Guosong Hong | Faculty Spotlight
Assistant Professor of Materials Science and Engineering
"I was born and raised in Hefei (pronounced like the Spanish word "Jefe"), the city that proudly hosts the University of Science and Technology of China, one of China's premier institutions for science and technology. My initial foray into the engineering realm began during my undergraduate studies in chemistry at Peking University. It was there that I discerned the profound synergy between groundbreaking discoveries in chemistry and their transformative potential in engineering design.
Subsequently, I pursued my PhD in chemistry at Stanford University, a decision that was both an academic and personal milestone. My academic journey later took me to Harvard for my postdoctoral training. However, the allure of Stanford, coupled with my deep-seated association as an alumnus, beckoned me back. I was immensely pleased when the opportunity presented itself, and Stanford welcomed me once again into its fold.
Currently, I'm privileged to contribute to the esteemed research community at Stanford that nurtured and shaped my academic pursuits. It's an honor to merge my foundational learning from Peking University, the advanced research skills honed at Stanford, and the invaluable experiences gathered at Harvard in my present role at Stanford Materials Science and Engineering.
My independent research at Stanford MSE introduces a new concept of circulation-delivered light sources, aiming to resolve a long-standing challenge in delivering light into deep tissues for a wide range of applications such as fluorescence imaging, optogenetics, and photodynamic therapy. Visible light has limited penetration in biological tissues due to scattering and absorption, thus necessitating invasive procedures to deliver light into the body. To address this challenge, we applied a biomineral-inspired strategy to synthesize colloidal nanoscopic light sources based on the physical chemistry of non-equilibrium thermodynamics. These colloidal light sources are composed of doped inorganic phosphors (e.g., SrMg2Si2O7:Eu2+,Dy3+), storing optical energy in their defect states until releasing it in response to an external stimulus, such as tissue-penetrant ultrasound. Notably, systemically-delivered colloidal light sources act as an “in vivo optical flow battery”, recharged by photoexcitation in superficial vessels near the skin, and gated by tissue-penetrant ultrasound to emit light in deep vessels. This circulatory light source enabled us to achieve noninvasive optogenetic neuromodulation and transcranial brain imaging in live mice, benefiting from an “inside-out” multicolor light source instead of the conventional “outside-in” illumination. Our work on the development of the intravascular light source has led to a series of publications, including PNAS 2019; Science 2020; Science Advances 2022; JACS 2022; JACS 2023; and Nature Protocols 2023.
Another research avenue in my lab is inspired by the distinct infrared sensation mechanisms observed in certain animals in nature. Our ability to sense heat is attributed to temperature-sensitive transmembrane proteins (the family of transient receptor potential ion channels, or TRP channels), whose discoverers received the 2021 Nobel Prize in Physiology or Medicine. This very family of TRP channels also provides the incredible infrared vision to certain animals such as rattlesnakes, enabling them to see a “thermal image” of their prey in the dark. Inspired by these findings, we borrowed the molecular mechanism underlying infrared and heat sensation and applied it to the mammalian brain, thus effectively making neurons responsive to brain-penetrant infrared light. Specifically, 1064-nm infrared light offers the deepest brain penetration in the 400-1800 nm optical spectrum owing to reduced scattering and minimal absorption. To render neurons responsive to light at this wavelength, we developed an injectable nanotransducer, termed “MINDS” (macromolecular infrared nanotransducer for deep-brain stimulation), based on the bandgap engineering of semiconducting polymers. MINDS can be injected directly into any targeted regions of the brain, sensitizing transgenically expressed TRP channels and modulating the animal’s free behavior under 1064-nm illumination. Therefore, MINDS acts as a minimally-invasive and molecular-driven alternative to traditional neuromodulation approaches that rely on implanted device hardware, yielding a molecular neural interface for potentially treating neurological disorders (e.g., Parkinson’s disease) and neurodegenerative diseases (e.g., Alzheimer’s disease).
For aspiring scientist researchers in the field, I'd recommend looking beyond the confines of materials science and engineering for inspiration. By integrating ideas and concepts from diverse disciplines, you can pave the way for innovative directions within materials science and engineering."