Poly(ethyleneimine)/Poly(acrylic acid) Multilayer Coatings with Peripherally Bound Staphylococcus aureus Bacteriophages Have Antibacterial Properties

Herein, polyelectrolyte (PEL)-based coatings including peripherally bound bacteriophages (PHAG) at model substrates are reported to showcase their applicability on surgically relevant implants with respect to surface protection against bacterial proliferation and biofilm formation. The established layer-by-layer concept based on the consecutive adsorption of oppositely charged PEL was applied to generate polyelectrolyte multilayer (PEM) coatings with either a cationic or anionic excess surface charge. PHAG were bound at the outermost layer of such PEM coatings utilizing electrostatic interaction forces. Branched poly­(ethyleneimine) (PEI) and poly­(acrylic acid) (PAA) as cationic and anionic PEL, respectively, and theEscherichia coli T4 bacteriophage (T4 PHAG) and the Staphylococcus aureus bacteriophage (S.a. PHAG) were used. At first, PEM of PEI/PAA were consecutively adsorbed from solutions at germanium model substrates with z = 4 and 5 adsorption steps providing PAA-terminated PEM-4 and PEI-terminated PEM-5, which were characterized by surface-sensitive in situ attenuated total reflection Fourier transform infrared spectroscopy. Second, both T4 and S.a. PHAG were bound to these PEM showing a higher bound amount at cationic PEM-5 compared to anionic PEM-4. Electrostatic interaction forces between anionic capsid proteins and respective PEM are suggested. Furthermore, scanning force microscopy revealed typical overall size (200–250 nm) and shape (head/tail) features of the bound PHAG and supported qualitatively the preference for cationic PEM-5 by number. Finally, PEM-4 and PEM-5 were deposited at standard agar plates, S.a. PHAG were bound to those PEM, and plaque assay was performed to check antibacterial properties. Thereby, coatings of PHAG/PEM-5 showed a higher antibacterial activity and PHAG/PEM-4 a lower one, which was evidenced by plaque formation testing. Conclusively, PHAG/PEM coatings are promising for the reduction of implant-associated infections at surgical implants and thus may replace or complement established coatings based on low molecular synthetic antibiotics.