Synthesis of near-infrared poly (IB-alt-MAnh)-aza-bodipy and its application in photoacoustic imaging

Near-infrared poly(isobutylene-alt-MAnh)-aza-bodipy, which can be used as photoacoustic imaging contrast agent in vivo mice, was synthesized by ring opening reaction of poly(isobutylene-alt-MAnh) with hydroxyl group. Near-infrared organic nanoparticle was formed in water with their hydrodynamic diameter of 60 nm. These nanoparticles were formed with a core of aza-bodipy dye and shell of polymer. Dynamic light scattering (DLS), transmission electron microscopy (TEM) and ultraviolet-visible absorption spectra (UV-Vis) were used to characterize the morphology, size and optical property of the nanoparticles in aqueous solution. The results showed that the nanoparticles had uniform appearance and strong absorption in near-infrared area. Moreover, DLS was used to observe the stability of nanoparticles in serum and the size of nanoparticles was kept pratically constant within 24 h. Photothermal experiment was conducted to study the nanoparticle performance at different power and concentration, which exhibited excellent photothermal performance. MTT assay demonstrated that the nanoparticles had a good biocompatibility and photothermal performance at different concentrations. In addition, the photoacoustic property of the nanoparticles was studied by photoacoustic imaging and the results showed that they had strong photoacoustic signals at a low concentration. Photoacoustic imaging experiments on mice were also studied. It was found that tumor location on mice had a significant photoacoustic signal enhancement after tail vein injection of the nanoparticles. With 24 h of circulation in blood after injection of the nanoparticles, the photoacoustic signal disappeared, which indicated that the nanoparticles had good metabolic and biocompatibility.