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Residence time, loading force, pH, and ionic strength affect adhesion forces between colloids and biopolymer-coated
Li-Chong Xu1, Virginia Vadillo-Rodriguez, Bruce E Logan
1Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 27, 2005
Summary
Biopolymer adhesion to surfaces increases with contact time and applied force. These molecular interactions are influenced by pH and ionic strength, revealing key factors in colloid-surface adhesion. Understanding these forces is crucial.
Area of Science:
- Surface science
- Biophysics
- Materials science
Background:
- Exopolymers significantly influence bacterial adhesion to surfaces.
- The time-dependent molecular interactions of biopolymers with surfaces are not well understood.
Purpose of the Study:
- To analyze adhesion forces between proteins/polysaccharides and colloids using colloid probe atomic force microscopy (AFM).
- To investigate the impact of residence time, loading force, pH, and ionic strength on colloid-surface adhesion.
Main Methods:
- Colloid probe atomic force microscopy (AFM) was employed.
- Adhesion forces were measured between various proteins (Bovine serum albumin, lysozyme) and polysaccharides (dextran) with uncoated or protein-coated latex microspheres.
- Experiments varied residence time, loading force, pH (4.5-10.6), and ionic strength (1-100 mM).
Main Results:
- Adhesion force increased with increasing residence time and loading force.
- At low loading force (0.6 nN) and short exposure (10 s), adhesion was minimal.
- Higher loading force (5.4 nN) and 10 s residence time significantly increased adhesion forces, especially for protein-coated surfaces.
- Adhesion decreased with increasing pH and was higher at low ionic strength (1 mM).
Conclusions:
- Polymer rearrangement significantly contributes to increased adhesion forces over time.
- Adhesion mechanisms are influenced by hydrogen bonding and electrostatic interactions, which are sensitive to pH.
- Solution chemistry, including pH and ionic strength, critically affects colloid-surface adhesion, highlighting the role of polymers.