Interaction of photosensitive surfactant with DNA and poly acrylic acid

Abstract

In this paper, we investigate interactions and phase transitions in polyelectrolyte-surfactant complexes formed between a cationic azobenzene-containing surfactant and two types of polyelectrolytes: natural (DNA) or synthetic (PAA: poly acrylic acid). The construction of a phase diagram allowed distancing between four major phases: extended coil conformation, colloidally stable compacted globules, colloidal instability range, and surfactant-stabilized compact state. Investigation on the complexes' properties in different phases and under irradiation with UV light provides information about the role of the surfactant's hydrophobic trans isomers both in the formation and destruction of DNA and PAA globules as well as in their colloidal stabilization. The trans isomer shows much stronger affinity to the polyelectrolytes than the hydrophilic cis counterpart. There is no need for complete compensation of the polyelectrolyte charges to reach the complete compaction. On contrary to the findings previously reported in the literature, we demonstrate - for the first time - complete polyelectrolyte compaction which occurs already at 20% of DNA (and at 50% of PAA) charge compensation. The trans isomer plays the main role in the compaction. The aggregation between azobenzene units in the photosensitive surfactant is a driving force of this process. The decompaction can be realized during UV light irradiation and is strongly influenced by the interplay between surfactant-surfactant and surfactant-DNA interactions in the compacted globules.

Manipulation of small particles at solid liquid interface: light driven diffusioosmosis

“…The photoisomerization behavior of the surfactant is described in detail elsewhere22. In short, in the dark state ( trans conformation) of the surfactant is characterized by an absorption band with a maximum at 353 nm, while the cis isomer is characterized by two absorption bands with maxima at 313 nm and at 437 nm (Fig.…”

“…Along with the conformational changes, the physical properties of the molecules are also altered: their shape switches from rod-like to “Γ -like” with a corresponding increase in free volume, the dipole moment increases from 0 Debye in the trans- to ~3 Debye in the cis- conformation. When incorporated into the hydrophobic tail of a surfactant molecule, photoisomerization can thus alter the hydrophobicity/hydrophilicity of the whole surfactant structure18, and can be toggled by alternating illumination with UV and blue light19. In this way, azobenzene containing surfactant bears an enormous potential for practical applications.…”

“…In this way, azobenzene containing surfactant bears an enormous potential for practical applications. One can, for instance, trigger compaction and decompaction of a DNA molecule by light in a reversible way2021222324252627282930, or remotely control the size of microgels by applying periodically UV and blue irradiation313233. One can modify polymer brushes with these molecules and make them photoresponsive with respect to topography and surface energy343536.…”

Phase diagrams of DNA–photosensitive surfactant complexes: Effect of ionic strength and surfactant structure

“…[39][40][41] Fig. 1 shows schematically such phase diagram; The transitions are also typical for azobenzene containing surfactant complexes with other polyelectrolytes.…”

“…Detailed dynamic light scattering (DLS) studies proved that this transition corresponds to the DNA compaction, which takes place before DNA charge compensation. 41 The complete DNA compaction was demonstrated when only 20% of its charge is compensated by the photosensitive surfactant (Z ≈ 0.2). It was also shown that such behavior is not only inherent to DNA but typical for other polyelectrolytes such as poly(acrylic acid), which can be compacted at Z ≈ 0.5.…”