3D nanochannel electroporation for high-throughput cell transfection with high uniformity and dosage control

Molecular interactions of the Omicron, Kappa, and Delta SARS-CoV-2 spike proteins with quantum dots of graphene oxide

CONTEXT

The Omicron, Kappa, and Delta variants are different strains of the SARS-CoV-2 virus. Graphene oxide quantum dots (GOQDs) represent a burgeoning class of oxygen-enriched, zero-dimensional materials characterized by their sub-20-nm dimensions. Exhibiting pronounced quantum confinement and edge effects, GOQDs manifest exceptional physical-chemical attributes. This study delves into the potential of graphene oxide quantum dots, elucidating their inherent properties pertinent to the surface structures of SARS-CoV-2, employing an integrated computational approach for the repositioning of inhibitory agents.

METHODS

Following rigorous adjustment tests, a spectrum of divergent bonding conformations emerged, with particular emphasis placed on identifying the conformation exhibiting optimal adjustment scores and interactions. The investigation employed molecular docking simulations integrating affinity energy evaluations, electrostatic potential clouds, molecular dynamics encompassing average square root calculations, and the computation of Gibbs-free energy. These values quantify the strength of interaction between GOQDs and SARS-CoV-2 spike protein variants. The receptor structures were optimized using the CHARM-GUI server employing force field AMBERFF14SB. The algorithm embedded in CHARMM offers an efficient interpolation scheme and automatic step size selection, enhancing the efficiency of the optimization process. The 3D structures of the ligands are constructed and optimized with density functional theory (DFT) method based on the most stable conformer of each binder. Autodock Vina Software (ADV) was utilized, where essential parameters were specified. Electrostatic potential maps (MEPs) provide a visual depiction of molecules' charge distributions and related properties. After this, molecular dynamics simulations employing the CHARM36 force field in Gromacs 2022.2 were conducted to investigate GOs' interactions with surface macromolecules of SARS-CoV-2 in an explicit aqueous environment. Furthermore, our investigation suggests that lower values indicate stronger binding. Notably, GO-E consistently showed the most negative values across interactions with different variants, suggesting a higher affinity compared to other GOQDs (GO-A to GO-D).

Advanced micro/nano-electroporation for gene therapy: recent advances and future outlook

Gene therapy is a promising disease treatment approach by editing target genes, and thus plays a fundamental role in precision medicine. To ensure gene therapy efficacy, the effective delivery of therapeutic genes into specific cells is a key challenge. Electroporation utilizes short electric pulses to physically break the cell membrane barrier, allowing gene transfer into the cells. It dodges the off-target risks associated with viral vectors, and also stands out from other physical-based gene delivery methods with its high-throughput and cargo-accelerating features. In recent years, with the help of advanced micro/nanotechnology, micro/nanostructure-integrated electroporation (micro/nano-electroporation) techniques and devices have significantly improved cell viability, transfection efficiency and dose controllability of the electroporation strategy, enhancing its application practicality especially in vivo. This technical advancement makes micro/nano-electroporation an effective and versatile tool for gene therapy. In this review, we first introduce the evolution of electroporation technique with a brief explanation of the perforation mechanism, and then provide an overview of the recent advancements and prospects of micro/nano-electroporation technology in the field of gene therapy. To comprehensively showcase the latest developments of micro/nano-electroporation technology in gene therapy, we focus on discussing micro/nano-electroporation devices and current applications at both in vitro and in vivo levels. Additionally, we outline the ongoing clinical studies of gene electrotransfer (GET), revealing the tremendous potential of electroporation-based gene delivery in disease treatment and healthcare. Lastly, the challenges and future directions in this field are discussed.

Genetic and phenotypic profiling of single living circulating tumor cells from patients with microfluidics

Accurate prediction of the efficacy of immunotherapy for cancer patients through the characterization of both genetic and phenotypic heterogeneity in individual patient cells holds great promise in informing targeted treatments, and ultimately in improving care pathways and clinical outcomes. Here, we describe the nanoplatform for interrogating living cell host-gene and (micro-)environment (NICHE) relationships, that integrates micro- and nanofluidics to enable highly efficient capture of circulating tumor cells (CTCs) from blood samples. The platform uses a unique nanopore-enhanced electrodelivery system that efficiently and rapidly integrates stable multichannel fluorescence probes into living CTCs for in situ quantification of target gene expression, while on-chip coculturing of CTCs with immune cells allows for the real-time correlative quantification of their phenotypic heterogeneities in response to immune checkpoint inhibitors (ICI). The NICHE microfluidic device provides a unique ability to perform both gene expression and phenotypic analysis on the same single cells in situ, allowing us to generate a predictive index for screening patients who could benefit from ICI. This index, which simultaneously integrates the heterogeneity of single cellular responses for both gene expression and phenotype, was validated by clinically tracing 80 non-small cell lung cancer patients, demonstrating significantly higher AUC (area under the curve) (0.906) than current clinical reference for immunotherapy prediction.

A Nano-Electroporation-DNA Tensioner Platform Enhances Intracellular Delivery and Mechanical Analysis Toward Rapid Drug Assessment

In vitro, drug assessment holds tremendous potential to success in novel drug development and precision medicine. Traditional techniques for drug assessment, however, face remarkable challenges to achieve high speed, as limited by incubation-based drug delivery (>several hours) and cell viability measurements (>1 d), which significantly compromise the efficacy in clinical trials. In this work, a nano-electroporation-DNA tensioner platform is reported that shortens the time of drug delivery to less than 3 s, and that of cellular mechanical force analysis to 30 min. The platform adopts a nanochannel structure to localize a safe electric field for cell perforation, while enhancing delivery speed by 103 times for intracellular delivery, as compared to molecular diffusion in coculture methods. The platform is further equipped with a DNA tensioner to detect cellular mechanical force for quantifying cell viability after drug treatment. Systematic head-to-head comparison, by analyzing FDA (food and drug administration)-approved drugs (paclitaxel, doxorubicin), demonstrated the platform with high speed, efficiency, and safety, showing a simple yet powerful tool for clinical drug screening and development.

Joule heating and electroosmotic flow in cellular micro/nano electroporation

Localized micro/nano-electroporation (MEP/NEP) shows tremendous potential in cell transfection with high cell viability, precise dose control, and good transfection efficacy. In MEP/NEP, micro or nanochannels are used to tailor the electric field distribution. Cells are positioned tightly by a micron or nanochannel, and the cargoes are delivered into the cell via the channel by electrophoresis (EP). Such confined geometries with micro and nanochannels are also widely used in sorting, isolation, and condensing of biomolecules and cells. Theoretical studies on the electrokinetic phenomena in these applications have been well established. However, for MEP/NEP applications, electrokinetic phenomena and their impact on the cell transfection efficiency and cell survival rate have not been studied comprehensively. In this work, we reveal the coupling between electric field, Joule heating, electroosmosis (EO), and EP in MEP/NEP at different channel sizes. A microfluidic biochip is used to investigate the electrokinetic phenomena in MEP/NEP on a single cell level. Bubble formation is observed at a threshold voltage due to Joule heating. The bubble is pushed to the cargo side due to EO and grows at the outlet of the nanochannel. As the voltage increases, the cargo transport efficiency decreases due to more intense EO, particularly for plasmid DNAs (3.5 kbp) with a low EP mobility. An 'electroporation zone' is defined for NEP/MEP systems with different channel sizes to avoid bubble formation and excessive EO velocity that may reduce the cargo delivery efficiency.

Optimizing mRNA transfection on a high-definition electroporation microelectrode array results in 98% efficiency and multiplexed gene delivery

Spatially resolved transfection, intracellular delivery of proteins and nucleic acids, has the potential to drastically speed up the discovery of biologically active cargos, for instance for the development of cell therapies or new genome engineering tools. We recently demonstrated the use of a high-density microelectrode array for the targeted electrotransfection of cells grown on its surface, a process called High-Definition Electroporation (HD-EP). We also developed a framework based on Design of Experiments to quickly establish optimized electroporation conditions across five different electrical pulse parameters. Here, we used this framework to optimize the transfection efficiency of primary fibroblasts with a mCherry-encoding mRNA, resulting in 98% of the cells expressing the desired fluorescent protein without any sign of cell death. That transfection yield is the highest reported so far for electroporation. Moreover, varying the pulse number was shown to modulate the fluorescence intensity of cells, indicating the dosage-controlled delivery of mRNA and protein expression. Finally, exploiting the single-electrode addressability of the microelectrode array, we demonstrated spatially resolved, high efficiency, sequential transfection of cells with three distinct mRNAs. Since the chip can be easily redesigned to feature a much large number of electrodes, we anticipate that this methodology will enable the development of dedicated screening platforms for analysis of mRNA variants at scale.

Nanochannel Electro-Injection as a Versatile Platform for Efficient RNA/DNA Programming on Dendritic Cells

The utilization of dendritic cell (DC) vaccines is a promising approach in cancer immunotherapy, and the modification of DCs for the expression of tumor-associated antigens is critical for successful cancer immunotherapy. A safe and efficient method for delivering DNA/RNA into DCs without inducing maturation is beneficial to achieve successful DC transformation for cell vaccine applications, yet remains challenging. This work presents a nanochannel electro-injection (NEI) system for the safe and efficient delivery of a variety of nucleic acid molecules into DCs. The device is based on track-etched nanochannel membrane as key components, where the nano-sized channels localize the electric field on the cell membrane, enabling lower voltage (<30 V) for cell electroporation. The pulse conditions of NEI are examined so that the transfection efficiency (>70%) and biosafety (viability >85%) on delivering fluorescent dyes, plasmid DNA, messenger RNA, and circular RNA (circRNA) into DC2.4 are optimized. Primary mouse bone marrow DC can also be transfected with circRNA with 68.3% efficiency, but without remarkably affecting cellular viability or inducing DC maturation. These results suggest that NEI can be a safe and efficient transfection platform for in vitro transformation of DCs and possesses a promising potential for developing DC vaccines against cancer.

Fluorinated Silane-Modified Filtroporation Devices Enable Gene Knockout in Human Hematopoietic Stem and Progenitor Cells

Intracellular delivery technologies that are cost-effective, non-cytotoxic, efficient, and cargo-agnostic are needed to enable the manufacturing of cell-based therapies as well as gene manipulation for research applications. Current technologies capable of delivering large cargoes, such as plasmids and CRISPR-Cas9 ribonucleoproteins (RNPs), are plagued with high costs and/or cytotoxicity and often require substantial specialized equipment and reagents, which may not be available in resource-limited settings. Here, we report an intracellular delivery technology that can be assembled from materials available in most research laboratories, thus democratizing access to intracellular delivery for researchers and clinicians in low-resource areas of the world. These filtroporation devices permeabilize cells by pulling them through the pores of a cell culture insert by the application of vacuum available in biosafety cabinets. In a format that costs less than $10 in materials per experiment, we demonstrate the delivery of fluorescently labeled dextran, expression plasmids, and RNPs for gene knockout to Jurkat cells and human CD34+ hematopoietic stem and progenitor cell populations with delivery efficiencies of up to 40% for RNP knockout and viabilities of >80%. We show that functionalizing the surfaces of the filters with fluorinated silane moieties further enhances the delivery efficiency. These devices are capable of processing 500,000 to 4 million cells per experiment, and when combined with a 3D-printed vacuum application chamber, this throughput can be straightforwardly increased 6-12-fold in parallel experiments.

Basic Principles of RNA Interference: Nucleic Acid Types and In Vitro Intracellular Delivery Methods

Since its discovery in 1989, RNA interference (RNAi) has become a widely used tool for the in vitro downregulation of specific gene expression in molecular biological research. This basically involves a complementary RNA that binds a target sequence to affect its transcription or translation process. Currently, various small RNAs, such as small interfering RNA (siRNA), micro RNA (miRNA), small hairpin RNA (shRNA), and PIWI interacting RNA (piRNA), are available for application on in vitro cell culture, to regulate the cells' gene expression by mimicking the endogenous RNAi-machinery. In addition, several biochemical, physical, and viral methods have been established to deliver these RNAs into the cell or nucleus. Since each RNA and each delivery method entail different off-target effects, limitations, and compatibilities, it is crucial to understand their basic mode of action. This review is intended to provide an overview of different nucleic acids and delivery methods for planning, interpreting, and troubleshooting of RNAi experiments.

Recent Advancements in Electroporation Technologies: From Bench to Clinic

Over the past decade, the increased adoption of electroporation-based technologies has led to an expansion of clinical research initiatives. Electroporation has been utilized in molecular biology for mammalian and bacterial transfection; for food sanitation; and in therapeutic settings to increase drug uptake, for gene therapy, and to eliminate cancerous tissues. We begin this article by discussing the biophysics required for understanding the concepts behind the cell permeation phenomenon that is electroporation. We then review nano- and microscale single-cell electroporation technologies before scaling up to emerging in vivo applications.

Cell membrane damage and cargo delivery in nano-electroporation

Nanochannel electroporation (NEP) is a new technology for cell transfection, which provides superior gene delivery and cell viability to conventional bulk electroporation (BEP). In NEP, the cells laid on a porous substrate are subjected to an asymmetric electric field which induces asymmetric membrane poration. The cell membrane near the channel outlet ('transfection membrane') is porated intensely, allowing direct delivery of genetic materials, while the rest of the cell membrane ('non-transfection membrane') remains much less perturbed for low cellular damage. In this work, the transfection window of NEP for the delivery of different sized molecules is systematically investigated. The results show that small molecules (∼0.6 kDa) can be delivered into cells at a relatively lower voltage without significantly impacting the non-transfection membrane. To deliver larger molecules (∼6 kDa), a higher working voltage is required at the cost of cell viability due to more severe damage of the non-transfection membrane. Through numerical analysis of both transient transmembrane potential (t-TMP) and dynamic transmembrane potential (d-TMP), here we show that the membrane damage on both transfection and non-transfection sides of the cell membrane can be predicted. The agreement between experimental results and numerical analysis provides a comprehensive understanding of cell membrane damage and cargo delivery in NEP.

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.

Exosomes as smart drug delivery vehicles for cancer immunotherapy

Exosomes (Exos) as drug delivery vehicles have been widely used for cancer immunotherapy owing to their good biocompatibility, low toxicity, and low immunogenicity. Some Exos-based cancer immunotherapy strategies such as tuning of immunosuppressive tumor microenvironment, immune checkpoint blockades, and cancer vaccines have also been investigated in recent years, which all showed excellent therapeutic effects for malignant tumor. Furthermore, some Exos-based drug delivery systems (DDSs) for cancer immunotherapy have also undergone clinic trails, indicating that Exos are a promising drug delivery carrier. In this review, in order to promote the development of Exos-based DDSs in cancer immunotherapy, the biogenesis and composition of Exos, and Exos as drug delivery vehicles for cancer immunotherapy are summarized. Meanwhile, their clinical translation and challenges are also discussed. We hope this review will provide a good guidance for Exos as drug delivery vehicles for cancer immunotherapy.

Sensitive Interrogation of Enhancer Activity in Living Cells on a Nanoelectroporation-Probing Platform

Enhancers involved in the upregulation of multiple oncogenes play a fundamental role in tumorigenesis and immortalization. Exploring the activity of enhancers in living cells has emerged as a critical path to a deep understanding of cancer properties, further providing important clues to targeted therapy. However, identifying enhancer activity in living cells is challenging due to the double biological barriers of a cell cytoplasmic membrane and a nuclear membrane, limiting the sensitivity and responsiveness of conventional probing methods. In this work, we developed a nanoelectroporation-probing (NP) platform, which enables intranuclear probe delivery for sensitive interrogation of enhancer activity in living cells. The nanoelectroporation biochip achieved highly focused perforation of the cell cytoplasmic membrane and brought about additional driving force to expedite the delivery of probes into the nucleus. The probes targeting enhancer activity (named "PH probe") are programmed with a cyclic amplification strategy and enable an increase in the fluorescence signals over 100-fold within 1 h. The platform was leveraged to detect the activity of CCAT1 enhancers (CCAT1, colon cancer-associated transcript-1, a long noncoding RNA that functions in tumor invasion and metastasis) in cell samples from clinical lung cancer patients, as well as reveal the heterogeneity of enhancers among different patients. The observations may extend the linkages between enhancers and cancer cells while validating the robustness and reliability of the platform for the assay of enhancer activity. This platform will be a promising toolbox with wide applicable potential for the intranuclear study of living cells.

Gene Electrotransfer into Mammalian Cells Using Commercial Cell Culture Inserts with Porous Substrate

Gene electrotransfer is one of the main non-viral methods for intracellular delivery of plasmid DNA, wherein pulsed electric fields are used to transiently permeabilize the cell membrane, allowing enhanced transmembrane transport. By localizing the electric field over small portions of the cell membrane using nanostructured substrates, it is possible to increase considerably the gene electrotransfer efficiency while preserving cell viability. In this study, we expand the frontier of localized electroporation by designing an electrotransfer approach based on commercially available cell culture inserts with polyethylene-terephthalate (PET) porous substrate. We first use multiscale numerical modeling to determine the pulse parameters, substrate pore size, and other factors that are expected to result in successful gene electrotransfer. Based on the numerical results, we design a simple device combining an insert with substrate containing pores with 0.4 µm or 1.0 µm diameter, a multiwell plate, and a pair of wire electrodes. We test the device in three mammalian cell lines and obtain transfection efficiencies similar to those achieved with conventional bulk electroporation, but at better cell viability and with low-voltage pulses that do not require the use of expensive electroporators. Our combined theoretical and experimental analysis calls for further systematic studies that will investigate the influence of substrate pore size and porosity on gene electrotransfer efficiency and cell viability.

Recent Advances in Microscale Electroporation

Electroporation (EP) is a commonly used strategy to increase cell permeability for intracellular cargo delivery or irreversible cell membrane disruption using electric fields. In recent years, EP performance has been improved by shrinking electrodes and device structures to the microscale. Integration with microfluidics has led to the design of devices performing static EP, where cells are fixed in a defined region, or continuous EP, where cells constantly pass through the device. Each device type performs superior to conventional, macroscale EP devices while providing additional advantages in precision manipulation (static EP) and increased throughput (continuous EP). Microscale EP is gentle on cells and has enabled more sensitive assaying of cells with novel applications. In this Review, we present the physical principles of microscale EP devices and examine design trends in recent years. In addition, we discuss the use of reversible and irreversible EP in the development of therapeutics and analysis of intracellular contents, among other noteworthy applications. This Review aims to inform and encourage scientists and engineers to expand the use of efficient and versatile microscale EP technologies.

Recent advances in microfluidic-based electroporation techniques for cell membranes

Electroporation is a fundamental technique for applications in biotechnology. To date, the ongoing research on cell membrane electroporation has explored its mechanism, principles and potential applications. Therefore, in this review, we first discuss the primary electroporation mechanism to help establish a clear framework. Within the context of its principles, several critical terms are highlighted to present a better understanding of the theory of aqueous pores. Different degrees of electroporation can be used in different applications. Thus, we discuss the electric factors (shock strength, shock duration, and shock frequency) responsible for the degree of electroporation. In addition, finding an effective electroporation detection method is of great significance to optimize electroporation experiments. Accordingly, we summarize several primary electroporation detection methods in the following sections. Finally, given the development of micro- and nano-technology has greatly promoted the innovation of microfluidic-based electroporation devices, we also present the recent advances in microfluidic-based electroporation devices. Also, the challenges and outlook of the electroporation technique for cell membrane electroporation are presented.

Microtrap array on a chip for localized electroporation and electro-gene transfection

We developed a localized single-cell electroporation chip to deliver exogenous biomolecules with high efficiency while maintaining high cell viability. In our microfluidic device, the cells are trapped in a microtrap array by flow, after which target molecules are supplied to the device and electrotransferred to the cells under electric pulses. The system provides the ability to monitor the electrotransfer of exogenous biomolecules in real time. We reveal through numerical simulations that localized electroporation is the mechanism of permeabilization in the microtrap array electroporation device. We demonstrate the simplicity and accuracy of this microtrap technology for electroporation by delivery of both small molecules using propidium iodide and large molecules using plasmid DNA for gene expression, illustrating the potential of this minimally invasive method to be widely used for precise intracellular delivery purposes (from bioprocess engineering to therapeutic applications).

In Situ Electroporation on PERFECT Filter for High-Efficiency and High-Viability Tumor Cell Labeling

Labeling-assisted visualization is a powerful strategy to track circulating tumor cells (CTCs) for mechanism study (e.g., tumor metastasis). Due to the rarity of CTCs in the whole blood, efficient simultaneous enrichment and labeling of CTCs are needed. Hereby, novel in situ electroporation on a previously-developed micropore-arrayed filter (PERFECT filter) is proposed. Benefiting from the ultra-small-thickness and high-porosity of the filter plus high precision pore diameter, target rare tumor cells were enriched with less damage and uniform size distribution, contributing to enhanced molecular delivery efficiency and cell viability in the downstream electroporation. Various biomolecules (e.g., small molecule dyes, plasmids, and functional proteins) were used to verify this in situ electroporation system. High labeling efficiency (74.08 ± 2.94%) and high viability (81.15 ± 3.04%, verified via live/dead staining) were achieved by optimizing the parameters of electric field strength and pulse number, ensuring the labeled tumor cells can be used for further culture and down-stream analysis. In addition, high specificity (99.03 ± 1.67%) probing of tumor cells was further achieved by introducing fluorescent dye-conjugated antibodies into target cells. The whole procedure, including cell separation and electroporation, can be finished quickly (<10 min). The proposed in situ electroporation on the PERFECT filter system has great potential to track CTCs for tumor metastasis studies.

An equivalent circuit model for localized electroporation on porous substrates

In vitro intracellular delivery is a fundamental challenge with no widely adopted methods capable of both delivering to millions of cells and controlling that delivery to a high degree of accuracy. One promising method is porous substrate electroporation (PSEP), where cells are cultured on porous substrates and electric fields are used to permeabilize discrete portions of the cell membrane for delivery. A major obstacle to the widespread use of PSEP is a poor understanding of the various impedances that constitute the system, including the impedances of the porous substrate and the cell monolayer, and how these impedances are influenced by experimental parameters. In response, we used impedance measurements to develop an equivalent circuit model that closely mimics the behavior of each of the main components of the PSEP system. This circuit model reveals for the first time the distribution of voltage across the electrode-electrolyte interface impedances, the channels of the porous substrate, the cell monolayer, and the transmembrane potential during PSEP. We applied sample waveforms through our model to understand how waveforms can be improved for future studies. Our model was validated from intracellular delivery of protein using PSEP.

In Situ Deployment of Engineered Extracellular Vesicles into the Tumor Niche via Myeloid-Derived Suppressor Cells

Extracellular vesicles (EVs) have emerged as a promising carrier system for the delivery of therapeutic payloads in multiple disease models, including cancer. However, effective targeting of EVs to cancerous tissue remains a challenge. Here, it is shown that nonviral transfection of myeloid-derived suppressor cells (MDSCs) can be leveraged to drive targeted release of engineered EVs that can modulate transfer and overexpression of therapeutic anticancer genes in tumor cells and tissue. MDSCs are immature immune cells that exhibit enhanced tropism toward tumor tissue and play a role in modulating tumor progression. Current MDSC research has been mostly focused on mitigating immunosuppression in the tumor niche; however, the tumor homing abilities of these cells present untapped potential to deliver EV therapeutics directly to cancerous tissue. In vivo and ex vivo studies with murine models of breast cancer show that nonviral transfection of MDSCs does not hinder their ability to home to cancerous tissue. Moreover, transfected MDSCs can release engineered EVs and mediate antitumoral responses via paracrine signaling, including decreased invasion/metastatic activity and increased apoptosis/necrosis. Altogether, these findings indicate that MDSCs can be a powerful tool for the deployment of EV-based therapeutics to tumor tissue.

High-Throughput and Dosage-Controlled Intracellular Delivery of Large Cargos by an Acoustic-Electric Micro-Vortices Platform

A high-throughput non-viral intracellular delivery platform is introduced for the transfection of large cargos with dosage-control. This platform, termed Acoustic-Electric Shear Orbiting Poration (AESOP), optimizes the delivery of intended cargo sizes with poration of the cell membranes via mechanical shear followed by the modulated expansion of these nanopores via electric field. Furthermore, AESOP utilizes acoustic microstreaming vortices wherein up to millions of cells are trapped and mixed uniformly with exogenous cargos, enabling the delivery of cargos into cells with targeted dosages. Intracellular delivery of a wide range of molecule sizes (<1 kDa to 2 MDa) with high efficiency (>90%), cell viability (>80%), and uniform dosages (<60% coefficient of variation (CV)) simultaneously into 1 million cells min-1 per single chip is demonstrated. AESOP is successfully applied to two gene editing applications that require the delivery of large plasmids: i) enhanced green fluorescent protein (eGFP) plasmid (6.1 kbp) transfection, and ii) clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-mediated gene knockout using a 9.3 kbp plasmid DNA encoding Cas9 protein and single guide RNA (sgRNA). Compared to alternative platforms, this platform offers dosage-controlled intracellular delivery of large plasmids simultaneously to large populations of cells while maintaining cell viability at comparable delivery efficiencies.

Micromotor-based localized electroporation and gene transfection of mammalian cells

Herein, we studied localized electroporation and gene transfection of mammalian cells using a metallodielectric hybrid micromotor that is magnetically and electrically powered. Much like nanochannel-based, local electroporation of single cells, the presented micromotor was expected to increase reversible electroporation yield, relative to standard electroporation, as only a small portion of the cell's membrane (in contact with the micromotor) is affected. In contrast to methods in which the entire membrane of all cells within the sample are electroporated, the presented micromotor can perform, via magnetic steering, localized, spatially precise electroporation of the target cells that it traps and transports. In order to minimize nonselective electrical lysis of all cells within the chamber, resulting from extended exposure to an electrical field, magnetic propulsion was used to approach the immediate vicinity of the targeted cell, after which short-duration, electric-driven propulsion was activated to enable contact with the cell, followed by electroporation. In addition to local injection of fluorescent dye molecules, we demonstrated that the micromotor can enhance the introduction of plasmids into the suspension cells because of the dielectrophoretic accumulation of the plasmids in between the Janus particle and the attached cell prior to the electroporation step. Here, we chose a different strategy involving the simultaneous operation of many micromotors that are self-propelling, without external steering, and pair with cells in an autonomic manner. The locally electroporated suspension cells that are considered to be very difficult to transfect were shown to express the transfected gene, which is of significant importance for molecular biology research.

Microfluidic and Nanofluidic Intracellular Delivery

Innate cell function can be artificially engineered and reprogrammed by introducing biomolecules, such as DNAs, RNAs, plasmid DNAs, proteins, or nanomaterials, into the cytosol or nucleus. This process of delivering exogenous cargos into living cells is referred to as intracellular delivery. For instance, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing begins with internalizing Cas9 protein and guide RNA into cells, and chimeric antigen receptor-T (CAR-T) cells are prepared by delivering CAR genes into T lymphocytes for cancer immunotherapies. To deliver external biomolecules into cells, tools, including viral vectors, and electroporation have been traditionally used; however, they are suboptimal for achieving high levels of intracellular delivery while preserving cell viability, phenotype, and function. Notably, as emerging solutions, microfluidic and nanofluidic approaches have shown remarkable potential for addressing this open challenge. This review provides an overview of recent advances in microfluidic and nanofluidic intracellular delivery strategies and discusses new opportunities and challenges for clinical applications. Furthermore, key considerations for future efforts to develop microfluidics- and nanofluidics-enabled next-generation intracellular delivery platforms are outlined.

Single Living Cell Analysis Nanoplatform for High-Throughput Interrogation of Gene Mutation and Cellular Behavior

The genetic heterogeneities in cancer cells pose challenges to achieving precise drug treatment in a widely applicable manner. Most single-cell gene analysis methods rely on cell lysis for gene extraction and identification, showing limited capacity to provide the correlation of genetic properties and real-time cellular behaviors. Here, we report a single living cell analysis nanoplatform that enables interrogating gene properties and drug resistance in millions of single cells. We designed a Domino-probe to identify intracellular target RNAs while releasing 10-fold amplified fluorescence signals. An on-chip addressable microwell-nanopore array was developed for enhanced electro-delivery of the Domino-probe and in situ observation of cell behaviors. The proof-of-concept of the system was validated in primary lung cancer cell samples, revealing the positive-correlation of the ratio of EGFR mutant cells with their drug susceptibilities. This platform provides a high-throughput yet precise tool for exploring the relationship between intracellular genes and cell behaviors at the single-cell level.

Microfluidic Based Physical Approaches towards Single-Cell Intracellular Delivery and Analysis

The ability to deliver foreign molecules into a single living cell with high transfection efficiency and high cell viability is of great interest in cell biology for applications in therapeutic development, diagnostics, and drug delivery towards personalized medicine. Various physical delivery methods have long demonstrated the ability to deliver cargo molecules directly to the cytoplasm or nucleus and the mechanisms underlying most of the approaches have been extensively investigated. However, most of these techniques are bulk approaches that are cell-specific and have low throughput delivery. In comparison to bulk measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. To elucidate distinct responses during cell genetic modification, methods to achieve transfection at the single-cell level are of great interest. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. This review article aims to cover various microfluidic-based physical methods for single-cell intracellular delivery such as electroporation, mechanoporation, microinjection, sonoporation, optoporation, magnetoporation, and thermoporation and their analysis. The mechanisms of various physical methods, their applications, limitations, and prospects are also elaborated.

Materials for Improving Immune Cell Transfection

Chimeric antigen receptor T cell (CAR-T) therapy holds great promise for preventing and treating deadly diseases such as cancer. However, it remains challenging to transfect and engineer primary immune cells for clinical cell manufacturing. Conventional tools using viral vectors and bulk electroporation suffer from low efficiency while posing risks like viral transgene integration and excessive biological perturbations. Emerging techniques using microfluidics, nanoparticles, and high-aspect-ratio nanostructures can overcome these challenges, and on top of that, provide universal and high-throughput cargo delivery. Herein, the strengths and limitations of traditional and emerging materials for immune cell transfection, and commercial development of these tools, are discussed. To enhance the characterization of transfection techniques and uptake by the clinical community, a list of in vitro and in vivo assays to perform, along with relevant protocols, is recommended. The overall aim, herein, is to motivate the development of novel materials to meet rising demand in transfection for clinical CAR-T cell manufacturing.

A Comprehensive Review on Intracellular Delivery

Intracellular delivery is considered an indispensable process for various studies, ranging from medical applications (cell-based therapy) to fundamental (genome-editing) and industrial (biomanufacture) approaches. Conventional macroscale delivery systems critically suffer from such issues as low cell viability, cytotoxicity, and inconsistent material delivery, which have opened up an interest in the development of more efficient intracellular delivery systems. In line with the advances in microfluidics and nanotechnology, intracellular delivery based on micro- and nanoengineered platforms has progressed rapidly and held great promises owing to their unique features. These approaches have been advanced to introduce a smorgasbord of diverse cargoes into various cell types with the maximum efficiency and the highest precision. This review differentiates macro-, micro-, and nanoengineered approaches for intracellular delivery. The macroengineered delivery platforms are first summarized and then each method is categorized based on whether it employs a carrier- or membrane-disruption-mediated mechanism to load cargoes inside the cells. Second, particular emphasis is placed on the micro- and nanoengineered advances in the delivery of biomolecules inside the cells. Furthermore, the applications and challenges of the established and emerging delivery approaches are summarized. The topic is concluded by evaluating the future perspective of intracellular delivery toward the micro- and nanoengineered approaches.

High Throughput and Highly Controllable Methods for In Vitro Intracellular Delivery

In vitro and ex vivo intracellular delivery methods hold the key for releasing the full potential of tissue engineering, drug development, and many other applications. In recent years, there has been significant progress in the design and implementation of intracellular delivery systems capable of delivery at the same scale as viral transfection and bulk electroporation but offering fewer adverse outcomes. This review strives to examine a variety of methods for in vitro and ex vivo intracellular delivery such as flow-through microfluidics, engineered substrates, and automated probe-based systems from the perspective of throughput and control. Special attention is paid to a particularly promising method of electroporation using micro/nanochannel based porous substrates, which expose small patches of cell membrane to permeabilizing electric field. Porous substrate electroporation parameters discussed include system design, cells and cargos used, transfection efficiency and cell viability, and the electric field and its effects on molecular transport. The review concludes with discussion of potential new innovations which can arise from specific aspects of porous substrate-based electroporation platforms and high throughput, high control methods in general.

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.

Nanochannel-Based Poration Drives Benign and Effective Nonviral Gene Delivery to Peripheral Nerve Tissue

While gene and cell therapies have emerged as promising treatment strategies for various neurological conditions, heavy reliance on viral vectors can hamper widespread clinical implementation. Here, the use of tissue nanotransfection as a platform nanotechnology to drive nonviral gene delivery to nerve tissue via nanochannels, in an effective, controlled, and benign manner is explored. TNT facilitates plasmid DNA delivery to the sciatic nerve of mice in a voltage-dependent manner. Compared to standard bulk electroporation (BEP), impairment in toe-spread and pinprick response is not caused by TNT, and has limited to no impact on electrophysiological parameters. BEP, however, induces significant nerve damage and increases macrophage immunoreactivity. TNT is subsequently used to deliver vasculogenic cell therapies to crushed nerves via delivery of reprogramming factor genes Etv2, Foxc2, and Fli1 (EFF). The results indicate the TNT-based delivery of EFF in a sciatic nerve crush model leads to increased vascularity, reduced macrophage infiltration, and improved recovery in electrophysiological parameters compared to crushed nerves that are TNT-treated with sham/empty plasmids. Altogether, the results indicate that TNT can be a powerful platform nanotechnology for localized nonviral gene delivery to nerve tissue, in vivo, and the deployment of reprogramming-based cell therapies for nerve repair/regeneration.

3D Nanochannel Electroporation for Macromolecular Nucleotide Delivery

Delivery of macromolecular nucleotides into the living cells holds a great promise for the development of new therapeutics. However, its abilities for adoptive immunotherapy, cell reprogramming, and primary cell transfection have been long-term hindered by the lack of a system that can locally deliver engineered therapeutic nucleotides (e.g., plasmids, siRNAs, miRNAs) without causing any side effects. In this chapter, the performance of a novel 3D nanoelectroporation system (3D NEP) is highlighted in three scenarios-adoptive immunotherapy, cell reprogramming, and adult mouse primary cardiomyocyte transfection. Detailed protocols were given to introduce the 3D NEP system assembly, as well as their applications in (1) natural killer (NK) cells transfection by delivery of chimeric antigen receptor (CAR) plasmids; (2) mouse embryonic fibroblasts transfection with OSKM factors; and (3) miR-29b molecular beacon (BMs) delivery into primary cardiomyocytes for interrogating the side effect of miR-29b-assisted treatment.

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.

Early Intervention in Ischemic Tissue with Oxygen Nanocarriers Enables Successful Implementation of Restorative Cell Therapies

Background

Tissue ischemia contributes to necrosis and infection. While angiogenic cell therapies have emerged as a promising strategy against ischemia, current approaches to cell therapies face multiple hurdles. Recent advances in nuclear reprogramming could potentially overcome some of these limitations. However, under severely ischemic conditions necrosis could outpace reprogramming-based repair. As such, adjunctive measures are required to maintain a minimum level of tissue viability/activity for optimal response to restorative interventions.

Methods

Here we explored the combined use of polymerized hemoglobin (PolyHb)-based oxygen nanocarriers with Tissue Nano-Transfection (TNT)-driven restoration to develop tissue preservation/repair strategies that could potentially be used as a first line of care. Random-pattern cutaneous flaps were created in a mouse model of ischemic injury. PolyHbs with high and low oxygen affinity were synthesized and injected into the tissue flap at various timepoints of ischemic injury. The degree of tissue preservation was evaluated in terms of perfusion, oxygenation, and resulting necrosis. TNT was then used to deploy reprogramming-based vasculogenic cell therapies to the flaps via nanochannels. Reprogramming/repair outcomes were evaluated in terms of vascularity and necrosis.

Results

Flaps treated with PolyHbs exhibited a gradual decrease in necrosis as a function of time-to-intervention, with low oxygen affinity PolyHb showing the best outcomes. TNT-based intervention of the flap in combination with PolyHb successfully curtailed advanced necrosis compared to flaps treated with only PolyHb or TNT alone.

Conclusions

These results indicate that PolyHb and TNT technologies could potentially be synergistically deployed and used as early intervention measures to combat severe tissue ischemia.

Ultrathin glass fiber microprobe for electroporation of arbitrary selected cell groups

A new type of ultrathin fiber microprobe for selective electroporation is reported. The microprobe is 10 cm long and has a diameter of 350 µm. This microprobe is a low cost tool, which allows electroporation of an arbitrary selected single cell or groups of cells among population with use of a standard microscope and cell culture plates. The microprobe in its basic form contains two metal microelectrodes made of a silver-copper alloy, running along the fiber, each with a diameter of 23 µm. The probe was tested in vitro on a population of normal and cancer cells. Successful targeted electroporation was observed by means of accumulation of trypan blue (TB) dye marker in the cell. The electroporation phenomenon was also verified with propidium iodide and AnnexinV in fluorescent microscopy.

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.

Massively-Parallelized, Deterministic Mechanoporation for Intracellular Delivery

Microfluidic intracellular delivery approaches based on plasma membrane poration have shown promise for addressing the limitations of conventional cellular engineering techniques in a wide range of applications in biology and medicine. However, the inherent stochasticity of the poration process in many of these approaches often results in a trade-off between delivery efficiency and cellular viability, thus potentially limiting their utility. Herein, we present a novel microfluidic device concept that mitigates this trade-off by providing opportunity for deterministic mechanoporation (DMP) of cells en masse. This is achieved by the impingement of each cell upon a single needle-like penetrator during aspiration-based capture, followed by diffusive influx of exogenous cargo through the resulting membrane pore, once the cells are released by reversal of flow. Massive parallelization enables high throughput operation, while single-site poration allows for delivery of small and large-molecule cargos in difficult-to-transfect cells with efficiencies and viabilities that exceed both conventional and emerging transfection techniques. As such, DMP shows promise for advancing cellular engineering practice in general and engineered cell product manufacturing in particular.

Nanoelectroporation and Collection of Genetically Modified Exosomes in Primary Cultures of Dendritic Cells

Dendritic cells (DCs) are cells of the immune system that behave as antigen presenters and assist in T cell activation. DCs have recently been used in cell-based immunotherapies for the treatment of different diseases due to the lack of adverse nonspecific immune responses, typically elicited by other approaches. Genetically modified DCs, for example, have been used to stimulate CD4/CD8 antigen presenting immune responses. However, genetic manipulation of primary DCs remains a challenge. Here we describe a protocol for nonviral, benign transfection of primary DCs using nanochannel-based electroporation, and the subsequent collection of genetically modified exosomes for downstream applications.

On-chip multiplexed single-cell patterning and controllable intracellular delivery

Conventional electroporation approaches show limitations in the delivery of macromolecules in vitro and in vivo. These limitations include low efficiency, noticeable cell damage and nonuniform delivery of cells. Here, we present a simple 3D electroporation platform that enables massively parallel single-cell manipulation and the intracellular delivery of macromolecules and small molecules. A pyramid pit micropore array chip was fabricated based on a silicon wet-etching method. A controllable vacuum system was adopted to trap a single cell on each micropore. Using this chip, safe single-cell electroporation was performed at low voltage. Cargoes of various sizes ranging from oligonucleotides (molecular beacons, 22 bp) to plasmid DNA (CRISPR-Cas9 expression vectors, >9 kb) were delivered into targeted cells with a significantly higher transfection efficiency than that of multiple benchmark methods (e.g., commercial electroporation devices and Lipofectamine). The delivered dose of the chemotherapeutic drug could be controlled by adjusting the applied voltage. By using CRISPR-Cas9 transfection with this system, the p62 gene and CXCR7 gene were knocked out in tumor cells, which effectively inhibited their cellular activity. Overall, this vacuum-assisted micropore array platform provides a simple, efficient, high-throughput intracellular delivery method that may facilitate on-chip cell manipulation, intracellular investigation and cancer therapy.

Review of the Application of Nanovesicles and the Human Interstitial Fluid in Gastrointestinal Premalignant Lesion Detection, Diagnosis, Prognosis and Therapy

Premalignant lesions arise from cells that abnormally proliferate and have a tendency to become cancerous. Developing methods to specifically target and remove these premalignant lesions is imperative to the prevention of malignant progression into gastrointestinal (GI) tumors. However, accurate detection and diagnosis of GI precancerous lesions is challenging, as these lesions show little or no structural change. Thus, this prevents early intervention and reduces the success rate of therapy. In this review, we performed a systematic analysis of the technological advancements in the combined application of nanovesicles (NVs) and the human interstitial fluid (HIF) to specifically target GI premalignant lesions. NVs, which include quantum dots (QDs), are small membranous vehicles of a nanometer diameter that are widely used as drug delivery vectors, therapeutic effectors and diagnostic sensors. HIF is the fluid that is present in human interstitial tissues (HITs) in which signaling molecules and agents travel and can be found throughout the body. HIF is exploited by tumor cells for their invasion, migration and spread. Because the HITs span the entire submucosa of the gastrointestinal tract, they have been increasingly targeted in GI tumor therapy. The challenges involved in the combined application of NVs and HIF in the detection, diagnosis, prognosis and therapy of GI premalignant lesions are also discussed.

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.

Nanostructured Materials for Intracellular Cargo Delivery

Intracellular cargo delivery is an essential step in many biomedical applications including gene editing and biologics therapy. Examples of cargo include nucleic acids (RNA and DNA), proteins, small biomolecules, and drugs, which can vary substantially in terms of their sizes, charges, solubility, and stability. Viruses have been used traditionally to deliver nucleic acids into cells, but the method suffers from limitations such as small cargo size, safety concerns, and viral genome integration into host cells, all of which complicate therapeutic applications. Commercially available techniques using biochemicals and bulk electroporation are, in general, poorly compatible with primary cells such as human induced pluripotent stem cells and immune cells, which are increasingly important candidates for adoptive cell therapy. Nanostructures, with dimensions ranging from tens of nanometers to a few micrometers, may play a critical role in overcoming cellular manipulation and delivery challenges and provide a powerful alternative to conventional techniques. A critical feature that differentiates nanostructures from viral, biochemical, and bulk electroporation techniques is that they interface with cells at a scale measuring ten to hundreds of nanometers in size. This highly local interaction enables application of stronger and more direct stimuli such as mechanical force, heat, or electric fields than would be possible in a bulk treatment. Compared to popular viral, biochemical, and bulk electroporation methods, nanostructures were found to minimally perturb cells with cells remaining in good health during postdelivery culture. These advantages have enabled nanostructures such as nanowires and nanotubes to successfully interface with a wide variety of cells, including primary immune cells and cardiomyocytes, for in vitro and in vivo applications. This Account is focused on using nanostructures for cargo delivery into biological cells. In this Account, we will first outline the historical developments using nanostructures for interfacing with cells. We will highlight how mechanistic understanding of nano-bio interactions has evolved over the last decade and how this improved knowledge has motivated coupling of electric and magnetic fields to nanostructures to improve delivery outcomes. There will also be an in-depth discussion on the merits of nanostructures in comparison to conventional methods using viruses, biochemicals, and bulk electroporation. Finally, motivated by our observations on the lack of consistency in reporting key metrics such as efficiency in literature, we suggest a set of metrics for documenting experimental results with the aim to promote standardization in reporting and ease in comparing. We suggest the use of more sophisticated tools such as RNA transcriptomics for thorough assessment of cell perturbation attributed to intracellular delivery. We hope that this Account can effectively capture the progress of nanostructure-mediated cargo delivery and encourage new innovations.

Soft Electroporation Through 3D Hollow Nanoelectrodes

Generally, electroporation of in vitro cells is performed under very high electric fields to overcome the physical barrier of plasma membrane. Since traditional electroporation techniques make use of very high voltages, which is critical to cell viability, this study presents a microfluidic platform able to perform cell membrane electroporation with the application of low voltages (1.5-2 V). The platform is manufactured based on the milling by mean of focused ionic beam, which offers an established approach to fabricate ordered arrays of 3D gold hollow nanoelectrodes protruding from an insulating substrate. The novelty of this fabrication relies on the fact that the nanoelectrodes used for electroporation are simultaneously metallic, hollow and communicate through its nanochannels with an isolated microfluidic chamber beneath the device. Adherent cultured cells on the nanoelectrodes can be electroporated in this platform, and molecules can be selectively delivered only inside the porated cells.

3D Nanochannel Array for High-Throughput Cell Manipulation and Electroporation

Electroporation has been one of the most commonly used physical methods for gene/drug delivery. Compared to other nonviral counterparts, electroporation enables optimization of delivery efficiency by tuning the electric field applied on cells. Commercial electroporation, however, results in stochastic transfection and significant cellular damage mostly due to its "bulk" environment. In this chapter, we introduce nanoelectroporation (NEP) which has demonstrated living cell transfection in a highly controllable manner. In NEP, the electric field can be precisely focused on a single cell positioned on nanochannels. Safe single-cell electroporation as well as "electrophoretic" molecular delivery can be achieved on the same device. This system achieves significantly higher transfection efficiency and cellular viability than commercial systems. This device is unique in that it can efficiently deliver genetic molecules (e.g., DNAs, RNAs) that exceed 10 kbp in size. The NEP device based on a 3D nanochannel array prototype was fabricated using cleanroom techniques. For achieving precise cell to nanochannel pairing, three on-chip high-throughput manipulation technologies were developed, that is, magnetic tweezers (MT), dielectrophoresis (DEP), and thin-film microfluidics.

A flow through device for simultaneous dielectrophoretic cell trapping and AC electroporation

Isolation of cells and their transfection in a controlled manner is an integral step in cell biotechnology. Electric field approaches such as dielectrophoresis (DEP) offers a more viable method for targeted immobilization of cells without any labels. For transfection of cells to incorporate exogenous materials, electrical methods such as electroporation, are preferred over chemical and viral delivery methods since they minimally affect cell viability and can target many types. However prior approaches to both methods required multiple excitation sources, an AC source for DEP-based trapping and another DC source for electroporation. In this paper, we present a first of its kind flow through lab-on-chip platform using a single AC excitation source for combined trapping using negative dielectrophoresis (nDEP) and AC electroporation. Use of AC fields for electroporation eliminates the unwanted side effects of electrolysis or joule heating at electrodes compared to DC electroporation. Adjusting the flow rate and the electrical parameters of the incident AC field precisely controls the operation (trap, trap with electroporation and release). The platform has been validated through trapping and simultaneous transfection of HEK-293 embryonic kidney cells with a plasmid vector containing a fluorescent protein tag. Numerical scaling analysis is provided that indicates promise for individual cell trapping and electroporation using low voltage AC fields.

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.

Edge Effect in Hot Embossing and its Influence on Global Pattern Replication of Polymer-Based Microneedles

Hot embossing was used to fabricate a microneedle array on poly(methyl methacrylate) (PMMA) substrates. Both experimental and numerical researches were carried out to investigate the whole formation process. The results showed that the edge effect would significantly influence the replication rate of final products. An optimization design of convex flow barrier was proposed to improve the replication efficiency and structure uniformity. Furthermore, optimum parameters of the flow barrier were found to be 2 mm in length and 0.2 mm in height. Reasonable high molding temperature and force were conducive to reduce the filling time and increase the average height of microneedles.

Nontoxic nanopore electroporation for effective intracellular delivery of biological macromolecules

We present a simple nanopore-electroporation (NanoEP) platform for delivery of nucleic acids, functional protein, and Cas9 single-guide RNA ribonucleoproteins into both adherent and suspension cells with up to 80% delivery efficiency and >95% cell viability. Low-voltage electric pulses permeabilize a small area of cell membrane as a cell comes into close contact with the nanopores. The biomolecule cargo is then electrophoretically drawn into the cells through the nanopores. In addition to high-performance delivery with low cell toxicity, the NanoEP system does not require specialized buffers, expensive materials, complicated fabrication processes, or cell manipulation; it simply consists of a generic nanopore-embedded water-filter membrane and a low-voltage square-wave generator. Ultimately, the NanoEP platform offers an effective and flexible method for universal intracellular delivery.