Heptamethine cyanine dye-1 is widely used in biomedical imaging due to its near-infrared (NIR) fluorescence properties. Its ability to absorb and emit light in the NIR range makes it ideal for deep tissue imaging, as NIR light penetrates tissues more effectively than visible light. This dye is commonly employed in fluorescence microscopy, in vivo imaging, and tumor detection, providing high contrast and sensitivity. It is also utilized in molecular probes for studying biological processes, such as tracking cellular uptake and monitoring drug delivery. Additionally, its photostability and low toxicity make it suitable for long-term imaging studies. Furthermore, it is applied in photothermal therapy (PTT), particularly for cancer treatment, where it absorbs NIR light and converts it into heat to ablate cancer cells.