Manipulating Cell Networks with Light

A new optical micro­scope system, SIFOM – Stimulation and Imaging-based Functional Optical Micro­scopy – can stimulate multiple cells simul­taneously by a holo­graphic method and monitor cell acti­vity after the stimu­lation using 3D measure­ments based on fluores­cence holo­graphy. This system has potential appli­cations as a tool for the reconstruction of lost nerve pathways, construc­ting arti­ficial neural networks, and food resources development.

Illustration of optical stimulation of cell activity in plant cells by holographic optogenetics. (Source: Kobe U.)

So far, many optical micro­scopies such as phase contrast micro­scopy, fluores­cence micro­scopy, multi-photon micro­scopy, and super-resolved fluores­cence micro­scopy have been developed. Recent break­throughs in optics tech­nology have enabled scien­tists to visualize the ultra­fine structure of cells and their functions even in vitro and in vivo. We can now use the light to mani­pulate cell activity as in opto­genetics by using channel­rhodopsin or other related proteins. However, the present opto­genetics-based light stimu­lation used to mani­pulate cell activity is too simple, using uniform exposure by LED or through optic fibers, so only a low level of cell mani­pulation is possible.

This study proposes a new optical micro­scope system. The SIFOM consists of two sub-functions: 3D obser­vation of cells and 3D stimu­lation of cells based on digital holo­graphy. This is the first micro­scope to be equipped with tech­nology that can simul­taneously carry out 3D obser­vation and stimu­lation, and it has potential appli­cations as a ground­breaking tool in the life sciences. Using high-speed scanless photo­graphy, this tech­nology makes it possible for us to gain infor­mation about multiple events occurring in 3D space within a very short time frame.

As a verifi­cation experiment, the team used lung cancer cells and fluorescent beads about ten micro­meters in size. They recorded a fluorescent hologram in a defocused state from the focal position in the direction of depth and achieved recon­struction of both the cells and the fluorescent beads. During the veri­fication experiment, they were able to observe light stimu­lation for a maximum of five cells at one time. The maximum number of stimulated cells is deter­mined mainly because there is insuffi­cient light power for stimu­lation. In 2D space, it is expected that simul­taneous light stimu­lation is possible for over 100 cells, and in the future, the team aims to expand the stimu­lation depth to a few hundred micro­meters using two-photon stimu­lation.

In order to observe living cells, there is a limit to the power of the fluores­cence to avoid damaging cells, so high-sensi­tivity measure­ments are required. The team aims to overcome these issues and prepare the new optical micro­scopy system for practical use. The study was carried out by a multi-insti­tution inter­disciplinary colla­borative research team led by Hiroaki Wake (Kobe Uni­versity, Graduate School of Medicine) and Osamu Matoba (Kobe University, Graduate School of System Infor­matics) in colla­boration with Yasuhiro Awatsuji (Kyoto Institute of Techno­logy, Faculty of Electrical Engi­neering and Elec­tronics) and Yoshio Hayasaki (Utsunomiya Uni­versity, Center for Optical Research and Education). (Source: Kobe U.)

Reference: X. Quan et al.: Three-dimensional stimulation and imaging-based functional optical microscopy of biological cells, Opt. Lett. 43, 5447 (2018); DOI: 10.1364/OL.43.005447

Link: Graduate School of System Informatics, Kobe University, Kobe, Japan

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