gms | German Medical Science

Objectives: Adhesive intermixed polyelectrolyte (PEL) coatings loaded with various bioactive compounds can be used to equip bone substitute materials (BSM) with a therapeutic delivery function. Such PEL coatings are prepared on the one hand by either premixing polycation (PC) and polyanion (PA) solutions in defined ratios and casting the formed nanoparticular polyelectrolyte complex (PEC) dispersion at the BSM. The major objective of the study is to coat the bacteriophages on PEL layers and test their antibacterial activity against implant-associated infections.

Methods: PEL coatings at planar model substrates, surgical Kirschner (K-) wires and agar plates are prepared by consecutive deposition from polycation and polyanion solutions forming alternate PEL multilayers (PEM). Phages (PHAG) an be either preloaded or post-loaded into PEM coatings. The analytical methods FTIR, UV-Vis, CD, DLS, Scanning Force Microscopy (SFM) are used to analyze the phage coating on PEL multilayers. The antimicrobial activity of these phage coated agar plates or K-wires were tested using a plaque assay against Staphylococcus aureus. Finally, the K-wires coated with phages were tested in the Galleria mellonella implant-associated infection model.

Results and conclusion: Defined PEM coatings of poly ethyleneimine (PEI) and either poly acrylic acid (PAC) or hyaluronic acid grafted with lactic acid (DAC®) were prepared with either PEI, PAC or DAC outermost layer. S. aureus phages showed higher binding at PEI compared to PAC or DAC terminated PEM. PEM/PHAG coatings at agar plates showed plaque formation towards S. aureus bacterial cultures, which was dependent on both the terminating layer and the amount of PHAG bound. K-wires with respective PEM/PHAG coatings were implanted into G. mellonella larvae and infected by bacteria. Generally, K-wires with PEM/PHAG coatings showed higher larvae survival rates compared to blank K-wire controls. Both outermost layer nature and bound PHAG amount affected the survival rate of the larvae, which supports the results of the agar experiments. PHAG/PEL functionalization of BSM based on aqueous systems, bio related products to address implant-associated infections, novel antibacterial concepts and bone healing.