In vivo biodistribution and toxicity assessment of triplet-triplet annihilation-based upconversion nanocapsules

Triplet-triplet annihilation (TTA)-based upconversion nanocapsules (UCNCs) have great potential in biological and medical applications. However, there are numerous unresolved issues with respect to the safety of these novel nanomaterials. In this work, for the first time, we studied the in vivo biodistribution of UCNCs which were synthesized by co-loading platinum (II)-tetraphenyl-tetrabenzoporphyrin (PtTPBP) and boron dipyrromethene derivative (BDP) into bovine serum albumin (BSA)-stabilized soybean oil droplets, and systematically assessed the potential toxicity of UCNCs both in vitro and in vivo. The results showed that UCNCs had no significant influence on the proliferation or the migration of HeLa cells even when the dosage was increased to 12 mg/mL. The biodistribution results demonstrated that UCNCs mainly accumulated in the mononuclear phagocyte system (MPS) including the liver and spleen after intravenous injection of the nanocapsules. When mice were intravenously injected with 1200 mg/kg of the UCNCs over a period of 60 days, no noticeable toxicity was observed under these treatment conditions as shown by body weight results, histological analyses, hematological analyses and blood biochemical examinations. This research inspires further studies on UCNCs for biomedical applications.