Biomedical Applications: Imaging‐Guided pH‐Sensitive Photodynamic Therapy Using Charge Reversible Upconversion Nanoparticles under Near‐Infrared Light (Adv. Funct. Mater. 24/2013)

Smart charge-reversible upconversion nanoparticles are reported on page 3077 by Zhuang Liu and co-workers for pH-responsive, in vivo, near-infrared light excited photodynamic therapy. While stable under normal physiological pH, highly sensitive acid-induced charge conversion of the nanoparticles is observed in a slightly acidic tumor microenvironment, resulting in significantly enhanced cellular internalization of nanoparticles and remarkably improved photodynamic cancer cell killing in vitro and in vivo.