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Organ-on-a-chip systems areminiaturizedmicrofluidic 3D human tissue and organ models designed to recapitulate the important biological and physiological parameters of their in vivo counterparts. They have recently emerged as a viable platform for personalized medicine and drug screening. These in vitro models, featuring biomimetic compositions, architectures, and functions, are expected to replace the conventional planar, static cell cultures and bridge the gap between the currently used preclinical animal models and the human body. Multiple organoid models may be further connected together through the microfluidics in a similar manner in which they are arranged in vivo, providing the capability to analyze multiorgan interactions. Although a wide variety of human organ-on-a-chip models have been created, there are limited efforts on the integration of multisensor systems. However, in situ continual measuring is critical in precise assessment of the microenvironment parameters and the dynamic responses of the organs to pharmaceutical compounds over extended periods of time. In addition, automated and noninvasive capability is strongly desired for long-term monitoring. Here, we report a fully integrated modular physical, biochemical, and optical sensing platform through a fluidics-routing breadboard, which operates organ-on-a-chip units in a continual, dynamic, and automated manner. We believe that this platform technology has paved a potential avenue to promote the performance of current organ-on-a-chip models in drug screening by integrating a multitude of real-time sensors to achieve automated in situ monitoring of biophysical and biochemical parameters. [ABSTRACT FROM AUTHOR]

Engineering cardiac tissues and organ models remains a great challenge due to the hierarchical structure of the native myocardium. The need of integrating blood vessels brings additional complexity, limiting the available approaches that are suitable to produce integrated cardiovascular organoids. In this work we propose a novel hybrid strategy based on 3D bioprinting, to fabricate endothelialized myocardium. Enabled by the use of our composite bioink, endothelial cells directly bioprinted within microfibrous hydrogel scaffolds gradually migrated towards the peripheries of the microfibers to form a layer of confluent endothelium. Together with controlled anisotropy, this 3D endothelial bed was then seeded with cardiomyocytes to generate aligned myocardium capable of spontaneous and synchronous contraction. We further embedded the organoids into a specially designed microfluidic perfusion bioreactor to complete the endothelialized-myocardium-on-a-chip platform for cardiovascular toxicity evaluation. Finally, we demonstrated that such a technique could be translated to human cardiomyocytes derived from induced pluripotent stem cells to construct endothelialized human myocardium. We believe that our method for generation of endothelialized organoids fabricated through an innovative 3D bioprinting technology may find widespread applications in regenerative medicine, drug screening, and potentially disease modeling. [ABSTRACT FROM AUTHOR]

Continual monitoring of secreted biomarkers from organ-on-a-chip models is desired to understand their responses to drug exposure in a noninvasive manner. To achieve this goal, analytical methods capable of monitoring trace amounts of secreted biomarkers are of particular interest However, a majority of existing biosensing techniques suffer from limited sensitivity, selectivity, stability, and require large working volumes, especially when cell culture medium is involved, which usually contains a plethora of nonspecific binding proteins and interfering compounds. Hence, novel analytical platforms are needed to provide noninvasive, accurate information on the status of organoids at low working volumes. Here, we report a novel microfluidic aptamer-based electrochemical biosensing platform for monitoring damage to cardiac organoids. The system is scalable, low-cost, and compatible with microfluidic platforms easing its integration with microfluidic bioreactors. T o create the creatine kinase (CK)-MB biosensor, the microelectrode was functionalized with aptamers that are specific to CK-MB biomarker secreted from a damaged cardiac tissue. Compared to antibody-based sensors, the proposed aptamer-based system was highly sensitive, selective, and stable. The performance of the sensors was assessed using a heart-on-a-chip system constructed from human embryonic stem cell-derived cardiomyocytes following exposure to a cardiotoxic drug, doxorubicin. The aptamer-based biosensor was capable of measuring trace amounts of CKMB secreted by the cardiac organoids upon drug treatments in a dose-dependent manner, which was in agreement with the beating behavior and cell viability analyses. We believe that, our microfluidic electrochemical biosensor using aptamer-based capture mechanism will find widespread applications in integration with organ-on-a-chip platforms for in situ detection of biomarkers at low abundance and high sensitivity. [ABSTRACT FROM AUTHOR]

Conventional blood vessel-on-a-chip models are typically based on microchannel-like structures enclosed within bulk elastomers such as polydimethylsiloxane (PDMS). However, these bulk vascular models largely function as individual platforms and exhibit limited flexibility particularly when used in conjunction with other organ modules. Oftentimes, lengthy connectors and/or tubes are still needed to interface multiple chips, resulting in a large waste volume counterintuitive to the miniaturized nature of organs-on-chips. In this work, we report the development of a novel form of a vascular module based on PDMS hollow tubes, which closely emulates the morphology and properties of human blood vessels to integrate multiple organs-on-chips. Specifically, we present two templating strategies to fabricate hollow PDMS tubes with adjustable diameters and wall thicknesses, where metal rods or airflow were employed as the inner templates, while plastic tubes were used as the outer template. The PDMS tubes could then be functionalized by human umbilical vein endothelial cells (HUVECs) in their interior surfaces to further construct elastomeric biomimetic blood vessels. The endothelium developed biofunctionality as demonstrated by the expression of an endothelial biomarker (CD31) as well as dose-dependent responses in the secretion of von Willebrand factor and nitric oxide upon treatment with pharmaceutical compounds. We believe that with their clear advantages including high optical transparency, gas permeability, and tunable elasticity matching those of native blood vessels, these free-form PDMS vascular modules can supplement bulk vascular organoids and likely replace inert plastic tubes in integrating multiple organoids into a single microfluidic circuitry. [ABSTRACT FROM AUTHOR]

We have designed and fabricated a miniature microscope from off-the-shelf components and a webcam, with built-in fluorescence capability for biomedical applications. The mini-microscope was able to detect both biochemical parameters, such as cell/tissue viability (e.g. live/dead assay), and biophysical properties of the microenvironment such as oxygen levels in microfabricated tissues based on an oxygen-sensitive fluorescent dye. This mini-microscope has adjustable magnifications from 8–60×, achieves a resolution as high as ＜2 μm, and possesses a long working distance of 4.5 mm (at a magnification of 8×). The mini-microscope was able to chronologically monitor cell migration and analyze beating of microfluidic liver and cardiac bioreactors in real time, respectively. The mini-microscope system is cheap, and its modularity allows convenient integration with a wide variety of pre-existing platforms including, but not limited to, cell culture plates, microfluidic devices, and organs-on-a-chip systems. Therefore, we envision its widespread application in cell biology, tissue engineering, biosensing, microfluidics, and organs-on-chips, which can potentially replace conventional bench-top microscopy where long-term in situ and large-scale imaging/analysis is required. [ABSTRACT FROM AUTHOR]

Generating microliver tissues to recapitulate hepatic function is of increasing importance in tissue engineering and drug screening. But the limited availability of primary hepatocytes and the marked loss of phenotype hinders their application. Human induced hepatocytes (hiHeps) generated by direct reprogramming can address the shortage of primary hepatocytes to make personalized drug prediction possible. Here, we simplify preparation of reprogramming reagents by expressing six transcriptional factors (HNF4A, FOXA2, FOXA3, ATF5, PROX1, and HNF1) from two lentiviral vectors, each expressing three factors. Transducing human fetal and adult fibroblasts with low vector dosage generated human induced hepatocyte-like cells (hiHeps) displaying characteristics of mature hepatocytes and capable of drug metabolism. To mimic the physiologic liver microenvironment and improve hepatocyte function, we prepared 3D scaffold-free microliver spheroids using hiHeps and human liver nonparenchymal cells through self-assembly without exogenous scaffolds. We then introduced the microliver spheroids into a two-organ microfluidic system to examine interactions between hepatocytes and tumor cells. The hiHeps-derived spheroids metabolized the prodrug capecitabine into the active metabolite 5-fluorouracil and induced toxicity in downstream tumor spheroids. Our results demonstrate that hiHeps can be used to make microliver spheroids and combined with a microfluidic system for drug evaluation. Our work could make it possible to use patient-specific hepatocyte-like cells to predict drug efficacy and side effects in various organs from the same patient. Image 1 [ABSTRACT FROM AUTHOR]