37
Interactions between chitosan- modified particles and mucin- coated surfaces Wenting Xu 2011.3.26
Interactions between chitosan-modified particles and mucin-coated
surfaces
Wenting Xu
2011.3.26
Aim
CS modified particles
Interaction &
Mucin-coated silica surfaces
Begin…
Cubosome® particles
o Model particles
o (PEO)-based polymer
o Interaction with mucin
Weak
Depending on the pH
Preparation
Autoclaved20 min , 125◦C
Mechanically mixed12–48h , homogenized with a microfluidizer at 345 bar and 25◦C
Coarse dispersionMelted lipid mixture -> Aqueous Lutrol F127 solution
Characteristics
o Lipid : polymer ratio: 9 : 1 (wt/wt)
o Lipid content: 50 mg/ml
o Mean size of the particles:
311 nm + 58 nm (in pure water)
CS-modified Cubosome®
particles
PreparationCS dissolved(10 mg/ml in 1 vol%
acetic acid )
Stirred (24 h)
Diluted(1 mg/mL in water)
Mixed
(1:1 by volume)
Stirred (30 min)
pH: 6.0 (1 mg/mL NaOH
solution)
Diluted (lipid conc.of 5
mg/mL & CS conc. of 0.1 mg/mL)
Characteristics
o Mean particle size
334 nm + 88 nm (in water)
Increase
o Indicating ->
CS: binding to surface
Electrostatic interactions
Mucin
o Bovine submaxillary gland mucin (BSM)
o Sialic acid content : 13%
o Molecular weights: 1.6 ~ 2.9 MDa
o Isoelectric point : 3
Zeta potential measurements
o Microelectrophoresis
Electrophoretic mobility (u)
-> Smoluchowski equation
zeta potential (ζ)
Silica surfaces
Preparation
o Silicon wafers
-> Oxidized silicon surfaces (Si/SiO2)
Oxide layer thickness : 300 Å
o Surfaces cleaning:
1. Plasma cleaning
2. Gentle boiling in an alkaline solution
3. Rinsing 3 times in water
4. Gentle boiling in an acidic solution
5. Rinsed in water three times
6. Rinsed in ethanol (96%) twice
o Storage: in ethanol
Ellipsometry
Action
oFilm:
Thickness
Refractive index
-> Calculate the adsorbed amount
Condition
o Ellipsometric measurements
Particle concentration
0.05 mg/mL (lipid content) IN
50 mM NaCl :pH 4±0.2 or pH 6±0.2
Result…
Electrophoretic
characterization
Characterization
o Zeta potential
+16 mV at pH 3
−7 mV at pH 8
o Isoelectric
point:
at pH 7
o CS :amino groups
Protonated at low pH
o Modified particles:
Neutral & not positive at pH 7
Intrinsic negative charge of the particles
Interactions with silica
surfaces
Modified particles
o pH 4
Amount and thickness
< unmodified particles
o pH 6
Amount: substantially lower
Thickness: similar
?
Free chitosan in the solution
Adsorb to the silica surface & affect
adsorption of the modified particles???
Two control experiments
CS solution pH 6 vs suface
o 0.001 g/mL
Amount: 0.5 mg/m2
Thickness: 8 nm
o 0.01 g/mL
Amount: 0.6 mg/m2
Thickness: 90 nm
Free CS does adsorb to a silica surface
Addition…
o (0.6 mg/m2 and 90 nm) Vs (4 mg/m2 and
204 nm)
CS adsorbs from the solution in the
dispersions
Reduces the binding of modified particles
Interactions with mucin-coated silica
surfaces
o Adsorbed amount and thickness Changes Increased
o 100 nm or more Not CS adsorption alone
Comparison pH 4 & pH 6
o Adsorbed amount : higherElectrostatic interactions StrongerNumber of protonated amino groups
o Thickness : lowerDeformation
Comparison o Unmodified particles
Only detected at pH 4 Reversible -> Weak interaction
o Modified particles Substantial amounts <15% -> strong interaction
Final experiment
Unmodified and modified
paticals
Sequential adsorption
o Unmodified particles
No adsorption
o Modified particles
Substantial adsorption
Conclusions
o Method: in situ & ellipsometric
measurements
o Modified particles adsorbed & adsorption
irreversible
o Electrostatic interactions & interaction
Thank you!
Question?
