On the design of tailored liposomes for KRX29 peptide delivery

The high interest in therapeutic peptides, due to the specificity of their mechanisms of action, has stimulated the research of new delivery strategies to overcome bioavailability problems concerning the use of peptides in their naked form. In particular, in this study, a novel small cyclic peptide, KRX29, with a potential therapeutic effect on Heart Failure (HF) pathology, was encapsulated into large and unilamellar small vesicles (LVs, SUVs) using the thin film-hydration method followed by ultrasound assisted size reduction processes, generating loaded liposomes with nanometric sizes. Loaded and unloaded liposomes were produced exploring three different formulations by changing the charge ratio (-/+) between the anionic phosphatidylglycerol (PG) and the cationic KRX29 peptide. LVs and SUVs were designed using a 1:1, 7:1 and 13:1 (-/+) PG/KRX29 charge ratio and, for each formulation, the charge effect on the liposome morphology, size and zeta potential was analyzed together with peptide encapsulation performance, load, recovery efficiencies and stability through an analytical HPLC protocol purposely developed. Best results in terms of encapsulation in nanoliposomal formulations for KRX29 delivery were achieved using a 13:1 (-/+) charge ratio (99% in 35 nm SUVs). The influence of the PG/KRX29 charge ratio on the recovery efficiencies was also investigated obtaining that the maximal peptide recovery from liposomes (81-94%) was achieved by using a 1:1 (-/+) charge ratio formulation and pure ethanol as a solvent for the extraction.