Analytical SPLITT fractionation in the diffusion mode operating as a dialysis-like system devoid of membrane. Application to drug-carrying liposomes

This work reports a new technique for the rapid measurement of the fraction of free substrates in colloidal suspensions, specifically drugs in liposomes, using analytical SPLITT fractionation. The SPLITT fractionation channel mimics a dialysis-like separation utilizing differential transport across an ultrathin (∼100 μm) lamina flowing through the cell. The fast-diffusing free drug molecules cross this thin lamina and dissipate over the channel, while the slowly diffusing colloids are confined to a narrow region next to their introduction side. The liquid stream in the cell is split into two substreams at the outlet. One of the substreams contains the colloids as well as the free drug, whereas the other substream contains only free drug molecules