A lab-on-a-chip device for investigating the fusion process of olfactory ensheathing cell spheroids

Lung carcinoma spheroids embedded in a microfluidic platform

Three-dimensional (3D) spheroid cell cultures are excellent models used in cancer biology research and drug screening. The objective of this study was to develop a lung carcinoma spheroid based microfluidic platform with perfusion function to mimic lung cancer pathology and investigate the effect of a potential drug molecule, panaxatriol. Spheroids were successfully formed on agar microtissue molds at the end of 10 days, reaching an average diameter of about 317.18 ± 4.05 μm and subsequently transferred to 3D dynamic microfluidic system with perfusion function. While the size of the 3D spheroids embedded in the Matrigel matrix in the platform had gradually increased both in the static and dynamic control groups, the size of the spheroids were reduced and fragmented in the drug treated groups. Cell viability results showed that panaxatriol exhibited higher cytotoxic effect on cancer cells than healthy cells and the IC₅₀ value was determined as 61.55 µM. Furthermore, panaxatriol has been more effective on single cells around the spheroid structure, whereas less in 3D spheroid tissues with a compact structure in static conditions compared to dynamic systems, where a flow rate of 2 µL/min leading to a shear stress of 0.002 dyne/cm² was applied. Application of such dynamic systems will contribute to advancing basic research and increasing the predictive accuracy of potential drug molecules, which may accelerate the translation of novel therapeutics to the clinic, possibly decreasing the use of animal models.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-021-00470-7.

Microneedle Arrays for Sampling and Sensing Skin Interstitial Fluid

Dermal interstitial fluid (ISF) is a novel source of biomarkers that can be considered as an alternative to blood sampling for disease diagnosis and treatment. Nevertheless, in vivo extraction and analysis of ISF are challenging. On the other hand, microneedle (MN) technology can address most of the challenges associated with dermal ISF extraction and is well suited for long-term, continuous ISF monitoring as well as in situ detection. In this review, we first briefly summarise the different dermal ISF collection methods and compare them with MN methods. Next, we elaborate on the design considerations and biocompatibility of MNs. Subsequently, the fabrication technologies of various MNs used for dermal ISF extraction, including solid MNs, hollow MNs, porous MNs, and hydrogel MNs, are thoroughly explained. In addition, different sensing mechanisms of ISF detection are discussed in detail. Subsequently, we identify the challenges and propose the possible solutions associated with ISF extraction. A detailed investigation is provided for the transport and sampling mechanism of ISF in vivo. Also, the current in vitro skin model integrated with the MN arrays is discussed. Finally, future directions to develop a point-of-care (POC) device to sample ISF are proposed.

The Tumor-on-Chip: Recent Advances in the Development of Microfluidic Systems to Recapitulate the Physiology of Solid Tumors

The ideal in vitro recreation of the micro-tumor niche-although much needed for a better understanding of cancer etiology and development of better anticancer therapies-is highly challenging. Tumors are complex three-dimensional (3D) tissues that establish a dynamic cross-talk with the surrounding tissues through complex chemical signaling. An extensive body of experimental evidence has established that 3D culture systems more closely recapitulate the architecture and the physiology of human solid tumors when compared with traditional 2D systems. Moreover, conventional 3D culture systems fail to recreate the dynamics of the tumor niche. Tumor-on-chip systems, which are microfluidic devices that aim to recreate relevant features of the tumor physiology, have recently emerged as powerful tools in cancer research. In tumor-on-chip systems, the use of microfluidics adds another dimension of physiological mimicry by allowing a continuous feed of nutrients (and pharmaceutical compounds). Here, we discuss recently published literature related to the culture of solid tumor-like tissues in microfluidic systems (tumor-on-chip devices). Our aim is to provide the readers with an overview of the state of the art on this particular theme and to illustrate the toolbox available today for engineering tumor-like structures (and their environments) in microfluidic devices. The suitability of tumor-on-chip devices is increasing in many areas of cancer research, including the study of the physiology of solid tumors, the screening of novel anticancer pharmaceutical compounds before resourcing to animal models, and the development of personalized treatments. In the years to come, additive manufacturing (3D bioprinting and 3D printing), computational fluid dynamics, and medium- to high-throughput omics will become powerful enablers of a new wave of more sophisticated and effective tumor-on-chip devices.

Directed fusion of cardiac spheroids into larger heterocellular microtissues enables investigation of cardiac action potential propagation via cardiac fibroblasts

Multicellular spheroids generated through cellular self-assembly provide cytoarchitectural complexities of native tissue including three-dimensionality, extensive cell-cell contacts, and appropriate cell-extracellular matrix interactions. They are increasingly suggested as building blocks for larger engineered tissues to achieve shapes, organization, heterogeneity, and other biomimetic complexities. Application of these tissue culture platforms is of particular importance in cardiac research as the myocardium is comprised of distinct but intermingled cell types. Here, we generated scaffold-free 3D cardiac microtissue spheroids comprised of cardiac myocytes (CMs) and/or cardiac fibroblasts (CFs) and used them as building blocks to form larger microtissues with different spatial distributions of CMs and CFs. Characterization of fusing homotypic and heterotypic spheroid pairs revealed an important influence of CFs on fusion kinetics, but most strikingly showed rapid fusion kinetics between heterotypic pairs consisting of one CF and one CM spheroid, indicating that CMs and CFs self-sort in vitro into the intermixed morphology found in the healthy myocardium. We then examined electrophysiological integration of fused homotypic and heterotypic microtissues by mapping action potential propagation. Heterocellular elongated microtissues which recapitulate the disproportionate CF spatial distribution seen in the infarcted myocardium showed that action potentials propagate through CF volumes albeit with significant delay. Complementary computational modeling revealed an important role of CF sodium currents and the spatial distribution of the CM-CF boundary in action potential conduction through CF volumes. Taken together, this study provides useful insights for the development of complex, heterocellular engineered 3D tissue constructs and their engraftment via tissue fusion and has implications for arrhythmogenesis in cardiac disease and repair.

Recent advances and current challenges in magnetophoresis based micro magnetofluidics

The combination of magnetism and microscale fluid flow has opened up a new era for handling and manipulation of samples in microfluidics. In particular, magnetophoresis, the migration of particles in a magnetic field, is extremely attractive for microfluidic handling due to its contactless nature, independence of ionic concentration, and lack of induced heating. The present paper focuses on recent advances and current challenges of magnetophoresis and highlights the key parameters affecting the manipulation of particles by magnetophoresis. The magnetic field is discussed according to their relative motion to the sample as stationary and dynamic fields. The migration of particles is categorized as positive and negative magnetophoresis. The applications of magnetophoresis are discussed according to the basic manipulation tasks such as mixing, separation, and trapping of particles or cells. Finally, the paper highlights the limitations of current approaches and provides the future perspective for this research area.

Liquid marbles as bioreactors for the study of three-dimensional cell interactions

Liquid marble as a bioreactor platform for cell-based studies has received significant attention, especially for developing 3D cell-based assays. This platform is particularly suitable for 3D in-vitro modeling of cell-cell interactions. For the first time, we demonstrated the interaction of olfactory ensheathing cells (OECs) with nerve debris and meningeal fibroblast using liquid marbles. As the transplantation of OECs can be used for repairing nerve injury, degenerating cell debris within the transplantation site can adversely affect the survival of transplanted OECs. In this paper, we used liquid marbles to mimic the hostile 3D environment to analyze the functional behavior of the cells and to form the basis for cell-based therapy. We show that OECs interact with debris and enhanced cellular aggregation to form a larger 3D spheroidal tissue. However, these spheroids indicated limitation in biological functions such as the inability of cells within the spheroids to migrate out and adherence to neighboring tissue by fusion. The coalescence of two liquid marbles allows for analyzing the interaction between two distinct cell types and their respective environment. We created a microenvironment consisting of 3D fibroblast spheroids and nerve debris and let it interact with OECs. We found that OECs initiate adherence with nerve debris in this 3D environment. The results suggest that liquid marbles are ideal for developing bioassays that could substantially contribute to therapeutic applications. Especially, insights for improving the survival and adherence of transplanted cells.

Microfluidic Technology for the Generation of Cell Spheroids and Their Applications

A three-dimensional (3D) tissue model has significant advantages over the conventional two-dimensional (2D) model. A 3D model mimics the relevant in-vivo physiological conditions, allowing a cell culture to serve as an effective tool for drug discovery, tissue engineering, and the investigation of disease pathology. The present reviews highlight the recent advances and the development of microfluidics based methods for the generation of cell spheroids. The paper emphasizes on the application of microfluidic technology for tissue engineering including the formation of multicellular spheroids (MCS). Further, the paper discusses the recent technical advances in the integration of microfluidic devices for MCS-based high-throughput drug screening. The review compares the various microfluidic techniques and finally provides a perspective for the future opportunities in this research area.

Magnetofluidic micromixer based on a complex rotating magnetic field

We report a magnetically actuated micromixer for mixing non-magnetic microparticles in a microfluidic system.