Thermal stability of biodegradable plasmonic nanoclusters in photoacoustic imaging.

The photothermal stability of plasmonic nanoparticles is critically important to perform reliable photoacoustic imaging and photothermal therapy. Recently, biodegradable nanoclusters composed of sub-5 nm primary gold particles and a biodegradable polymer have been reported as clinically-translatable contrast agents for photoacoustic imaging. After cellular internalization, the nanoclusters degrade into 5 nm primary particles for efficient excretion from the body. In this paper, three different sizes of biodegradable nanoclusters were synthesized and the optical properties and photothermal stability of the nanoclusters were investigated and compared to that of gold nanorods. The results of our study indicate that 40 nm and 80 nm biodegradable nanoclusters demonstrate higher photothermal stability compared to gold nanorods. Furthermore, 40 nm nanoclusters produce higher photoacoustic signal than gold nanorods at a given concentration of gold. Therefore, the biodegradable plasmonic nanoclusters can be effectively used for photoacoustic imaging and photothermal therapy.