Synthesis and antibacterial evaluation of liposomal particles containing the recombinant peptide CAP18

Antibacterial peptides have been widely investigated as potential bio-antibiotics against bacteria. However, the proteolytic degradation and structural changes may lead to a decrease in their antibacterial activity. Encapsulating peptides in liposomes may be a suitable method to solve such problems.

This study used the recombinant CAP18 (rCAP18) as an antibacterial peptide. After production and purification, encapsulation was done inside the liposomes constructed by phosphatidylcholine. The main characteristics of liposomes, such as size, morphology, type of functional groups, and encapsulation efficiency, were investigated. Antibacterial activity of free and encapsulated rCAP18 in the liposomes (Lipo@rCAP18) against Escherichia coli, Pseudomonas aeruginosa, Xanthomonas citri subsp. citri, and Staphylococcus aureus was evaluated and compared based on the MIC and MBC values.

The obtained findings showed that the lowest inhibitory concentration of free rCAP18 for E. coli, P. aeruginosa, X. citri, and S. aureus strains was determined to be 135, 101, 80, and > 320 µg/ml. MIC value of rCAP18 enclosed in liposomes was >320, 135, 180, and 320 µg/ml, for the strains mentioned above, respectively. The comparison of MIC results showed that free and encapsulated forms of rCAP18 have a more growth-inhibitory effect against P. aeruginosa, X. citri strains. Consequently, vesicles containing antibacterial peptides can be used as a powerful method to preserve their function and maintain the active peptides over time.