Entrapment of Peptidoglycans and Adamantyltripeptides into Liposomes: An HPLC Assay for Determination of Encapsulation Efficiency

Abstract

The encapsulation of different immunomodulating peptides, the peptidoglycan monomer, its semisynthetic derivatives (Adamant-1-yl)-acetyl-peptidoglycan monomer and Boc-Tyr-peptidoglycan monomer, respectively, and of two diastereoisomers of adamantyltripeptides into the large negatively charged multilamellar liposomes was investigated. The reproducible quantitative method using HPLC was established for the determination of the entrapped compounds. It was shown that the tested compounds could be efficiently incorporated into liposomes using either the film or modified film method. The results confirmed that the peptidoglycans with lipophilic substituents and particularly the adamantyltripeptides were incorporated into liposomes with higher efficiency than the peptidoglycan monomer using either of the described methods. Liposome preparations were stable at 4°C up to seven days as shown by minimal leaking of the entrapped material.

Key Words :

• Peptidoglycan monomer
• Adamantyltripeptides
• Liposomes
• HPLC
• Encapsulation

Acknowledgment

This work was supported by the Ministry of Science and Technology of Croatia, Research Project 0021-002. The authors thank Dr. J. Petres and R. Kašnar for helping with ultracentrifugation and Mrs. R. Jožinec for technical assistance in HPLC analyses.