On December 12th, Nano Letters magazine published the latest research results of exosome nanozymes catalyzing tumor photoacoustic imaging. For the first time, the researchers used the enzymatic catalytic properties of nanozymes to achieve photoacoustic imaging of nasopharyngeal carcinoma xenografts.
Photoacoustic imaging combines the high contrast ratio of pure optical imaging with the high penetration depth of pure ultrasound imaging to provide high contrast and high resolution tissue imaging. It is a very promising imaging mode. Photoacoustic imaging contrast agent is the key to determine the performance of photoacoustic imaging. It improves the imaging contrast and resolution by changing the optical and acoustic properties of the lesion tissue, and has become a research hotspot in the field of bioimaging. At present, the difficulty in photoacoustic imaging applications is to design a responsive photoacoustic imaging reaction system that occurs at the tumor site.
The use of the characteristics of the tumor microenvironment is the key to designing a tumor-responsive response system. Tumor metabolism has different characteristics from normal tissues. For example, the tumor area is weakly acidic, and tumor cells accumulate a large amount of H2O2. Based on the characteristics of the tumor microenvironment, the researchers designed and synthesized graphene quantum dot nanozymes with high catalytic activity, and self-assembled the substrate diazane diammonium salt (ABTS) onto the nanozyme. In order to make the nano-enzyme-substrate complex obtain the targeting of nasopharyngeal carcinoma and prolong the blood circulation time of nano-enzyme in vivo, a folic acid-modified erythrocyte membrane was designed, and the nano-enzyme-substrate complex was wrapped in the membrane to create Exosomal nanozyme bodies. The exosomal nanozyme bodies that enter the blood circulation are guided by the outer membrane and eventually locate and enter the tumor site, and release the nanozyme and its substrate. The weak acidic environment of the tumor site and the high concentration of H2O2 trigger nanozyme activity, and efficiently catalyze the conversion of its substrate ABTS to oxidized ABTS. The latter has a strong near-infrared light absorbing ability, and the release of thermal energy after absorbing light energy causes the local temperature of the tumor tissue to rise, thereby causing thermal expansion to generate a pressure wave and generating a photoacoustic signal. By detecting the photoacoustic signal, the light absorption distribution image in the tissue can be reconstructed, and the photoacoustic imaging diagnosis of the tumor can be realized. This study provides an example for the design of tumor-responsive photoacoustic imaging and provides a new idea and new technology for the diagnosis of nasopharyngeal carcinoma.
The research was completed by the research team of the Institute of Biophysics of the Chinese Academy of Sciences and the Nie Guohui team of the Shenzhen Second People's Hospital. Among them, Fan Kelong, associate researcher of Biophysics, Yan Xiyun, researcher, and Nie Guohui, professor of Shenzhen Second People's Hospital, are the co-authors of the paper. The postdoctoral researcher Ding Hui, co-cultivated by the Institute of Biophysics and Shenzhen Second People's Hospital, is the first author of the paper. The research was supported by three projects in Shenzhen, the special project of the Chinese Academy of Sciences, the National Science and Technology Major, the National Natural Science Foundation, and the Young Talents Project.
Schematic diagram of photocatalog imaging of exocytosis nano-enzymes
Source: Institute of Biophysics, Chinese Academy of Sciences
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