In vivo characterization of the biodistribution profile of amphipol A8-35.

Amphipols (APols) are polymeric surfactants that keep membrane proteins (MPs) water-soluble in the absence of detergent, while stabilizing them. They can be used to deliver MPs and other hydrophobic molecules in vivo for therapeutic purposes, e.g., vaccination or targeted delivery of drugs. The biodistribution and elimination of the best characterized APol, a polyacrylate derivative called A8-35, have been examined in mice, using two fluorescent APols, grafted with either Alexa Fluor 647 or rhodamine. Three of the most common injection routes have been used, intravenous (IV), intraperitoneal (IP), and subcutaneous (SC). The biodistribution has been studied by in vivo fluorescence imaging and by determining the concentration of fluorophore in the main organs. Free rhodamine was used as a control. Upon IV injection, A8-35 distributes rapidly throughout the organism and is found in most organs but the brain and spleen, before being slowly eliminated (10-20 days). A similar pattern is observed after IP injection, following a brief latency period during which the polymer remains confined to the peritoneal cavity. Upon SC injection, A8-35 remains essentially confined to the point of injection, from which it is only slowly released. An interesting observation is that A8-35 tends to accumulate in fat pads, suggesting that it could be used to deliver anti-obesity drugs.