Advances in Hydrogels in Organoids and Organs‐on‐a‐Chip

Abstract

The major motivation is to better mimic human physiology and functions at multiscales from the molecular to the cellular, tissue, organ or even whole organism level. Current model systems primarily rely on the monolayer cell cultures and animal models. Simplistic monolayer cultures have their advantages, but they are often significantly different in gene expression, epigenetics, and cell function compared to native 3D tissues. [1,2] Also, they often lack cell-cell and cell-matrix interactions, [2,3] leading to the absence of tissue specific properties. Although animal models are widely used in biomedical research, they fail to faithfully predict human responses in a physiologically relevant manner due to the significant species divergences. [4] The limitations of these systems have provided an impetus for the development of alternative cell-based 3D models in vitro that better resemble the complex functionalities of living organs. Over the last several years, organoids and organ-on-a-chip (OOC), representing the major technological breakthrough, have emerged as two distinct model systems to achieve the same goal of building 3D organotypic models in vitro by bridging the gap between animal models and monolayer cultures. These engineered models are different in terms of cell source, tissue composition, architectural variability, functional features, scales, cellular fidelity, etc. Organoids, primarily evolving from developmental principles, refer to 3D multicellular tissues by self-organization of stem cells or organ-specific progenitors, which can recapitulate the intricate architectures and functionalities of in vivo organs. [5][6][7] Recent breakthroughs in organoid technology have enabled the successful generation of a variety of human organoids, such as the brain, [8,9] intestine, [10,11] liver, [12] kidney, [13,14] lung, [15] etc. These near physiological 3D organoids have garnered momentum for their potential applications in human organ development and disease modeling, drug screening and regenerative medicine. The explosion of organoids research has been catalyzed by the significant progress of stem cell biology and availability of human stem cells. In contrast, the OOC, relying on the bioengineering design principle, is a miniaturized in vitro model that can recreate the functional units of living organs on a microfluidic cell culture device using predifferentiated cells, often cell lines. [1,16] The OOC is primarily evolved from the convergence of tissue engineering and microfabricated technologies, which is characterized by the capability to simulate cellular microenvironment by precise control over fluid flow, mechanical forces and biochemical factors. [4,17] Remarkable progress has been made Significant advances in materials, microscale technology, and stem cell biology have enabled the construction of 3D tissues and organs, which will ultimately lead to more effective diagnostics and therapy. Organoids and organs-on-a-chip (OOC), evolved from developmental biology and bioengineering principles, have e...

Stretchable, Transparent, and Thermally Stable Triboelectric Nanogenerators Based on Solvent‐Free Ion‐Conducting Elastomer Electrodes

“…Alternatively, TENGs with ultrahigh stretchability have been reported by using ionic conductors of hydrogels or ionogels 22–34. Hydrogels are composed of hydrophilic polymer networks swollen with water or ionic aqueous solution, which can be stretchable, biocompatible and transparent 35–37. However, these devices suffer from poor environmental stability because the ionic conductivity and stretchability of hydrogels or ionogels can be severely deteriorated due to the dehydration or evaporation of liquid solvent 38–41…”

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

“…As a kind of long, thin, flexible material, fibers can be used to fabricate various functional 3D objects via folding, bundling, reeling, and weaving, and these features facilitate higher‐order assemblies such as biomedical materials and tissue function material 1–7. It is well known that fiber‐shaped complex 3D structures are common in the human body, such as vessels,8,9 the trachea, and other lumen‐like structures,10 neural pathways,11,12 and muscle fibers 13.…”

Gastrointestinal tract modeling using organoids engineered with cellular and microbiota niches

“…The focus must be not only on surrounding cells and microbiota but also on the surrounding extracellular matrix (ECM) because most research to date has utilized Matrigel ® , which does not provide a tissue-specific environment. Various technologies are being developed for this purpose, such as 3D bioprinting and the use of microfluidic devices and biomaterials [103][104][105][106][107][108] . Bioprinting has the capacity to encapsulate various cells in a compatible hydrogel and to place them in the desired position suitable for coculture.…”

“…Microfluidic devices are also well suited for modeling because of their ability to provide fluid flow that is similar to what is observed in vivo. The coupling of a microfluidic device with an organoid has recently been termed "organoid-ona-chip", and this represents an innovative approach in biomedical research 105,106 . Moreover, various engineered materials for organoid culture containing a decellularized matrix and a chemically defined matrix are being actively developed 106,107,111 .…”