Bacterial Adhesion on Soft Materials: Passive Physicochemical Interactions or Active Bacterial Mechanosensing?

Area of Science:

• Biomaterials Science
• Microbiology
• Surface Chemistry

Background:

• The relationship between biomaterial mechanical stiffness and bacterial adhesion is poorly understood.
• Existing theories on bacterial mechanosensing may not fully explain adhesion patterns on varying stiffness surfaces.

Purpose of the Study:

• To investigate the influence of polydimethylsiloxane (PDMS) stiffness on the adhesion of specific bacterial species.
• To differentiate between intrinsic material properties and active bacterial mechanisms in adhesion.

Main Methods:

• Bacterial adhesion assays were performed on PDMS samples with Young's moduli ranging from 0.06 to 4.52 MPa.
• Abiotic polystyrene (PS) beads with different surface modifications (carboxylate and amine) were used as controls to mimic bacterial properties.

Main Results:

• Escherichia coli and Pseudomonas aeruginosa showed significantly higher adhesion on soft PDMS compared to stiff PDMS (7- and 27-fold increase, respectively).
• Staphylococcus aureus exhibited similar adhesion levels across all tested stiffnesses.
• Carboxylate-modified PS beads mirrored the adhesion pattern of E. coli and P. aeruginosa, while amine-modified beads showed no stiffness-dependent adhesion, similar to S. aureus.

Conclusions:

• Intrinsic physicochemical properties of PDMS substrates, influenced by stiffness, play a crucial role in bacterial adhesion.
• The findings challenge the sole reliance on active bacterial mechanosensing as the driving force for adhesion.
• This study provides novel insights for designing effective antifouling surfaces by considering material stiffness.