Self-Assembled Polysaccharide–Diphenylalanine/Au Nanospheres for Photothermal Therapy and Photoacoustic Imaging

[Image: see text] Gold-based nanomaterials have attracted extensive interest for potential application in photothermal therapy (PTT) owing to their distinctive properties including high photothermal transduction, biocompatibility, and low cytotoxicity. Herein, assembled gold nanoparticle architecture-based photothermal conversion agents were synthesized by using polysaccharides (alginate dialdehyde, ADA) as both the cross-linker to induce self-assembly of diphenylalanine (FF) and the reducer for in situ reduction of Au(3+) ions into Au nanoparticles (Au NPs). The extinction spectrum of the obtained self-assembled ADA–FF/Au nanospheres was finely modulated into a near-infrared region by controlling the growth of Au NPs inside the assemblies. The strong plasmonic coupling effect of the assembled Au NPs also leads to high photothermal conversion (η = 40%) of the ADA–FF/Au nanospheres, hence presenting good performance in PTT and photoacoustic imaging. This synthesis technique is promising to construct nanomaterials with desired functions for potential biomedical application by self-assembly of various nanocrystals in situ.