Optogenetics is a revolutionary technique in the field of neuroscience that allows the control of neuronal activity in living organisms with unprecedented precision [1,2]. By fusing methods from genetics and optics, this technique facilitates the control of neurons genetically engineered to express light-sensitive ion channels. This innovative approach has opened up new avenues for understanding how specific patterns of neural activity influence behaviors, emotions, and cognitive processes, and has laid the groundwork for the development of innovative therapies for neurological disorders [3].
Opsins: The Core of Optogenetics
At the heart of optogenetics are opsins, light-sensitive proteins that, once expressed in neurons, enable their activation or inhibition by exposure to light of certain wavelengths. The choice of opsin aligns with the experimental objective, either to activate or inhibit specific neuronal populations, taking into account properties such as wavelength sensitivity and activation/deactivation kinetics. To achieve their expression in the cell membrane, these opsins are introduced into target neurons by viral vectors or transfection techniques, and their specificity can be fine-tuned using tissue- or cell-type-specific promoters [3].
Channelrhodopsins (ChRs)
Channelrhodopsins, which are usually activated by light in the blue spectrum, are excitatory opsins capable of opening ion channels for the flow of positive ions, inducing neuronal depolarization and facilitating the firing of action potentials.
Halorhodopsins (NpHR) → Archaerhodopsins (Arch)
On the other hand, halorodopsins and archaerodopsins function as inhibitory opsins that, activated by light at longer wavelengths, allow the flow of chloride ions out of the cell, hyperpolarizing the neuron and inhibiting its activity.
Light Sources in Optogenetics
Optogenetics also critically relies on chosen light sources to activate opsins without harming the surrounding tissue.
Lasers
Lasers are preferred for their ability to generate coherent, high-intensity beams of light that can be precisely targeted and focused on specific areas of the brain, allowing for highly localized neural stimulation.
LEDs (Light Emitting Diodes)
LEDs, on the other hand, present a versatile and cost-effective alternative, being able to produce light over a wide range of wavelengths, although their intensity is usually lower than that of lasers [4]. At Pyroistech, we have specially designed LED light sources to meet the requirements of optogenetic research.
The Importance of Fiber Optics
Fiber optics emerge as a crucial component for precise light delivery in optogenetics applications, allowing deep areas of the brain that would otherwise be inaccessible to be reached with minimal invasion. Its ability to direct light with great precision and minimize damage to surrounding tissue is essential for studies requiring specific neuronal activation or inhibition. Fiber optics is distinguished by its precision and its ability to be customized in terms of length, diameter and final configuration, adapting to the specific needs of each experiment.
Fiber-optic tools integrate seamlessly with advanced experimental techniques, expanding the possibilities of optogenetics in research and its potential therapeutic applications. There is a remarkable synergy in the use of opsins and the use of light sources at specific wavelengths, together with the use of systems for light transport based on fiber optics, presenting a unique opportunity for the advancement of optogenetics towards new horizons, promising discoveries and innovative applications in the field of neuroscience.
References:
[1] Samarendra K. Mohanty & Vasudevan Lakshminarayananan (2015) Optical techniques in optogenetics, Journal of Modern Optics, 62:12, 949-970, DOI: 10.1080/09500340.2015.1010620
[2] Emiliani, V., Entcheva, E., Hedrich, R. et al. Optogenetics for light control of biological systems. Nat Rev Methods Primers 2, 55 (2022). https://doi.org/10.1038/s43586-022-00136-4
[3]Sun, Y.; Li, M.; Cao, S.; Xu, Y.; Wu, P.; Xu, S.; Pan, Q.; Guo, Y.; Ye, Y.; Wang, Z.; et al. Optogenetics for Understanding and Treating Brain Injury: Advances in the Field and Future Prospects. Int. J. Mol. Sci. 2022, 23, 1800. https://doi.org/10.3390/ijms23031800
[4] https://nicneuro.net/2022/10/26/optogenetics-led-systems/