In the newly released issue of ACS Nano, a scientific journal with impact factor of 13.942 published by the American Chemical Society (ACS), Yanlin Lv, a Ph. D candidate from Prof. Zhiyuan Tian’s group (School of Chemical Sciences, UCAS), published an article titled “Cancer Cell Membrane-Biomimetic Nanoprobes with Two-Photon Excitation and Near-Infrared Emission for Intravital Tumor Fluorescence Imaging” (ACS Nano, 2018, 12, 1350-1358). In this work, a new type of biomimetic nanoprobes characterized with near-infrared (NIR) fluorescence emission upon two-photon excitation was developed; and the ability of the probes for generating in vivo high-contrast and high-sharpness fluorescence images of intravital tumor fine structure in tumor-bearing model mice with was definitely verified. This is one of the research progresses in developing NIR photoactive materials and their biological applications that this group made in recent years.
Fluorescence imaging has played active roles at the forefront of biological detection and biomedical diagnosis owing to the advantages in terms of sensitivity, spatiotemporal resolution, and biocompatibility as compared to other techniques. For mapping intravital deep-seated targets, however, fluorescence imaging using conventional probes with excitation and beaconing signals in ultraviolet or visible region generally suffers from limited penetration depth due to the attenuating influence that the optically turbid tissues exerted. Keeping this in mind, Tian’s group has been committed to novel photoactive materials for circumventing the abovementioned barriers in recent years. They developed hybrid fluorescent nanoprobes capable of NIR fluorescence emission based on two-photon excitation, which enabled NIR-input-NIR-outgoing performance of the probes for imaging deep-seated targets with penetration depth up to 1200 μm (ACS Applied Mater. Interfaces, 2015, 7, 20640-20648). They also developed a new type of feature-packed NIR photoactive photodynamic therapy (PDT) agents and their improved therapeutic efficacy in tumor-bearing mice was clearly confirmed, which proclaimed the potential of this type of agents as an effective modality for PDT treatment (Nanoscale, 2015，7，9806-9815). Additionally, they designed and constructed photoswitchable nanoprobes with super large Stokes shift (>200 nm) and high-contrast on/off photoswitching NIR fluorescence. NIR-fluorescence photoswitching launched by visible excitation dramatically catapulted the excitation energy beyond typical fluorescence noises and interferences, which resulted in enhanced detection sensitivity in cellular fluorescence imaging and thus opened up a path of exploring photoswitchable fluorescent agents with signals in the biological window for biological and biomedical imaging (ACS Appl. Mater. Interfaces, 2016, 8, 4399-4406).
As a further step, they developed novel cancer cell membrane-biomimetic NIR-input-NIR-outgoing fluorescent nanoprobes based on a new class of conjugated polymer characterized with two-photon absorption moiety and NIR fluorescing moiety integrated into the polymer chains. Such type of feature-packed probes demonstrated superior performance in both in vitro and intravital biological fluorescence imaging in terms of targeting specificity as well as penetration depth. Specifically, in vivo imaging experiments on tumor-bearing model mice clearly verified the ability of the probes for generating fluorescence image of intravital tumor fine structure with high contrast and sharpness, which proclaiming such new type of probe as an ideal agent for biological fluorescence imaging of thick samples in practical applications (ACS Nano, 2018, 12, 1350-1358).
This work was financially supported by the National Natural Science Foundation of China, the “Hundred-Talent Program” of CAS and University of Chinese Academy of Sciences (UCAS). Prof. Guanghui Ma and Prof. Wei Wei from National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, and Prof. Yong Zhang from School of Materials Science and Engineering, Harbin Institute of Technology also made significant contribution to this work.