Biodistribution and Biotoxicity Assessment of Fluorescent Conjugated Polymer Dots.

Conjugated polymer dots (Pdots) have shown potential in the biomedical fields due to their optical properties and customizable design. However, the limited research on the biotoxicity of Pdots hinders their further application and translation. Lipophilic Pdots are prone to adsorbing specific proteins, leading to targeted tissue accumulation. Therefore, lipophilic fluorescent Pdots (Bare-Pdots) are synthesized using the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) to systematically evaluate their biodistribution and biotoxicity in stem cells, zebrafish embryos, and mice. It is observed that Bare-Pdots are readily internalized by cells and adhered to the embryonic chorion. Additionally, Bare-Pdots exhibit a distinct distribution in brown adipose tissue and heart, closely associated with phagocytosis of capillary endothelial cells involved in lipid metabolism. Notably, injection of Bare-Pdots at 5 mg kg results in dysfunction of brown adipose tissue and an increased risk of obesity 90 days post-injection. Furthermore, hydrophilic COOH-Pdots and NH-Pdots with reduced lipophilicity are synthesized using amphiphilic ligands. NH-Pdots show similar distribution but lower biotoxicity compared to Bare-Pdots. Nevertheless, injection of COOH-Pdots at 5 mg kg causes a decrease in white blood cells and renal tubular damage. These findings provide valuable insights for optimizing dosage to ensure the safe use of Pdots in preclinical applications.