A reduction-responsive polypeptide nanogel encapsulating NIR photosensitizer for imaging guided photodynamic therapy

A new bromine substituted near infrared (NIR) cyanine Br2-IR808 has been synthesized, and the heavy atom effect makes it an efficient photosensitizer with NIR fluorescence properties, and it can be used as both a photosensitizer and a fluorescent dye synchronously. An intelligent reduction-sensitive polypeptide nanogel has also been synthesized, and it worked as the nano-carrier for the Br2-IR808 dye. The as-prepared NIR nanogel showed imaging guided PDT properties for in vitro studies, and the reduction-induced disassembly of the nanogel could promote the delivery of the hydrophobic cyanine dye inside the cell, and it also enhances the efficiency of the photosensitizer release, which makes the nanogel potential for application in NIR theranosis of cancer. In addition, only 2 μM photosensitizer Br2-IR808 is required for efficient PDT here while 30 μM IR808 is required solely as reported.