Mikrokapslar av PLGA f¨ or inkapsling och fris¨ attning av den antimikrobiella peptiden AMC-109

Abstract

With today’s challenge of antibiotic resistance development, the world is in need of new antimicrobial substances. Antimicrobial peptides (AMPs) are promising candidates for replacing conventional antibiotics. However, AMPs are broken down quickly when used in the human body and have cytotoxicity against eukaryote cells at high concentrations. By encapsulation of AMPs, these issues can be reduced as a carrier matrix protects against degradation and enables controlled release, which reduces exposure to eukaryotic cells. AMC-109 is a synthetic AMP produced by the company Amicoat AS, and works through disruption of the lateral organizaion of bacterial cell membranes and lysing the membrane. Previous studies have shown that AMC-109 can be encapsulated in the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) in the presence of negatively charged endgroups on the polymer. This project studied the release of AMC-109 from microcapsules consisting of PLGA. The purpose was to determine whether the release profile was affected by varying two different parameters; the number of end groups of the polymer, which is regulated by the molecular weight of PLGA (800 Da vs. 15 kDa), and AMC-109 loading in the microcapsules. Microcapsules were formulated with three different formulation contents, 1, 3 and 15 weight-% with respect to polymer weight. At a formulation content at 15 weight-%, the encapsulated amount of AMC-109 was 10.6 weight-% and 4.1 weight-% for 800 Da and 15kDa PLGA, respectively. This indicated that the microcapsules were saturated with AMC-109 at a formulation content of 15 weight-%, but not at a formulation content of 1 and 3 weight-%. The release was studied by adding microcapsules of PLGA and AMC-109 to a bath with phosphate buffered saline (PBS) and a hydrophilic non-ionic surfactant at 37°C. Samples were taken throughout the release process and the fractional release of AMC-109 was determined via UV-Vis spectroscopy. A model based on the diffusion equation was fitted to the release data and capsule size distribution to obtain release profiles and the effective diffusion coefficient D of AMC-109 in the capsule. For release systems with microcapsules formulated with 800 Da PLGA and that were not saturated with AMC-109 the release was driven primarily by degradation of PLGA, and not by diffusion. However, systems with microcapsules saturated with AMC-109 showed a diffusion-controlled release for both molecular weights. For systems formulated with 15 kDa and non-saturated with AMC-109 no release could be detected within the study period. These findings clearly suggest that both the molecular weight of the polymer and AMC-109 loadning impact the release profile of PLGA- and AMC-109 release systems.