In vivo biodistribution and passive accumulation of upconversion nanoparticles in colorectal cancer models via intraperitoneal injection

Colorectal cancer is a leading cause of death worldwide. Accurate diagnosis and evaluation of malignant extent are crucial for disease treatment. In order to improve the current limited effectiveness of agents for the current theranostics of this disease, we selected upconversion nanoparticles (UCNPs) as an alternative agent, due to their unique luminescence properties. Considering tumorigenesis in the abdominal cavity, intraperitoneal (IP) administration is utilized, based on spatial proximity. Accordingly, citrate-modified UCNPs (cit-UCNPs) were synthesized and injected into mice via the IP route, compared with the IV route. The results demonstrated that cit-UCNPs following IP administration encountered significantly different biological processes from those following IV administration. Cit-UCNPs intraperitoneally injected primarily accumulated in the organs in the abdominal cavity, including the pancreas and the mesentery, while the intravenously injected UCNPs mainly gathered in the liver and the spleen. Through the IP route, the majority of cit-UCNPs accumulated in the cancerous cecum tissues, while the minority gathered in the normal cecum tissues. Consequently, cit-UCNPs administrated via the IP route to treat colorectal cancer are superior for clinical applications.