Photostimulation

What is photostimulation?

Photostimulation refers to an experimental method where samples such as living organisms or cells are stimulated with light, and the resulting reactions are observed. Various experimental techniques utilize photostimulation, including FRAP (fluorescence recovery after photobleaching), optogenetics, photoconversion, and photoswitching. The following sections describe FRAP and optogenetics.

What is FRAP?

FRAP is the measurement of the time required for the fluorescence brightness of a specific fluorescent molecule in the observation area to recover after photobleaching with strong excitation light. It is a method that can estimate the movement speed of molecules from outside the observation area. The less movement of molecules, the slower the recovery speed of fluorescence, and the more movement of molecules, the faster the recovery speed.

To achieve photobleaching in a specific region, FRAP requires very strong excitation light and optical systems that can precisely target the excitation light to that area. Commonly, lasers used in confocal microscopy are employed for excitation. Spatial light modulators (SLMs) or digital mirror devices (DMDs) are used to focus the laser exclusively on the desired region.

Principle of FRAP

Figure 1: Principle of FRAP

What is optogenetics?

Optogenetics is an interdisciplinary field that combines optics and genetics. It is also known as light genetics. In optogenetics, membrane proteins such as channelrhodopsin and halorhodopsin, which respond to light energy, are expressed in neurons. By irradiating specific wavelengths of light, it is possible to excite or inhibit target neurons. This technique can be applied to elucidate the structure and function of neural networks.

Traditionally, electrical stimulation methods were primarily used to study neural function. However, these methods had a drawback: they stimulated not only the targeted neurons but also neighboring neurons connected to them. Optogenetics overcomes this limitation by allowing precise stimulation of only the neurons expressing membrane proteins like channelrhodopsin. As a result, researchers can observe neural cell movement more accurately.

In optogenetics, there are cases where only specific neurons need to be stimulated with light. In such situations, it is necessary to irradiate light only to specific areas. Additionally, when stimulating multiple neurons simultaneously, light must be directed to multiple areas. Our LCOS-SLM allows customizable illumination patterns, enabling precise light irradiation to specific regions.

Differences between optogenetics and electrical stimulation

Figure 2: Differences between optogenetics and electrical stimulation

Research introduction: Light-controlled tools for intracellular cAMP generation

In recent years, various light manipulation techniques have made significant advancements in the field of life sciences. Since 2006, light-sensitive ion channels have become an essential tool for optogenetics, the manipulation of light, in the field of neuroscience. However, within living organisms, numerous signals exist beyond ion channels. Notably, cyclic nucleotides such as cAMP and cGMP play crucial roles in diverse intracellular signal transduction pathways. In the main signaling pathway involving cAMP, activation of adenylate cyclase or inhibition of phosphodiesterase leads to an increase in intracellular cAMP concentration, subsequently activating protein kinase A (PKA). This activation is followed by the appearance of voltage-dependent Ca²⁺ channels and various cellular responses. Hamamatsu Photonics is researching an optogenetics tool called ‘PAC’ that allows light-controlled cAMP generation to induce these responses.

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LCOS-SLM (optical phase modulator) X15213 series

LCOS-SLM Optical phase modulator

The LCOS-SLM (liquid crystal on silicon - spatial light modulator) is a device that allows electrical control of the phase of laser light. It consists of a structure where a liquid crystal is sandwiched between a CMOS chip with pixel electrodes arranged in a two-dimensional pattern and transparent electrodes deposited on a glass substrate. Digital images output from a PC are converted to analog signals by a dedicated driving circuit and applied with voltage to the pixel electrodes on the CMOS chip.

The LCOS-SLM enables precise controls over light patterns, which enables real-time holographic beam steering for cells, tissues, and microorganisms. Additionally, the LCOS-SLM can create 3D holograms, which are helpfup for target illumination in 3D space for neuroscience, life science, and microscopy applications.

H12056-40

Photomultiplier tube module H12056-40

The Hamamatsu H12056-40 is a photomultiplier tube (PMT) module equipped with a built-in gate function, making it ideal for photo stimulation experiments.

In such experiments, there's a risk of detector saturation or damage due to high incident light levels. The H12056-40's gate function allows users to turn off the PMT during periods of intense light exposure, protecting the detector from potential damage and preventing the detection of unwanted light. This feature is particularly beneficial in applications like fluorescence recovery after photobleaching (FRAP) and optogenetics, where precise control over light exposure and detection is crucial.

Additionally, the H12056-40 offers high sensitivity throughout the visible spectrum, enhancing the detection of weak fluorescence signals that follow photostimulation. This combination of high sensitivity and gating capability makes the H12056-40 a great choice for photostimulation setups, ensuring accurate and reliable measurements.

Photomultiplier tube module H11706-40

The Hamamatsu H110706-40 is a photomultiplier tube (PMT) module equipped with a built-in gate function, making it ideal for experiments with risk of high light levels, like photostimulation. The H110706-40 's gate function allows users to turn off the PMT, protecting the detector from potential damage and preventing the detection of unwanted light. This feature is particularly beneficial in applications like fluorescence recovery after photobleaching (FRAP) and optogenetics, where precise control over light exposure and detection is crucial.

Additionally, the H110706-40 offers high sensitivity throughout the visible spectrum, enhancing the detection of weak fluorescence signals. This combination of high sensitivity and gating capability makes the H12056-40 a great choice for photostimulation setups, ensuring accurate and reliable measurements.

PMT module

Photomultiplier tube modules

Our photomultiplier tube (PMT) modules are ideal for photostimulation experiments by providing high sensitivity and low noise, essential for detecting weak fluorescence signals. With fast response times, they support precise, high-speed imaging required for capturing dynamic biological responses. Additionally, Hamamatsu's PMTs feature a broad spectral range, allowing detection of many wavelengths commonly used in photo stimulation setups. This wide spectral range combined with high sensitivity, ensures Hamamatsu’s PMTs deliver the clear, detailed data collection, necessary for accurate, reproducible photostimulation results.

mppc_module

MPPC modules

Our Multi-Pixel Photon Counter (MPPC) modules offering high photon detection efficiency and excellent signal-to-noise ratios for photo stimulation experiments. The solid-state design of MPPCs ensures exceptional stability and longevity, with low dark counts and high gain for reliable, repeatable results. In high background environments, they offer higher QE leading to more accurate data. Their compact, durable construction facilitates seamless integration into photostimulation setups. This makes Hamamatsu's MPPC modules an ideal choice for achieving accurate, high-resolution data in photostimulation experiments.

MEMs mirrors

MEMS mirrors enhance photostimulation experiments by enabling precise, rapid scanning with high stability and minimal distortion, crucial for directing light to targeted regions with pinpoint accuracy. Their compact design provides fine control over the light path, ensuring accurate delivery of photostimulation to specific areas while minimizing unintended exposure. With high-speed scanning capabilities, these mirrors can effectively keep up with dynamic biological responses, all while maintaining durability and low power consumption. This blend of compactness, high speed scanning, agility, efficiency, and stability makes Hamamatsu’s MEMS mirrors an invaluable asset for researchers aiming for precise, controlled outcomes in photostimulation applications.

Photostimulation

What is photostimulation?

What is FRAP?

What is optogenetics?

Research introduction: Light-controlled tools for intracellular cAMP generation

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