The antimicrobial peptide Ab-Cath, is a promising candidate for development as treatment for antimicrobial resistant (AMR) bacterial infections. Future clinical use is hampered by Ab-Cath's... Show moreThe antimicrobial peptide Ab-Cath, is a promising candidate for development as treatment for antimicrobial resistant (AMR) bacterial infections. Future clinical use is hampered by Ab-Cath's cationic peptidic nature and limited therapeutic window. Here, we evaluated hyaluronic acid-based nanogels for encapsulation of Ab-Cath to circumvent these limitations. Using microfluidics, monodispersed anionic nanogels of 156–232 nm encapsulating >99 % Ab-Cath were prepared. Unprecedented, lyophilization using polyvinyl alcohol and dextran-40 provided Ab-Cath nanogel protection and allowed easy dose adjustment. Lyophilized and redispersed Ab-Cath nanogels were as effective as Ab-Cath solution in killing AMR Staphylococcus aureus, Acinetobacter baumannii and Escherichia coli in biological fluids, and in reducing S. aureus and A. baumanniibiofilms. Importantly, encapsulation of Ab-Cath in nanogels reduced Ab-Cath's cytotoxic effects on human fibroblasts by ≥10-fold. Moreover, cutaneous application of Ab-Cath nanogels eliminated bacteria colonizing 3D human skin. These findings affirm the use of nanogels to increase the selectivity index of antimicrobial peptides. Show less
Bacterial infections are becoming harder-to-treat with current antibiotics, due to antimicrobial resistance and biofilm-formation. Therefore, there is an urgent need for novel antibacterial agents... Show moreBacterial infections are becoming harder-to-treat with current antibiotics, due to antimicrobial resistance and biofilm-formation. Therefore, there is an urgent need for novel antibacterial agents and antimicrobial peptides (AMPs) may fulfill this role. Herein, three strategies were explored for optimization of our lead AMP SAAP-148 to combat bacterial infections: i) chemical lead-optimization, ii) combination therapy with other antimicrobial agents and iii) innovative AMP delivery systems. The latter strategy was also applied to another promising AMP, the snake cathelicidin Ab-Cath. First, we demonstrated that conjugation of short polyethylene glycol chains to SAAP-148 reduced the peptide’s cytotoxicity and remarkably improved its ability to modulate the immune system to a more pro-inflammatory subset. Second, it was shown that combinations of SAAP-148 and novel antibiotic halicin were more effective than single agent treatment against planktonic bacteria of specific resistant bacterial strains, also in clinically relevant cell models. Third, we demonstrated that hyaluronic acid-based nanogels allow for efficient encapsulation of SAAP-148 and Ab-Cath, thereby improving the selectivity index of both peptides by maintaining antimicrobial activities against resistant bacteria and reducing cytotoxic activities against mammalian cells. Thus, the findings described in this thesis contribute to the development of SAAP-148 and Ab-Cath as therapeutics to combat bacterial infections. Show less
