The engineered three-dimensional (3-D) cell cultivation system for the production of multicellular spheroids has attracted considerable attention due to its improved in vivo relevance to cellular communications compared to the traditional two-dimensional (2-D) cell culture platform. The formation and maintenance of cell spheroids in healthy condition is the critical factor for tissue engineering applications such as the repair of damaged tissues, the development of organ replacement parts, and preclinical drug tests. However, culturing spheroids in conventional isolated single wells show limit ted yield and maintenance periods due to the lack of proper supplies of nutrition as well as intercellular chemical signaling. Here we develop the novel networked concave microwell arrays for effective construction of 3-D multi-cellular spheroids. The proposed method provides a suitable structure for the diffusion of oxygen, water-soluble nutrients, and cytokines for cell-cell interactions among the spheroids in neighboring microwells. We have further demonstrated in hepatocyte spheroids-cultured networked concave microwells showed enhanced cell viability and albumin secretion compared to the un-networked control group for two weeks. Our results reveal multi-cellular functionality could be tuned up by networking individual 3-D spheroids without supplying additional chemicals or biological supplements. We anticipate our result to be used in high-throughput cellular screening platforms to study cell-cell interactions in response to diverse chemical stimuli as well as development of in vivo mimicking customized 3-D tissue culture system.
In the last decade, microfabrication techniques have been combined with microfluidics and applied to cell biology. Utilizing such new techniques, various cell studies have been performed for the research of stem cells, immune cells, cancer, neurons, etc. Among the various biological applications of microtechnology-based platforms, cell separation technology has been highly regarded in biological and clinical fields for sorting different types of cells, finding circulating tumor cells (CTCs), and blood cell separation, amongst other things. Many cell separation methods have been created using various physical principles. Representatively, these include hydrodynamic, acoustic, dielectrophoretic, magnetic, optical, and filtering methods. In this review, each of these methods will be introduced, and their physical principles and sample applications described. Each physical principle has its own advantages and disadvantages. The engineers who design the systems and the biologists who use them should understand the pros and cons of each method or principle, to broaden the use of microsystems for cell separation. Continuous development of microsystems for cell separation will lead to new opportunities for diagnosing CTCs and cancer metastasis, as well as other elements in the bloodstream.
In living tissue, cells exist in three-dimensional (3D) microenvironments with intricate cell-cell interactions. To model these cellular environments, numerous techniques for generating cell spheroids have been proposed and improved. However, previously reported methods still have limitations in uniformity, reproducibility, scalability, throughput, etc. Here, we present a centrifugal microfluidic-based spheroid (CMS) formation method for generating both co-culture and mono-culture 3D spheroids in a highly controlled manner. We designed circularly arrayed microwells to allow the even distribution of cells introduced at the center of a rotating platform and to provide identical hypergravity conditions at each well by the centrifugal forces generated. Compared with conventional well plate-based spheroid formation, the CMS formation method significantly promotes sphericity and consistency in both size and shape with high production yields. In addition to mono-culture spheroids, we successfully generated co-culture spheroids in concentric, Janus, and sandwich shapes using human adipose-derived stem cells and human lung fibroblasts, demonstrating the versatility of our CMS formation method. We believe that our new method for generating 3D spheroids will become one of the essential technologies in the field of 3D cell culture. We also expect that we are providing an innovative means to assess cellular responses, including cell motility under different hypergravity conditions.
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