Strain-Dependent Adsorption of Pseudomonas aeruginosa-Derived Adhesin-Like Peptides at Abiotic Surfaces

Abstract

Implant-associated infections are an increasingly severe burden on healthcare systems worldwide and many research activities currently focus on inhibiting microbial colonization of biomedically relevant surfaces. To obtain molecular-level understanding of the involved processes and interactions, we investigate the adsorption of synthetic adhesin-like peptide sequences derived from the type IV pili of the Pseudomonas aeruginosa strains PAK and PAO at abiotic model surfaces, i.e., Au, SiO2, and oxidized Ti. These peptides correspond to the sequences of the receptor-binding domain 128–144 of the major pilin protein, which is known to facilitate P. aeruginosa adhesion at biotic and abiotic surfaces. Using quartz crystal microbalance with dissipation monitoring (QCM-D), we find that peptide adsorption is material- as well as strain-dependent. At the Au surface, PAO(128–144) shows drastically stronger adsorption than PAK(128–144), whereas adsorption of both peptides is markedly reduced at the oxide surfaces with less drastic differences between the two sequences. These observations suggest that peptide adsorption is influenced by not only the peptide sequence, but also peptide conformation. Our results furthermore highlight the importance of molecular-level investigations to understand and ultimately control microbial colonization of surfaces.

Effect of Surface Hydrophobicity on the Adsorption of a Pilus-Derived Adhesin-like Peptide

“…While the low Γ value obtained with the OH surface may at first glance be surprising, in particular considering the apparent saturation of adsorption visible in the QCM-D data shown in Figure 2 , it is nevertheless comparable in magnitude to those determined previously for PAK128-144ox adsorption at hydrophilic SiO 2 and TiO x surfaces based on the hydrodynamic radius of the peptide. 10 Also in these cases, adsorption saturated well below 1 ML coverage, similar to that observed in the present experiments for the OH surface. Regarding the CH 3 surface, the coverage of 0.82 derived from the contact area in MD simulations raises some doubts as well since at such a high surface coverage, peptide–peptide interactions will undoubtedly affect the conformation of adsorbed peptides.…”

“…This was explained by residue-driven conformational changes in the peptides during adsorption resulting from electrostatic interactions (SiO 2 and TiO x ) and covalent bond formation (Au) between peptide and surface, respectively. 10 For the SAM surfaces studied in the present work, such effects appear to be absent. In summary, the results of the QCM-D experiments are in perfect agreement with the MD simulations.…”

“…As can be seen in Table 1 , an adsorbed peptide mass of about 55 and about 24 ng/cm 2 is obtained at the CH 3 and the OH surface, respectively. Using the peptide’s estimated hydrodynamic radius 10 of about 0.8 nm, these mass values translate to surface coverage values Γ of about 0.34 and about 0.15 monolayers (ML), respectively. Using the contact areas between the peptide and the different surface as obtained from the MD simulations yields much larger Γ values of about 0.82 and 0.32 ML for the CH 3 and the OH surface, respectively, highlighting the important role of surface-specific variations in peptide conformation.…”

“…It furthermore features three positively charged, three negatively charged, and four hydrophobic amino acid residues, allowing it to adsorb to both hydrophobic and hydrophilic surfaces. Consequently, PAK128-144ox was found to adsorb also at other abiotic surfaces, namely, Au, SiO 2 , and oxidized Ti, albeit with strongly different affinities …”

“…Consequently, PAK128-144ox was found to adsorb also at other abiotic surfaces, namely, Au, SiO 2 , and oxidized Ti, albeit with strongly different affinities. 10 …”