Equilibrium gels of trivalent DNA-nanostars: Effect of the ionic strength on the dynamics

Abstract

Self-assembling DNA-nanostars are ideal candidates to explore equilibrium gelation in systems composed of limited-valence particles. We present here a light scattering study of the dynamics in a trivalent DNA-nanostars equilibrium gel and of its dependence on ionic strength and concentration. Reversible bonds between different nanostars, whose formation is sensitively dependent on temperature, concentration and ionic strength, are provided by complementary DNA sticky ends. We find that the decay of the density correlations is described by a two-step relaxation process characterised by: i) a slow time scale that varies over nearly four orders of magnitude in a temperature window of less than 30 degrees; ii) an increase of the amplitude (the so-called non-ergodicity factor) of the slow relaxation. The slow process follows an Arrhenius law with temperature. We observe that the activation enthalpy does not depend on the ionic strength and that the dependence of the relaxation time on the ionic strength can be rationalized in terms of the free-energy cost of forming a sticky-end duplex. Finally, we observe that dynamics is insensitive to nanostar concentration, in full agreement with the predicted behaviour in equilibrium gels.

Structure and phase behavior of polymer-linked colloidal gels

“…2,13,[17][18][19] This concept was originally demonstrated in Monte Carlo simulations for a model where the number of bonds between colloids was artificially constrained 13 and for an anisotropic ("patchy") colloid model. [17][18][19] These computational studies motivated the discovery of several materials that can form equilibrium gels, including an anisotropic colloidal clay, 20 DNA nanostars with complementary sticky ends, [21][22][23] and a dipeptide with several aromatic rings that allowed for specific π-π stacking interactions. 24 Nevertheless, the preparation of equilibrium gels from patchy nanoparticles is challenged by difficulties in fabricating the latter with sufficient precision and in large enough quantities.…”

Condensation and Demixing in Solutions of DNA Nanostars and Their Mixtures

“… 19 We also show that the salt concentration plays a major role in determining the phase behavior of these DNA constructs, which helps rationalizing recent experimental results on their dynamical properties. 32 We demonstrate the generality of our theoretical approach by computing the critical points, coexistence regions, the degree of demixing as well as the cloud/shadow curves of binary mixtures of DNA nanostars with different valences, for several values of the salt concentration.…”

DNA-GEL, Novel Nanomaterial for Biomedical Applications and Delivery of Bioactive Molecules

“…One important class of DNA constructs is represented by limited-valence DNA nanostars (NSs), that is, DNA nanoparticles with a finite number f of arms departing from a common central junction. These NSs have attracted increasing interest, encouraging the rational design of soft materials with unconventional behavior and tunable properties such as controllable shape (Um et al, 2006), kinetics, and structure (Nguyen and Saleh, 2017), permanent network structure formation via enzymatic reaction (Um et al, 2006;Xiang et al, 2016), re-entrant phase diagram (Bomboi et al, 2016), tunable viscosity (Bomboi et al, 2015), and self-healing (Bomboi et al, 2019). NSs can be experimentally produced by mixing in solution equimolar quantities of f purposely designed single-stranded (ss) DNA sequences, which are able to spontaneously self-assemble into a branched geometry with f double-helical arms.…”