Jun Nakanishi

Dexterous manipulation with a highly redundant movement system is one of the hallmarks of human motor skills. From numerous behavioral studies, there is strong evidence that humans employ compliant task space control, i.e. they focus control only on task variables while keeping redundant degrees-of-freedom as compliant as possible. This strategy is robust towards unknown disturbances and simultaneously safe for the operator and the environment. The theory of operational space control in robotics

Cell-culturing substrates where cell adhesion can be switched on by external stimuli during cell cultivation are useful scaffolds for tissue engineering, cell-based drug screening, and fundamental cellular studies. Here, we show a new strategy for photoactivation of a substrate for cell adhesion under standard fluorescence microscopes. A glass substrate chemically modified with an alkylsiloxane having a photocleavable 2-nitrobenzyl group was coated with bovine serum albumin to prevent cell adhes

Spatiotemporal control of cell migration was achieved on a photoactivatable cell-culturing substrate. Single cells were micropatterned on the substrate and were induced to extend protrusions led by lamellipodia or filopodia alternatively by the subsequent formation of wide or narrow paths in their surroundings, respectively. By tracking the migration of single cells in a microarray format, we performed quantitative analysis of the migration rates of single cells.

There is a growing interest in the development of dynamic adaptive biomaterials for regulation of cellular functions. However, existing materials are limited to two-state switching of the presentation and removal of cell-adhesive bioactive motifs that cannot emulate the native extracellular matrix (ECM) in vivo with continuously adjustable characteristics. Here, tunable adaptive materials composed of a protein monolayer assembled at a liquid-liquid interface are demonstrated, which adapt dynamic

We demonstrate herein a new method for imaging conformational changes of proteins in live cells using a new synthetic environment-sensitive fluorescent probe, 9-amino-6,8-bis(1,3,2-dithioarsolan-2-yl)-5H-benzo[a]phenoxazin-5-one. This fluorescent probe can be attached to recombinant proteins containing four cysteine residues at the i, i + 1, i + 4, and i + 5 positions of an alpha-helix. The specific binding of the fluorescent probe to this 4Cys motif enables fluorescent labeling inside cells by

Mechanical cues of cellular microenvironments can modulate cell functions including cell spreading and differentiation. Most studies of cellular functions are performed using a solid substrate, and it is thought that cells cannot spread on fluid substrates because of rapid relaxation, which cannot resist against actomyosin-based cell contractility. Here, the spreading and growth of anchorage-dependent cells such as human mesenchymal stem cells at the liquid interface between a perfluorocarbon fl

Stem cells and their microenvironment interact cooperatively to dictate their fates. Biomaterials are dynamically remodeled by stem cells, and stem cells sense and translate the changes into cell fate decisions. We have previously reported that adaptive biomaterials composed of fibronectin inserted into protein nanosheets at a liquid interface enhance neuronal differentiation of human mesenchymal stem cells (hMSCs). However, we could not decouple clearly the effect of ligand density from that of

Dynamic control of cell adhesion on substrates is a useful technology in tissue engineering and basic biology. This paper describes a method for the control of cell adhesion on amino-bearing surfaces by reversible conjugation of an anti-fouling polymer, poly(ethylene glycol) (PEG), via a newly developed photocleavable linker, 1-(5-methoxy-2-nitro-4-prop-2-ynyloxyphenyl)ethyl N-succinimidyl carbonate (1). This molecule has alkyne and succinimidyl carbonate at each end, which are connected by phot

A photoresponsive nanocarrier for amines based on gold nanoparticles (GNPs) having a photocleavable succinimidyl ester has been developed. It offers a useful platform for the synthesis of caged compounds. Using the GNPs, we have developed caged histamine for the first time and applied it to evoke intracellular signaling by controlled near-UV irradiation. The present work will allow for new possibilities in studies of inter- and intracellular signaling networks.