“Optical communication with brain cells by means of an implanted duplex micro-device with optogenetics and Ca2+ fluoroimaging”

Abstract

To better understand the brain function based on neural activity, a minimally invasive analysis technology in a freely moving animal is necessary. Such technology would provide new knowledge in neuroscience and contribute to regenerative medical techniques and prosthetics care. An application that combines optogenetics for voluntarily stimulating nerves, imaging to visualize neural activity, and a wearable micro-instrument for implantation into the brain could meet the abovementioned demand. To this end, a micro-device that can be applied to the brain less invasively and a system for controlling the device has been newly developed in this study. Since the novel implantable device has dual LEDs and a CMOS image sensor, photostimulation and fluorescence imaging can be performed simultaneously. The device enables bidirectional communication with the brain by means of light. In the present study, the device was evaluated in an in vitro experiment using a new on-chip 3D neuroculture with an extracellular matrix gel and an in vivo experiment involving regenerative medical transplantation and gene delivery to the brain by using both photosensitive channel and fluorescent Ca2+ indicator. The device succeeded in activating cells locally by selective photostimulation, and the physiological Ca2+ dynamics of neural cells were visualized simultaneously by fluorescence imaging.

Wide and Deep Imaging of Neuronal Activities by a Wearable NeuroImager Reveals Premotor Activity in the Whole Motor Cortex

“…Wearable imaging instruments represent an emerging class of powerful and versatile measurement tools for in vivo functional analysis of the brain in freely moving animals 1–4 . Wearable microscopes such as head-mounted 2-photon microscopes, miniature endoscopes, fiber photometers, and other implantable devices have already made significant contributions in neuroscience 5–9 . Many of these instruments also incorporate recent improvements in fluorescent probe technology, such as the genetically encoded Ca 2+ indicators 10–13 , which enable long-period, real-time imaging of neuronal activity at high signal-to-noise ratios in the living animal brain.…”

High-selectivity neural probe based on a Fabry–Perot optical filter and a CMOS silicon photodiodes array at visible wavelengths

“…8 ChR2 allows the cation inflow of Ca 2þ , promoting cell depolarization. 9 In addition to Ca 2þ inflow, after the blue light stimulation, it is possible to use a fluorophore coelectroporated into the neuron cells, such as a genetically encoded calcium indicator for optical imaging (GECO). 9 The O-GECO1 is such an example, it is a fluorophore with an increased capacity of fluorescence when bonded to Ca 2þ .…”

“…9 In addition to Ca 2þ inflow, after the blue light stimulation, it is possible to use a fluorophore coelectroporated into the neuron cells, such as a genetically encoded calcium indicator for optical imaging (GECO). 9 The O-GECO1 is such an example, it is a fluorophore with an increased capacity of fluorescence when bonded to Ca 2þ . 10 When O-GECO1 is bonded to Ca 2þ and it is excited with green light (at ∼540 nm), it emits fluorescence with an emission peak at ∼570 nm.…”

“…10,11 As a result, neuron cells respond to photostimulation and their physiological state can be determined based on fluorescence. 9 Several authors have developed neural devices with CMOS image sensors for fluorescence imaging or intrinsic signal imaging. 12,13 Kobayashi et al 9 reported an implantable device with a CMOS image sensor and dual light emitting diodes (LEDs) for photostimulation and fluorescence imaging.…”

“…9 Several authors have developed neural devices with CMOS image sensors for fluorescence imaging or intrinsic signal imaging. 12,13 Kobayashi et al 9 reported an implantable device with a CMOS image sensor and dual light emitting diodes (LEDs) for photostimulation and fluorescence imaging. The authors reported the use of blue LEDs for photostimulation, green LEDs for fluorescence excitation, and an absorption filter (long-pass liquid photoresist filter: >600 nm) superimposed on the CMOS image sensor, to pass the fluorescence and intercept the stimulation and excitation light.…”