טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentYair Goldfeder
SubjectExperimental Conditions that Enhance Potency of
Antibacterial Oligo-Acyl-Lysyls
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Full Professors Mor Amram
Full Thesis textFull thesis text - English Version


Abstract

Oligo-acyl-lysyls (OAKs) are synthetic mimics of host defense peptides known to exert antibacterial activity both in cultures and in animal models of disease. In the first part of this study, we investigated how environmental conditions (temperature, pH and ionic strength) affect the antibacterial properties of two OAKs, C12K-7a8 and C16ω7-12, representing two different molecules with diverse mechanisms of action, target bacteria and molecular properties.

Data obtained with representatives bacteria including the Gram-negative E. coli and the Gram-positives L. monocytogenes and S. aureus, showed that the OAKs’ potency was proportionally affected by pH changes and subsided essentially throughout a wide range of salts concentrations and temperature values. It was rather the mode of action that was most susceptible to the environmental changes.

Thus, the OAKs’ bactericidal effect was limited to growth-inhibitory effect under acidic pH, low temperatures or high salt concentrations, whereas basic pH or high temperatures have enhanced the bactericidal kinetics.

Binding properties to model phospholipid membranes that mimic the cytoplasmic membrane lipid composition of E. coli, have provided evidence that correlated the differential modes of action with variable binding affinities, showing that higher potencies are an outcome to the higher propensity of the OAKs to be incorporated within the bilayer at alkaline pH, while the opposite was observed for low pH values or extremely high salt concentrations.

Finally, combination of the optimal incubation conditions resulted in a remarkable increase in potency, as expressed by 16 to 250-fold reduction in the MIC value and by much faster bactericidal rates (>99% death induced within minutes versus hours) compared with the standard incubation conditions.

In the second part of this study, we report preliminary data aiming to assess novel lipid-OAK encapsulation systems, designed to facilitate the simultaneous delivery of OAKS and antibiotics displaying synergistic properties. Our results show a correlation between lipid compositions, efficient drug encapsulation and stability, including in whole blood.

Collectively, the data suggest that OAKs might be useful in developing design strategies for robust antimicrobial peptides that are able to affect pathogen viability under a large spectrum of incubation conditions.