J-aggregates of Br- and piperazine-modified cyanine dye with the assistance of amphiphilic polypeptides for efficient NIR-IIa phototheranostics under 1064 nm irradiation

The second near-infrared IIa window (NIR-IIa, 130 0nm similar to 140 0nm) enables high-resolution imaging and deep-tissue tumor treatment due to its unique low tissue scattering and autofluorescence, high temporalspatial resolution, and deep tissue penetration. Therefore, NIR-IIa fluorescence imaging-guided phototherapy is of specific interest. However, organic dyes and their nanoparticles for NIR-IIa phototheranostics are still scarce. Here, we have synthesized a Br- and piperazine-modified cyanine dye (FN) and its nanomicelles encapsulated by an amphiphilic polypeptide with sidechains of tertiary amine (PEA). The Jaggregates of P@FN 9 with 1116 nm absorption and efficient NIR-IIa fluorescence emission were formed by the self-assembly of FN and PEA. P@FN 9 nanoparticles (NPs) showed good stability and high photothermal conversion efficiency (55.4%). In addition, the high spatial resolution and signal-to-background ratio (SBR) of P@FN 9 were demonstrated by NIR-IIa fluorescence imaging of mouse vasculature. The P@FN 9 NPs successfully performed the NIR-IIa fluorescence imaging-guided photothermal therapy, and both in vitro and in vivo experiments indicated that the P@FN 9 NPs exhibited effective antitumor effects under the NIR-II (1064 nm) laser irradiation.