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Adhesion forces between hybrid colloidal particles and concanavalin A
Lizandra B R Castro1, Michael Kappl, Denise F S Petri
1Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-900 São Paulo, Brazil.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 6, 2006
Summary
Hybrid particles with poly(methyl methacrylate) and carboxymethylcellulose (PMMA/CMC) were used to probe concanavalin A (ConA) films. Adhesion forces varied based on substrate, with ConA on silicon showing stronger interactions than on CMC, and mannose reduced adhesion.
Area of Science:
- Biomaterials Science
- Surface Chemistry
- Atomic Force Microscopy
Background:
- Atomic Force Microscopy (AFM) is crucial for probing molecular interactions.
- Carboxymethylcellulose (CMC) and poly(methyl methacrylate) (PMMA) hybrid particles offer unique surface properties.
- Concanavalin A (ConA) is a lectin that binds to specific carbohydrate residues.
Purpose of the Study:
- To investigate the adhesion forces between PMMA/CMC hybrid particles and ConA films.
- To evaluate the influence of different substrates (Si wafer and CMC) on ConA-PMMA/CMC interactions.
- To explore the effect of mannose on ConA-ligand binding dynamics.
Main Methods:
- Atomic Force Microscopy (AFM) was utilized to measure adhesion forces.
- Hybrid particles of PMMA/CMC were functionalized onto AFM cantilevers.
- ConA films were prepared on silicon wafers and CMC substrates for probing.
- In situ ellipsometry and capillary electrophoresis were employed to validate hypotheses.
Main Results:
- PMMA/CMC particles exhibited distinct approach curves, indicating a soft CMC layer (20 ± 10 nm) on the probe.
- Higher adhesion forces (-11 ± 7 nN) were observed between PMMA/CMC and ConA on Si wafers compared to ConA on CMC substrates (-3 ± 1 nN).
- Mannose significantly reduced adhesion forces, supporting hypotheses of ConA desorption or mannose layer formation.
Conclusions:
- The substrate significantly impacts the binding availability of ConA to PMMA/CMC hybrid particles.
- The interaction mechanism involves multiple adhesions between CMC sugar residues and ConA.
- Mannose competitively inhibits ConA binding, likely through substrate desorption or forming a mannose-mannose interaction layer.