More Than a Glow: How Cyanine Dyes Shape Tracer Pharmacokinetics

Fluorescence molecular imaging stands as a crucial method for tracking physiological or pathological biomarkers within living organisms. In clinical practice, this technology is increasingly applied to assist physicians in decision-making during interventional or surgical procedures. To develop imaging tracers, targeting molecules are covalently labeled with fluorescent organic dyes. Yet, it is often overlooked that such modifications to the molecule can influence and even alter its pharmacokinetics and distribution within the body. This review aims to provide an overview of the advancements in fluorophores commonly used in translational and clinical fluorescence molecular imaging, with a specific focus on long-wavelength cyanine dyes. Additionally, we will illustrate how the fluorophore's structure and labeling parameters influence the in vivo behavior of molecules, underscoring the importance of considering these aspects when designing fluorescent tracers.