Semiconducting Polymer Nanospherical Nucleic Acid Probe for Transcriptomic Imaging of Cancer Chemo‐Immunotherapy

Real‐time in vivo imaging of RNA can enhance the understanding of physio‐pathological processes. However, most nucleic acid‐based sensors have poor resistance to nucleases and limited photophysical properties, making them suboptimal for this purpose. To address this, a semiconducting polymer nanospherical nucleic acid probe (SENSE) for transcriptomic imaging of cancer immunity in living mice is developed. SENSE comprises a semiconducting polymer (SP) backbone covalently linked with recognition DNA strands, which are complemented by dye‐labeled signal DNA strands. Upon detection of targeted T lymphocyte transcript (Gzmb: granzyme B), the signal strands are released, leading to a fluorescence enhancement correlated to transcript levels with superb sensitivity. The always‐on fluorescence of the SP core also serves as an internal reference for tracking SENSE uptake in tumors. Thus, SENSE has the dual‐signal channel that enables ratiometric imaging of Gzmb transcripts in the tumor of living mice for evaluating chemo‐immunotherapy; moreover, it has demonstrated sensitivity and specificity comparable to flow cytometry and quantitative polymerase chain reaction, yet offering a faster and simpler means of T cell detection in resected tumors. Therefore, SENSE represents a promising tool for in vivo RNA imaging. Semiconducting polymer nanospherical nucleic acid probe (SENSE) responds to targeted granzyme B transcripts of T lymphocytes by releasing the signaling strand, leading to an increase in fluorescence signal of Cyanine 5 dye (NIRF670). With the always‐on fluorescence (NIRF810) of semiconducting polymer nanosphere, SENSE enables the self‐referenced longitudinal imaging of RNA transcript in vivo for the first time.