| 1. |
- Cárdenas, Marité, et al.
(author)
-
DNA and cationic surfactants at solid surfaces
- 2005
-
In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 270-271, s. 33-43
-
Journal article (peer-reviewed)abstract
- The behavior of DNA at different types of interfaces and how the formed structures DNA at an interface could be affected by cationic surfactant has been studied. Particular attention was paid to how the type of cationic surfactant and DNA (single or double stranded and length) affects the compaction/decompaction of DNA. Adsorption of DNA-cationic surfactant complexes is determined by a delicate balance of DNA-surface, cationic surfactant-surface, and cationic surfactant-DNA interactions. DNA do not adsorb on hydrophilic negatively charged surfaces due to effective electrostatic repulsion between DNA and the surfacs. However, the interaction between DNA cationic surfactant ions leads to a substantial adsorption of the formed DNA-cationic surfactant complex once the charge density of both the DNA macromolecule and the surface is sufficiently decreased. On hydrophobic surfaces, where both DNA and cationic surfactant interact with the surface, the presence of the cationic surfactant leads to a considerable increase in adsorbed amount and a significant layer compaction of DNA. The stability of the mixed adsorbed layer largely depends on the strength of the interactions between DNA and the cationic surfactant, as well as between the surface and the cationic surfactant. DNA interacts with small latex particles in a similar way as to the macroscopic hydrophobic flat surfaces. (c) 2005 Elsevier B.V All rights reserved.
|
|
| 2. |
- Cárdenas, Marité, et al.
(author)
-
DNA compaction onto hydrophobic surfaces by different cationic surfactants
- 2005
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:14, s. 6495-6502
-
Journal article (peer-reviewed)abstract
- DNA compaction by alkyltrimethylammonium surfactants at hydrophobized silica surfaces and the effect of the counterion, as well as the hydrocarbon chain length, was investigated by in situ null-ellipsometry. In addition, DNA compaction in the presence of a gemini surfactant, hexyl-alpha,omega-bis(dodecyldimethylammonium bromide), was studied. The type of cationic amphiphile used was found not to have a pronounced effect on the mixed DNA-cationic surfactant adsorbed layer thickness, although the surface concentration excess for the mixed layers seemed to follow the same trend as that for DNA-free surfactant layers. Interestingly, it was also found that the stability of the mixed adsorbed layer largely depends on the cationic surfactant used.
|
|
| 3. |
- Cárdenas, Marité, et al.
(author)
-
Human Saliva Forms a Complex Film Structure on Alumina Surfaces
- 2007
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:1, s. 65-69
-
Journal article (peer-reviewed)abstract
- Films formed from saliva on surfaces are important for the maintenance of oral health and integrity by protection against chemical and/or biological agents. The aim of the present study was to investigate adsorbed amounts, thickness, and structure of films formed from human whole saliva on alumina surfaces by means of in situ ellipsometry, neutron reflectivity, and atomic force microscopy. Alumina (Al2O3, synthetic sapphire) is a relevant and interesting substrate for saliva adsorption studies as it has an isoelectric point close to that of tooth enamel. The results showed that saliva adsorbs rapidly on alumina. The film could be modeled in two layers: an inner and dense thin region that forms a uniform layer and an outer, more diffuse and thicker region that protrudes toward the bulk of the solution. The film morphology described a uniformly covering dense layer and a second outer layer containing polydisperse adsorbed macromolecules or aggregates.
|
|
| 4. |
- Cárdenas, Marité, et al.
(author)
-
Interaction between DNA and charged colloids could be hydrophobically driven
- 2005
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 6:2, s. 832-837
-
Journal article (peer-reviewed)abstract
- The interaction of DNA with amino-functionalized polystyrene particles has been studied by using a dynamic light scattering (DLS) technique. In 10 mM NaBr solution the particles have a hydrodynamic radius of 76 nm and the DNA macromolecule investigated (double stranded) has a hydrodynamic radius of 107 nm. At very low DNA concentrations, DNA adopts a flat conformation on the particle surface. If the DNA concentration is increased above 0.1 mu g/mL, the thickness of the DNA layer increases, suggesting the presence of large loops and tails. Although the particles contain primary amino groups, they have a negative net charge under the conditions used in this work. Thus, the driving force for DNA adsorption is not of electrostatic origin but rather due to a hydrophobic effect. Addition of cationic surfactant to the DNA-precoated amino functionalized particles induces changes in the adsorbed layer conformation, in agreement with the coadsorption of cationic surfactant.
|
|
| 5. |
- Cárdenas, Marité, et al.
(author)
-
Interactions of hydroxyapatite surfaces: Conditioning films of human whole saliva
- 2008
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:14, s. 7262-7268
-
Journal article (peer-reviewed)abstract
- Hydroxyapatite is a very interesting material given that it is the main component in tooth enamel and because of its uses in bone implant applications. Therefore, not only the characterization of its surface is of high relevance but also designing reliable methods to study the interfacial properties of films adsorbed onto it. In this paper we apply the colloidal probe atomic force microscopy method to investigate the surface properties of commercially available hydroxyapatite surfaces (both microscopic particles and macroscopic discs) in terms of interfacial and frictional forces. In this way, we find that hydroxyapatite surfaces at physiological relevant conditions are slightly negatively charged. The surfaces were then exposed to human whole saliva, and the surface properties were re-evaluated. A thick film was formed that was very resistant to mechanical stress. The frictional measurements demonstrated that the film was indeed highly lubricating, supporting the argument that this system may prove to be a relevant model for evaluating dental and implant systems.
|
|
| 6. |
- Cárdenas, Marité, et al.
(author)
-
Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: An in situ ellipsometry and atomic force microscopy study
- 2007
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:4, s. 1149-1156
-
Journal article (peer-reviewed)abstract
- This paper describes a combined investigation of the salivary and MUC5B films structure and topography in conditions similar to those found in the oral cavity in terms of ionic strength, pH, and protein concentration. AFM and ellipsometry were successfully used to give a detailed picture of the film structure and topography both on hydrophilic and on hydrophobic substrata. Regardless of the substrata, the salivary film can be described as having a two sublayer structure in which an inner dense layer is decorated by large aggregates. However, the shape and height of these larger aggregates largely depend on the type of substrata used. Additionally, we show that the adsorption of MUC5B is controlled by the type of substrata and the MUC5B film topography is similar to that of the larger aggregates present in the salivary films, especially on hydrophobic substrates. Therefore, we conclude that MUC5B is a major component in the salivary film when formed on hydrophobic substrates. Furthermore, we studied how resistant the salivary and MUC5B films are against elutability by buffer rinsing and addition of SDS solution. We conclude that the adsorbed proteins contain fractions with varying binding strengths to the two types of surfaces. Specifically, we have shown that the large MUC5B biomacromolecules on the hydrophobic substrates are especially resistant to both elution with buffer solution and SDS. Therefore, these large mucins can be responsible for the increased resistance of HWS films on hydrophobic substrates and can protect the intraoral surfaces against surface-active components present in oral health care products.
|
|
| 7. |
- Cárdenas, Marité, et al.
(author)
-
SANS study of the interactions among DNA, a cationic surfactant, and polystyrene latex particles
- 2005
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:8, s. 3578-3583
-
Journal article (peer-reviewed)abstract
- The compaction of DNA by a cationic surfactant both in the bulk and adsorbed on the surface of latex particles was followed for the first time by SANS. In the bulk, a decrease in the overall size of the DNA coil in the presence of the cationic surfactant was observed at a negative-to-positive charge ratio far below the phase separation region, at a negative-to-positive charge ratio of 18. Additionally, large surfactant aggregates seem to form within the DNA-surfactant complex. On the other hand, DNA adsorbs onto the surface of latex particles, forming a thick layer, as evidenced by the fitting of the SANS data to a core-shell form factor. Addition of a cationic surfactant to the DNA-coated latex particles at a negative-to-positive charge ratio of 38 induces a slight decrease in the size of the particle layer, where the cationic surfactant is evenly distributed within the adsorbed layer. A further decrease of the negative-to-positive charge ratio to 18 induces a dramatic change in the SANS data that suggests significant compaction of the adsorbed layer and the formation of large surfactant aggregates, similar to those detected in the bulk.
|
|
| 8. |
- Cárdenas, Marité, et al.
(author)
-
Solubilization of sphingomyelin vesicles by addition of a bile salt.
- 2008
-
In: Chemistry and Physics of Lipids. - : Elsevier BV. - 0009-3084 .- 1873-2941. ; 151:Sep 25, s. 10-17
-
Journal article (peer-reviewed)abstract
- The interactions of the bile salt sodium taurocholate (TC) in 50mM Trizma-HCl buffer and 150mM NaCl (pH 9) at 37 degrees C with membranes composed of sphingomyelin (SM) were studied by dynamic light scattering, cryogenic transmission electron microscopy (cryo-TEM) and turbidity measurements. Small unilamellar SM vesicles were prepared by extrusion. Below the CMC of TC, taurocholate addition leads to vesicle growth due to incorporation of the taurocholate molecules into the vesicle bilayer. At around half the CMC of the bile salt, the SM vesicles are transformed into SM/TC mixed worm-like micelles, which are visualized by cryo-TEM for the first time. Further increase in the taurocholate concentration leads to the rupture of these structures into small spherical micelles. Interestingly, large non-spherical micelles were also identified for pure taurocholate solutions. Similar threadlike structures have been reported earlier for the bile salt sodium taurodeoxycholate [Rich, A., Blow, D., 1958. Nature 182, 1777; Blow, D.M., Rich, A., 1960. J. Am. Chem. Soc. 82, 3566-3571; Galantini, L., Giglio, E., La Mesa, C., Viorel-Pavel, N., Punzo, F., 2002. Langmuir 18, 2812] and for mixtures of taurocholate and phosphatidylcholate [Ulmius, J., Lindblom, G., Wennerström, H., Johansson, L.B.-A., Fontel, K., Söderman, O., Ardvisson, G., 1982. Biochemistry 21, 1553; Hjelm, R.P., Thiyagarajan, P., Alkan-Onyuksel, H., 1992. J. Phys. Chem. 96, 8653] as determined by various scattering methods.
|
|
| 9. |
- Cárdenas, Marité, et al.
(author)
-
The interaction between DNA and cationic lipid films at the air-water interface
- 2005
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 286:1, s. 166-175
-
Journal article (peer-reviewed)abstract
- The interaction between DNA and positively charged dioctadecyldimethylammonium bromide (DODAB) and DODAB/disteroylphosphatidylcholine (DSPC) monolayers at the air-aqueous interface was studied by a combination of the surface film balance and Brewster angle microscopy. In presence of DNA, the &UPi;-A isotherm of the cationic monolayer shifts to larger mean molecular areas due to the electrostatic interaction with DNA while the typical liquid expanded-liquid condensed phase transition for DODAB monolayers disappear and the monolayer remains to be in the liquid expanded phase. Furthermore, the morphology of the film dramatically changes, where the large dendritic-like condensed aggregates observed for DODAB monolayers vanish. The charge density of the monolayer was varied by using mixed monolayers with the zwitterionic DSPC and no large effect was observed on the interaction with DNA. By modeling the electrostatic interactions with the linearized Poisson-Boltzmann equation using the finite-element method and taking into account the assumption in the dielectric constants of the system, it was possible to corroborate the expansion of the cationic monolayer upon interaction with DNA as well as the fact that DNA does not seem to penetrate into the monolayer. © 2005 Elsevier Inc. All rights reserved.
|
|
| 10. |
- Cárdenas, Marité, et al.
(author)
-
Thiol-Specific and Non-Specific Interactions Between DNA and Gold Nanoparticles
- 2006
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22, s. 3294-3299
-
Journal article (peer-reviewed)abstract
- The contribution of nonspecific interactions to the overall interactions of thiol-ssDNA and dsDNA macromolecules with gold nanoparticles was investigated. A systematic investigation utilizing dynamic light scattering and cryogenic transmission electron microscopy has been performed to directly measure and visualize the changes in particle size and appearance during functionalization of gold nanoparticles with thiol-ssDNA and nonthiolated dsDNA. The results show that both thiol-ssDNA and dsDNA do stabilize gold nanoparticle dispersions, but possible nonspecific interactions between the hydrophobic DNA bases and the gold surface promote interparticle interactions and cause aggregation within rather a short period of time. We also discuss the adsorption mechanisms of dsDNA and thiol-ssDNA to gold particles.
|
|
