Engineering cell microenvironment using novel functional hydrogels

Programmable Anisotropic Hydrogel Composites for Soft Bioelectronics

Fabrication of hydrogel composites embedded with aligned one-dimensional nanoparticles has shown substantial growth over the last five years. Direct ink printing technology (DIW) has been used in this work to create the alignment of the one-dimensional nanoparticles due to the shear gradient of the pesudoplastic precursor (2-hydroxyethyl methacrylate (HEMA) with thickening agents). Orderly distributed one-dimensional particles constructing anisotropic nanostructures endow the hydrogel composite with unique mechanical, electric, or electromechanical coupling properties. Quasi-static uniaxial tensile test, electric resistivity and piezoresistivity measurements have been conducted for investigating the mechanical, electric, and the electromechanical coupling properties of the hydrogel composites, respectively. Based on the experimental results, it can be speculated that the developed printing process is able to fabricate hydrogel composites with programmable anisotropic mechanical, electric, and electromechanical properties. The products pumped out from this work has the potential of being substrate for soft devices, and may have great impact on the fields of flexible bioelectronics. This article is protected by copyright. All rights reserved.

Mechanotransduction assays for neural regeneration strategies: A focus on glial cells

Glial cells are mechanosensitive, and thus, engineered systems have taken a step forward to design mechanotransduction platforms in order to impart diverse mechanical stresses to cells. Mechanical strain encountered in the central nervous system can arise from diverse mechanisms, such as tissue reorganization, fluid flow, and axon growth, as well as pathological events including axon swelling or mechanical trauma. Biomechanical relevance of the in vitro mechanical testing requires to be placed in line with the physiological and mechanical changes in central nervous tissues that occur during the progression of neurodegenerative diseases. Mechanotransduction signaling utilized by glial cells and the recent approaches intended to model altered microenvironment adapted to pathological context are discussed in this review. New insights in systems merging substrate's stiffness and topography should be considered for further glial mechanotransduction studies, while testing platforms for drug discoveries promise great advancements in pharmacotherapy. Potential leads and strategies for clinical outcomes are expected to be developed following the exploration of these glial mechanosensitive signaling pathways.

Innovative Tools for Mechanobiology: Unraveling Outside-In and Inside-Out Mechanotransduction

Cells and tissues can sense and react to the modifications of the physico-chemical properties of the extracellular environment (ECM) through integrin-based adhesion sites and adapt their physiological response in a process called mechanotransduction. Due to their critical localization at the cell-ECM interface, transmembrane integrins are mediators of bidirectional signaling, playing a key role in “outside-in” and “inside-out” signal transduction. After presenting the basic conceptual fundamentals related to cell mechanobiology, we review the current state-of-the-art technologies that facilitate the understanding of mechanotransduction signaling pathways. Finally, we highlight innovative technological developments that can help to advance our understanding of the mechanisms underlying nuclear mechanotransduction.

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.

Stem cell culture and differentiation in microfluidic devices toward organ-on-a-chip

Microfluidic lab-on-a-chip provides a new platform with unique advantages to mimic complex physiological microenvironments in vivo and has been increasingly exploited to stem cell research. In this review, we highlight recent advances of microfluidic devices for stem cell culture and differentiation toward the development of organ-on-a-chip, especially with an emphasis on vital innovations within the last 2 years. Various aspects for improving on-chip stem-cell culture and differentiation, particularly toward organ-on-a-chip, are discussed, along with microenvironment control, surface modification, extracellular scaffolds, high throughput and stimuli. The combination of microfluidic technologies and stem cells hold great potential toward versatile systems of ‘organ-on-a-chip’ as desired.

Adapted with permission from [1–8].

Stem cells, capable of self-renewing and differentiating into cells of various tissue types, are drawing more and more attention for their enormous potential in many clinically associated applications that include drug screening, disease modeling and regenerative medicine. Conventional cell culture methods, however, have proven to be difficult to mimic in vivo like microenvironments and to provide a number of well-controlled stimuli that are critical for stem cell culture and differentiation. In contrast, microfluidic devices offer new capacities and unique advantages to mimic complex physiological microenvironments in vivo, and has been increasingly applied to stem cell research.

A simple fabricated thickness-based stiffness gradient for cell studies

In this work, we developed a simple method to fabricate a thickness-based continuous stiffness gradient for biological studies. It was made by glass slides, polydimethylsiloxane (PDMS) pre-polymer, spacer and clips only, without any sophisticated equipment. It is easy to fabricate in any general biological and pharmaceutical laboratories. The stiffness gradient was characterized in terms of apparent Young's modulus by atomic force microscopy (AFM) and the Young's modulus along the gradient was found to be 8.5-120kPa, which is within the physiological relevant range. HeLa-C3 cells were cultured on the gradient to study their morphological behavior according to the substrate stiffness. Furthermore, the drug efficiency of etoposide, an anti-cancer drug, was studied along the substrate stiffness gradient. It was found that HeLa-C3 cells cultured on the soft region of the gradient (8.5-11kPa) are more sensitive to etoposide. We believe the proposed device could promote cell investigations and drug screenings on a substrate with comparable stiffness to the native tissue.