Hydrogen‐Bond Network‐Directed Controllable Assembly of Stable Cyanine J‐Aggregates for Long‐Term and High‐Contrast In Vivo Imaging

ABSTRACT Optical probes based on near‐infrared region (NIR) small‐molecule dyes have emerged as an indispensable tool for contemporary in vivo biomedical research. Nevertheless, the majority of the reported NIR small‐molecule probes are plagued by issues such as poor stability, short excitation wavelength, and inadequate lesion retention ability, all of which significantly hinder accuracy in vivo imaging. Herein, we introduce a strategy to construct ultra‐stable and optically controllable J‐aggregated cyanine ( JCy ) with rapid in vivo self‐assembly ability by incorporating carboxyl groups and adjusting the alkyl chain length of classical heptamethine cyanine dye. Single‐crystal x‐ray diffraction analysis reveals that the strong hydrogen bonds formed by carboxyl groups enable JCy dyes to assemble into Z‐shaped dimers and the dimers interlocking “linear supramolecular arrays (LSA)” within the crystal. These LSAs then undergo a tight and ordered J‐aggregation through the electrostatic interactions, C─H⋯O hydrogen bonds and π–π interactions. This unique J‐aggregation mechanism confers JCy dyes with carrier‐independent in vivo self‐assembly and superior stability. As a proof‐of‐concept, we selected JCy‐Bu , which exhibits low concentration dependence, remarkable resistance to protein interference, and outstanding photochemical stability, for in vivo biological study, and have achieved long‐term, high‐contrast in situ imaging of mouse gastric and tumor tissues.