Generation of hydroxyl radicals from photothermal decomposition of H2O2 initiated by gold nanorods and its applications for cellular oxidative damage
image: Two methods based on the electron spin resonance (ESR) technique were developed to characterize the average local temperature (Tlocal) around the excited gold nanorods: (1) temperature-dependent •OH generation from thermal decomposition of H2O2, and (2) 15N-PDT linewidth change from collisions with paramagnetic molecular O2. The Tlocal obtained was 20-30℃ higher than the global temperature (Tglobal) of the irradiated suspension measured using a thermocouple.
Credit: Nano Research, Tsinghua University Press
Upon resonant excitation, plasmonic nanoparticles (NPs) interact strongly with light and induce localized surface plasmon resonance (LSPR) resulting from the collective oscillations of free electrons. One of the most important nanoscale features for LSPR arises from the decay of hot carriers. The decay of hot carriers via electron-phonon interaction causes a local photothermal effect, which heats the nanostructures and acts as a nanoscale thermal source. The unique local heating feature of nanoscale thermal sources is more advantageous than conventional homogeneous heating for specific applications, such as biomedical field.
A research team led by Xiaochun Wu from National Center for Nanoscience and Technology in Beijing, China recently found H2O2 can be decomposed to produce hydroxyl radicals when raising the temperature in slightly acidic solution. As the most active ROS, hydroxyl radicals can be used for cellular oxidative damage. Local photothermal effect of AuNRs gives rise to high local temperatures. Two methods based on electron spin resonance (ESR) technique were developed to characterize the local temperature (Tlocal) around the excited rod. The obtained Tlocal is 20-30℃ higher than the global temperature (Tglobal) of the illuminated suspension measured using thermocouple. The generation of ·OH can be modulated by pH, H2O2 concentration, AuNRs concentration, sizes and laser power. The AuNRs + H2O2 system can be used as a light-triggered hydroxyl radical source to regulate the generation of hydroxyl radical by time and space. They demonstrated the cellular oxidative damage in vitro using hydroxyl radicals generated from excited AuNRs+H2O2 system. Considering its unique spatiotemporal controllability, the local photothermal effect of plasmonic nanostructures has great potential for precision medicine.
The team published their research article in Nano Research on September 26, 2025.
“In this article, we use the local photothermal effect of AuNRs as a local heat source to assist the thermal decomposition of H2O2 under weak acidic conditions to generate hydroxyl radicals. We use the average local temperature (Tlocal) as the parameter to characterize the spatial confinement of the local photothermal effect of photoexcited AuNRs. We develop two ESR-based approaches, namely H2O2 thermal decomposition and 15N-PDT ESR linewidth change, to characterize the local photothermal effect. The obtained Tlocal is 20-30℃ higher than Tglobal measured using thermocouple.” said Xiaochun Wu, corresponding author of the paper, professor in the National Center for Nanoscience and Technology, Chinese Academy of Sciences. She has led multiple research projects funded by the National Natural Science Foundation of China and served as the Chief Scientist of the National Key R&D Program (Nanotechnology) under the Ministry of Science and Technology.
Among various thermoplasmonic nanostructures, gold nanoparticles offer extremely efficient conversion of light into heat due to their efficient light absorption, low luminescence yield, rapid relaxation of the LSPR and excellent photostability. H2O2 pyrolysis can produce hydroxyl radicals (•OH). As the most chemically and biologically reactive and damaging reactive oxygen species, •OH can react with almost every type of biomolecule, including various antioxidant molecules, DNA, proteins, and lipids, and it can eventually cause cell damage. Thus the research team were inspired to explore the production of •OH using the AuNR photothermal effect and its potential as a stimulus-responsive •OH source for oxidative damage.
The research team optimize •OH generation by tuning H2O2 pyrolysis conditions. “Stimulus-responsive generation of •OH as the most reactive ROS from H2O2, modulated by AuNRs concentration, environmental pH, and laser power, may have additional advantages in disease treatments.” Xiaochun Wu said.
The photothermal efficiency of AuNRs as nanoscale heat sources undoubtedly plays a critical role. In general, AuNRs with smaller sizes have higher photothermal efficiencies due to their higher absorbance/scattering ratio. But they have a lower extinction coefficient, which requires higher rod concentrations to reach the same local temperature. Hence, optimum sizes will balance the above two points. To address this issue, three AuNRs with similar aspect ratios but different sizes were employed to conduct theoretical calculations and experimental verification. Xiaochun Wu said “The medium-sized, or normal AuNRs are a better choice when weighing the light absorption, photothermal conversion efficiency and required rod amount.”
The oxidation of two anti-oxidants, ascorbic acid (AA) and glutathione (GSH), by photoexcited AuNRs in the presence of H2O2 have been studied to confirm the damage to the intracellular anti-oxidant system. Cellular oxidative damage were produced using •OH obtained from the photothermal decomposition of H2O2 by resonant excited AuNRs.
The research team expects these findings will potentially enable the design of better photothermal systems for targeted bio/chemical reactions and/or biomedical applications.
Other contributors include Hui Zhang from Anhui Province Key Laboratory of Conservation and Utilization for Dabie Mountain Special Bio-Resources, School of Materials and Chemical Engineering at West Anhui University in Anhui, China; Haiyun Li, Rui Cai, Huizhen Fan at National Center for Nanoscience and Technology in Beijing China; Xiumei Jiang at Northeast Normal University in Changchun, China; and Xiaowei Zhang at Jiangsu University of Science and Technology in Jiangsu, China.
This work was supported by the National Key Basic Research Program of China (2016YFA0200903 and 2011CB932802), the Open Project of Anhui Province Key Laboratory of Conservation and Utilization for Dabie Mountain Special Bio-Resources (WXZR202319), the High-level Talent Project of West Anhui University (WGKQ2022091), Key Project of Education Department of Anhui Province(2024AH052001).
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.