Molecular sensors & devices for interfacing with electrical activities in live cells.

TSUTSUI Laboratory
Associate Professor：TSUTSUI Hidekazu

E-mail：
［Research areas］
biophysics, neurophysiology, molecular & cell biology, bioengineering
［Keywords］
neuron, synapse, molecular sensor, next generation electrophysiology, bio-imaging

Skills and background we are looking for in prospective students

Background knowledge in brain science, molecular and cell biology, biophysics and/or electrical engineering may help to smoothly lunch a solid research project. However, we support students with limited prior knowledge in the related subjects. We rather give a high importance to scientific motivations and intellectual curiosity.

What you can expect to learn in this laboratory

Basic and advanced experimental techniques concerning molecular biology, electrophysiology, fluorescence imaging, and bio-engineering; Comprehensive understanding of principles underlying various cellular phenomena and their applications to biomedical science.

【Job category of graduates】
Research and development in biomedical industry, manufacture, information technology

Research outline

We seek to develop molecular sensors and devices that permit precise spatiotemporal detections of dynamic functions in live cells. Our main focus is given to parallel measurements of cellular electrical activities.

Cellular electrical signal occurs as a voltage difference across cell membrane and rapidly propagates, playing essential roles in a variety of physiological functions. Those include secretion, contraction and neural transmission. In particular, dynamic modulation of the flow of electrical signals in the neuron networks is thought to underlie the neural function. In seeking to reveal its fundamental　principles, one of the most awaited techniques is the sensitive detection of spatiotemporal electrical activity in a complex network of excitable cells.　

One on-going approach is a protein-based voltage probe that can be genetically encoded under the control of cell-type specific promoters. We investigate biophysical properties of membrane proteins that undergo voltage dependent structural transitions and feedback the knowledge to the design of robust voltage probes. We are also interested in visualizing electrical phenomena in organelle membrane as well as biomedical applications of the sensor technologies including the development of an efficient drug screen platform. Techniques used in this topic are the conventional molecular biology, electrophysiology, photometry, and fluorescence imaging.

By taking an advantage of the advanced facilities in the JAIST nanomaterial and technology center, we have launched a new project: innovative micro-fabrication based electrophysiology combined with organic electronics. Techniques used in this topic are micro-fabrications, electrical engineering, as well as molecular biology.

Apart from these topics, we pursuit various curiosity-driven researches, mainly focusing on fluoresce proteins. For example, we have developed a variant of coral fluorescent protein that forms diffraction-quality crystals within mammalian cells. This expression system allowed the direct determination of its crystal structure as well as observation of the crystallization process and cellular responses. We are trying to reveal general mechanism underlying intracellular protein crystallizations. We also focus on interactions of fluoresce proteins with metal thin film and particles, and their potential applications to cell biology.

Figure 1.
(left) A hippocampal neuron expressing a fluorescence sensor for membrane voltage.
(center) Simultaneous photometry and electrophysiological recordings.
(right) A SEM image of the prototype device for parallel interfacing of cells.

Key publications

1. Farha et al., Interface-specific mode of protonation–deprotonation reactions underlies the cathodic modulation of fluorescence protein emission. Appl. Phys. Express 13 (2020).
2. Farha et al., Electric-field control of fluorescence protein emissions at the metal-solution interface. Appl. Phys. Express 12 (2019).
3. Tsutsui, H. et al., Improved detection of electrical activity with a voltage probe based on a voltage-sensing phosphatase. J. Physiol., 591, 4427- 4437 (2013).

Equipment

fluorescence/luminescence live cell imaging systems
electrophysiology and photometry rigs
electrochemical analyzer
cell/tissue culture & molecular biology equipment
Sputtering system; SEM (JAIST common facilities)