Probing tumor microtissue formation and epithelial-mesenchymal transition on a well-mesh microchip

Hollow Microfiber Assembly-Based Endocrine Pancreas-on-a-Chip for Sugar Substitute Evaluation

With the increasing demand for low-sugar, low-calorie healthy diets, artificial sweeteners are widely used as substitutes for sugar in the food industry. Therefore, developing models that can better predict the effects of sugar substitutes on the human body is necessary. Here, a new type of endocrine pancreas-on-a-chip is developed based on a microfiber assembly and its stimulation of pancreatic secretion by glucose or sugar substitutes is evaluated. This new endocrine pancreas-on-a-chip is assembled using two components: (1) a cell-loaded hollow methacrylate gelatin (GelMA)/calcium alginate (CaA) composite microfiber prepared by microfluidic spinning to achieve vascular simulation and material transport, and (2) a 3D pancreatic islet culture layer, which also serves as a fiber assembly microchip. Using this established organ chip, the effects of five sweeteners (glucose, erythritol, xylitol, sodium cyclamate, and sucralose) were investigated on pancreatic islet cell viability and insulin and glucagon secretion. The constructed endocrine pancreas-on-a-chip has potential for the safety evaluation of sugar-substituted food additives, which can expand the application of organ chips in the field of food safety and provide a new platform for evaluating various food additives.

Microfiber Fabricated via Microfluidic Spinning toward Tissue Engineering Applications

Microfibers, a type of long, thin, and flexible material, can be assembled into functional 3D structures by folding, binding, and weaving. As a novel spinning method, combining microfluidic technology and wet spinning, microfluidic spinning technology can precisely control the size, morphology, structure, and composition of the microfibers. Particularly, the process is mild and rapid, which is suitable for preparing microfibers using biocompatible materials and without affecting the viability of cells encapsulated. Furthermore, owing to the controllability of microfluidic spinning, microfibers with well-defined structures (such as hollow structures) will contribute to the exchange of nutrients or guide cell orientation. Thus, this method is often used to fabricate microfibers as cell scaffolds for cell encapsulation or adhesion and can be further applied to biomimetic fibrous tissues. In this review, the focus is on different fiber structures prepared by microfluidic spinning technology, including solid, hollow, and heterogeneous structures, generated from three essential elements: spinning platform, fiber composition, and solidification methods. Furthermore, the application of microfibers is described with different structures in tissue engineering, such as blood vessels, skeletal muscle, bone, nerves, and lung bronchi. Finally, the challenges and future development prospects of microfluidic spinning technology in tissue engineering applications are discussed.

3D printing of heterogeneous microfibers with multi-hollow structure via microfluidic spinning

Tissues with tubular structures play important roles in the human bodies, such as mass transport, nutrition exchange, and waste filtration. However, it remains a challenge to generate micro-scaffolds with well-defined luminal structure in biomedical field. In this study, we proposed a novel method to fabricate multi-component microfibers with multi-hollow structure via microfluidic spinning, which can subsequently be integrated with 3D printing for tissue-like block assembling. To achieve this goal, we fabricated a microchip using a 3D printed template with adjustable heights. Utilizing this microchip, we successfully generated the Calcium alginate microfibers with multi-components and defined hollow structures in a controllable manner. Then this microfluidic spinning method was integrated with a 3D mobile platform to assemble the microfibers into a grid-like 3D architecture. The resulted 3D scaffolds exhibited good organization and maintained the hollow structure of the fibers. Furthermore, we successfully developed a bronchus model utilizing this strategy by loading pulmonary bronchial epithelium cells and endothelial cells into microfibers with two hollow structures. The present strategy provides a potential platform to rebuild the lumen-like tissues using microfibers.

Oncoimmunology Meets Organs-on-Chip

Oncoimmunology represents a biomedical research discipline coined to study the roles of immune system in cancer progression with the aim of discovering novel strategies to arm it against the malignancy. Infiltration of immune cells within the tumor microenvironment is an early event that results in the establishment of a dynamic cross-talk. Here, immune cells sense antigenic cues to mount a specific anti-tumor response while cancer cells emanate inhibitory signals to dampen it. Animals models have led to giant steps in this research context, and several tools to investigate the effect of immune infiltration in the tumor microenvironment are currently available. However, the use of animals represents a challenge due to ethical issues and long duration of experiments. Organs-on-chip are innovative tools not only to study how cells derived from different organs interact with each other, but also to investigate on the crosstalk between immune cells and different types of cancer cells. In this review, we describe the state-of-the-art of microfluidics and the impact of OOC in the field of oncoimmunology underlining the importance of this system in the advancements on the complexity of tumor microenvironment.

PLGA Nanofiber/PDMS Microporous Composite Membrane-Sandwiched Microchip for Drug Testing

Lung-on-a-chip devices could provide new strategies for a biomimetic lung cell microenvironment and construction of lung disease models in vitro, and are expected to greatly promote the development of drug evaluation, toxicological detection, and disease model building. In this study, we developed a novel poly (lactic-co-glycolic acid) (PLGA) nanofiber/polydimethylsiloxane (PDMS) microporous composite membrane-sandwiched lung-on-a-chip to perform anti-tumor drug testing. The composite membrane was characterized, and the results showed that it was permeable to molecules and thus could be used to study small-molecule drug diffusion. In addition, the microchip could apply perfusion fluids to simulate blood flow under extremely low fluid shear stress, and could also simulate the spherical-like shape of the alveoli by deformation of the composite membrane. Using this chip, we evaluated the anti-tumor drug efficacy of gefitinib in two kinds of non-small cell lung cancer cells, the lung adenocarcinoma NCI-H1650 cell line and the large cell lung cancer NCI-H460 cell line. We further probed the resistance of NCI-H460 cells to gefitinib under normoxic and hypoxic conditions. The established composite membrane-sandwiched lung chip can simulate more biochemical and biophysical factors in the lung physiological and pathological microenvironment, and it has important applications in the personalized treatment of lung tumors. It is expected to play a potential role in clinical diagnosis and drug screening.

Simple Fabrication of Multicomponent Heterogeneous Fibers for Cell Co-Culture via Microfluidic Spinning

Microfluidic spinning, as a combination of wet spinning and microfluidic technology, has been used to develop microfibers with special structures to facilitate cell 3D culture/co-culture and microtissue formation in vitro. In this study, a simple microchip-based microfluidic spinning strategy is presented for the fabrication of multicomponent heterogeneous calcium alginate microfibers. The use of two kinds of microchip enables the one-step preparation of multicomponent heterogeneous microfibers with various arrangement patterns, including the preparation of one-, two-, and three-component microfibers by a two-layer microchip and preparation of four component microfibers with different arrangement by a membrane-sandwiched three-layer microchip. The obtained microfibers could be used to encapsulate various kinds of cells, such as the human non-small cell lung cancer cell NCI-H1650, the human fetal lung fibroblast HFL1, the normal pulmonary bronchial epithelial cell 16HBE, and human umbilical vein endothelial cells. By adding chitosan to the medium to keep the fibers stable, 3D long-term in vitro cell co-culture has been carried out up to 21 days. This method is very simple and easy to operate, continuously produces spatially well-defined heterogeneous microfibers, has important applications for composite functional biomaterials, and shows great potential in organs-on-a-chip and biomimetic systems.

Biomimetic human lung-on-a-chip for modeling disease investigation

The lung is the primary respiratory organ of the human body and has a complicated and precise tissue structure. It comprises conductive airways formed by the trachea, bronchi and bronchioles, and many alveoli, the smallest functional units where gas-exchange occurs via the unique gas-liquid exchange interface known as the respiratory membrane. In vitro bionic simulation of the lung or its microenvironment, therefore, presents a great challenge, which requires the joint efforts of anatomy, physics, material science, cell biology, tissue engineering, and other disciplines. With the development of micromachining and miniaturization technology, the concept of a microfluidics-based organ-on-a-chip has received great attention. An organ-on-a-chip is a small cell-culture device that can accurately simulate tissue and organ functions in vitro and has the potential to replace animal models in evaluations of drug toxicity and efficacy. A lung-on-a-chip, as one of the first proposed and developed organs-on-a-chip, provides new strategies for designing a bionic lung cell microenvironment and for in vitro construction of lung disease models, and it is expected to promote the development of basic research and translational medicine in drug evaluation, toxicological detection, and disease model-building for the lung. This review summarizes current lungs-on-a-chip models based on the lung-related cellular microenvironment, including the latest advances described in studies of lung injury, inflammation, lung cancer, and pulmonary fibrosis. This model should see effective use in clinical medicine to promote the development of precision medicine and individualized diagnosis and treatment.

Biomimetic human lung-on-a-chip for modeling disease investigation

The lung is the primary respiratory organ of the human body and has a complicated and precise tissue structure. It comprises conductive airways formed by the trachea, bronchi and bronchioles, and many alveoli, the smallest functional units where gas-exchange occurs via the unique gas-liquid exchange interface known as the respiratory membrane. In vitro bionic simulation of the lung or its microenvironment, therefore, presents a great challenge, which requires the joint efforts of anatomy, physics, material science, cell biology, tissue engineering, and other disciplines. With the development of micromachining and miniaturization technology, the concept of a microfluidics-based organ-on-a-chip has received great attention. An organ-on-a-chip is a small cell-culture device that can accurately simulate tissue and organ functions in vitro and has the potential to replace animal models in evaluations of drug toxicity and efficacy. A lung-on-a-chip, as one of the first proposed and developed organs-on-a-chip, provides new strategies for designing a bionic lung cell microenvironment and for in vitro construction of lung disease models, and it is expected to promote the development of basic research and translational medicine in drug evaluation, toxicological detection, and disease model-building for the lung. This review summarizes current lungs-on-a-chip models based on the lung-related cellular microenvironment, including the latest advances described in studies of lung injury, inflammation, lung cancer, and pulmonary fibrosis. This model should see effective use in clinical medicine to promote the development of precision medicine and individualized diagnosis and treatment.