Black Pigment Gallstone Inspired Platinum‐Chelated Bilirubin Nanoparticles for Combined Photoacoustic Imaging and Photothermal Therapy of Cancers

Bilirubin (BR), a bile pigment that exerts potent antioxidant and anti‐inflammatory effects, is also a major constituent of black pigment gallstones found in bile ducts under certain pathological conditions. Inspired by the intrinsic metal‐chelating power of BR found in gallstones, herein we report a cisplatin‐chelated BR‐based nanoparticle (cisPt@BRNP) for use as a new photonic nanomedicine for combined photoacoustic imaging and photothermal therapy of cancers. The cisPt@BRNPs were prepared by simply mixing cisplatin with BRNPs, yielding ca. 150‐nm‐size NPs. Upon near‐IR laser irradiation at 808 nm, cisPt@BRNPs generated considerable heat and induced clear death of cancer cells in vitro. Following intravenous injection into human colon cancer‐bearing mice, cisPt@BRNPs allowed effective tumor visualization by photoacoustic imaging and remarkable antitumor efficacy by photothermal therapy, suggesting their potential for use as a new photonic nanomedicine for cancer therapy.