Micropassage-embedding composite hydrogel fibers enable quantitative evaluation of cancer cell invasion under 3D coculture conditions

Engineering Heterogeneous Tumor Models for Biomedical Applications

Tumor tissue engineering holds great promise for replicating the physiological and behavioral characteristics of tumors in vitro. Advances in this field have led to new opportunities for studying the tumor microenvironment and exploring potential anti-cancer therapeutics. However, the main obstacle to the widespread adoption of tumor models is the poor understanding and insufficient reconstruction of tumor heterogeneity. In this review, the current progress of engineering heterogeneous tumor models is discussed. First, the major components of tumor heterogeneity are summarized, which encompasses various signaling pathways, cell proliferations, and spatial configurations. Then, contemporary approaches are elucidated in tumor engineering that are guided by fundamental principles of tumor biology, and the potential of a bottom-up approach in tumor engineering is highlighted. Additionally, the characterization approaches and biomedical applications of tumor models are discussed, emphasizing the significant role of engineered tumor models in scientific research and clinical trials. Lastly, the challenges of heterogeneous tumor models in promoting oncology research and tumor therapy are described and key directions for future research are provided.

Fabrication and Cell Culture Applications of Core-Shell Hydrogel Fibers Composed of Chitosan/DNA Interfacial Polyelectrolyte Complexation and Calcium Alginate: Straight and Beaded Core Variations

Core-shell hydrogel fibers are widely used in cell culture applications. A simple and rapid method is presented for fabricating core-shell hydrogel fibers, consisting of straight or beaded core fibers, for cell culture applications. The core fibers are prepared using interfacial polyelectrolyte complexation (IPC) with chitosan and DNA. Briefly, two droplets of chitosan and DNA are brought in contact to form an IPC film, which is dragged to prepare an IPC fiber. The incubation time and DNA concentration are adjusted to prepare straight and beaded IPC fibers. The fibers with Ca2+ are immersed in an alginate solution to form calcium alginate shell hydrogels around the core IPC fibers. To the best of the knowledge, this is the first report of core-shell hydrogel fibers with IPC fiber cores. To demonstrate cell culture, straight hydrogel fibers are applied to fabricate hepatic models consisting of HepG2 and 3T3 fibroblasts, and vascular models consisting of human umbilical vein endothelial cells and 3T3 fibroblasts. To evaluate the effect of co-culture, albumin secretion, and angiogenesis are evaluated. Beaded hydrogel fibers are used to fabricate many size-controlled spheroids for fiber and cloning applications. This method can be widely applied in tissue engineering and cell analysis.

Microfluidic platforms in diagnostic of ovarian cancer

The most important reason for death from ovarian cancer is the late diagnosis of this disease. The standard treatment of ovarian cancer includes surgery and chemotherapy based on platinum, which is associated with side effects for the body. Due to the nonspecific nature of clinical symptoms, developing a platform for early detection of this disease is needed. In recent decades, the advancements of microfluidic devices and systems have provided several advantages for diagnosing ovarian cancer. Designing and manufacturing new platforms using specialized technologies can be a big step toward improving the prevention, diagnosis, and treatment of this group of diseases. Organ-on-a-chip microfluidic devices are increasingly used as a promising platform in cancer research, with a focus on specific biological aspects of the disease. This review focusing on ovarian cancer and microfluidic application technologies in its diagnosis. Additionally, it discusses microfluidic platforms and their potential future perspectives in advancing ovarian cancer diagnosis.

Lab-on-a-chip systems for cancer biomarker diagnosis

Lab-on-a-chip (LOC) or micro total analysis system is one of the microfluidic technologies defined as the adaptation, miniaturization, integration, and automation of analytical laboratory procedures into a single instrument or "chip". In this article, we review developments over the past five years in the application of LOC biosensors for the detection of different types of cancer. Microfluidics encompasses chemistry and biotechnology skills and has revolutionized healthcare diagnosis. Superior to traditional cell culture or animal models, microfluidic technology has made it possible to reconstruct functional units of organs on chips to study human diseases such as cancer. LOCs have found numerous biomedical applications over the past five years, including integrated bioassays, cell analysis, metabolomics, drug discovery and delivery systems, tissue and organ physiology and disease modeling, and personalized medicine. This review provides an overview of the latest developments in microfluidic-based cancer research, with pros, cons, and prospects.

Microfluidic Formulation of Topological Hydrogels for Microtissue Engineering

Microfluidics has recently emerged as a powerful tool in generation of submillimeter-sized cell aggregates capable of performing tissue-specific functions, so-called microtissues, for applications in drug testing, regenerative medicine, and cell therapies. In this work, we review the most recent advances in the field, with particular focus on the formulation of cell-encapsulating microgels of small "dimensionalities": "0D" (particles), "1D" (fibers), "2D" (sheets), etc., and with nontrivial internal topologies, typically consisting of multiple compartments loaded with different types of cells and/or biopolymers. Such structures, which we refer to as topological hydrogels or topological microgels (examples including core-shell or Janus microbeads and microfibers, hollow or porous microstructures, or granular hydrogels) can be precisely tailored with high reproducibility and throughput by using microfluidics and used to provide controlled "initial conditions" for cell proliferation and maturation into functional tissue-like microstructures. Microfluidic methods of formulation of topological biomaterials have enabled significant progress in engineering of miniature tissues and organs, such as pancreas, liver, muscle, bone, heart, neural tissue, or vasculature, as well as in fabrication of tailored microenvironments for stem-cell expansion and differentiation, or in cancer modeling, including generation of vascularized tumors for personalized drug testing. We review the available microfluidic fabrication methods by exploiting various cross-linking mechanisms and various routes toward compartmentalization and critically discuss the available tissue-specific applications. Finally, we list the remaining challenges such as simplification of the microfluidic workflow for its widespread use in biomedical research, bench-to-bedside transition including production upscaling, further in vivo validation, generation of more precise organ-like models, as well as incorporation of induced pluripotent stem cells as a step toward clinical applications.

A Temperature-Based Easy-Separable (TempEasy) 3D Hydrogel Coculture System

Interactions between different cell types are crucial for their behavior in tissues, but are rarely considered in 3D in vitro cell culture experiments. One reason is that such coculture experiments are sometimes difficult to perform in 3D or require specialized equipment or know-how. Here, a new 3D cell coculture system is introduced, TempEasy, which is readily applied in any cell culture lab. The matrix material is based on polyisocyanide hydrogels, which closely resemble the mechanical characteristics of the natural extracellular matrix. Gels with different gelation temperatures, seeded with different cells, are placed on top of each other to form an indirect coculture. Cooling reverses gelation, allowing cell harvesting from each layer separately, which benefits downstream analysis. To demonstrate the potential of TempEasy , human adipose stem cells (hADSCs) with vaginal epithelial fibroblasts are cocultured. The analysis of a 7-day coculture shows that hADSCs promote cell-cell interaction of fibroblasts, while fibroblasts promote proliferation and differentiation of hADSCs. TempEasy provides a straightforward operational platform for indirect cocultures of cells of different lineages in well-defined microenvironments.

Controlled Fabrication of Bioactive Microtubes for Screening Anti-Tongue Squamous Cell Migration Drugs

The treatment of tongue squamous cell carcinoma (TSCC) faces challenges because TSCC has an aggressive biological behavior and manifests usually as widespread metastatic disease. Therefore, it is particularly important to screen out and develop drugs that inhibit tumor invasion and metastasis. Two-dimensional (2D) cell culture has been used as in vitro models to study cellular biological behavior, but growing evidence now shows that the 2D systems can result in cell bioactivities that deviate appreciably the in vivo response. It is urgent to develop a novel 3D cell migration model in vitro to simulate the tumor microenvironment as much as possible and screen out effective anti-migration drugs. Sodium alginate, has a widely used cell encapsulation material, as significant advantages. We have designed a microfluidic device to fabricate a hollow alginate hydrogel microtube model. Based on the difference in liquid flow rate, TSCC cells (Cal27) were able to be evenly distributed in the hollow microtubes, which was confirmed though fluorescence microscope and laser scanning confocal microscope (LSCM). Our microfluidic device was cheap, and commercially available and could be assembled in a modular way, which are composed of a coaxial needle, silicone hose, and syringes. It was proved that the cells grow well in artificial microtubes with extracellular matrix (ECM) proteins by LSCM and flow cytometry. Periodic motility conferred a different motor state to the cells in the microtubes, more closely resembling the environment in vivo. The quantitative analysis of tumor cell migration could be achieved simply by determining the position of the cell in the microtube cross-section. We verified the anti-migration effects of three NSAIDs drugs (aspirin, indomethacin, and nimesulide) with artificial microtubes, obtaining the same results as conventional migration experiments. The results showed that among the three NSAIDs, nimesulide showed great anti-migration potential against TSCC cells. Our method holds great potential for application in the more efficient screening of anti-migration tumor drugs.

A flexible and cost-effective manual droplet operation platform for miniaturized cell assays and single cell analysis

Herein, we developed a flexible and cost-effective manual droplet operation system (MDOS) for performing miniaturized cell assays as well as single cell analysis. The MDOS consists of a manual x-y-z translation stage for liquid transferring and switching, a high-precision syringe pump for liquid driving and metering, a tapered capillary probe for droplet manipulation, a droplet array chip for droplet loading and reaction, sample/reagent reservoirs for storage, and a microscope for droplet observation, with a total expense of only $4,000. By using the flexible combination of three elementary operations of the x-y-z stage's moving and the pump's aspirating and depositing, the MDOS can manually achieve multiple droplet handling operations in the nanoliter to picoliter range, including droplet generation, assembling, fusion, diluting, and splitting. On this basis, multiple cell-related operations could be performed, such as nanoliter-scale in-droplet cell culture, cell coculture, drug stimulation, cell washing, and cell staining, as well as formation of picoliter single-cell droplets. The feasibility and flexibility of the MDOS was demonstrated in multi-mode miniaturized cell assays, including cell-based drug test, first-pass effect assay, and single-cell enzyme assay. The MDOS with the features of low cost, easy to build and flexible to use, could provide a promising alternative for performing miniaturized assays in routine laboratories, in addition to conventional microfluidic chip-based systems and automated robot systems.

Multicellular 3D Models to Study Tumour-Stroma Interactions

Two-dimensional (2D) cell cultures have been the standard for many different applications, ranging from basic research to stem cell and cancer research to regenerative medicine, for most of the past century. Hence, almost all of our knowledge about fundamental biological processes has been provided by primary and established cell lines cultured in 2D monolayer. However, cells in tissues and organs do not exist as single entities, and life in multicellular organisms relies on the coordination of several cellular activities, which depend on cell–cell communication across different cell types and tissues. In addition, cells are embedded within a complex non-cellular structure known as the extracellular matrix (ECM), which anchors them in a three-dimensional (3D) formation. Likewise, tumour cells interact with their surrounding matrix and tissue, and the physical and biochemical properties of this microenvironment regulate cancer differentiation, proliferation, invasion, and metastasis. 2D models are unable to mimic the complex and dynamic interactions of the tumour microenvironment (TME) and ignore spatial cell–ECM and cell–cell interactions. Thus, multicellular 3D models are excellent tools to recapitulate in vitro the spatial dimension, cellular heterogeneity, and molecular networks of the TME. This review summarizes the biological significance of the cell–ECM and cell–cell interactions in the onset and progression of tumours and focuses on the requirement for these interactions to build up representative in vitro models for the study of the pathophysiology of cancer and for the design of more clinically relevant treatments.

Multifunctional microfluidic chip for cancer diagnosis and treatment

Microfluidic chip is not a chip in the traditional sense. It is technologies that control fluids at the micro level. As a burgeoning biochip, microfluidic chips integrate multiple disciplines, including physiology, pathology, cell biology, biophysics, engineering mechanics, mechanical design, materials science, and so on. The application of microfluidic chip has shown tremendous promise in the field of cancer therapy in the past three decades. Various types of cell and tissue cultures, including 2D cell culture, 3D cell culture and tissue organoid culture could be performed on microfluidic chips. Patient-derived cancer cells and tissues can be cultured on microfluidic chips in a visible, controllable, and high-throughput manner, which greatly advances the process of personalized medicine. Moreover, the functionality of microfluidic chip is greatly expanding due to the customizable nature. In this review, we introduce its application in developing cancer preclinical models, detecting cancer biomarkers, screening anti-cancer drugs, exploring tumor heterogeneity and producing nano-drugs. We highlight the functions and recent development of microfluidic chip to provide references for advancing cancer diagnosis and treatment.

Sacrificial Alginate-Assisted Microfluidic Engineering of Cell-Supportive Protein Microfibers for Hydrogel-Based Cell Encapsulation

Although many types of technologies for hydrogel-based cell cultivation have recently been developed, strategies to integrate cell-adhesive micrometer-sized supports with bulk-scale hydrogel platforms have not been fully established. Here, we present a highly unique approach to produce cell-adhesive, protein-based microfibers assisted by the sacrificial template of alginate; we applied these fibers as microengineered scaffolds for hydrogel-based cell encapsulation. Two types of microfluidic devices were designed and fabricated: a single-layered device for producing relatively thick (Φ of 10-60 μm) alginate-protein composite fibers with a uniform cross-sectional morphology and a four-layered device for preparing thinner (Φ of ∼4 μm) ones through the formation of patterned microfibers with eight distinct alginate-protein composite regions. Following chemical cross-linking of protein molecules and the subsequent removal of the sacrificial alginate from the double-network matrices, microfibers composed only of cross-linked proteins were obtained. We used gelatin, albumin, and hemoglobin as the protein material, and the gelatin-based cell-adhesive fibers were further encapsulated in hydrogels together with the mammalian cells. We clarified that the thinner fibers were especially effective in promoting cell proliferation, and the shape of the constructs was maintained even after removing the hydrogel matrices. The presented approach offers cells with biocompatible solid supports that enhance cell adhesion and proliferation, paving the way for the next generation of techniques for tissue engineering and multicellular organoid formation.

Evaluation of intercellular communication between breast cancer cells and adipose-derived stem cells via passive diffusion in a two-layer microfluidic device

Breast cancer tumorigenesis and response to therapy is regulated by cancer cell interactions with the tumor microenvironment (TME). Breast cancer signaling to the surrounding TME results in a heterogeneous and diverse tumor microenvironment, which includes the production of cancer-associated fibroblasts, macrophages, adipocytes, and stem cells. The secretory profile of these cancer-associated cell types results in elevated chemokines and growth factors that promote cell survival and proliferation within the tumor. Current co-culture approaches mostly rely on transwell chambers to study intercellular signaling between adipose-derived stem cells (ASCs) and cancer cells; however, these methods are limited to endpoint measurements and lack dynamic control. In this study, a 4-channel, "flow-free" microfluidic device was developed to co-culture triple-negative MDA-MB-231 breast cancer cells and ASCs to study intercellular communication between two distinct cell types found in the TME. The device consists of two layers: a top PDMS layer with four imprinted channels coupled with a bottom agarose slab enclosed in a Plexiglas chamber. For dynamic co-culture, the device geometry contained two centered, flow-free channels, which were supplied with media from two outer flow channels via orthogonal diffusion through the agarose. Continuous fresh media was provided to the cell culture channel via passive diffusion without creating any shearing effect on the cells. The device geometry also allowed for the passive diffusion of cytokines and growth factors between the two cell types cultured in parallel channels to initiate cell-to-cell crosstalk. The device was used to show that MDA-MB-231 cells co-cultured with ASCs exhibited enhanced growth, a more aggressive morphology, and polarization toward the ASCs. The MDA-MB-231 cells were found to exhibit a greater degree of resistance to the drug paclitaxel when co-cultured with ASCs when compared to single culture studies. This microfluidic device is an ideal platform to study intercellular communication for many types of cells during co-culture experiments and allows for new investigations into stromal cell-mediated drug resistance in the tumor microenvironment.

3D biofabrication of microfiber-laden minispheroids: a facile 3D cell co-culturing system

Hierarchical tissues composed of spheroid and fiber structures such as tumors, embryos and glomeruli widely exist in organisms. Methods have been developed to build spheroid and fiber structures, independently, as tissue models in vitro. However, it is still a challenge to print them simultaneously and integrated for effectively mimicking the complicated situations in vivo. Here, we propose a novel 3D cell co-culturing system, "microfiber-laden minispheroid", applying two fluidic phenomena, namely the "rope coiling effect" and "electrohydrodynamics", with a co-axial bioprinting nozzle and high voltage system. Gelatin methacryloyl (GelMA) hydrogels were extruded from the outer nozzle and separated by electrical attraction to form spheroids (∼1800 μm). GelMA mixed with sodium alginate was extruded from the inner nozzle to form fibers (∼180 μm) inside spheroids, whose morphology could be controlled by the ratio of inner and outer nozzle extruding flow rates. We analyzed the fabrication process and the material system in detail, verifying the fabrication feasibility and suitable microenvironment. The encapsulated cells possessed high viabilities. Importantly, the actin of human umbilical vein endothelial cells tended to elongate towards the co-cultured tumor cells, in contrast to the HUVECs cultured alone. We believe that "microfiber-laden minispheroids" could be a potential system for 3D cell co-culturing research in the future.

Multifunctional Micro/Nanoscale Fibers Based on Microfluidic Spinning Technology

Superfine multifunctional micro/nanoscale fibrous materials with high surface area and ordered structure have attracted intensive attention for widespread applications in recent years. Microfluidic spinning technology (MST) has emerged as a powerful and versatile platform because of its various advantages such as high surface-area-to-volume ratio, effective heat transfer, and enhanced reaction rate. The resultant well-defined micro/nanoscale fibers exhibit controllable compositions, advanced structures, and new physical/chemical properties. The latest developments and achievements in microfluidic spun fiber materials are summarized in terms of the underlying preparation principles, geometric configurations, and functionalization. Variously architected structures and shapes by MST, including cylindrical, grooved, flat, anisotropic, hollow, core-shell, Janus, heterogeneous, helical, and knotted fibers, are emphasized. In particular, fiber-spinning chemistry in MST for achieving functionalization of fiber materials by in situ chemical reactions inside fibers is introduced. Additionally, the applications of the fabricated functional fibers are highlighted in sensors, microactuators, photoelectric devices, flexible electronics, tissue engineering, drug delivery, and water collection. Finally, recent progress, challenges, and future perspectives are discussed.

Preparation of Cell-Paved and -Incorporated Polysaccharide Hollow Fibers Using a Microfluidic Device

Cellular constructs having hollow tubular structures are expected to be used as artificial blood vessels. We have recently demonstrated that water-insoluble polyion complexes (PICs) were formed from water-soluble polysaccharides with opposite charges at the interface of coaxial flows, which resulted in the formation of hollow fibers. In this study, both inside- and outside-cell-laden chondroitin sulfate C (CS)/chitosan (CHI) hollow fibers were prepared by utilizing a microfluidic device and modification with cell adhesive molecules. Loading of type I collagen (COL) and surface modification with fibronectin and gelatin using layer-by-layer assembly techniques improved the adhesion and spreading of fibroblast cells to/on the surface of CS/CHI hollow fibers. On the other hand, by suspending mesenchymal stem cells (MSCs) in the core flow solution, cells were successfully loaded in the walls of the hollow fibers. As the culture time extended, cells trapped in the PIC structures constituting the wall of the hollow fibers migrated to the interface between the hollow fibers and the medium: cells adhered to and stretched "on" the lumen surfaces in the COL-loaded fibers. In contrast, for the case of unmodified hollow fibers, it was difficult for cells to adhere to the lumen surfaces. Therefore, cell aggregates were formed "in" the lumen. Results of the live/dead assay and MTT assay clearly demonstrated that MSCs possessed certain levels of cell viability and proliferated for up to 10 days, especially for the cases of COL-loaded hollow fibers. On the basis of these results, the utility of the present hollow fibers in the formation of cellular constructs corresponding to blood vessels is also discussed.

Generation of perfusable hollow calcium alginate microfibers with a double co-axial flow capillary microfluidic device

This paper describes a highly controllable method to generate hollow calcium alginate microfibers using a double co-axial flow microdevice. The microdevice was fabricated by concentric assembly of two modules; each module consisted of a shortened cone-pulled glass capillary embedded in a polymethylmethacrylate fluidic block. Using this microdevice, cylindrical hollow calcium alginate microfibers with either straight or helical inner walls were stably and continuously generated. The radii of the hollow microfibers were not arbitrary, and in fact, the ratio of the outer to inner diameter was inversely correlated with the combination of core flow rate and the first sheath flow rate. The relationships between the geometrical features of the helix and the flow rates were also analyzed. The helical pitch and the spiral radius of the helical hollow microfibers were strongly influenced by the second sheath flow rate. Finally, guidelines for generating highly controllable straight and helical hollow microfibers and fabricating a seamless flow connector using this microfluidic device are suggested.

Engineering approaches to studying cancer cell migration in three-dimensional environments

Cancer is one of the most devastating diseases of our time, with 17 million new cancer cases and 9.5 million cancer deaths in 2018 worldwide. The mortality associated with cancer results primarily from metastasis, i.e. the spreading of cancer cells from the primary tumour to other organs. The invasion and migration of cells through basement membranes, tight interstitial spaces and endothelial cell layers are key steps in the metastatic cascade. Recent studies demonstrated that cell migration through three-dimensional environments that mimic the in vivo conditions significantly differs from their migration on two-dimensional surfaces. Here, we review recent technological advances made in the field of cancer research that provide more 'true to the source' experimental platforms and measurements for the study of cancer cell invasion and migration in three-dimensional environments. These include microfabrication, three-dimensional bioprinting and intravital imaging tools, along with force and stiffness measurements of cells and their environments. These techniques will enable new studies that better reflect the physiological environment found in vivo, thereby producing more robust results. The knowledge achieved through these studies will aid in the development of new treatment options with the potential to ultimately lighten the devastating cost cancer inflicts on patients and their families. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.

3D models in the new era of immune oncology: focus on T cells, CAF and ECM

Immune checkpoint inhibitor therapy has changed clinical practice for patients with different cancers, since these agents have demonstrated a significant improvement of overall survival and are effective in many patients. However, an intrinsic or acquired resistance frequently occur and biomarkers predictive of responsiveness should help in patient selection and in defining the adequate treatment options. A deep analysis of the complexity of the tumor microenvironment is likely to further advance the field and hopefully identify more effective combined immunotherapeutic strategies. Here we review the current knowledge on tumor microenvironment, focusing on T cells, cancer associated fibroblasts and extracellular matrix. The use of 3D cell culture models to resemble tumor microenvironment landscape and to screen immunomodulatory drugs is also reviewed.

Formation of pressurizable hydrogel-based vascular tissue models by selective gelation in composite PDMS channels

Vascular tissue models created in vitro are of great utility in the biomedical research field, but versatile, facile strategies are still under development. In this study, we proposed a new approach to prepare vascular tissue models in PDMS-based composite channel structures embedded with barium salt powders. When a cell-containing hydrogel precursor solution was continuously pumped in the channel, the precursor solution in the vicinity of the channel wall was selectively gelled because of the barium ions as the gelation agent supplied to the flow. Based on this concept, we were able to prepare vascular tissue models, with diameters of 1–2 mm and with tunable morphologies, composed of smooth muscle cells in the hydrogel matrix and endothelial cells on the lumen. Perfusion culture was successfully performed under a pressurized condition of ∼120 mmHg. The presented platform is potentially useful for creating vascular tissue models that reproduce the physical and morphological characteristics similar to those of vascular tissues in vivo.

A new approach for the preparation of vascular tissue models in PDMS-based composite channel structures embedded with barium salt powders.

Analysis of Cancer Cell Invasion and Anti-metastatic Drug Screening Using Hydrogel Micro-chamber Array (HMCA)-based Plates

Cancer metastasis is known to cause 90% of cancer lethality. Metastasis is a multistage process which initiates with the penetration/invasion of tumor cells into neighboring tissue. Thus, invasion is a crucial step in metastasis, making the invasion process research and development of anti-metastatic drugs, highly significant. To address this demand, there is a need to develop 3D in vitro models which imitate the architecture of solid tumors and their microenvironment most closely to in vivo state on one hand, but at the same time be reproducible, robust and suitable for high yield and high content measurements. Currently, most invasion assays lean on sophisticated microfluidic technologies which are adequate for research but not for high volume drug screening. Other assays using plate-based devices with isolated individual spheroids in each well are material consuming and have low sample size per condition. The goal of the current protocol is to provide a simple and reproducible biomimetic 3D cell-based system for the analysis of invasion capacity in large populations of tumor spheroids. We developed a 3D model for invasion assay based on HMCA imaging plate for the research of tumor invasion and anti-metastatic drug discovery. This device enables the production of numerous uniform spheroids per well (high sample size per condition) surrounded by ECM components, while continuously and simultaneously observing and measuring the spheroids at single-element resolution for medium throughput screening of anti-metastatic drugs. This platform is presented here by the production of HeLa and MCF7 spheroids for exemplifying single cell and collective invasion. We compare the influence of the ECM component hyaluronic acid (HA) on the invasive capacity of collagen surrounding HeLa spheroids. Finally, we introduce Fisetin (invasion inhibitor) to HeLa spheroids and nitric oxide (NO) (invasion activator) to MCF7 spheroids. The results are analyzed by in-house software which enables semi-automatic, simple and fast analysis which facilitates multi-parameter examination.

Dehydration-triggered shape morphing based on asymmetric bubble hydrogel microfibers

Inspired by nature, scientists have been engaged in developing deformable artificial systems. Here, we propose an innovative method to realize controllable deformations using asymmetric bubble hydrogel microfibers produced by microfluidic cascaded coaxial devices. Asymmetric geometries, coupled with the mismatched shrinkage ratio, contribute to deformations upon dehydration. The dynamic process can be controlled by regulating bubble sizes, distances and packing modes. Various 4D structures have been constructed. Combined with the 3D printing technique, this proof-of-concept study may open new avenues for bio-engineering and beyond.