Activatable Fluorescence/Photoacoustic Macromolecular Probe for Imaging of Tumor-Associated Natural Killer Cells
Related Experiment Video
Updated: Sep 19, 2025
Field-Deployable Lens-Free Imaging Platform for Rapid Label-Free Analysis of Natural Killer Cell Activation
Published on: August 8, 2025
Yanbin Feng1, Yuxuan Hu2, Jing Liu2
1Lab of Molecular Imaging and Translational Medicine (MITM), Engineering Research Center of Molecular & Neuroimaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, 710126, China.
Abstract:
Detection of tumor-associated natural killer cells (TANKs) is crucial for evaluating cancer immunotherapy because they are found to be associated with improved overall survival rate. However, existing analytical methods relying on tissue biopsy are invasive and static, restricting their capacity to deliver dynamic information. Herein, we report an activatable near-infrared fluorescence (NIRF)/photoacoustic (PA) macromolecular reporter (BhCyNK) for real-time imaging of TANKs. To optimize the PA performance, the fluorophore scaffold of BhCyNK is screened. Among four hemicyanine derivatives, BhCyS with the longest absorption maximum (∼800 nm) as well as the highest photothermal conversion efficiency (71.13%) and PA brightness is constructed into BhCyNK, which specifically triggers its NIRF signal (by 10-fold increase) and PA signal (by 8.3-fold increase) in the presence of a TANK-overexpressed protease. BhCyNK effectively distinguishes natural killer cells from other immune cells including T cells, neutrophils, and macrophages. The high specificity of BhCyNK enables real-time monitoring of TANKs population in the tumor of living mice amid cancer immunotherapies. The imaging results reveal that the increasing intratumoral signal of BhCyNK after combination immunotherapy correlates well with the increasing population of TANKs. Thus, this study not only reports a molecular strategy to develop efficient PA fluorophores but also provides an ideal tool for noninvasive monitoring of immune cells.
Insights
We developed a novel imaging agent, BhCyNK, for real-time, noninvasive detection of tumor-associated natural killer cells (TANKs). This tool enhances cancer immunotherapy evaluation by tracking TANKs dynamically in living mice.
Area of Science:
- Biomedical Imaging
- Molecular Imaging
- Cancer Immunotherapy
Background:
- Accurate monitoring of tumor-associated natural killer cells (TANKs) is vital for assessing cancer immunotherapy efficacy and patient survival.
- Current methods like tissue biopsy are invasive and provide only static data, limiting dynamic monitoring.
- There is a need for noninvasive, real-time imaging techniques to track TANKs populations.
Purpose of the Study:
- To develop an activatable macromolecular reporter for real-time near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging of TANKs.
- To optimize the photoacoustic performance of the reporter by screening hemicyanine derivatives.
- To validate the reporter's specificity and efficacy in monitoring TANKs during cancer immunotherapy.
Main Methods:
- Screening of four hemicyanine derivatives to identify the optimal scaffold (BhCyS) for PA performance.
- Construction of the BhCyNK reporter, which exhibits signal enhancement in the presence of TANK-overexpressed protease.
- In vitro and in vivo evaluation of BhCyNK's specificity for TANKs and its ability to monitor TANKs population changes in mice during immunotherapy.
Main Results:
- BhCyS demonstrated superior photothermal conversion efficiency and PA brightness, with maximal absorption near 800 nm.
- BhCyNK showed a significant 10-fold increase in NIRF signal and an 8.3-fold increase in PA signal upon protease activation.
- BhCyNK specifically detected TANKs, distinguishing them from other immune cells, and enabled real-time monitoring of TANKs in mouse tumors.
- Intratumoral BhCyNK signal correlated with TANKs population increases following combination immunotherapy.
Conclusions:
- A novel activatable NIRF/PA macromolecular reporter (BhCyNK) was developed for sensitive and specific detection of TANKs.
- The study presents a molecular strategy for creating efficient PA fluorophores.
- BhCyNK serves as an ideal tool for noninvasive, real-time monitoring of immune cells in cancer immunotherapy research.
