Wenting ppt
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Interactions between chitosan-modified particles and mucin-coated surfaces
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Wenting ppt
- 1. Interactions between chitosan-modified particles and mucin-coated surfaces Wenting Xu 2011.3.26
- 2. Aim CS modified particles Interaction & Mucin-coated silica surfaces
- 3. Begin…
- 8. Weak
- 11. Lipid content: 50 mg/ml
- 12. Mean size of the particles:
- 14. Preparation
- 16. 334 nm + 88 nm (in water)
- 17. Increase
- 18. Indicating ->
- 19. CS: binding to surface Electrostatic interactions
- 20. Mucin
- 22. Sialic acid content : 13%
- 23. Molecular weights: 1.6 ~ 2.9 MDa
- 26. Silica surfaces
- 30. Thickness
- 31. Refractive index-> Calculate the adsorbed amount
- 33. Particle concentration0.05 mg/mL (lipid content) IN 50 mM NaCl :pH 4±0.2 or pH 6±0.2
- 34. Result…
- 37. Protonated at low pH
- 38. Modified particles:
- 39. Neutral & not positive at pH 7
- 42. Free chitosan in the solution Adsorb to the silica surface & affect adsorption of the modified particles???
- 44. Amount:0.5 mg/m2
- 45. Thickness:8 nm
- 46. 0.01 g/mL
- 47. Amount:0.6 mg/m2
- 48. Thickness:90 nmFree CS does adsorb to a silica surface
- 50. Interactions with mucin-coated silica surfaces
- 52. Changes
- 53. Increased
- 56. Only detected at pH 4
- 57. Reversible -> Weak interaction
- 61. Unmodified and modified paticals Sequential adsorption
- 63. Conclusions
- 65. Modified particles adsorbed & adsorption irreversible
Editor's Notes
- CS dissolved(10 mg/ml in 1 vol% acetic acid )Stirred (24 h)Diluted(1 mg/mL in water) CS solution & particle dispersion: mixed (1:1 by volume) Stirred (30 min) pH: adjusted to 6.0 (1 mg/mL NaOH solution) Diluted (lipid conc.of 5 mg/mL and a CS conc. of 0.1 mg/mL)
- mean particle size after modification 334 nm + 88 nm in water increase indicating CS: binding to surface size distribution: broadened promoted by electrostatic interactions
- The electrophoretic mobility was determined for the modified particles by particle microelectrophoresisA thermostated rectangular cell setup was utilized with platinum electrodes, and a zeta potential standard (MRK403- 02, Malvern Instruments Ltd., UK) was used to determine the interelectrode distance of the cell. From the electrophoretic mobility (u) the zeta potential (ζ) was subsequently calculated using the Smoluchowski equation (κ R ≫ 1). All measurements were conducted on dilute particle dispersions (0.05 mg/mL lipid) in 50 mM NaCl at 37◦C. Values of relative permittivity (εr) and vis- cosity (η) in the calculations of zeta potentials were 74.2 and 0.695 · 10−3 Pa s, respectively [16]. Adjustment of the pH was done with small additions of aqueous solutions of NaOH (1 mg/mL) or HCl (5 mg/mL). Each data point represents the mean value of ten measurements and confidence intervals (95%) are presented.
- Oxidized silicon surfaces (Si/SiO2) & an oxide layer thickness of 300 Å silicon wafers The surfaces were cleaned by plasma cleaning for 5 min in low-pressure residual air in a glow discharge unit (Plasma Cleaner PDC-32 G, Harrick Scientific Corp., USA). Plasma cleaning was followed by gentle boiling in an alkaline solution for 5 min, rinsing three times in water, and gentle boiling in an acidic solution for 5 min. The components of the first solu- tion were NH3 (25%), H2O2 (30%) and water (1:1:5 by volume), and the second solution was composed of HCl (37%), H2O2 (30%) and water (1:1:5 by volume). Finally, the surfaces were rinsed in water three times and then in ethanol (96%) twice and stored in ethanol.
- The adsorption of modified particles to silica surfaces and mucin-coated silica surfaces was monitored in situ by ellipsometry to obtain time-resolved values of the thickness and refractive index of the film that were used to calculate the adsorbed amount.
- All ellipsometric measurements were performed with a particle concentration of 0.05 mg/mL (lipid content) in 50 mM NaCl at either pH 4±0.2 or at pH 6±0.2.
- CS contains amino groups that are protonated at low pH and our results are in good agreement with potentiometric titration of CS in solution with the same degree of acetylation [25]. At pH 4 CS is fully protonated and at pH 7 only 20% of the amino groups are protonated. The fact that the modified particles are neutral and not positive at pH 7 can be attributed to the intrinsic negative charge of the particles compensating for the positively charged amino groups.