Thermo-reversible capture and release of DNA by zwitterionic surfactants

Abstract

The thermo-reversible capture and release of DNA were studied by the protonation and deprotonation of alkyldimethylamine oxide (CnDMAO, n = 10, 12 and 14) in Tris-HCl buffer solution. DNA/C14DMAO in Tris-HCl buffer solution with pH = 7.2 is transparent at 25 °C, indicating that DNA molecules exist mainly in individuals and the binding of C14DMAO is weak. With the increase of temperature, the pH of the buffer solution continuously decreases, which leads to protonation of C14DMAO (C14DMAO + H(+)→ C14DMAOH(+)) and an obvious increase of the turbidity of the samples. This indicates a stronger binding of the protonated C14DMAOH(+) to DNA. Further investigations demonstrated the formation of DNA/C14DMAOH(+) complexes, in which the stretched DNA molecules are effectively compacted as evidenced from UV-vis absorptions, circular dichroism (CD) measurements, atomic force microscopy (AFM) observations, dynamic light scattering (DLS) measurements and agarose gel electrophoresis (AGE). Interestingly, when the temperature is turned back to 25 °C, the compacted DNA molecules can fully recover to the stretched conformation. This cycle can be repeated several times without obvious loss of efficiency. The effect of the chain length of CnDMAO has also been investigated. When C14DMAO was replaced by C12DMAO, similar phenomena can be observed with a slightly higher critical surfactant concentration for DNA compaction and a slightly lower pH of Tris-HCl buffer solution with pH = 6.8. For the DNA/C10DMAO system, however, no DNA compaction was observed even in Tris-HCl buffer solution with a much lower pH and a much higher C10DMAO concentration. The negative charges of DNA molecules can easily be neutralized by positive charges of cationic CnDMAOH(+) (n = 12 and 14) micelles. DNA was compacted and then insoluble DNA/CnDMAOH(+) complexes were formed. Because of the much higher critical micelle concentration (cmc) of the shorter chain length C10DMAOH(+), cationic C10DMAOH(+) micelles cannot form under the studied condition to compact DNA. The strategy may provide an efficient and alternative approach for stimuli-responsive gene therapy and drug release.

Zwitterionic Surfactant Micelle-Directed Self-Assembly of Eu-Containing Polyoxometalate into Organized Nanobelts with Improved Emission and pH Responsiveness

“…It should be noted that only a part of C 14 DMAO molecules could be protonated now at the solution pH value of about 6.5. 32,40 Meanwhile, C 14 DMAO and its protonated form were in an acid−base equilibrium, and they could couple into dimers through hydrogen-bonding interaction. 41 The protonated C 14 DMAO also easily formed hydrogen bonding with EuW 10 via hydroxyl.…”

“…41 The protonated C 14 DMAO also easily formed hydrogen bonding with EuW 10 via hydroxyl. 42 Considering the much low critical micellar concentration (cmc = 0.075 mM) and then the high surface activity of C 14 DMAO, 32,43 it can be understood that the surfactant first aggregated as micelles, carrying a small amount of positive charges. Therefore, the ζ potential variations here could confirm that the electrostatic interaction occurred between EuW 10 and C 14 DMAO cationic micelles for aggregate formation.…”

Functional Nano-Objects by Electrostatic Self-Assembly: Structure, Switching, and Photocatalysis

“…That is because a temperature shift of course changes the dynamics of the system, including the one of the hydration shell and thereby screening and interaction, while switches that directly access the charged nature and valency lead to more expressed changes. The group of Hao studied the capture and release of DNA by the protonation and deprotonation of alkyldimethylamine oxide in Tris-HCl buffer in dependence on temperature ( Feng et al, 2016 ). At room temperature, the pH value is pH = 7.2 and the DNA molecules only weakly interact with the alkyldimethylamine oxide.…”

Properties and applications of amphoteric surfactant: A concise review

“…The tris-HCl-buffer solution of alkyldimethylamine oxide (CnDMAO, n = 12 and 14) is utilized for capturing and releasing the negative charges of DNA molecules, as they can be quickly protonated (C 14 DMAO + H + ! C 14 DMAOH + ) in acidic solution and deprotonated in basic solution by changing the pH and temperature (Feng et al, 2016). Without any apparent loss of efficacy, this thermo-reversible cycle can be repeated multiple times and is extremely advantageous for stimulating gene therapy and drug release systems (Table 4).…”

“…Alkyldimethylamine oxide (DMAO-m) m = 12,14 1. Thermo-reversible capture and release of DNA for gene delivery (Feng et al, 2016). 2.…”