Peptide release from SEDDS containing hydrophobic ion pair therapeutic peptides measured by Taylor dispersion analysis.

Therapeutic peptides are facing an increasing interest as drugs for the treatment of many diseases. The challenge in the administration of such drugs, due to inherent properties of these peptides, is to make them bioavailable. Self-emulsifying drug delivery systems (SEDDS) are considered a suitable and promising strategy to deliver the peptides and increase their bioavailability. However, to enter into the SEDDS nanodroplets, the peptides must be made hydrophobic by complexation with surfactants (formation of hydrophobic ion pair, HIP). The aim of this work is to assess the possibility to quantify the amount of released peptides and of the remaining docusate/peptide HIP in the nanodroplets by Taylor Dispersion Analysis (TDA) on two therapeutic peptides (leuprorelin and desmopressin). It also clearly demonstrates that the logP value of the peptide has a strong influence on the extent of HIP inside of the SEDDS nanodroplets. For instance leuprorelin-docusate complex (logP = 3) was 100% inside of the nanodroplets at low ionic strength, while for desmopressin-docusate complex (logP = 0.5) only 30% were able to enter the nanodroplets. It was also shown that an increase in the ionic strength of the release media allowed to increase the amount of released peptide up to 80% for leuprorelin and 100% for desmopressin, at physiological ionic strength. TDA experiments allowed to determine the partitioning coefficient, logD value, of the peptide between the SEDDS and continuous aqueous phases. In conclusion, this work demonstrates that TDA is a rapid, straightforward and useful technique for developing SEDDS formulations.