Interaction between Covalent DNA Gels and a Cationic Surfactant

Abstract

The interaction of covalently cross-linked double-stranded (ds) DNA gels and cetyltrimethylammonium bromide (CTAB) is investigated. The volume transition of the gels that follows the absorption of the oppositely charged surfactant from aqueous solution is studied. As do other polyelectrolyte networks, DNA networks form complexes with oppositely charged surfactant micelles at surfactant concentrations far below the critical micelle concentration (cmc) of the polymer-free solution. The size of the absorbed surfactant aggregates is determined from timeresolved fluorescence quenching (TRFQ). At low surfactant concentrations, small discrete micelles (160 < N < 210) are found, whereas large micelles (N > 500) form at surfactant concentrations of 1 mM. When the DNA is in excess of the surfactant, the surfactant binding is essentially quantitative. The gel volume decreases by 90% when the surfactant to DNA charge ratio, , increases from 0 to 1.

PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies

“…Two other interesting points deserve attention: (a) the shrinkage of PVA−DNA−NaBr is much more dramatic than that of the DNA-containing gel without NaBr and (b) the Q sw (PVA−DNA−NaBr) > Q sw (PVA−DNA). Regarding point a, such a behavior clearly suggests that the presence of ds-DNA chains is in agreement with the previous results; in this case the presence of increasing concentrations of salt inside the polymer matrix will contribute to a further screening of ionic interactions, and consequently, the shrinkage is more efficient . In fact, this effect comes from the polyelectrolyte character of DNA; the counterions in the solution reduce the interpolymer electrostatic repulsion making DNA molecules more compact.…”

PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies

“…Two other interesting points deserve attention: (a) the shrinkage of PVA−DNA−NaBr is much more dramatic than that of the DNA-containing gel without NaBr and (b) the Q sw (PVA−DNA−NaBr) > Q sw (PVA−DNA). Regarding point a, such a behavior clearly suggests that the presence of ds-DNA chains is in agreement with the previous results; in this case the presence of increasing concentrations of salt inside the polymer matrix will contribute to a further screening of ionic interactions, and consequently, the shrinkage is more efficient . In fact, this effect comes from the polyelectrolyte character of DNA; the counterions in the solution reduce the interpolymer electrostatic repulsion making DNA molecules more compact.…”

Effect of Additives on Swelling of Covalent DNA Gels

“…The cmc values for C 16 TAB, C 14 TAB, C 12 TAB, and C 8 TAB are 0.9, 0.23, 15, and 144 mM, respectively. We found that the surfactants induce the volume transition starting at a certain rather well-defined concentration ∼0.02 mM for C 16 TAB, ∼0.05 mM for C 14 TAB, ∼0.1 mM for C 12 TAB, and ∼1 mM for C 8 TAB; these values are similar to the observed cac values in bulk solution. The initial plateau, indicating no volume transition of the gels, in the concentration range under study, is thus very narrow for C 16 TAB but increases for C 14 TAB and C 12 TAB, while C 8 TAB shows a very large plateau.…”

Transport of poly-l-lysine into oppositely charged poly(acrylic acid) microgels and its effect on gel deswelling

“…When oppositely charged substances interact with swollen polyelectrolyte gels, osmotic deswelling occurs. This deswelling behavior has been reported for a number of cationic surfactants [7][8][9][10][11][12][13][14], drug molecules [15][16][17], polymers [18], and proteins [19][20][21][22][23][24] binding to anionic gel networks. The rate and extent of this deswelling depends on the strength of interaction, which can be tuned, e.g., by changing salt concentration and pH, but also on the concentration of added substance and on its distribution within the gel during the shrinking process.…”

PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies

“…Two other interesting points deserve attention: (a) the shrinkage of PVA−DNA−NaBr is much more dramatic than that of the DNA-containing gel without NaBr and (b) the Q sw (PVA−DNA−NaBr) > Q sw (PVA−DNA). Regarding point a, such a behavior clearly suggests that the presence of ds-DNA chains is in agreement with the previous results; in this case the presence of increasing concentrations of salt inside the polymer matrix will contribute to a further screening of ionic interactions, and consequently, the shrinkage is more efficient . In fact, this effect comes from the polyelectrolyte character of DNA; the counterions in the solution reduce the interpolymer electrostatic repulsion making DNA molecules more compact.…”

Effect of Additives on Swelling of Covalent DNA Gels

“…The cmc values for C 16 TAB, C 14 TAB, C 12 TAB, and C 8 TAB are 0.9, 0.23, 15, and 144 mM, respectively. We found that the surfactants induce the volume transition starting at a certain rather well-defined concentration ∼0.02 mM for C 16 TAB, ∼0.05 mM for C 14 TAB, ∼0.1 mM for C 12 TAB, and ∼1 mM for C 8 TAB; these values are similar to the observed cac values in bulk solution. The initial plateau, indicating no volume transition of the gels, in the concentration range under study, is thus very narrow for C 16 TAB but increases for C 14 TAB and C 12 TAB, while C 8 TAB shows a very large plateau.…”

Transport of poly-l-lysine into oppositely charged poly(acrylic acid) microgels and its effect on gel deswelling

“…When oppositely charged substances interact with swollen polyelectrolyte gels, osmotic deswelling occurs. This deswelling behavior has been reported for a number of cationic surfactants [7][8][9][10][11][12][13][14], drug molecules [15][16][17], polymers [18], and proteins [19][20][21][22][23][24] binding to anionic gel networks. The rate and extent of this deswelling depends on the strength of interaction, which can be tuned, e.g., by changing salt concentration and pH, but also on the concentration of added substance and on its distribution within the gel during the shrinking process.…”

PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies

“…Two other interesting points deserve attention: (a) the shrinkage of PVA−DNA−NaBr is much more dramatic than that of the DNA-containing gel without NaBr and (b) the Q sw (PVA−DNA−NaBr) > Q sw (PVA−DNA). Regarding point a, such a behavior clearly suggests that the presence of ds-DNA chains is in agreement with the previous results; in this case the presence of increasing concentrations of salt inside the polymer matrix will contribute to a further screening of ionic interactions, and consequently, the shrinkage is more efficient . In fact, this effect comes from the polyelectrolyte character of DNA; the counterions in the solution reduce the interpolymer electrostatic repulsion making DNA molecules more compact.…”

Effect of Additives on Swelling of Covalent DNA Gels

“…The cmc values for C 16 TAB, C 14 TAB, C 12 TAB, and C 8 TAB are 0.9, 0.23, 15, and 144 mM, respectively. We found that the surfactants induce the volume transition starting at a certain rather well-defined concentration ∼0.02 mM for C 16 TAB, ∼0.05 mM for C 14 TAB, ∼0.1 mM for C 12 TAB, and ∼1 mM for C 8 TAB; these values are similar to the observed cac values in bulk solution. The initial plateau, indicating no volume transition of the gels, in the concentration range under study, is thus very narrow for C 16 TAB but increases for C 14 TAB and C 12 TAB, while C 8 TAB shows a very large plateau.…”

Transport of poly-l-lysine into oppositely charged poly(acrylic acid) microgels and its effect on gel deswelling

“…When oppositely charged substances interact with swollen polyelectrolyte gels, osmotic deswelling occurs. This deswelling behavior has been reported for a number of cationic surfactants [7][8][9][10][11][12][13][14], drug molecules [15][16][17], polymers [18], and proteins [19][20][21][22][23][24] binding to anionic gel networks. The rate and extent of this deswelling depends on the strength of interaction, which can be tuned, e.g., by changing salt concentration and pH, but also on the concentration of added substance and on its distribution within the gel during the shrinking process.…”