Nanoscale Tips in Microwells

Efficient intracellular delivery of biomolecules into cells that grow in suspension is of great interest for biomedical research, such as for applications in cancer immunotherapy. Although tremendous effort has been expended, it remains challenging for existing transfer platforms to deliver materials efficiently into suspension cells. Here, we demonstrate a high-efficiency photothermal delivery approach for suspension cells using sharp nanoscale metal-coated tips positioned at the edge of microwells, which provide controllable membrane disruption for each cell in an array. Self-aligned microfabrication generates a uniform microwell array with three-dimensional nanoscale metallic sharp tip structures. Suspension cells self-position by gravity within each microwell in direct contact with eight sharp tips, where laser-induced cavitation bubbles generate transient pores in the cell membrane to facilitate intracellular delivery of extracellular cargo. A range of cargo sizes were tested on this platform using Ramos suspension B cells with an efficiency of >84% for Calcein green (0.6 kDa) and >45% for FITC-dextran (2000 kDa), with retained viability of >96% and a throughput of >100 000 cells delivered per minute. The bacterial enzyme β-lactamase (29 kDa) was delivered into Ramos B cells and retained its biological activity, whereas a green fluorescence protein expression plasmid was delivered into Ramos B cells with a transfection efficiency of >58%, and a viability of >89% achieved.

Single-cell micro- and nano-photonic technologies

Since the advent of optogenetics, the technology development has focused on new methods to optically interact with single nerve cells. This gave rise to the field of photonic neural interfaces, intended as the set of technologies that can modify light radiation in either a linear or non-linear fashion to control and/or monitor cellular functions. This set includes the use of plasmonic effects, up-conversion, electron transfer and integrated light steering, with some of them already implemented in vivo. This article will review available approaches in this framework, with a particular emphasis on methods operating at the single-unit level or having the potential to reach single-cell resolution.

Advanced nanostructures for cell membrane poration

Nanostructured devices are able to foster the technology for cell membrane poration. With the size smaller than a cell, nanostructures allow efficient poration on the cell membrane. Emerging nanostructures with various physical transduction have been demonstrated to accommodate effective intracellular delivery. Aside from improving poration and intracellular delivery performance, nanostructured devices also allow for the discovery of novel physiochemical phenomena and the biological response of the cell. This article provides a brief introduction to the principles of nanostructured devices for cell poration and outlines the intracellular delivery capability of the technology. In the future, we envision more exploration on new nanostructure designs and creative applications in biomedical fields.

Nanostraw membrane stamping for direct delivery of molecules into adhesive cells

Delivering ions and molecules into living cells has become an important challenge in medical and biological fields. Conventional molecular delivery, however, has several issues such as physical and chemical damage to biological cells. Here, we present a method of directly delivering molecules into adhesive cells with an Au-based nanostraw membrane stamp that can physically inject a target molecule into the cytoplasm through a nanostraw duct. We successfully delivered calcein target molecules into adhesive cells with high efficiency (85%) and viability (90%). Furthermore, we modeled the molecular flow through Au nanostraws and then demonstrated the control of calcein flow by changing the concentration and geometry of Au nanostraws. Our Au membrane stamping provides a new way of accessing the cytoplasm to modulate cellular functions via injected molecules.

On-Demand Intracellular Delivery of Single Particles in Single Cells by 3D Hollow Nanoelectrodes

Delivery of molecules into intracellular compartments is one of the fundamental requirements in molecular biology. However, the possibility of delivering a precise number of nano-objects with single-particle resolution is still an open challenge. Here we present an electrophoretic platform based on 3D hollow nanoelectrodes to enable delivery of single nanoparticles into single selected cells and monitoring of the single-particle delivery by surface-enhanced Raman scattering (SERS). The gold-coated hollow nanoelectrode capable of confinement and enhancement of electromagnetic fields upon laser illumination can distinguish the SERS signals of a single nanoparticle flowing through the nanoelectrode. Tight wrapping of cell membranes around the nanoelectrodes allows effective membrane electroporation such that single gold nanorods are delivered on demand into a living cell by electrophoresis. The capability of the 3D hollow nanoelectrodes to porate cells and reveal single emitters from the background in continuous flow is promising for the analysis of both intracellular delivery and sampling.

Selective intracellular delivery and intracellular recordings combined in MEA biosensors

Biological studies on in vitro cell cultures are of fundamental importance to investigate cell response to external stimuli, such as new drugs for the treatment of specific pathologies, or to study communication between electrogenic cells. Although three-dimensional (3D) nanostructures brought tremendous improvements on biosensors used for various biological in vitro studies, including drug delivery and electrical recording, there is still a lack of multifunctional capabilities that could help gain deeper insights in several bio-related research fields. In this work, the electrical recording of large cell ensembles and the intracellular delivery of few selected cells are combined on the same device by integrating microfluidic channels on the bottom of a multi-electrode array decorated with 3D hollow nanostructures. The novel platform allows the recording of intracellular-like action potentials from large ensembles of cardiomyocytes derived from human induced pluripotent stem cells (hiPSC) and from the HL-1 line, while different molecules are selectively delivered into single/few targeted cells. The proposed approach shows high potential for enabling new comprehensive studies that can relate drug effects to network level cell communication processes.

Plasmonic meta-electrodes allow intracellular recordings at network level on high-density CMOS-multi-electrode arrays

The ability to monitor electrogenic cells accurately plays a pivotal role in neuroscience, cardiology and cell biology. Despite pioneering research and long-lasting efforts, the existing methods for intracellular recording of action potentials on the large network scale suffer limitations that prevent their widespread use. Here, we introduce the concept of a meta-electrode, a planar porous electrode that mimics the optical and biological behaviour of three-dimensional plasmonic antennas but also preserves the ability to work as an electrode. Its synergistic combination with plasmonic optoacoustic poration allows commercial complementary metal-oxide semiconductor multi-electrode arrays to record intracellular action potentials in large cellular networks. We apply this approach to measure signals from human-induced pluripotent stem cell-derived cardiac cells, rodent primary cardiomyocytes and immortalized cell types and demonstrate the possibility of non-invasively testing a variety of relevant drugs. Due to its robustness and easiness of use, we expect the method will be rapidly adopted by the scientific community and by pharmaceutical companies.

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.

Using porous magnetic iron oxide nanomaterials as a facile photoporation nanoplatform for macromolecular delivery

The intracellular delivery of exogenous macromolecules such as functional proteins, antibodies, polysaccharides and nucleic acids into living cells for biomedical applications is of great interest. Even though great efforts have been devoted to this task, universal delivery systems that provide excellent intracellular delivery performance combined with easy cell recovery are urgently needed. Magnetic iron oxide nanoparticles show promising potential for various biomedical applications because of their advantages such as high biocompatibility and cost-effectiveness. Herein, a new facile platform for macromolecular delivery was developed based on the photothermal properties of porous magnetic iron oxide nanoparticles (P-MNPs). The near-infrared radiation (NIR) absorption behavior of P-MNPs remarkably facilitates the delivery of macromolecules into cells while maintaining high cell viability. Furthermore, the assistance of polycationic polyethylenimine improves the efficiency of DNA delivery. Most importantly, the cells could be easily recovered after macromolecular delivery by trypsinization, which is of great significance for further practical application of the delivery system. The facile and cost-effective platform proposed in this work provides a new avenue for the utilization of P-MNPs in macromolecular delivery.

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.

Nongenetic Optical Methods for Measuring and Modulating Neuronal Response

The ability to probe and modulate electrical signals sensitively at cellular length scales is a key challenge in the field of electrophysiology. Electrical signals play integral roles in regulating cellular behavior and in controlling biological function. From cardiac arrhythmias to neurodegenerative disorders, maladaptive phenotypes in electrophysiology can result in serious and potentially deadly medical conditions. Understanding how to monitor and to control these behaviors precisely and noninvasively represents an important step in developing next-generation therapeutic devices. As we develop a deeper understanding of neural network formation, electrophysiology has the potential to offer fundamental insights into the inner working of the brain. In this Perspective, we explore traditional methods for examining neural function, discuss recent genetic advances in electrophysiology, and then focus on the latest innovations in optical sensing and stimulation of action potentials in neurons. We emphasize nongenetic optical methods, as these provide high spatiotemporal resolution and can be achieved with minimal invasiveness.

Long-Range Capture and Delivery of Water-Dispersed Nano-objects by Microbubbles Generated on 3D Plasmonic Surfaces

The possibility of investigating small amounts of molecules, moieties, or nano-objects dispersed in solution constitutes a central step for various application areas in which high sensitivity is necessary. Here, we show that the rapid expansion of a water bubble can act as a fast-moving net for molecules or nano-objects, collecting the floating objects in the surrounding medium in a range up to 100 μm. Thanks to an engineered 3D patterning of the substrate, the collapse of the bubble could be guided toward a designed area of the surface with micrometric precision. Thus, a locally confined high density of particles is obtained, ready for evaluation by most optical/spectroscopic detection schemes. One of the main relevant strengths of the long-range capture and delivery method is the ability to increase, by a few orders of magnitude, the local density of particles with no changes in their physiological environment. The bubble is generated by an ultrafast IR laser pulse train focused on a resonant plasmonic antenna; due to the excitation process, the technique is trustworthy and applicable to biological samples. We have tested the reliabilities of the process by concentrating highly dispersed fluorescence molecules and fluorescent beads. Lastly, as an ultimate test, we have applied the bubble clustering method on nanosized exosome vesicles dispersed in water; due to the clustering effect, we were able to effectively perform Raman spectroscopy on specimens that were otherwise extremely difficult to measure.