Interaction forces measured using AFM between colloids and surfaces coated with both dextran and protein.

Area of Science:

• Biophysics
• Surface Science
• Microbiology

Background:

• Bacterial surface biopolymers, including proteins and polysaccharides, play a crucial role in adhesion.
• Understanding the combined effects of these biopolymers on bacterial attachment is essential for controlling microbial interactions.

Purpose of the Study:

• To investigate the influence of combined protein and polysaccharide coatings on bacterial adhesion forces.
• To examine the role of residence time and ionic strength in modulating adhesion between biopolymer-coated surfaces and colloids.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to measure adhesion forces between colloid probes and polymer-coated glass surfaces.
• Surfaces were coated with mixtures of proteins (BSA, lysozyme) and dextran, with varying compositions.
• Experiments were conducted across a range of residence times (0.1–100 s) and ionic strengths.

Main Results:

• At short residence times (<1 s), proteins were shielded by dextran, resulting in lower adhesion forces for protein+dextran coatings compared to dextran alone.
• Adhesion forces for protein+dextran coated surfaces significantly increased with longer residence times (50–100 s).
• The protein+dextran combination yielded the highest adhesion forces at extended interaction periods, suggesting molecular rearrangement.

Conclusions:

• The combined presence of proteins and polysaccharides on bacterial surfaces dynamically affects adhesion forces.
• Residence time is a critical factor, influencing the accessibility and interaction of surface biopolymers.
• These findings underscore the importance of considering multi-biopolymer interactions and temporal dynamics in adhesion studies.