Recent development in upconversion nanoparticles and their application in optogenetics: A review

Ion channels present in the plasma membrane are responsible for integration and propagation of electric signals, which transmit information in nerve cells. Malfunction of these ion channels leads to many neurological diseases. Recently, optogenetic technology has gained a lot of attention for the manipulation of neuronal circuits. Optogenetics is a neuromodulation approach that has been developed to control neuronal functions and activities using light. The lanthanide-doped upconversion nanoparticles (UCNPs) absorb low energy photons in near-infrared (NIR) window and emit high energy photons in the visible spectrum region via nonlinear processes. In the last few decades, UCNPs have gained great attention in various bio-medical applications such as bio-imaging, drug delivery and optogenetics. The near-infrared illumination is considered more suitable for optogenetics application, due to its lower degree of light attenuation and higher tissue penetration compared to visible light. Therefore, UCNPs have been considered as the new promising candidates for optogenetics applications. Upconversion nanoparticle-mediated optogenetic systems provide a great opportunity to manipulate the ion channel in deep tissue. Herein, we summarize the upconversion photoluminescence in lanthanide doped nanomaterials and its mechanisms and several approaches adopted to tune emission color or enhance upconversion efficiency. Recent advances of lanthanide-doped UCNPs design strategy and their mechanism are reviewed. Then, we discuss the neural circuitry modulation using upconversion nanoparticles mediated optogenetics. Moreover, the future perspectives towards optogenetics are also included. (c) 2021 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

Ion channels in nerve cells are responsible for transmitting electric signals, and their malfunction can lead to neurological diseases. Optogenetic technology, which utilizes light to control neuronal functions, has gained attention. Lanthanide-doped upconversion nanoparticles (UCNPs) are a promising candidate for optogenetics due to their ability to absorb low energy photons and emit high energy photons. UCNPs have potential for deep tissue manipulation of ion channels. This article summarizes the photoluminescence and tuning mechanisms of UCNPs, explores their application in neural circuit modulation through optogenetics, and discusses future perspectives in this field.