Manipulating Living Cells to Construct a 3D Single-Cell Assembly without an Artificial Scaffold

Formation of Lymphoma Hybrid Spheroids and Drug Testing in Real Time with the Use of Fluorescence Optical Tweezers

Interactions between stromal and lymphoma cells in the bone marrow are closely related to drug resistance and therapy failure. Physiologically relevant pre-clinical three-dimensional (3D) models recapitulating lymphoma microenvironmental complexity do not currently exist. In this study, we proposed a scheme for optically controlled hybrid lymphoma spheroid formation with the use of optical tweezers (OT). Following the preparation of stromal spheroids using agarose hydrogel, two aggressive non-Hodgkin lymphoma B-cell lines, Ri-1 (DLBCL) and Raji (Burkitt lymphoma), were used to conduct multi-cellular spheroid formation driven by in-house-developed fluorescence optical tweezers. Importantly, the newly formed hybrid spheroid preserved the 3D architecture for the next 24 h. Our model was successfully used for the evaluation of the influence of the anticancer agents doxorubicin (DOX), ibrutinib (IBR), and AMD3100 (plerixafor) on the adhesive properties of lymphoma cells. Importantly, our study revealed that a co-treatment of DOX and IBR with AMD3100 affects the adhesion of B-NHL lymphoma cells.

Emergence of uniform linearly-arranged micro-droplets entrapping DNA and living cells through water/water phase-separation

Living cells maintain their lives through self-organization in an environment crowded with a rich variety of biological species. Recently, it was found that micro-droplets containing biomacromolecules, which vary widely in size, are generated accompanied by water/water phase-separation by simple mechanical mixing of an aqueous solution with binary polymers. Here, we report that cell-sized droplets of nearly the same size are generated as a linear array within a glass capillary upon the introduction of a binary polymer solution of polyethylene glycol (PEG) and dextran (DEX). Interestingly, when DNA molecules are added to the polymer solution, stable droplets entrapping DNA molecules are obtained. Similarly, living cells are entrapped spontaneously for the linearly-arranged cell-sized droplets. This simple method for generating micro-droplets entrapping DNA and also living cells is expected to stimulate further study on the self-construction of protocells and micro organoids.

Microfluidics-Based Single-Cell Research for Intercellular Interaction

Intercellular interaction between cell-cell and cell-ECM is critical to numerous biology and medical studies, such as stem cell differentiation, immunotherapy and tissue engineering. Traditional methods employed for delving into intercellular interaction are limited by expensive equipment and sophisticated procedures. Microfluidics technique is considered as one of the powerful measures capable of precisely capturing and manipulating cells and achieving low reagent consumption and high throughput with decidedly integrated functional components. Over the past few years, microfluidics-based systems for intercellular interaction study at a single-cell level have become frequently adopted. This review focuses on microfluidic single-cell studies for intercellular interaction in a 2D or 3D environment with a variety of cell manipulating techniques and applications. The challenges to be overcome are highlighted.

Optimizing the Conditions and Use of Synthetic Matrix for Three-Dimensional In Vitro Retinal Differentiation from Mouse Pluripotent Cells

IMPACT STATEMENT

The development of retinal regenerative therapies relies on the reproducible and renewable source of retinal neurons for drug discovery and cell transplantation. Three-dimensional approach for retinal differentiation from pluripotent cells recently emerged as the robust strategy for retinal tissue differentiation. In this work, we present the combination of optimized conditions and techniques for three-dimensional retinal differentiation from mouse embryonic cells that improves reproducibility and efficiency of retinal differentiation in organoid cultures. We also show that the retinal induction can be achieved with the synthetic oligopeptide instead of Matrigel that allows to approach xeno-free conditions for cell production.

Nonspecific characteristics of macromolecules create specific effects in living cells

Recently, the important role of microphase separation in living cells has been attracting considerable interest in relation to cell organization and function. For example, many studies have focused on liquid-liquid phase separation (LLPS) as a very plausible mechanism for the presence of membraneless organelles. To confirm the role of phase separation in living cells, experimental studies on models and/or reconstructed systems are needed. In this short review, we discuss current paradigms of LLPS and provide some example "review data" to demonstrate particular points relating to the specific localization of biological macromolecules like DNAs and actin proteins with spontaneous domain formation in microdroplets emerging in an aqueous two-phase system (ATPS) (we use polyethylene glycol (PEG)/dextran (DEX)-a binary polymer solution). We also suggest that phase separation and transition may play basic roles in regulation of the biochemical reactivity of individual long genomic DNAs.

Construction of 3D Cellular Composites with Stem Cells Derived from Adipose Tissue and Endothelial Cells by Use of Optical Tweezers in a Natural Polymer Solution

To better understand the regulation and function of cellular interactions, three-dimensional (3D) assemblies of single cells and subsequent functional analysis are gaining popularity in many research fields. While we have developed strategies to build stable cellular structures using optical tweezers in a minimally invasive state, methods for manipulating a wide range of cell types have yet to be established. To mimic organ-like structures, the construction of 3D cellular assemblies with variety of cell types is essential. Our recent studies have shown that the presence of nonspecific soluble polymers in aqueous solution is the key to creating stable 3D cellular assemblies efficiently. The present study further expands on the construction of 3D single cell assemblies using two different cell types. We have successfully generated 3D cellular assemblies, using GFP-labeled adipose tissue-derived stem cells and endothelial cells by using optical tweezers. Our findings will support the development of future applications to further characterize cellular interactions in tissue regeneration.

Opto-thermophoretic fiber tweezers

Recent advances in opto-thermophoretic tweezers open new avenues for low-power trapping and manipulation of nanoparticles with potential applications in colloidal assembly, nanomanufacturing, life sciences, and nanomedicine. However, to fully exploit the opto-thermophoretic tweezers for widespread applications, the enhancement of their versatility in nanoparticle manipulations is pivotal. For this purpose, we translate our newly developed opto-thermophoretic tweezers onto an optical fiber platform known as opto-thermophoretic fiber tweezers (OTFT). We have demonstrated the applications of OTFT as a nanoparticle concentrator, as a nanopipette for single particle delivery, and as a nanoprobe. The simple setup and functional versatility of OTFT would encourage its use in various fields such as additive manufacturing, single nanoparticle-cell interactions, and biosensing.

Aqueous/Aqueous Micro Phase Separation: Construction of an Artificial Model of Cellular Assembly

To artificially construct a three-dimensional cell assembly, we investigated the availability of long-duration microdroplets that emerged near a critical point in an aqueous two-phase system (ATPS) with the hydrophilic binary polymers, polyethylene glycol (PEG), and dextran (DEX), as host containers. We found that erythrocytes (horse red blood cells; RBCs) and NAMRU mouse mammary gland epithelial cells (NMuMG cells) were completely and spontaneously entrapped inside DEX-rich microdroplets. RBCs and NMuMG cells were located in the interior and at the periphery of the droplets at PEG/DEX = 5%:5%. In contrast, the cells exhibited opposite localizations at PEG/DEX = 10%:5%, where, interestingly, NMuMG cells apparently assembled to achieve cell adhesion. We simply interpreted such specific localizations by considering the alternative responses of these cells to the properties of the PEG/DEX interfaces with different gradients in polymer concentrations.