Preventing bacterial infections of hip prostheses : study of interactions between antimicrobial agents and of LL-37 release from a coating

Details

Supervisors

Dupont-Gillain, Christine C. ; Vranckx, Cédric

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Currently, hip replacement surgeries affect one million of patients each year worldwide, a number expected to increase because of the ageing population and the enhanced sedentary lifestyle. As a consequence, the number of hip revision procedures due to bacterial infections, a main cause of hip arthroplasty failure, is expected to rise too. In answer to this, an antibacterial surface coating has been developed with the purpose of avoiding biofilm formation on the prosthesis and prevent bacterial infections in the surrounding tissues. The antimicrobial peptide LL-37 was chosen to meet these demands, as it holds both antibacterial and antibiofilm activities against \textit{S. aureus} and \textit{S. epidermidis}, two main pathogens involved in implant-associated infections. The Layer-by-Layer assembly was used for the immobilisation of the peptide, together with heparin and chitosan, two polyelectrolytes which were selected because of their biological properties. The first objective of this work was to investigate the nature of the interaction of LL-37 with antibiotics, to establish whether LL-37 could decrease the amount of antibiotic needed to prevent infections. This would be a promising result as a part of the fight against antibiotic resistance. This was studied by testing bacterial growth in presence of antibiotics from two different families, glycopeptides and aminoglycosides, in combination with the LL-37 peptide. The obtained results suggest that a positive interaction, i.e synergy or additive effects, arises from the combination of LL-37 with aminoglycosides. This may be explained by an entry of such antibiotics in cells that is facilitated by the action of LL-37. These results allowed to evaluate the amount of antibiotic and LL-37 required to inhibit bacterial growth in solution. A second objective was to study the construction of the coating in order to investigate whether it would be able to prevent both biofilm formation and infections in the surrounding tissues. For this, the amount of immobilised LL-37 was determined for two different pH of construction (3.5 and 5) and either with bare LL-37 or with protein-polyelectrolyte complexes (PPCs) in the constructed multilayers. It appeared that constructions at pH 3.5 with bare LL-37 allow to immobilise higher quantities of LL-37. After this, the release kinetics of the different constructions were monitored in a dynamic way over 14 days. The results show that part of the LL-37 is released and may then exert its antibacterial activity in the surrounding tissue, while part of it remains in the implant coating to pursue its antibiofilm activity. While much work remains to be done to optimize the coating and study its activity, the obtained results are promising in the context of the fight against implant-associated infections as they bring an increased understanding of the mode of action of the coating and demonstrate the possibility to tune its activity.