Abstract Summary/Description
Conjugated small molecules which can absorb and emit light in the near infrared (NIR) region have been used for several biomedical applications such as imaging different tissues and tumor cells, and cancer treatment. The NIR region is known as the therapeutic window and ideal region for bioimaging since biomolecules like hemoglobin, oxyhemoglobin and DNA don’t have absorbance in this region and NIR light can penetrate deeper into the tissue with less scattering. These compounds are very bright, and they are used as biomarkers for tissues which helps surgeons to differentiate for diagnosis or treatment. The compounds absorb light from a light source and when they emit light according to the fluorescence phenomenon, emitted light can be detected with a NIR camera. The targeted tissue shines very bright due to the dye present, and the other tissues are seen as dark. We employ this methodology in our lab to target various tissues. In this study, we report the synthesis of new heptamethine cyanine dyes for cartilage targeting. Cartilage is one of the important tissues that gets damaged due to aging, trauma and injury, and detection of the damage is key for treatment. Compounds modified at the meso position with thiochlorine moiety to introduce three positive charges to introduce cartilage targeting ability to compounds in the NIR window. Due to the negatively charged nature of cartilage tissue, the positively charged molecules have shown better targeting ability. The synthesized compounds were characterized by 1H, 13C NMR and high-resolution mass spectroscopy. They have minimal tissue scattering and high brightness.
