Optimisation of the antimicrobial peptide Smp24 and its derivatives

The global increase in antimicrobial resistance development has created a critical need for the development of novel antimicrobial agents. Antimicrobial peptides (AMPs) are one such class of novel antimicrobials, but they have several disadvantages such as high manufacturing cost and low selectivity that must be addressed before they can achieve clinical use. In this study the relatively large size and high cytotoxic activity of the natural, venom derived AMP Smp24 were addressed using several different approaches. A formulation approach was investigated by incorporation of the peptide into sol-gel coatings in order to inhibit or prevent the growth of bacterial biofilms, showing that the unique physiochemical properties of the peptide can be utilized to improve and control the properties of the coating. Furthermore, a drug design approach was also used, based on several stages. Firstly, an investigation of the peptide structure was done creating a regional breakdown of the 3D structure and mechanism of action of the early stages of the pore formation using planar patch clamp electrophysiology. A bridge was built between the structure and mechanism via the use of molecular dynamics simulations of the peptide-bilayer interactions in order to establish a structure mechanism relationship. Based on this relationship several truncated variants of the parent peptide were designed an evaluated, first in silico showing that the simulations can give direct feedback during the design process and in vitro showing that two of the truncated analogs had both smaller size, improved antimicrobial properties and reduced cytotoxic properties compared to the parent peptide. The best analogs were further developed via amino acids substitutions in two iterations, with a total of 19 analogs evaluated in silico with 11 of those also being evaluated in vitro. Again, multiple analogs were produced with improved antimicrobial activity and selectivity. Overall, additional insight into the structure and biophysical behaviour of Smp24 was gained and utilized to guide the design of new analogs with significantly smaller size and improved selectivity without loss of antimicrobial activity relative to the parent peptide.