Self‐Assembly of Semiconducting Polymer Amphiphiles for In Vivo Photoacoustic Imaging

Abstract

Despite the advantages of semiconducting polymer nanoparticles (SPNs) over other inorganic nanoparticles for photoacoustic (PA) imaging, their synthetic method is generally limited to nanoprecipitation, which is likely to cause the issue of nanoparticle dissociation. The synthesis of near‐infrared (NIR) absorbing semiconducting polymer amphiphiles (SPAs) that can spontaneously self‐assemble into homogeneous nanoparticles for in vivo PA imaging is reported. As compared with their counterpart nanoparticles (SPN1) prepared through nanoprecipitation, SPAs generally have higher fluorescence quantum yields but similar size and PA brightness, making them superior over SPN1. Optical and simulation studies reveal that the poly(ethylene glycol) (PEG) grafting density plays a critical role in determining the packing of SP segments inside the core of nanoparticles, consequently affecting the optical properties. The small size and structurally stable nanostructure, in conjunction with a dense PEG shell, allow SPAs to passively target tumors of living mice after systemic administration, permitting both PA and fluorescence imaging of the tumors at signals that are ≈1.5‐fold higher than that of liver. This study thus not only provides the first generation of amphiphilic optically active polymers for PA imaging, but also highlights the molecular guidelines for the development of organic NIR imaging nanomaterials.

Self-Assembly of Semiconducting-Plasmonic Gold Nanoparticles with Enhanced Optical Property for Photoacoustic Imaging and Photothermal Therapy

“…To acquire a PA image of tumor with high CNR, the near infrared (NIR) PA probes should exhibit strong NIR absorption and high photothermal conversion efficiency 6-8. Semiconducting molecules including small molecules and polymers, such as perylene diimide (PDI) 9, 10 and polypyrrole 11, have been widely investigated as PA and photothermal agents, due to their high light absorption efficiency and absorption spectra in the NIR region 12, 13.…”

Synthesis of PEGylated Semiconducting Polymer Amphiphiles for Molecular Photoacoustic Imaging and Guided Therapy

“…The influence of grafting density of PEG on the optical properties of SPAs was examined. Four SPAs (SPA1, SPA2, SPA3 and SPA4) with different molecular weights and grafting densities of PEG were synthesized . Poly(2,5‐bis(2‐hexyldecyl)‐3,6‐di(thiophen‐2‐yl)‐2,5dihydropyrrolo[3,4c]pyrrolo‐1,4‐dione‐ alt 9,9‐dioctyl‐9 H ‐fluorene) (PDPPF) was chosen as the backbone because PDPPF derivatives were suitable for both fluorescence and PA imaging.…”

Semiconducting polymer dots as near‐infrared fluorescent probes for bioimaging and sensing

“…[76] They found that a high PEG grafting density is beneficial for increasing fluorescence quantum yields, reducing reticuloendothelial uptake, and enhancing permeability and the retention effect. For instance, Pu's group also synthesized amphiphilic Pdots by incorporting hydrophilic PEG chains on the polymer backbones.…”