Because of their low imaging depth and high light scattering, fluorescent probes are difficult to achieve high-resolution imaging of bacterial infection in deep tissues. Photoacoustic imaging relies on photoacoustic effect, that is, light absorbs the thermal expansion of the object to produce ultrasonic signals, which overcomes the high scattering of photons in biological tissues. Among many photoacoustic imaging contrast agents, large-size gold nanoparticles are widely used in high-resolution photoacoustic imaging of mammalian cells in deep tissues because of their strong near-infrared absorption ability. However, large-size gold nanoparticles are not suitable for bacterial cell imaging because the diameter of bacterial cells is only 0.5-5 μ m, around one tenth the diameter of mammalian cells. In addition, the outermost layer of mammalian cells is a flexible cell membrane composed of lipid bilayer. On the contrary, the outermost layer of bacterial cells is a relatively hard cell wall, which is composed of peptidoglycans. Therefore, large-size gold nanoparticles can passively enter mammalian cells through endocytosis, but they cannot enter bacterial cells freely due to the hard barrier of bacterial cell wall.
To address this problem, Dr. Houyu Wang and Prof. Yao He et al. from Suzhou Key Laboratory of nanotechnology and biomedicine & FUNSOM, Soochow University recently have leverage bacterial specific ABC transporter to deliver glucose polymer, NHS diazopropyridine and Ce6 modified small-size gold nanoparticles into bacterial cells based on their previous work (Nat. Commun. 2019, 10: 4057). After internalization into bacterial cells, the nanoparticles can aggregate under laser-induced, resulting in obvious photoacoustic signals, which realizes high-resolution photoacoustic imaging of bacteria in deep tissues. This strategy enables photoacoustic imaging analysis of bacteria in tumors and gut at concentrations as low as ~ 107 CFU (Fig. 1). This strategy can visualize and process a variety of bacteria in deep tissue, which is an important step for the research of microbial ecosystem. The related results were published in Nature Communications (Nat. Commun. 2022, 13: 1255). The first authors of this article are Miss Yunmin Yang and Dr. Binbin Chu.
Fig.1
Article link: https://doi.org/10.1038/s41467-022-28920-6
Article title: Bacteria eat nanoprobes for aggregation-enhanced imaging and killing diverse microorganisms.
Author Information: Yunmin Yang, Binbin Chu, Jiayi Cheng, Jiali Tang, Bin Song, Houyu Wang* & Yao He*
Project funding: The authors acknowledge financial support from the National Natural Science Foundation of China (No. 21825402 and 22074101), Natural Science Foundation of Jiangsu Province of China (No. BK20191417 and BK20200851), China Postdoctoral Science Foundation (No. 2021M692347), and the Program for Jiangsu Specially Appointed Professors to the Prof. Yao He, a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, 111 Project as well as the Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC).
Editor: Guo Jia