Microfluidic cell culture models for tissue engineering

Lab-on-a-chip: emerging analytical platforms for immune-mediated diseases

Miniaturization of analytical procedures has a significant impact on diagnostic testing since it provides several advantages such as: reduced sample and reagent consumption, shorter analysis time and less sample handling. Lab-on-a-chip (LoC), usually silicon, glass, or silicon-glass, or polymer disposable cartridges, which are produced using techniques inherited from the microelectronics industry, could perform and integrate the operations needed to carry out biochemical analysis through the mechanical realization of a dedicated instrument. Analytical devices based on miniaturized platforms like LoC may provide an important contribution to the diagnosis of high prevalence and rare diseases. In this paper we review some of the uses of Lab-on-a-chip in the clinical diagnostics of immune-mediated diseases and we provide an overview of how specific applications of these technologies could improve and simplify several complex diagnostic procedures.

Chemistry with spatial control using particles and streams()

Spatial control of chemical reactions, with micro- and nanometer scale resolution, has important consequences for one pot synthesis, engineering complex reactions, developmental biology, cellular biochemistry and emergent behavior. We review synthetic methods to engineer this spatial control using chemical diffusion from spherical particles, shells and polyhedra. We discuss systems that enable both isotropic and anisotropic chemical release from isolated and arrayed particles to create inhomogeneous and spatially patterned chemical fields. In addition to such finite chemical sources, we also discuss spatial control enabled with laminar flow in 2D and 3D microfluidic networks. Throughout the paper, we highlight applications of spatially controlled chemistry in chemical kinetics, reaction-diffusion systems, chemotaxis and morphogenesis.

Magnetic force-based cell patterning for evaluation of the effect of stromal fibroblasts on invasive capacity in 3D cultures

Biomimetic cell culture systems that recreate tumor microenvironments are necessary in understanding the progression of cancer cells in cell-to-cell interaction and in cell-to-extracellular matrix interaction. We have developed a three-dimensional spheroid array embedded in collagen for evaluation of the effect of stromal fibroblasts associated with cancer cells. When the breast epithelial cancer cell model MCF10A/myr-Akt1 was magnetically labeled and aligned in the array by an external magnetic force using a pin-holder device and a magnet, a stellate configuration was observed. Changes in MCF10A/myr-Akt1 cell behavior were only slight when normal human dermal fibroblasts (NHDF) cells coexisted in collagen (indirect-interaction array). In contrast, when NHDF were magnetically labeled and patterned together with MCF10A/myr-Akt1 (direct-interaction array), spreading and progression were observed along with NHDF. Cell image analysis indicated that the length and area were statistically significantly increased in the direct-interaction array compared to the MCF10A/myr-Akt1 alone or to the indirect-interaction array. A cell susceptibility assay was undertaken with breast cancer MDA-MB-231 associated with NHDF in the indirect-interaction array. Interestingly, although distinct suppression of cell movement and proliferation was observed with 100 μM of collagenase inhibitor, formation of invadepodia significantly increased with coexistent NHDF. Since cancer progression is influenced by its microenvironment, this magnetic cell-patterning method which clarifies direct and indirect effects of stromal cells on invasion and proliferation, is well suited for evaluation and design of more efficient approaches in cancer prevention and treatment.

Microscale Strategies for Generating Cell-Encapsulating Hydrogels

Hydrogels in which cells are encapsulated are of great potential interest for tissue engineering applications. These gels provide a structure inside which cells can spread and proliferate. Such structures benefit from controlled microarchitectures that can affect the behavior of the enclosed cells. Microfabrication-based techniques are emerging as powerful approaches to generate such cell-encapsulating hydrogel structures. In this paper we introduce common hydrogels and their crosslinking methods and review the latest microscale approaches for generation of cell containing gel particles. We specifically focus on microfluidics-based methods and on techniques such as micromolding and electrospinning.

Probing the role of mesenchymal stem cells in salivary gland cancer on biomimetic microdevices

Mesenchymal stem cells (MSCs) are the progenitors of stromal cells, which have been found to interact with cancer cells and represent an important target for cancer therapies. Salivary gland cancer is an aggressive malignant epithelial tumor and can easily disseminate to distant sites in vivo. In this work, we probed the role of MSCs in salivary gland cancer in an in vivo like tumor microenvironment by using a series of functional microfluidic devices for 2D and 3D assays. The results demonstrated that MSCs could be recruited by salivary gland cancer cells (ACC-M) and this effect was potentially mediated by TGF-β secreted by cancer cells. In addition, MSCs exhibited the ability to squeeze into ACC-M spheroids by dispersing the cell-cell connection and reducing the expression of E-cadherin in cancer cells. In particular, MSCs exhibited the ability to enhance the invasion of salivary cancer under a chemokine CXCL12 gradient, indicating the involvement of a CXCL12-CXCR4 pathway and the tumor-promoting properties of MSCs in cancer progression. This study recreated an in vivo-like tumor microenvironment by constructing a series of functional microdevices and explored the role of MSCs in ACC invasion for the first time. It provides a unique platform to open up new options to target stromal cells for cancer therapy and also analyzed the potential risk of using MSCs as drug delivery carriers for therapeutic purposes in carcinoma treatment.

Emerging technologies for assembly of microscale hydrogels

Assembly of cell encapsulating building blocks (i.e., microscale hydrogels) has significant applications in areas including regenerative medicine, tissue engineering, and cell-based in vitro assays for pharmaceutical research and drug discovery. Inspired by the repeating functional units observed in native tissues and biological systems (e.g., the lobule in liver, the nephron in kidney), assembly technologies aim to generate complex tissue structures by organizing microscale building blocks. Novel assembly technologies enable fabrication of engineered tissue constructs with controlled properties including tunable microarchitectural and predefined compositional features. Recent advances in micro- and nano-scale technologies have enabled engineering of microgel based three dimensional (3D) constructs. There is a need for high-throughput and scalable methods to assemble microscale units with a complex 3D micro-architecture. Emerging assembly methods include novel technologies based on microfluidics, acoustic and magnetic fields, nanotextured surfaces, and surface tension. In this review, we survey emerging microscale hydrogel assembly methods offering rapid, scalable microgel assembly in 3D, and provide future perspectives and discuss potential applications.