Advancing Intelligent Organ-on-a-Chip Systems with Comprehensive In Situ Bioanalysis

In vitro models are essential to a broad range of biomedical research, such as pathological studies, drug development, and personalized medicine. As a potentially transformative paradigm for 3D in vitro models, organ-on-a-chip (OOC) technology has been extensively developed to recapitulate sophisticated architectures and dynamic microenvironments of human organs by applying the principles of life sciences and leveraging micro- and nanoscale engineering capabilities. A pivotal function of OOC devices is to support multifaceted and timely characterization of cultured cells and their microenvironments. However, in-depth analysis of OOC models typically requires biomedical assay procedures that are labor-intensive and interruptive. Herein, the latest advances toward intelligent OOC (iOOC) systems, where sensors integrated with OOC devices continuously report cellular and microenvironmental information for comprehensive in situ bioanalysis, are examined. It is proposed that the multimodal data in iOOC systems can support closed-loop control of the in vitro models and offer holistic biomedical insights for diverse applications. Essential techniques for establishing iOOC systems are surveyed, encompassing in situ sensing, data processing, and dynamic modulation. Eventually, the future development of iOOC systems featuring cross-disciplinary strategies is discussed.

Numerical evaluation and experimental validation of fluid flow behavior within an organ-on-a-chip model

BACKGROUND AND OBJECTIVE

By combining biomaterials, cell culture, and microfluidic technology, organ-on-a-chip (OoC) platforms have the ability to reproduce the physiological microenvironment of human organs. For this reason, these advanced microfluidic devices have been used to resemble various diseases and investigate novel treatments. In addition to the experimental assessment, numerical studies of biodevices have been performed aiming at their improvement and optimization. Despite considerable progress in numerical modeling of biodevices, the validation of these computational models through comparison with experimental assays remains a significant gap in the current literature. This step is critical to ensure the accuracy and reliability of numerical models, and consequently enhance confidence in their predictive results. The aim of the present work is to develop a numerical model capable of reproducing the fluid flow behavior within an OoC, for future investigations, encompassing the geometry optimization.

METHODS

In this study, the validation of a numerical model for an OoC microfluidic device was undertaken. This comprised both quantitative and qualitative assessments of trace microparticles flowing through a physical OoC model. High-speed microscopy images of the flow, using a blood analog fluid, were analyzed and compared with the numerical simulations run using the Ansys Fluent software. For a qualitative analysis, the particles' paths through the inlet and bifurcations were observed whereas, for a quantitative analysis, the particle velocities were measured. Furthermore, oxygen transport was simulated and evaluated for different Reynolds numbers.

RESULTS

In both qualitative and quantitative analyses, the results predicted by the numerical model and the ones outputted by the experimental model were in good agreement. These findings underscore the capability and potential of the developed numerical model. The examination of oxygen transport at various vertical positions within the organoid has revealed that for lower positions, oxygen transport predominantly occurs through diffusion, leading to a symmetric distribution of oxygen. Contrastingly, the convection phenomenon becomes more evident in the upper region of the organoid.

CONCLUSIONS

The successful validation of the numerical model against experimental data shows its accuracy and reliability in simulating the fluid flow within the OoC, which consequently can expedite the OoC design process by reducing the need for prototypes' fabrication and costly laboratory experiments.

Computational Simulations in Advanced Microfluidic Devices: A Review

Numerical simulations have revolutionized research in several engineering areas by contributing to the understanding and improvement of several processes, being biomedical engineering one of them. Due to their potential, computational tools have gained visibility and have been increasingly used by several research groups as a supporting tool for the development of preclinical platforms as they allow studying, in a more detailed and faster way, phenomena that are difficult to study experimentally due to the complexity of biological processes present in these models—namely, heat transfer, shear stresses, diffusion processes, velocity fields, etc. There are several contributions already in the literature, and significant advances have been made in this field of research. This review provides the most recent progress in numerical studies on advanced microfluidic devices, such as organ-on-a-chip (OoC) devices, and how these studies can be helpful in enhancing our insight into the physical processes involved and in developing more effective OoC platforms. In general, it has been noticed that in some cases, the numerical studies performed have limitations that need to be improved, and in the majority of the studies, it is extremely difficult to replicate the data due to the lack of detail around the simulations carried out.

Design and experimental investigation of a novel spiral microfluidic chip to separate wide size range of micro-particles aimed at cell separation

Isolation of microparticles and biological cells on microfluidic chips has received considerable attention due to their applications in numerous areas such as medical and engineering fields. Microparticles separation is of great importance in bioassays due to the need for smaller sample and device size and lower manufacturing costs. In this study, we first explain the concepts of separation and microfluidic science along with their applications in the medical sciences, and then, a conceptual design of a novel inertial microfluidic system is proposed and analyzed. The PDMS spiral microfluidic device was fabricated, and its effects on the separation of particles with sizes similar to biological particles were experimentally analyzed. This separation technique can be used to separate cancer cells from the normal ones in the blood samples. These components required for testing were selected, assembled, and finally, a very affordable microfluidic kit was provided. Different experiments were designed, and the results were analyzed using appropriate software and methods. Separator system tests with polydisperse hollow glass particles (diameter 2-20 µm), and monodisperse Polystyrene particles (diameter 5 & 15 µm), and the results exhibit an acceptable chip performance with 86% of efficiency for both monodisperse particles and polydisperse particles. The microchannel collects particles with an average diameter of 15.8, 9.4, and 5.9 μm at the proposed reservoirs. This chip can be integrated into a more extensive point-of-care diagnostic system to test blood samples.

Patient-Specific Organoid and Organ-on-a-Chip: 3D Cell-Culture Meets 3D Printing and Numerical Simulation

The last few decades have witnessed diversified in vitro models to recapitulate the architecture and function of living organs or tissues and contribute immensely to advances in life science. Two novel 3D cell culture models: 1) Organoid, promoted mainly by the developments of stem cell biology and 2) Organ-on-a-chip, enhanced primarily due to microfluidic technology, have emerged as two promising approaches to advance the understanding of basic biological principles and clinical treatments. This review describes the comparable distinct differences between these two models and provides more insights into their complementarity and integration to recognize their merits and limitations for applicable fields. The convergence of the two approaches to produce multi-organoid-on-a-chip or human organoid-on-a-chip is emerging as a new approach for building 3D models with higher physiological relevance. Furthermore, rapid advancements in 3D printing and numerical simulations, which facilitate the design, manufacture, and results-translation of 3D cell culture models, can also serve as novel tools to promote the development and propagation of organoid and organ-on-a-chip systems. Current technological challenges and limitations, as well as expert recommendations and future solutions to address the promising combinations by incorporating organoids, organ-on-a-chip, 3D printing, and numerical simulation, are also summarized.