Abstract
Superhydrophilic and superhydrophobic substrates are widely known to inhibit the attachment of a variety of motile and/or nonmotile bacteria. However, the thermodynamics of attachment are complex. Surface energy measurements alone do not address the complexities of colloidal (i.e., bacterial) dispersions but do affirm that polar (acid-base) interactions () are often more significant than nonpolar (Lifshitz-van der Waals) interactions (). Classical DLVO theory alone also fails to address all colloidal interactions present in bacterial dispersions such as and Born repulsion () yet accounts for the significant electrostatic double layer repulsion (). We purpose to model both motile (e.g., P. aeruginosa and E. coli) and nonmotile (e.g., S. aureus and S. epidermidis) bacterial attachment to both superhydrophilic and superhydrophobic substrates via surface energies and extended DLVO theory corrected for bacterial geometries. We used extended DLVO theory and surface energy analyses to characterize the following Gibbs interaction energies for the bacteria with superhydrophobic and superhydrophilic substrates: , , , and . The combination of the aforementioned interactions yields the total Gibbs interaction energy () of each bacterium with each substrate. Analysis of the interaction energies with respect to the distance of approach yielded an equilibrium distance () that seems to be independent of both bacterial species and substrate. Utilizing both and Gibbs interaction energies, substrates could be designed to inhibit bacterial attachment.
Highlights
Reducing nosocomial infection rates is a significant concern in the medical community.Many of the microorganisms contributing to the aforementioned infections originate in biofilms
Bacteria may be treated as a colloidal dispersion which abides by Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory which relates dispersion stability, ∆G tot, to Gibbs interaction energy shown in Equation (1) [19,20,21,22,23,24]:
We can use extended DLVO theory to determine (1) the equilibrium distance where adhesive forces are equivalent to repulsive interactions and (2) the contribution of the individual adhesive and repulsive components to the dynamic equilibrium of bacterial attachment leading toward primary colonization
Summary
Reducing nosocomial infection rates is a significant concern in the medical community.Many of the microorganisms contributing to the aforementioned infections originate in biofilms. Bacteria may be treated as a colloidal dispersion which abides by Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory which relates dispersion stability, ∆G tot , to Gibbs interaction energy shown in Equation (1) [19,20,21,22,23,24]:. Classical DLVO theory can account for dilute bacterial dispersions in a solvent of known zeta potential (ζ) and ionic strength (I) and requires a smooth, homogeneous substrate surface for the substrate interactions [23,25,26,27]. Classical DLVO theory does not account for either acid-base adhesive interactions (∆G AB ) or Born repulsion (∆G Born ) between
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