Biodegradable and switchable near-infrared fluorescent probes for hypoxia detection

Aims: Among solid tumors, hypoxia is a common characteristic and responsible for chemotherapeutic resistance. Hypoxia-sensitive imaging probes are therefore essential for early tumor detection, growth monitoring and drug-response evaluation. Despite significant efforts, detecting hypoxic oxygen levels remains challenging. Materials & methods: This paper demonstrates the use of an amine-rich carbon dot probe functionalized with an imidazole group that exhibits reversible fluorescence switching in normoxic and hypoxic environments. Results & conclusion: We demonstrate the ability to emit near-infrared light only under hypoxic conditions. The probes are found to be biodegradable in the presence of human digestive enzymes such as lipase. Ex vivo tissue imaging experiments revealed promising near-infrared signals even at a depth of 5 mm for the probe under ex vivo imaging conditions. Plain language summary Hypoxia is the state where oxygen is not adequately available at the tissue level and is the common cause of resistance toward chemotherapeutics. Hence, probes that can detect hypoxia are important in detecting early tumor progression. Here in this paper, we have developed a fluorescent probe which helps in determining normoxic and hypoxic environments. This probe emits near-infrared light only under hypoxic conditions. The phenomena have been established herein by extensive experiments.