Construction of near infrared light triggered nanodumbbell for cancer photodynamic therapy.

The application of photodynamic therapy (PDT) in deep tissue has been severely restricted by the poor photosensitizers loading and tissue-penetration of visible light for exciting the photosensitizers. How to prepare a nanocarrier with high drug loading amount and remote controllability still remains the challenge. In this article, a novel drug delivery system nanodumbbell was designed. The nanodumbbell was assembled from the hydrophobic upconverting nanoparticle (UCN) core and hydrophilic polymersome shell. The "nanodumbbell" offers possibilities to overcome the problem mentioned above. The UCN core works as a transducer to convert deeply penetrating near-infrared light to visible light to activate photosensitizers zinc (II) phthalocyanine (ZnPc) for photodynamic therapy. The polymersome lipid shell is used for loading ZnPc and protecting the whole system from nonspecific absorbance or corrosion during the transportation. The nanodumbbell is appealing because it can simultaneously achieve the high loading amount of ZnPc while avoiding UCNs aggregation. The reactive oxygen species (ROS) production test and PDT test in vitro suggested that the fluorescence emitted from the UCNs can be effectively transferred to the photosensitizers to produce cytotoxic ROS. When the UCN@lipid@polymersome nanodumbbell was decorated with targeting peptide (RGD), it presented better target specificity to cells. Our data suggest that this nanoparticle may serve as a useful nanoplatform for PDT treatment in deep-cancer therapy based on upconverting mechanism.