Highly efficient mRNA delivery with nonlinear microfluidic cell stretching for cellular engineering

Current Advances and Future Prospects of Bulk and Microfluidic-Enabled Electroporation Systems

Reversible electroporation (EP) is a pivotal biophysical technology that leverages pulsed electric fields to enhance the permeability of cell membranes, thereby facilitating the introduction of foreign material into cells. In this review, we provide an overview of bulk electroporators and microfluidic-enabled EP systems, focusing on their controversial points of mechanisms, architectures, and parameter settings. Bulk electroporators have been extensively commercialized with settled form including pulse generator and accessories (i.e., EP cuvette and plates). Researchers have made efforts to increase the throughput and simplify the operation of bulk EP systems. Additionally, microfluidics has emerged as a promising technology for optimizing EP parameters and enhancing the performance. Given the significant structural differences between these two types of EP systems, their operating conditions such as temperature, voltage, and pulse parameters are discussed. Research tend to operate single cells under more concentrated electric field induced by low voltage, enabling a quantitative exogenous materials delivery and numerical simulation. However, due to cost constraints and properties of materials utilized in laboratories, the commercialization of laboratory prototypes has been impeded. Furthermore, the technological limitations, current commercialization status, and development trends have been examined.

Intracellular Delivery Enabled by Squeezing Mechanoporation

Squeeze mechanoporation, as an emerging method, plays an important role in intracellular delivery. It brings new opportunities to cutting-edge fields such as cell therapy, gene editing, and vaccine production, and it promises to revolutionize traditional drug delivery and treatment paradigms. By leveraging the viscoelastic properties of cells, this technique induces cell deformation under external force, creating transient micropores in cell membranes for the efficient and high-throughput delivery of diverse exogenous substances, such as nucleic acids, antibodies, nanomaterials, and drugs. This review comprehensively summarizes current advances in mechanical squeezing-mediated intracellular delivery, delving deeply into its fundamental principles, unique advantages, latest applications, optimization strategies, existing challenges, corresponding solutions, and future development directions. With the aim of highlighting the immense potential and promising prospects of these techniques in the field of biomanufacturing and cell therapy.

Single-cell technology for cell-based drug delivery and pharmaceutical research

Leveraging the capacity to precisely manipulate and analyze individual cells, single-cell technology has rapidly become an indispensable tool in the advancement of cell-based drug delivery systems and innovative cell therapies. This technology offers powerful means to address cellular heterogeneity and significantly enhance therapeutic efficacy. Recent breakthroughs in techniques such as single-cell electroporation, mechanical perforation, and encapsulation, particularly when integrated with microfluidics and bioelectronics, have led to remarkable improvements in drug delivery efficiency, reductions in cytotoxicity, and more precise targeting of therapeutic effects. Moreover, single-cell analyses, including advanced sequencing and high-resolution sensing, offer profound insights into complex disease mechanisms, the development of drug resistance, and the intricate processes of stem cell differentiation. This review summarizes the most significant applications of these single-cell technologies, highlighting their impact on the landscape of modern biomedicine. Furthermore, it provides a forward-looking perspective on future research directions aimed at further optimizing drug delivery strategies and enhancing therapeutic outcomes in the treatment of various diseases.

Transient flow-induced deformation of cancer cells in microchannels: a general computational model and experiments

Recently, the present authors proposed a three-dimensional computational model for the transit of suspended cancer cells through a microchannel (Wang et al. in Biomech Model Mechanobiol 22: 1129-1143, 2023). The cell model takes into account the three major subcellular components: A viscoelastic membrane that represents the lipid bilayer supported by the underlying cell cortex, a viscous cytoplasm, and a nucleus modelled as a smaller microcapsule. The cell deformation and its interaction with the surrounding fluid were solved by an immersed boundary-lattice Boltzmann method. The computational model accurately recovered the transient flow-induced deformation of the human leukaemia HL-60 cells in a constricted channel. However, as a general modelling framework, its applicability to other cell types in different flow geometries remains unknown, due to the lack of quantitative experimental data. In this study, we conduct experiments of the transit of human prostate cancer (PC-3) and leukaemia (K-562) cells, which represent solid and liquid tumour cell lines, respectively, through two distinct microchannel geometries, each dominated by shear and extension flow. We find that the two cell lines have qualitatively similar flow-induced dynamics. Comparisons between experiments and numerical simulations suggest that our model can accurately predict the transient cell deformation in both geometries, and that it can serve as a general modelling framework for the dynamics of suspended cancer cells in microchannels.

Enhancing Chimeric Antigen Receptor T-Cell Generation via Microfluidic Mechanoporation and Lipid Nanoparticles

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment by engineering patients' T cells to specifically target cancer cells. Traditional CAR-T cell manufacturing methods use viral transduction to integrate CAR genes into T cells, but this can cause severe side effects and immune reactions and is costly. To overcome these challenges, non-viral methods, such as plasmid DNA (pDNA) transfection, are being explored. Here, a high-throughput intracellular delivery platform that integrates microfluidic mechanoporation with lipid nanoparticle (LNP)-based delivery, LNP + Squeeze, is introduced. This system enhances pDNA transfection efficiency in T cells while maintaining cell viability compared to other non-viral transfection methods like electroporation. This platform successfully engineers CAR-T cells using primary human T cells with a high transfection efficiency and demonstrates potent cytotoxicity against melanoma cells. This approach offers a promising, cost-effective, and scalable alternative to viral methods, potentially improving the accessibility and efficacy of CAR-T cell therapies.

Efficient in-droplet cell culture and cytomechanics measurement for assessment of human cellular responses to alcohol

BACKGROUND

Excessive alcohol consumption poses a significant threat to human health, leading to cellular dehydration, degeneration, and necrosis. Alcohol-induced cellular damage is closely linked to alterations in cellular mechanical properties. However, characterizing these changes following alcohol-related injury remains challenging. Moreover, current research on single-cell mechanics often struggles to culture and measure cells within a controlled microenvironment, leading to complex experimental procedures and imprecise results. (63).

RESULTS

In this study, we developed a novel single cell measurement method that combines cell microculture in alcohol-containing solutions with cytomechanics assessment within microdroplets. This approach integrates key operations, including single-cell encapsulation and culture in droplets, droplet reinjection, and cell deformation analysis within droplets, enabling high-throughput and multi-parameter quantification of single-cell mechanical properties. The use of droplets provides a precisely regulated microculture environment, effectively avoiding channel clogging issues. Additionally, the integration of cytomechanics measurement simplifies the analytical process by eliminating the need for complex techniques within the droplets. Gastric mucosal epithelial cells (GES-1) and human umbilical vein endothelial cells (HUVECs) were selected as models for ethanol-induced injury to validate the proposed technique. The results demonstrate a bidirectional response in cellular deformability following ethanol treatment, with cells becoming stiffer at lower ethanol concentrations and softer at higher concentrations. (136).

SIGNIFICANCE

The integration of droplet microfluidics and cell mechanics offers a powerful platform for investigating the underlying mechanisms of ethanol-induced cellular damage. This approach is also applicable for studying changes in cellular mechanical properties by precisely modulating the microculture environment, providing a reliable tool for drug screening and disease modeling in biochemistry and biomedical engineering. (54).

Mechanically mediated cargo delivery to cells using microfluidic devices

Drug delivery technologies, which are a crucial area of research in the field of cell biology, aim to actively or passively deliver drugs to target cells to enhance therapeutic efficacy and minimize off-target effects. In recent years, with advances in drug development, particularly, the increasing demand for macromolecular drugs (e.g., proteins and nucleic acids), novel drug delivery technologies and intracellular cargo delivery systems have emerged as promising tools for cell and gene therapy. These systems include various viral- and chemical-mediated methods as well as physical delivery strategies. Physical methods, such as electroporation and microinjection, have shown promise in early studies but have not been widely adopted due to concerns regarding efficiency and cellular viability. Recently, microfluidic technologies have provided new opportunities for cargo delivery by allowing for precise control of fluid dynamic parameters to achieve efficient and safe penetration of cell membranes, as well as for foreign material transport. Microfluidics-based mechanical delivery methods utilize biophysical phenomena, such as cell constriction and fluid shear, and are associated with high throughput and high transfection efficiency. In this review, we summarize the latest advancements in microfluidic mechanical delivery technologies, and we discuss constriction- and fluid shear-induced delivery strategies. Furthermore, we explore the potential application of artificial intelligence in optimizing cargo delivery technologies, aiming to provide theoretical support and practical guidance for the future development of novel cellular drug delivery technologies.

Intelligent sensing for the autonomous manipulation of microrobots toward minimally invasive cell surgery

The physiology and pathogenesis of biological cells have drawn enormous research interest. Benefiting from the rapid development of microfabrication and microelectronics, miniaturized robots with a tool size below micrometers have widely been studied for manipulating biological cells in vitro and in vivo. Traditionally, the complex physiological environment and biological fragility require human labor interference to fulfill these tasks, resulting in high risks of irreversible structural or functional damage and even clinical risk. Intelligent sensing devices and approaches have been recently integrated within robotic systems for environment visualization and interaction force control. As a consequence, microrobots can be autonomously manipulated with visual and interaction force feedback, greatly improving accuracy, efficiency, and damage regulation for minimally invasive cell surgery. This review first explores advanced tactile sensing in the aspects of sensing principles, design methodologies, and underlying physics. It also comprehensively discusses recent progress on visual sensing, where the imaging instruments and processing methods are summarized and analyzed. It then introduces autonomous micromanipulation practices utilizing visual and tactile sensing feedback and their corresponding applications in minimally invasive surgery. Finally, this work highlights and discusses the remaining challenges of current robotic micromanipulation and their future directions in clinical trials, providing valuable references about this field.

HiViPore: a highly viable in-flow compression for a one-step cell mechanoporation in microfluidics to induce a free delivery of nano- macro-cargoes

BACKGROUND

Among mechanoporation techniques for intracellular delivery, microfluidic approaches succeed in high delivery efficiency and throughput. However, especially the entry of large cargoes (e.g. DNA origami, mRNAs, organic/inorganic nanoparticles) is currently impaired since it requires large cell membrane pores with the need to apply multi-step processes and high forces, dramatically reducing cell viability.

RESULTS

Here, HiViPore presents as a microfluidic viscoelastic contactless compression for one-step cell mechanoporation to produce large pores while preserving high cell viability. Inducing an increase of curvature at the equatorial region of cells, formation of a pore with a size of ~ 1 μm is obtained. The poration is coupled to an increase of membrane tension, measured as a raised fluorescence lifetime of 12% of a planarizable push-pull fluorescent probe (Flipper-TR) labelling the cell plasma membrane. Importantly, the local disruptions of cell membrane are transient and non-invasive, with a complete recovery of cell integrity and functions in ~ 10 min. As result, HiViPore guarantees cell viability as high as ~ 90%. In such conditions, an endocytic-free diffusion of large nanoparticles is obtained with typical size up to 500 nm and with a delivery efficiency up to 12 times higher than not-treated cells.

CONCLUSIONS

The proposed one-step contactless mechanoporation results in an efficient and safe approach for advancing intracellular delivery strategies. In detail, HiViPore solves the issues of low cell viability when multiple steps of poration are required to obtain large pores across the cell plasma membrane. Moreover, the compression uses a versatile, low-cost, biocompatible viscoelastic fluid, thus also optimizing the operational costs. With HiViPore, we aim to propose an easy-to-use microfluidic device to a wide range of users, involved in biomedical research, imaging techniques and nanotechnology for intracellular delivery applications in cell engineering.

Microfluidic characterization of single-cell biophysical properties and the applications in cancer diagnosis

Single-cell biophysical properties play a crucial role in regulating cellular physiological states and functions, demonstrating significant potential in the fields of life sciences and clinical diagnostics. Therefore, over the last few decades, researchers have developed various detection tools to explore the relationship between the biophysical changes of biological cells and human diseases. With the rapid advancement of modern microfabrication technology, microfluidic devices have quickly emerged as a promising platform for single-cell analysis offering advantages including high-throughput, exceptional precision, and ease of manipulation. Consequently, this paper provides an overview of the recent advances in microfluidic analysis and detection systems for single-cell biophysical properties and their applications in the field of cancer. The working principles and latest research progress of single-cell biophysical property detection are first analyzed, highlighting the significance of electrical and mechanical properties. The development of data acquisition and processing methods for real-time, high-throughput, and practical applications are then discussed. Furthermore, the differences in biophysical properties between tumor and normal cells are outlined, illustrating the potential for utilizing single-cell biophysical properties for tumor cell identification, classification, and drug response assessment. Lastly, we summarize the limitations of existing microfluidic analysis and detection systems in single-cell biophysical properties, while also pointing out the prospects and future directions of their applications in cancer diagnosis and treatment.

A computational study of cell membrane damage and intracellular delivery in a cross-slot microchannel

We propose a three-dimensional computational framework to simulate the flow-induced cell membrane damage and the resulting enhanced intracellular mass transport in a cross-slot microchannel. We model the cell as a liquid droplet enclosed by a viscoelastic membrane and solve the cell deformation using a well-tested immersed-boundary lattice-Boltzmann method. The cell membrane damage, which is directly related to the membrane permeability, is considered using continuum damage mechanics. The transport of the diffusive solute into the cell is solved by a lattice-Boltzmann model. After validating the computational framework against several benchmark cases, we consider a cell flowing through a cross-slot microchannel, focusing on the effects of the flow strength, channel fluid viscosity and cell membrane viscosity on the membrane damage and enhanced intracellular transport. Interestingly, we find that under a comparable pressure drop across the device, for cells with low membrane viscosity, the inertial flow regime, which can be achieved by driving a low-viscosity liquid at a high speed, often leads to much larger membrane damage, compared with the high-viscosity low-speed viscous flow regime. However, the enhancement can be significantly reduced or even reversed by an increase of the cell membrane viscosity, which limits cell deformation, particularly in the inertial flow regime. Our computational framework and simulation results may guide the design and optimisation of microfluidic devices, which use cross-slot geometry to disrupt cell membranes to enhance intracellular delivery of solutes.

Expanding CAR-T cell immunotherapy horizons through microfluidics

Chimeric antigen receptor (CAR)-T cell therapies have revolutionized cancer treatment, particularly in hematological malignancies. However, their application to solid tumors is limited, and they face challenges in safety, scalability, and cost. To enhance current CAR-T cell therapies, the integration of microfluidic technologies, harnessing their inherent advantages, such as reduced sample consumption, simplicity in operation, cost-effectiveness, automation, and high scalability, has emerged as a powerful solution. This review provides a comprehensive overview of the step-by-step manufacturing process of CAR-T cells, identifies existing difficulties at each production stage, and discusses the successful implementation of microfluidics and related technologies in addressing these challenges. Furthermore, this review investigates the potential of microfluidics-based methodologies in advancing cell-based therapy across various applications, including solid tumors, next-generation CAR constructs, T-cell receptors, and the development of allogeneic "off-the-shelf" CAR products.

Biophysical Control of the Glioblastoma Immunosuppressive Microenvironment: Opportunities for Immunotherapy

GBM is the most aggressive and common form of primary brain cancer with a dismal prognosis. Current GBM treatments have not improved patient survival, due to the propensity for tumor cell adaptation and immune evasion, leading to a persistent progression of the disease. In recent years, the tumor microenvironment (TME) has been identified as a critical regulator of these pro-tumorigenic changes, providing a complex array of biomolecular and biophysical signals that facilitate evasion strategies by modulating tumor cells, stromal cells, and immune populations. Efforts to unravel these complex TME interactions are necessary to improve GBM therapy. Immunotherapy is a promising treatment strategy that utilizes a patient's own immune system for tumor eradication and has exhibited exciting results in many cancer types; however, the highly immunosuppressive interactions between the immune cell populations and the GBM TME continue to present challenges. In order to elucidate these interactions, novel bioengineering models are being employed to decipher the mechanisms of immunologically "cold" GBMs. Additionally, these data are being leveraged to develop cell engineering strategies to bolster immunotherapy efficacy. This review presents an in-depth analysis of the biophysical interactions of the GBM TME and immune cell populations as well as the systems used to elucidate the underlying immunosuppressive mechanisms for improving current therapies.

High throughput intracellular delivery by viscoelastic mechanoporation

Brief pulses of electric field (electroporation) and/or tensile stress (mechanoporation) have been used to reversibly permeabilize the plasma membrane of mammalian cells and deliver materials to the cytosol. However, electroporation can be harmful to cells, while efficient mechanoporation strategies have not been scalable due to the use of narrow constrictions or needles which are susceptible to clogging. Here we report a high throughput approach to mechanoporation in which the plasma membrane is stretched and reversibly permeabilized by viscoelastic fluid forces within a microfluidic chip without surface contact. Biomolecules are delivered directly to the cytosol within seconds at a throughput exceeding 250 million cells per minute. Viscoelastic mechanoporation is compatible with a variety of biomolecules including proteins, RNA, and CRISPR-Cas9 ribonucleoprotein complexes, as well as a range of cell types including HEK293T cells and primary T cells. Altogether, viscoelastic mechanoporation appears feasible for contact-free permeabilization and delivery of biomolecules to mammalian cells ex vivo.

Biophysical and mechanobiological considerations for T-cell-based immunotherapy

Immunotherapies modulate the body's defense system to treat cancer. While these therapies have shown efficacy against multiple types of cancer, patient response rates are limited, and the off-target effects can be severe. Typical approaches in developing immunotherapies tend to focus on antigen targeting and molecular signaling, while overlooking biophysical and mechanobiological effects. Immune cells and tumor cells are both responsive to biophysical cues, which are prominent in the tumor microenvironment. Recent studies have shown that mechanosensing - including through Piezo1, adhesions, and Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) - influences tumor-immune interactions and immunotherapeutic efficacy. Furthermore, biophysical methods such as fluidic systems and mechanoactivation schemes can improve the controllability and manufacturing of engineered T cells, with potential for increasing therapeutic efficacy and specificity. This review focuses on leveraging advances in immune biophysics and mechanobiology toward improving chimeric antigen receptor (CAR) T-cell and anti-programmed cell death protein 1 (anti-PD-1) therapies.

High throughput intracellular delivery by viscoelastic mechanoporation

Brief and intense electric fields (electroporation) and/or tensile stresses (mechanoporation) have been used to temporarily permeabilize the plasma membrane of mammalian cells for the purpose of delivering materials to the cytosol. However, electroporation can be harmful to cells, while efficient mechanoporation strategies have not been scalable due to the use of narrow constrictions or needles which are susceptible to clogging. Here we report a method of mechanoporation in which cells were stretched and permeabilized by viscoelastic flow forces without surface contact. Inertio-elastic cell focusing aligned cells to the center of the device, avoiding direct contact with walls and enabling efficient (95%) intracellular delivery to over 200 million cells per minute. Functional biomolecules such as proteins, RNA, and ribonucleoprotein complexes were successfully delivered to Jurkat cells. Efficient intracellular delivery to HEK293T cells and primary activated T cells was also demonstrated. Contact-free mechanoporation using viscoelastic fluid forces appears to be feasible method for efficient and high throughput intracellular delivery of biomolecules to mammalian cells ex vivo.