Molecular Engineering of Hemicyanine Scaffold for Peroxynitrite-Activated Chemiluminescence Imaging.

Chemiluminescence eliminates interference from real-time excitation light, thereby maximizing the signal-to-noise ratio of imaging. However, the reported chemiluminescent scaffolds remain limited, and the development of novel and efficient chemiluminescent scaffolds is critical and urgent. Herein, we synthesized a series of peroxynitrite (ONOO-)-activated chemiluminescent probes based on a hemicyanine scaffold through molecular engineering, and systematically investigated optical properties as well as their response mechanisms. Upon reaction with ONOO-, the vinylene units in the hemicyanine scaffold are oxidatively degraded, thereby emitting a chemiluminescent signal in the 400-650 nm wavelength range. Furthermore, under the defined conditions, it was found that the tissue penetration of ONOO--activated chemiluminescence (up to 12 mm) is deeper than that of 660 nm-activated afterglow luminescence and the fluorescence of hemicyanine scaffolds. In cell imaging, in addition to sensitive ONOO- response via chemiluminescence, it can also respond superiorly to ONOO- through well-separated dual fluorescence channels. In conjunction with satisfactory biocompatibility, the probe showed favorable responsiveness and high sensitivity toward ONOO- levels in lipopolysaccharide-induced inflammation induced. These findings provide solid and reliable experience for the discovery and construction of novel and versatile chemiluminescent scaffolds.