Substrate viscosity plays an important role in bacterial adhesion under fluid flow

Area of Science:

• Biomaterials Science
• Microbiology
• Rheology

Background:

• Many medical materials, including catheters and contact lenses, exhibit viscoelastic properties, unlike purely elastic materials.
• While substrate elasticity's effect on bacterial adhesion is known, the role of substrate viscosity remains unexplored.
• Viscoelasticity is a critical factor in biological tissues and medical implants.

Purpose of the Study:

• To investigate the impact of substrate viscosity on bacterial adhesion.
• To explore how varying the viscoelastic properties of polydimethylsiloxane (PDMS) affects bacterial interactions.
• To determine if substrate viscosity influences the adhesion and desorption of bacteria under flow conditions.

Main Methods:

• Utilized polydimethylsiloxane (PDMS) with tunable cross-linking degrees to create substrates with varying viscoelastic properties.
• Employed interfacial rheology and atomic force microscopy (AFM) to characterize substrate mechanical properties (stiffness and viscosity).
• Conducted bacterial adhesion assays with Escherichia coli under flow conditions to quantify adhesion and resistance to shear stress.

Main Results:

• PDMS with a low cross-linking degree demonstrated low stiffness and high viscosity, exhibiting significant stress relaxation and increased adhesive force.
• Viscous PDMS substrates significantly enhanced Escherichia coli adhesion compared to highly elastic PDMS.
• Viscous PDMS provided greater resistance to bacterial desorption under shear stress at the air/liquid interface.

Conclusions:

• Substrate viscosity is a critical, previously overlooked factor influencing bacterial adhesion in medical settings.
• Viscoelastic properties of materials play a significant role in bacterial colonization and biofilm formation.
• These findings necessitate a re-evaluation of material selection for medical devices to mitigate bacterial adhesion.