Single clonal tracking on biomimetic microtextured platforms for real-time guided migration analysis of myeloid-derived suppressor cell dissemination characteristics ex vivo

Current strategies to undermine the deleterious influence of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment (TME) are lacking effective clinical solutions, in large part, due to insufficient knowledge on susceptible cellular and molecular targets. We describe here the application of biomimetic microfabricated platforms designed to analyze migratory phenotypes of MDSCs in the tumor niche ex vivo, which may enable accelerated therapeutic discovery. By mimicking the guided structural cues present in the physiological architecture of the TME, aligned microtopography substrates can elucidate potential interventions on migratory phenotypes of MDSCs at the single clonal level. Coupled with cellular and molecular biology analysis tools, our approach employs real-time tracking analysis of cell motility to probe the dissemination characteristics of MDSCs under guided migration conditions. These methods allow us to identify cellular subpopulations of interest based on their disseminative and suppressive capabilities. By doing so, we illustrate the potential of applying microscale engineering tools, in concert with dynamic live cell imaging and bioanalysis methods to uncover novel exploitable motility targets for advancing cancer therapy discovery. The inherent simplicity and extended application to a variety of contexts in tumor-associated cell migration render this method widely accessible to existing biological laboratory conditions and interests.

Injectable pulverized electrospun poly(lactic-co-glycolic acid) fibers improve human adipose tissue engraftment and volume retention

Autologous adipose tissue is commonly used for tissue engraftment for the purposes of soft tissue reconstruction due to its relative abundance in the human body and ease of acquisition using liposuction methods. This has led to the adoption of autologous adipose engraftment procedures that allow for the injection of adipose tissues to be used as a "filler" for correcting cosmetic defects and deformities in soft tissues. However, the clinical use of such methods has several limitations, including high resorption rates and poor cell survivability, which lead to low graft volume retention and inconsistent outcomes. Here, we describe a novel application of milled electrospun poly(lactic-co-glycolic acid) (PLGA) fibers, which can be co-injected with adipose tissue to improve engraftment outcomes. These PLGA fibers had no significant negative impact on the viability of adipocytes in vitro and did not elicit long-term proinflammatory responses in vivo. Furthermore, co-delivery of human adipose tissue with pulverized electrospun PLGA fibers led to significant improvements in reperfusion, vascularity, and retention of graft volume compared to injections of adipose tissue alone. Taken together, the use of milled electrospun fibers to enhance autologous adipose engraftment techniques represents a novel approach for improving upon the shortcomings of such methods.

ICAM-1-decorated extracellular vesicles loaded with miR-146a and Glut1 drive immunomodulation and hinder tumor progression in a murine model of breast cancer

Tumor-associated immune cells play a crucial role in cancer progression. Myeloid-derived suppressor cells (MDSCs), for example, are immature innate immune cells that infiltrate the tumor to exert immunosuppressive activity and protect cancer cells from the host's immune system and/or cancer-specific immunotherapies. While tumor-associated immune cells have emerged as a promising therapeutic target, efforts to counter immunosuppression within the tumor niche have been hampered by the lack of approaches that selectively target the immune cell compartment of the tumor, to effectively eliminate "tumor-protecting" immune cells and/or drive an "anti-tumor" phenotype. Here we report on a novel nanotechnology-based approach to target tumor-associated immune cells and promote "anti-tumor" responses in a murine model of breast cancer. Engineered extracellular vesicles (EVs) decorated with ICAM-1 ligands and loaded with miR-146a and Glut1, were biosynthesized (in vitro or in vivo) and administered to tumor-bearing mice once a week for up to 5 weeks. The impact of this treatment modality on the immune cell compartment and tumor progression was evaluated via RT-qPCR, flow cytometry, and histology. Our results indicate that weekly administration of the engineered EVs (i.e., ICAM-1-decorated and loaded with miR-146a and Glut1) hampered tumor progression compared to ICAM-1-decorated EVs with no cargo. Flow cytometry analyses of the tumors indicated a shift in the phenotype of the immune cell population toward a more pro-inflammatory state, which appeared to have facilitated the infiltration of tumor-targeting T cells, and was associated with a reduction in tumor size and decreased metastatic burden. Altogether, our results indicate that ICAM-1-decorated EVs could be a powerful platform nanotechnology for the deployment of immune cell-targeting therapies to solid tumors.

Engineered Extracellular Vesicle-Based Therapies for Valvular Heart Disease

Introduction

Valvular heart disease represents a significant burden to the healthcare system, with approximately 5 million cases diagnosed annually in the US. Among these cases, calcific aortic stenosis (CAS) stands out as the most prevalent form of valvular heart disease in the aging population.  CAS is characterized by the progressive calcification of the aortic valve leaflets, leading to valve stiffening. While aortic valve replacement is the standard of care for CAS patients, the long-term durability of prosthetic devices is poor, calling for innovative strategies to halt  or reverse disease progression. Here, we explor the potential use of novel extracellular vesicle (EV)-based nanocarriers for delivering molecular payloads to the affected valve tissue. This approach aims to reduce inflammation and potentially promote resorption of the calcified tissue.

Methods

Engineered EVs loaded with the reprogramming myeloid transcription factors, CEBPA and Spi1, known to mediate the transdifferentiation of committed endothelial cells into macrophages. We evaluated the ability of these engineered EVs to deliver DNA and transcripts encoding CEBPA and Spil into calcified aortic valve tissue obtained from patients undergoing valve replacement due to aortic stenosis. We also investigated whether these EVs could induce the transdifferentiation of endothelial cells into macrophage-like cells.

Results

Engineered EVs loaded with CEBPA + Spi1 were successfully derived from human dermal fibroblasts. Peak EV loading was found to be at 4 h after nanotransfection of donor cells.  These CEBPA + Spi1 loaded EVs effectively transfected aortic valve cells, resulting in the successful induction of transdifferentiation, both in vitro with  endothelial cells and ex vivo with valvular endothelial cells, leading to the development of anti-inflammatory macrophage-like cells.

Conclusions

Our findings highlight the potential of engineered EVs as a next generation nanocarrier to target aberrant calcifications on diseased heart valves. This development holds promise as a novel therapy for high-risk patients who may not be suitable candidates for valve replacement surgery.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00783-x.

Engineered Extracellular Vesicles Derived from Dermal Fibroblasts Attenuate Inflammation in a Murine Model of Acute Lung Injury

Acute respiratory distress syndrome (ARDS) represents a significant burden to the healthcare system, with ≈200 000 cases diagnosed annually in the USA. ARDS patients suffer from severe refractory hypoxemia, alveolar-capillary barrier dysfunction, impaired surfactant function, and abnormal upregulation of inflammatory pathways that lead to intensive care unit admission, prolonged hospitalization, and increased disability-adjusted life years. Currently, there is no cure or FDA-approved therapy for ARDS. This work describes the implementation of engineered extracellular vesicle (eEV)-based nanocarriers for targeted nonviral delivery of anti-inflammatory payloads to the inflamed/injured lung. The results show the ability of surfactant protein A (SPA)-functionalized IL-4- and IL-10-loaded eEVs to promote intrapulmonary retention and reduce inflammation, both in vitro and in vivo. Significant attenuation is observed in tissue damage, proinflammatory cytokine secretion, macrophage activation, influx of protein-rich fluid, and neutrophil infiltration into the alveolar space as early as 6 h post-eEVs treatment. Additionally, metabolomics analyses show that eEV treatment causes significant changes in the metabolic profile of inflamed lungs, driving the secretion of key anti-inflammatory metabolites. Altogether, these results establish the potential of eEVs derived from dermal fibroblasts to reduce inflammation, tissue damage, and the prevalence/progression of injury during ARDS via nonviral delivery of anti-inflammatory genes/transcripts.

Engineered Vasculogenic Extracellular Vesicles Drive Nonviral Direct Conversions of Human Dermal Fibroblasts into Induced Endothelial Cells and Improve Wound Closure

Vasculogenic cell therapies have emerged as a powerful tool to increase vascularization and promote tissue repair/regeneration. Current approaches to cell therapies, however, rely mostly on progenitor cells, which pose significant risks (e.g., uncontrolled differentiation, tumorigenesis, and genetic/epigenetic abnormalities). Moreover, reprogramming methodologies used to generate induced endothelial cells (iECs) from induced pluripotent stem cells rely heavily on viral vectors, which pose additional translational limitations. This work describes the development of engineered human extracellular vesicles (EVs) capable of driving reprogramming-based vasculogenic therapies without the need for progenitor cells and/or viral vectors. The EVs were derived from primary human dermal fibroblasts (HDFs), and were engineered to pack transcription factor genes/transcripts of ETV2, FLI1, and FOXC2 (EFF). Our results indicate that in addition of EFF, the engineered EVs were also loaded with transcripts of angiogenic factors (e.g., VEGF-A, VEGF-KDR, FGF2). In vitro and in vivo studies indicate that such EVs effectively transfected HDFs and drove direct conversions towards iECs within 7-14 days. Finally, wound healing studies in mice indicate that engineered EVs lead to improved wound closure and vascularity. Altogether, our results show the potential of engineered human vasculogenic EVs to drive direct reprogramming processes of somatic cells towards iECs, and facilitate tissue repair/regeneration.

Leukemia-initiating HSCs in chronic lymphocytic leukemia reveal clonal leukemogenesis and differential drug sensitivity

The existence of "leukemia-initiating cells" (LICs) in chronic lymphocytic leukemia (CLL) remains controversial due to the difficulty in isolating and identifying the tumor-initiating cells. Here, we demonstrate a microchannel electroporation (MEP) microarray that injects RNA-detecting probes into single live cells, allowing the imaging and characterization of heterogeneous LICs by intracellular RNA expression. Using limited-cell FACS sequencing (LC-FACSeq), we can detect and monitor rare live LICs during leukemogenesis and characterize their differential drug sensitivity. Disease-associated mutation accumulation in developing B lymphoid but not myeloid lineage in CLL patient hematopoietic stem cells (CLL-HSCs), and development of independent clonal CLL-like cells in murine patient-derived xenograft models, suggests the existence of CLL LICs. Furthermore, we identify differential protein ubiquitination and unfolding response signatures in GATA2^high CLL-HSCs that exhibit increased sensitivity to lenalidomide and resistance to fludarabine compared to GATA2^lowCLL-HSCs. These results highlight the existence of therapeutically targetable disease precursors in CLL.

Nanotechnology-Driven Cell-Based Therapies in Regenerative Medicine

The administration of cells as therapeutic agents has emerged as a novel approach to complement the use of small molecule drugs and other biologics for the treatment of numerous conditions. Although the use of cells for structural and/or functional tissue repair and regeneration provides new avenues to address increasingly complex disease processes, it also faces numerous challenges related to efficacy, safety, and translational potential. Recent advances in nanotechnology-driven cell therapies have the potential to overcome many of these issues through precise modulation of cellular behavior. Here, we describe several approaches that illustrate the use of different nanotechnologies for the optimization of cell therapies and discuss some of the obstacles that need to be overcome to allow for the widespread implementation of nanotechnology-based cell therapies in regenerative medicine.

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.

Designer Extracellular Vesicles Modulate Pro-Neuronal Cell Responses and Improve Intracranial Retention

Gene/oligonucleotide therapies have emerged as a promising strategy for the treatment of different neurological conditions. However, current methodologies for the delivery of neurogenic/neurotrophic cargo to brain and nerve tissue are fraught with caveats, including reliance on viral vectors, potential toxicity, and immune/inflammatory responses. Moreover, delivery to the central nervous system is further compounded by the low permeability of the blood brain barrier. Extracellular vesicles (EVs) have emerged as promising delivery vehicles for neurogenic/neurotrophic therapies, overcoming many of the limitations mentioned above. However, the manufacturing processes used for therapeutic EVs remain poorly understood. Here, we conducted a detailed study of the manufacturing process of neurogenic EVs by characterizing the nature of cargo and surface decoration, as well as the transfer dynamics across donor cells, EVs, and recipient cells. Neurogenic EVs loaded with Ascl1, Brn2, and Myt1l (ABM) are found to show enhanced neuron-specific tropism, modulate electrophysiological activity in neuronal cultures, and drive pro-neurogenic conversions/reprogramming. Moreover, murine studies demonstrate that surface decoration with glutamate receptors appears to mediate enhanced EV delivery to the brain. Altogether, the results indicate that ABM-loaded designer EVs can be a promising platform nanotechnology to drive pro-neuronal responses, and that surface functionalization with glutamate receptors can facilitate the deployment of EVs to the brain.

Transient Middle Cerebral Artery Occlusion with an Intraluminal Suture Enables Reproducible Induction of Ischemic Stroke in Mice

Ischemic stroke is a leading cause of mortality and chronic disability worldwide, underscoring the need for reliable and accurate animal models to study this disease's pathology, molecular mechanisms of injury, and treatment approaches. As most clinical strokes occur in regions supplied by the middle cerebral artery (MCA), several experimental models have been developed to simulate an MCA occlusion (MCAO), including transcranial MCAO, micro- or macro-sphere embolism, thromboembolisation, photothrombosis, Endothelin-1 injection, and - the most common method for ischemic stroke induction in murine models - intraluminal MCAO. In the intraluminal MCAO model, the external carotid artery (ECA) is permanently ligated, after which a partially-coated monofilament is inserted and advanced proximally to the common carotid artery (CCA) bifurcation, before being introduced into the internal carotid artery (ICA). The coated tip of the monofilament is then advanced to the origin of the MCA and secured for the duration of occlusion. With respect to other MCAO models, this model offers enhanced reproducibility regarding infarct volume and cognitive/functional deficits, and does not require a craniotomy. Here, we provide a detailed protocol for the surgical induction of unilateral transient ischemic stroke in mice, using the intraluminal MCAO model. Graphic abstract: Overview of the intraluminal monofilament method for transient middle cerebral artery occlusion (MCAO) in mouse.

Nanotransfection-based vasculogenic cell reprogramming drives functional recovery in a mouse model of ischemic stroke

Ischemic stroke causes vascular and neuronal tissue deficiencies that could lead to substantial functional impairment and/or death. Although progenitor-based vasculogenic cell therapies have shown promise as a potential rescue strategy following ischemic stroke, current approaches face major hurdles. Here, we used fibroblasts nanotransfected with Etv2, Foxc2, and Fli1 (EFF) to drive reprogramming-based vasculogenesis, intracranially, as a potential therapy for ischemic stroke. Perfusion analyses suggest that intracranial delivery of EFF-nanotransfected fibroblasts led to a dose-dependent increase in perfusion 14 days after injection. MRI and behavioral tests revealed ~70% infarct resolution and up to ~90% motor recovery for mice treated with EFF-nanotransfected fibroblasts. Immunohistological analysis confirmed increases in vascularity and neuronal cellularity, as well as reduced glial scar formation in response to treatment with EFF-nanotransfected fibroblasts. Together, our results suggest that vasculogenic cell therapies based on nanotransfection-driven (i.e., nonviral) cellular reprogramming represent a promising strategy for the treatment of ischemic stroke.

Non-viral reprogramming of human nucleus pulposus cells with FOXF1 via extracellular vesicle delivery: an in vitro and in vivo study

Intervertebral disc (IVD) degeneration is characterized by decreased cellularity and proteoglycan synthesis and increased inflammation, catabolism, and neural/vascular ingrowth. Regenerative methods for IVD degeneration are largely cell-therapy-based or involve viral vectors, which are associated with mutagenesis and undesired immune responses. The present study used bulk electroporation and engineered extracellular vesicles (EVs) to deliver forkhead-box F1 (FOXF1) mRNA to degenerate human nucleus pulposus (NP) cells as a minimally invasive therapeutic strategy for IVD regeneration. Bulk electroporation was used to investigate FOXF1 effects on human NP cells during a 4-week culture in 3D agarose constructs. Engineered EV delivery of FOXF1 into human IVD cells in monolayer was determined, with subsequent in vivo validation in a pilot mouse IVD puncture model. FOXF1 transfection significantly altered gene expression by upregulating healthy NP markers [FOXF1, keratin 19 (KRT19)], decreasing inflammatory cytokines [interleukin (IL)-1β, -6], catabolic enzymes [metalloproteinase 13 (MMP13)] and nerve growth factor (NGF), with significant increases in glycosaminoglycan accumulation in human NP cells. Engineered EVs loaded with FOXF1 demonstrated successful encapsulation of FOXF1 cargo and effective uptake by human NP cells cultured in monolayer. Injection of FOXF1-loaded EVs into the mouse IVD in vivo resulted in a significant upregulation of FOXF1 and Brachyury, compared to controls at 7 d post-injection, with no evidence of cytotoxicity. This is the first study to demonstrate non-viral delivery of FOXF1 and reprogramming of human NP cells in vitro and mouse IVD cells in vivo. This strategy represents a non-addictive approach for treating IVD degeneration and associated back pain.

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.

A Novel Endocrine Role for the BAT-Released Lipokine 12,13-diHOME to Mediate Cardiac Function

BACKGROUND

Brown adipose tissue (BAT) is an important tissue for thermogenesis, making it a potential target to decrease the risks of obesity, type 2 diabetes, and cardiovascular disease, and recent studies have also identified BAT as an endocrine organ. Although BAT has been implicated to be protective in cardiovascular disease, to this point there are no studies that identify a direct role for BAT to mediate cardiac function.

METHODS

To determine the role of BAT on cardiac function, we utilized a model of BAT transplantation. We then performed lipidomics and identified an increase in the lipokine 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME). We utilized a mouse model with sustained overexpression of 12,13-diHOME and investigated the role of 12,13-diHOME in a nitric oxide synthase type 1 deficient (NOS1^-/-) mouse and in isolated cardiomyocytes to determine effects on function and respiration. We also investigated 12,13-diHOME in a cohort of human patients with heart disease.

RESULTS

Here, we determined that transplantation of BAT (+BAT) improves cardiac function via the release of the lipokine 12,13-diHOME. Sustained overexpression of 12,13-diHOME using tissue nanotransfection negated the deleterious effects of a high-fat diet on cardiac function and remodeling, and acute injection of 12,13-diHOME increased cardiac hemodynamics via direct effects on the cardiomyocyte. Furthermore, incubation of cardiomyocytes with 12,13-diHOME increased mitochondrial respiration. The effects of 12,13-diHOME were absent in NOS1^-/- mice and cardiomyocytes. We also provide the first evidence that 12,13-diHOME is decreased in human patients with heart disease.

CONCLUSIONS

Our results identify an endocrine role for BAT to enhance cardiac function that is mediated by regulation of calcium cycling via 12,13-diHOME and NOS1.

Neurogenic tissue nanotransfection in the management of cutaneous diabetic polyneuropathy

This work rests on our recent report on the successful use of tissue nanotransfection (TNT) delivery of Ascl1, Brn2, and Myt1l (TNTABM) to directly convert skin fibroblasts into electrophysiologically active induced neuronal cells (iN) in vivo. Here we report that in addition to successful neurogenic conversion of cells, TNTABM caused neurotrophic enrichment of the skin stroma. Thus, we asked whether such neurotrophic milieu of the skin can be leveraged to rescue pre-existing nerve fibers under chronic diabetic conditions. Topical cutaneous TNTABM caused elevation of endogenous NGF and other co-regulated neurotrophic factors such as Nt3. TNTABM spared loss of cutaneous PGP9.5+ mature nerve fibers in db/db diabetic mice. This is the first study demonstrating that under conditions of in vivo reprogramming, changes in the tissue microenvironment can be leveraged for therapeutic purposes such as the rescue of pre-existing nerve fibers from its predictable path of loss under conditions of diabetes.

Reciprocal Signaling between Myeloid Derived Suppressor and Tumor Cells Enhances Cellular Motility and is Mediated by Structural Cues in the Microenvironment

Myeloid derived suppressor cells (MDSCs) have gained significant attention for their immunosuppressive role in cancer and their ability to contribute to tumor progression and metastasis. Understanding the role of MDSCs in driving cancer cell migration, a process fundamental to metastasis, is essential to fully comprehend and target MDSC-tumor cell interactions. This study employs microfabricated platforms, which simulate the structural cues present in the tumor microenvironment (TME) to elucidate the effects of MDSCs on the migratory phenotype of cancer cells at the single cell level. The results indicate that the presence of MDSCs enhances the motility of cancer-epithelial cells when directional cues (either topographical or spatial) are present. This behavior appears to be independent of cell-cell contact and driven by soluble byproducts from heterotypic interactions between MDSCs and cancer cells. Moreover, MDSC cell-motility is also impacted by the presence of cancer cells and the cancer cell secretome in the presence of directional cues. Epithelial dedifferentiation is the likely mechanism for changes in cancer cell motility in response to MDSCs. These results highlight the biochemical and biostructural conditions under which MDSCs can support cancer cell migration, and could therefore provide new avenues of research and therapy aimed at stemming cancer progression.

Nanomedicine-Based Strategies for Diabetes: Diagnostics, Monitoring, and Treatment

Traditional methods for diabetes management require constant and tedious glucose monitoring (GM) and insulin injections, impacting quality of life. The global diabetic population is expected to increase to 439 million, with approximately US$490 billion in healthcare expenditures by 2030, imposing a significant burden on healthcare systems worldwide. Recent advances in nanotechnology have emerged as promising alternative strategies for the management of diabetes. For example, implantable nanosensors are being developed for continuous GM, new nanoparticle (NP)-based imaging approaches that quantify subtle changes in β cell mass can facilitate early diagnosis, and nanotechnology-based insulin delivery methods are being explored as novel therapies. Here, we provide a holistic summary of this rapidly advancing field compiling all aspects pertaining to the management of diabetes.

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.

Nonviral Transfection With Brachyury Reprograms Human Intervertebral Disc Cells to a Pro-Anabolic Anti-Catabolic/Inflammatory Phenotype: A Proof of Concept Study

Intervertebral disc (IVD) degeneration is a major contributor to chronic low back pain and is characterized by decreases in cellularity and proteoglycan synthesis, upregulation of matrix degradation, and increases in pro-inflammatory factors with neurovascular invasion. Current treatments fail to target the underlying pathology or promote tissue repair and approaches such as viral transfection raise safety concerns due to mutagenesis and unwarranted immune responses. To avoid such concerns, nonviral transfection is a viable method of gene delivery into the host cell while bypassing the caveats of viral delivery. Brachyury is expressed in the developing notochord and is associated with an immature healthy nucleus pulposus (NP). We hypothesize that Brachyury can reprogram degenerate NP cells to a healthy pro-anabolic phenotype with increased proteoglycan content and decreased expression of catabolic, inflammatory, and neurovascular markers. NP cells obtained from human autopsy and surgical tissues were transfected with plasmids encoding for Brachyury or an empty vector control via bulk electroporation. Post transfection, cells were seeded in three-dimensional agarose constructs cultured over 4 weeks and analyzed for viability, gene expression, and proteoglycan. Results demonstrated successful transfection of both autopsy and surgical NP cells. We observed long-term Brachyury expression, significant increased expression of NP phenotypic markers FOXF1, KRT19, and chondrogenic marker SOX9 with decreases in inflammatory cytokines IL1-β/IL6, NGF, and MMPs and significant increases in glycosaminoglycan accumulation. These results highlight nonviral transfection with developmental transcription factors, such as Brachyury, as a promising method to reprogram degenerate human disc cells toward a healthy NP phenotype. Clinical significance: This project proposes a novel translational approach for the treatment of intervertebral disc degeneration via direct reprogramming of diseased human patient-derived IVD cells to a healthy phenotype. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2389-2400, 2019.

Lab-on-a-Chip Platforms for Biophysical Studies of Cancer with Single-Cell Resolution

Recent cancer research has more strongly emphasized the biophysical aspects of tumor development, progression, and microenvironment. In addition to genetic modifications and mutations in cancer cells, it is now well accepted that the physical properties of cancer cells such as stiffness, electrical impedance, and refractive index vary with tumor progression and can identify a malignant phenotype. Moreover, cancer heterogeneity renders population-based characterization techniques inadequate, as individual cellular features are lost in the average. Hence, platforms for fast and accurate characterization of biophysical properties of cancer cells at the single-cell level are required. Here, we highlight some of the recent advances in the field of cancer biophysics and the development of lab-on-a-chip platforms for single-cell biophysical analyses of cancer cells.

Topical tissue nano-transfection mediates non-viral stroma reprogramming and rescue

Although cellular therapies represent a promising strategy for a number of conditions, current approaches face major translational hurdles, including limited cell sources and the need for cumbersome pre-processing steps (for example, isolation, induced pluripotency). In vivo cell reprogramming has the potential to enable more-effective cell-based therapies by using readily available cell sources (for example, fibroblasts) and circumventing the need for ex vivo pre-processing. Existing reprogramming methodologies, however, are fraught with caveats, including a heavy reliance on viral transfection. Moreover, capsid size constraints and/or the stochastic nature of status quo approaches (viral and non-viral) pose additional limitations, thus highlighting the need for safer and more deterministic in vivo reprogramming methods. Here, we report a novel yet simple-to-implement non-viral approach to topically reprogram tissues through a nanochannelled device validated with well-established and newly developed reprogramming models of induced neurons and endothelium, respectively. We demonstrate the simplicity and utility of this approach by rescuing necrotizing tissues and whole limbs using two murine models of injury-induced ischaemia.

Controllable Large-Scale Transfection of Primary Mammalian Cardiomyocytes on a Nanochannel Array Platform

While electroporation has been widely used as a physical method for gene transfection in vitro and in vivo, its application in gene therapy of cardiovascular cells remains challenging. Due to the high concentration of ion-transport proteins in the sarcolemma, conventional electroporation of primary cardiomyocytes tends to cause ion-channel activation and abnormal ion flux, resulting in low transfection efficiency and high mortality. In this work, a high-throughput nanoelectroporation technique based on a nanochannel array platform is reported, which enables massively parallel delivery of genetic cargo (microRNA, plasmids) into mouse primary cardiomyocytes in a controllable, highly efficient, and benign manner. A simple "dipping-trap" approach was implemented to precisely position a large number of cells on the nanoelectroporation platform. With dosage control, our device precisely titrates the level of miR-29, a potential therapeutic agent for cardiac fibrosis, and determines the minimum concentration of miR-29 causing side effects in mouse primary cardiomyocytes. Moreover, the dose-dependent effect of miR-29 on mitochondrial potential and homeostasis is monitored. Altogether, our nanochannel array platform provides efficient trapping and transfection of primary mouse cardiomyocyte, which can improve the quality control for future microRNA therapy in heart diseases.

Micro-/nanoscale electroporation

Electroporation has been one of the most popular non-viral technologies for cell transfection. However, conventional bulk electroporation (BEP) shows significant limitations in efficiency, cell viability and transfection uniformity. Recent advances in microscale-electroporation (MEP) resulted in improved cell viability. Further miniaturization of the electroporation system (i.e., nanoscale) has brought up many unique advantages, including negligible cell damage and dosage control capabilities with single-cell resolution, which has enabled more translational applications. In this review, we give an insight into the fundamental and technical aspects of micro- and nanoscale/nanochannel electroporation (NEP) and go over several examples of MEP/NEP-based cutting-edge research, including gene editing, adoptive immunotherapy, and cellular reprogramming. The challenges and opportunities of advanced electroporation technologies are also discussed.

Length of time in Ghana is associated with the likelihood of exclusive breastfeeding among Liberian refugees living in Buduburam

While literature describing immigrant's breastfeeding practices exists, especially among those living within developed countries, there is a significant gap in knowledge on how the host culture may influence the EBF behaviors of refugees, especially those living in protracted situations within sub-Saharan Africa. A cross-sectional study was conducted in the Buduburam Refugee Settlement in Ghana from July-August 2008 to explore the association between the amount of time living in Ghana and exclusive breastfeeding practices among Liberian refugees and Ghanaians in surround villages. The study included 480 women: 239 Liberians living in 12 settlement zones (in two of which Liberians and Ghanaians co-exist), 121 Ghanaians living in two settlement zones, and 120 Ghanaians living in nearby urban village of Awutu. Liberian mothers who lived in Ghana at least eight years were significantly more likely to exclusively breastfeed (OR: 1.78, 95% CI: 1.02, 3.09) compared to Ghanaian mothers living in Awutu. These findings suggest that increased time living in Buduburam improved the chances of EBF success among Liberians, perhaps as a result of unique EBF education/support opportunities offered in the settlement to Liberian refugees that were not readily available to Ghanaians. Further research to understand the "mechanisms" explaining exclusive breastfeeding differences as a function of time spent in host country is needed for improving breastfeeding support in refugee settlements and host communities.

On-Chip Clonal Analysis of Glioma-Stem-Cell Motility and Therapy Resistance

Enhanced glioma-stem-cell (GSC) motility and therapy resistance are considered to play key roles in tumor cell dissemination and recurrence. As such, a better understanding of the mechanisms by which these cells disseminate and withstand therapy could lead to more efficacious treatments. Here, we introduce a novel micro-/nanotechnology-enabled chip platform for performing live-cell interrogation of patient-derived GSCs with single-clone resolution. On-chip analysis revealed marked intertumoral differences (>10-fold) in single-clone motility profiles between two populations of GSCs, which correlated well with results from tumor-xenograft experiments and gene-expression analyses. Further chip-based examination of the more-aggressive GSC population revealed pronounced interclonal variations in motility capabilities (up to ∼4-fold) as well as gene-expression profiles at the single-cell level. Chip-supported therapy resistance studies with a chemotherapeutic agent (i.e., temozolomide) and an oligo RNA (anti-miR363) revealed a subpopulation of CD44-high GSCs with strong antiapoptotic behavior as well as enhanced motility capabilities. The living-cell-interrogation chip platform described herein enables thorough and large-scale live monitoring of heterogeneous cancer-cell populations with single-cell resolution, which is not achievable by any other existing technology and thus has the potential to provide new insights into the cellular and molecular mechanisms modulating glioma-stem-cell dissemination and therapy resistance.

The human PMR1 endonuclease stimulates cell motility by down regulating miR-200 family microRNAs

The motility of MCF-7 cells increases following expression of a human PMR1 transgene and the current study sought to identify the molecular basis for this phenotypic change. Ensemble and single cell analyses show increased motility is dependent on the endonuclease activity of hPMR1, and cells expressing active but not inactive hPMR1 invade extracellular matrix. Nanostring profiling identified 14 microRNAs that are downregulated by hPMR1, including all five members of the miR-200 family and others that also regulate invasive growth. miR-200 levels increase following hPMR1 knockdown, and changes in miR-200 family microRNAs were matched by corresponding changes in miR-200 targets and reporter expression. PMR1 preferentially cleaves between UG dinucleotides within a consensus YUGR element when present in the unpaired loop of a stem–loop structure. This motif is present in the apical loop of precursors to most of the downregulated microRNAs, and hPMR1 targeting of pre-miRs was confirmed by their loss following induced expression and increase following hPMR1 knockdown. Introduction of miR-200c into hPMR1-expressing cells reduced motility and miR-200 target gene expression, confirming hPMR1 acts upstream of Dicer processing. These findings identify a new role for hPMR1 in the post-transcriptional regulation of microRNAs in breast cancer cells.

Serine/Threonine Kinase MLK4 Determines Mesenchymal Identity in Glioma Stem Cells in an NF-κB-dependent Manner

Activation of nuclear factor κB (NF-κB) induces mesenchymal (MES) transdifferentiation and radioresistance in glioma stem cells (GSCs), but molecular mechanisms for NF-κB activation in GSCs are currently unknown. Here, we report that mixed lineage kinase 4 (MLK4) is overexpressed in MES but not proneural (PN) GSCs. Silencing MLK4 suppresses self-renewal, motility, tumorigenesis, and radioresistance of MES GSCs via a loss of the MES signature. MLK4 binds and phosphorylates the NF-κB regulator IKKα, leading to activation of NF-κB signaling in GSCs. MLK4 expression is inversely correlated with patient prognosis in MES, but not PN high-grade gliomas. Collectively, our results uncover MLK4 as an upstream regulator of NF-κB signaling and a potential molecular target for the MES subtype of glioblastomas.

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

Of great interest to modern medicine and biomedical research is the ability to inject individual target cells with the desired genes or drug molecules. Some advances in cell electroporation allow for high throughput, high cell viability, or excellent dosage control, yet no platform is available for the combination of all three. In an effort to solve this problem, here we show a "3D nano-channel electroporation (NEP) chip" on a silicon platform designed to meet these three criteria. This NEP chip can simultaneously deliver the desired molecules into 40,000 cells per cm(2) on the top surface of the device. Each 650 nm pore aligns to a cell and can be used to deliver extremely small biological elements to very large plasmids (>10 kbp). When compared to conventional bulk electroporation (BEP), the NEP chip shows a 20 fold improvement in dosage control and uniformity, while still maintaining high cell viability (>90%) even in cells such as cardiac cells which are characteristically difficult to transfect. This high-throughput 3D NEP system provides an innovative and medically valuable platform with uniform and reliable cellular transfection, allowing for a steady supply of healthy, engineered cells.

Deterministic transfection drives efficient nonviral reprogramming and uncovers reprogramming barriers

Safety concerns and/or the stochastic nature of current transduction approaches have hampered nuclear reprogramming's clinical translation. We report a novel non-viral nanotechnology-based platform permitting deterministic large-scale transfection with single-cell resolution. The superior capabilities of our technology are demonstrated by modification of the well-established direct neuronal reprogramming paradigm using overexpression of the transcription factors Brn2, Ascl1, and Myt1l (BAM). Reprogramming efficiencies were comparable to viral methodologies (up to ~9-12%) without the constraints of capsid size and with the ability to control plasmid dosage, in addition to showing superior performance relative to existing non-viral methods. Furthermore, increased neuronal complexity could be tailored by varying BAM ratio and by including additional proneural genes to the BAM cocktail. Furthermore, high-throughput NEP allowed easy interrogation of the reprogramming process. We discovered that BAM-mediated reprogramming is regulated by AsclI dosage, the S-phase cyclin CCNA2, and that some induced neurons passed through a nestin-positive cell stage.

FROM THE CLINICAL EDITOR

In the field of regenerative medicine, the ability to direct cell fate by nuclear reprogramming is an important facet in terms of clinical application. In this article, the authors described their novel technique of cell reprogramming through overexpression of the transcription factors Brn2, Ascl1, and Myt1l (BAM) by in situ electroporation through nanochannels. This new technique could provide a platform for further future designs.

Nanochannel Electroporation as a Platform for Living Cell Interrogation in Acute Myeloid Leukemia

A living cell interrogation platform based on nanochannel electroporation is demonstrated with analysis of RNAs in single cells. This minimally invasive process is based on individual cells and allows both multi-target analysis and stimulus-response analysis by sequential deliveries. The unique platform possesses a great potential to the comprehensive and lysis-free nucleic acid analysis on rare or hard-to-transfect cells.

Dielectrophoresis-assisted 3D nanoelectroporation for non-viral cell transfection in adoptive immunotherapy

Current transfection technologies lead to significant inter-clonal variations. Previously we introduced a unique electrotransfection technology, Nanochannel-Electroporation (NEP), which can precisely and benignly transfect small cell populations (~100-200 cells) with single-cell resolution. Here we report on the development of a novel 3D NEP system for large scale transfection. A properly-engineered array of nanochannels, capable of handling/transfecting ~60 000 cells cm(-2), was fabricated using cleanroom technologies. Positive dielectrophoresis was used to selectively position cells on the nanochannels, thus allowing highly efficient transfection. Single-cell dosage control was demonstrated using both small and large molecules, and different cell types. The potential clinical relevance of this system was tested with difficult-to-transfect natural killer cell suspensions, and plasmids encoding for the chimeric antigen receptor (CAR), a model of high relevance for adoptive immunotherapy. Our results show significantly higher CAR transfection efficiencies for the DEP-NEP system (>70% vs. <30%), as well as enhanced cell viabilities.

Targeted delivery of tumor suppressor microRNA-1 by transferrin-conjugated lipopolyplex nanoparticles to patient-derived glioblastoma stem cells

OBJECTIVE

Among heterogeneous glioblastoma multiforme (GBM) cells, glioblastoma stem cells (GSCs) is a subpopulation having a critical role in tumor initiation and therapy resistance. Thus targeting GSCs would be an essential step to completely eradicate this lethal disease. MicroRNA-1 (miR-1) expression is deregulated in GBM patients and restoration of miR-1 by viral-vector in GBM cells has been demonstrated to inhibit tumor initiation and attenuate cell migration. Here, we show that a transferrin-targeting non-invasive nanoparticle delivery system (Tf-NP) can efficiently deliver miR-1 to GBM patient-derived GSC-enriched sphere cultures (GBM spheres).

METHODS

Delivery efficiency of the transferrin- targeting non-invasive nanoparticle was investigated by flow cytometry and further confirmed by confocal microscopy. The levels of miR-1 and its target molecules in GBM spheres were measured by qRT-PCR and immunoblotting. Migration capacity of Tf-NP-miR-1 treated GBM spheres were evaluated by transwell migration assay.

RESULTS

Tf-NPmiR- 1 treatment resulted in an over 200-fold increase of mature miR-1 compared to free miR-1 and Tf-NP-miR negative control (Tf-NP-miR-NC). Transferrin-mediated NP delivery resulted in a 3-fold higher delivery efficiency compared to NP without transferrin modification. Tf-NP-miR-1 treatment on GBM spheres significantly inhibited migration of GBM spheres by 30-50% with associated decline of MET and EGFR expression. Our data supported that Tf-NP could be used as an efficient and effective delivery system which has high potential to benefit the development of miR-based therapeutics for GBM treatment.

Microwell array-mediated delivery of lipoplexes containing nucleic acids for enhanced therapeutic efficacy

Many delivery methods have been developed to improve the therapeutic efficacy and facilitate the clinical translation of nucleic acids-based therapeutics. We present a facile microwell array to mediate the delivery of nucleic acids carried by lipoplexes, which combines the advantages of lipoplexes as an efficient carrier system, the surface mediated delivery, and the control of surface topography. This method shows much higher transfection efficiency than conventional transfection method for oligodeoxynucleotides and microRNAs, and thus significantly reduces the effective therapeutic dosages. Microwell array is also a very flexible platform. Multifunctional lipoplexes containing both nucleic acid therapeutics and imaging reagents can be easily prepared in the microwell array and efficiently delivered to cells, demonstrating its potential applications in theranostic medicine.

Magnetic tweezers-based 3D microchannel electroporation for high-throughput gene transfection in living cells

A novel high-throughput magnetic tweezers-based 3D microchannel electroporation system capable of transfecting 40 000 cells/cm(2) on a single chip for gene therapy, regenerative medicine, and intracellular detection of target mRNA for screening cellular heterogeneity is reported. A single cell or an ordered array of individual cells are remotely guided by programmable magnetic fields to poration sites with high (>90%) cell alignment efficiency to enable various transfection reagents to be delivered simultaneously into the cells. The present technique, in contrast to the conventional vacuum-based approach, is significantly gentler on the cellular membrane yielding >90% cell viability and, moreover, allows transfected cells to be transported for further analysis. Illustrating the versatility of the system, the GATA2 molecular beacon is delivered into leukemia cells to detect the regulation level of the GATA2 gene that is associated with the initiation of leukemia. The uniform delivery and a sharp contrast of fluorescence intensity between GATA2 positive and negative cells demonstrate key aspects of the platform for gene transfer, screening and detection of targeted intracellular markers in living cells.

Effect of nonendocytic uptake of nanoparticles on human bronchial epithelial cells

The toxicity of artificial nanoparticles is a major concern in industrial applications. Cellular uptake of hard nanoparticles could follow either endocytic or nonendocytic pathways, leading to different stimuli to the cells. Yet the cellular responses to nanoparticles following different pathways have not been compared due to the lack of an independent nonendocytic delivery method. We applied a unique delivery method, nanochannel electroporation (NEP), to produce predominantly nonendocytic uptakes of quantum dots (Q-dots) and multiwalled carbon nanotubes (MWCNTs) with different chemical modifications. NEP delivery bypassed endocytosis by electrophoretic injection of nanoparticles into human bronchial epithelial (BEAS-2B) cells at different dosages. Conventional exposure by direct nanoparticle suspending in cell culture medium was also performed as control. The dosage-dependent responses to nanoparticles under different uptake pathways were compared. Fluorescence colocalization demonstrated that nanoparticles followed both endocytic and nonendocytic pathways for cell entry in contact exposure, whereas NEP delivery of nanoparticles bypassed endocytosis. Nonendocytic entry resulted in much higher oxidation stress and, for MWCNTs, more cell death in BEAS-2B cells. Despite the observation that most nanoparticles were taken up by cells through endocytosis, the minor nonendocytic entry of nanoparticles seemed to dominate the overall cellular response in conventional contact exposure. Our finding suggests that prevention against nonendocytic uptake could help reduce the toxicity of hard nanoparticles.

DNA translocation through short nanofluidic channels under asymmetric pulsed electric field

Investigation of single molecule DNA dynamics in confined environments has led to important applications in DNA analysis, separation, and sequencing. Here, we studied the electrophoretic transport of DNA molecules through nanochannels shorter than the DNA contour length and calculated the associated translocation time curves. We found that the longer T4 DNA molecules required a longer time to traverse a fixed length nanochannel than shorter λ DNA molecules and that the translocation time decreased with increasing electric field which agreed with theoretical predictions. We applied this knowledge to design an asymmetric electric pulse and demonstrate the different responses of λ and T4 DNA to the pulses. We used Brownian dynamics simulations to corroborate our experimental results on DNA translocation behaviour. This work contributes to the fundamental understanding of polymer transport through nanochannels and may help in designing better separation techniques in the future.

Atomic carbide bonding leading to superior graphene networks

A versatile method for achieving atomic carbide-bonded graphene networks on both metallic and non-metallic substrates is described. This consists of vacuum-assisted thermal exfoliation and floatation of functional graphenes at elevated temperatures, followed by deposition on substrates and in situ formation of carbide bonds. The cross-linked graphene networks with an interlayer distance of angstroms exhibits a unique combination of unprecedented properties.

Surface-mediated nucleic acid delivery by lipoplexes prepared in microwell arrays

Many delivery methods have been developed to improve the therapeutic efficacy and facilitate the clinical translation of nucleic acid-based therapeutics. A facile surface-mediated nucleic acid delivery by lipoplexes is prepared in a microwell array, which combines the advantages of lipoplexes as an efficient carrier system, surface-mediated delivery, and the control of surface topography. Uniform disc-like lipoplexes containing nucleic acids are formed in the microwell array with a diameter of ∼818 nm and thickness of ∼195 nm. The microwell array-mediated delivery of lipoplexes containing FAM-oligodeoxynucleotides is ∼18.6 and ∼10.6 times more efficient than the conventional transfection method in an adherent cell line (A549 non-small cell lung cancer cells) and a suspension cell line (KG-1a acute myelogenous leukemia cells), respectively. MicroRNA-29b is then used as a model nucleic acid to investigate the therapeutic efficacy of lipoplexes delivered by the microwell array. Compared to conventional transfection methods, the effective therapeutic dosage of microRNA-29b is reduced from the microgram level to the nanogram level by lipoplexes prepared in the microwell array. The microwell array is also a very flexible platform. Both nucleic acid therapeutics and imaging reagents are incorporated in lipoplexes and successfully delivered to A549 cells, demonstrating its potential applications in theranostic medicine.

Micro/nanoscale technologies for the development of hormone-expressing islet-like cell clusters

Insulin-expressing islet-like cell clusters derived from precursor cells have significant potential in the treatment of type-I diabetes. Given that cluster size and uniformity are known to influence islet cell behavior, the ability to effectively control these parameters could find applications in the development of anti-diabetic therapies. In this work, we combined micro and nanofabrication techniques to build a biodegradable platform capable of supporting the formation of islet-like structures from pancreatic precursors. Soft lithography and electrospinning were used to create arrays of microwells (150-500 μm diameter) structurally interfaced with a porous sheet of micro/nanoscale polyblend fibers (~0.5-10 μm in cross-sectional size), upon which human pancreatic ductal epithelial cells anchored and assembled into insulin-expressing 3D clusters. The microwells effectively regulated the spatial distribution of the cells on the platform, as well as cluster size, shape and homogeneity. Average cluster cross-sectional area (~14000-17500 μm(2)) varied in proportion to the microwell dimensions, and mean circularity values remained above 0.7 for all microwell sizes. In comparison, clustering on control surfaces (fibers without microwells or tissue culture plastic) resulted in irregularly shaped/sized cell aggregates. Immunoreactivity for insulin, C-peptide and glucagon was detected on both the platform and control surfaces; however, intracellular levels of C-peptide/cell were ~60 % higher on the platform.

Microfabricated mimics of in vivo structural cues for the study of guided tumor cell migration

Guided cell migration plays a crucial role in tumor metastasis, which is considered to be the major cause of death in cancer patients. Such behavior is regulated in part by micro/nanoscale topographical cues present in the parenchyma or stroma in the form of fiber-like and/or conduit-like structures (e.g., white matter tracts, blood/lymphatic vessels, subpial and subperitoneal spaces). In this paper we used soft lithography micromolding to develop a tissue culture polystyrene platform with a microscale surface pattern that was able to induce guided cell motility along/through fiber-/conduit-like structures. The migratory behaviors of primary (glioma) and metastatic (lung and colon) tumors excised from the brain were monitored via time-lapse microscopy at the single cell level. All the tumor cells exhibited axially persistent cell migration, with percentages of unidirectionally motile cells of 84.0 ± 3.5%, 58.3 ± 6.8% and 69.4 ± 5.4% for the glioma, lung, and colon tumor cells, respectively. Lung tumor cells showed the highest migratory velocities (41.8 ± 4.6 μm h(-1)) compared to glioma (24.0 ± 1.8 μm h(-1)) and colon (26.7 ± 2.8 μm h(-1)) tumor cells. This platform could potentially be used in conjunction with other biological assays to probe the mechanisms underlying the metastatic phenotype under guided cell migration conditions, and possibly by itself as an indicator of the effectiveness of treatments that target specific tumor cell motility behaviors.

Micropatterned thermoresponsive surfaces by polymerization of monomer crystals: modulating cellular morphology and cell-substrate interactions

A novel and facile approach has been developed to create thermoresponsive surfaces with macroscale patterns together with microscale features. The surface patterns were formed by applying macroscale nucleation agent patterns onto saturated N-isopropylacrylamide monomer solution membranes to induce the divergent growth of needlelike monomer crystals; the patterned monomer crystals were then photopolymerized to form patterned thermoresponsive films. A series of analytical tools (i.e., scanning electron microscopy, profilometry, and contact angle measurement) were used to characterize the properties of the patterned films. Cell coculture on this patterned thermoresponsive films enables cell separation and sorting by modulating temperature- and topography-dependent cell-substrate interactions and cell morphology, respectively. This versatile technique allows the formation of various macroscale patterns with microscale features over large areas, and on most solid substrates, within minutes, all of this without the need for expensive equipment and facilities. Such patterned surfaces can act as both in vitro tumor models and separation platforms for cancer studies. This method can also be applied to other cell-based biological studies and clinical applications.