Photoliquefiable DNA-surfactant ionic crystals: Anhydrous self-healing biomaterials at room temperature

DNA nanotechnology in ionic liquids and deep eutectic solvents

Nucleic acids have the ability to generate advanced nanostructures in a controlled manner and can interact with target sequences or molecules with high affinity and selectivity. For this reason, they have applications in a variety of nanotechnology applications, from highly specific sensors to smart nanomachines and even in other applications such as enantioselective catalysis or drug delivery systems. However, a common disadvantage is the use of water as the ubiquitous solvent. The use of nucleic acids in non-aqueous solvents offers the opportunity to create a completely new toolbox with unprecedented degrees of freedom. Ionic liquids (ILs) and deep eutectic solvents (DESs) are the most promising alternative solvents due to their unique electrolyte and solvent roles, as well as their ability to maintain the stability and functionality of nucleic acids. This review aims to be a comprehensive, critical, and accessible evaluation of how much this goal has been achieved and what are the most critical parameters for accomplishing a breakthrough.

Photoresponsive heparin ionic complexes toward controllable therapeutic efficacy of anticoagulation

Controllable heparin-release is of great importance and necessity for the precise anticoagulant regulation. Efforts have been made on designing heparin-releasing systems, while, it remains a great challenge for gaining the external-stimuli responsive heparin-release in either intravenous or catheter delivery. In this study, an azobenzene-containing ammonium surfactant is designed and synthesized for the fabrication of photoresponsive heparin ionic complexes through the electrostatic complexation with heparin. Under the assistance of photoinduced trans-cis isomerization of azobenzene, the obtained heparin materials perform reversible athermal phase transition between ordered crystalline and isotropic liquid state at room temperature. Compared to the ordered state, the formation of isotropic state can effectively improve the dissolving of heparin from ionic materials in aqueous condition, which realizes the photo-modulation on the concentration of free heparin molecules. With good biocompatibility, such a heparin-releasing system addresses photoresponsive anticoagulation in both in vitro and in vivo biological studies, confirming its great potential clinical values. This work provides a new designing strategy for gaining anticoagulant regulation by light, also opening new opportunities for the development of photoresponsive drugs and biomedical materials based on biomolecules.

Azobenzene-containing surfactant directs small features of DNA thermotropic liquid crystals via bottom-up and top-down strategies

Compared to classical block copolymers, the self-assembly of small molecules shows an advantage in addressing small features. As a new type of solvent-free ionic complexes, azobenzene-containing DNA thermotropic liquid crystals (TLCs) form an assembly as block copolymers when using small DNA. However, the self-assembly behavior of such biomaterials has not been fully investigated. In this study, photoresponsive DNA TLCs are fabricated by employing an azobenzene-containing surfactant with double flexible chains. For these DNA TLCs, the self-assembly behavior of DNA and surfactants could be guided by the factors of the molar ratio of azobenzene-containing surfactant, dsDNA/ssDNA, and presence or absence of water, which addresses the bottom-up control on domain spacing of mesophase. Meanwhile, such DNA TLCs also gain top-down control on morphology via photoinduced phase change. This work would provide a strategy for regulating the small features of solvent-free biomaterials, facilitating the development of patterning templates based on photoresponsive biomaterials. STATEMENT OF SIGNIFICANCE: The relationship between nanostructure and function is attractive in the science of biomaterials. With biocompatibility and degradability, photoresponsive DNA materials in solutions have been widely studied in biological and medical areas, but they are still hard to obtain in a condensed state. The complex created with designed azobenzene-containing surfactants paves the way for obtaining condensed photoresponsive DNA materials. However, fine control of the small features of such biomaterials has not yet been achieved. In this study, we present a bottom-up strategy of controlling the small features of such DNA materials and, simultaneously, the top-down control of morphology via photoinduced phase change. This work provides a bi-directional approach to controlling the small features of condensed biomaterials.

Photoliquefiable Azobenzene Surfactants toward Solar Thermal Fuels that Upgrade Photon Energy Storage via Molecular Design

Photoresponsive phase change materials (PPCMs) are capable of storing photon and heat energy simultaneously and releasing the stored energy as heat in a controllable way. While, the azobenzene-based PPCMs exhibit a contradiction between gravimetric energy storage density and photoinduced phase change. Here, a type of azobenzene surfactants with balance between molecular free volume and intermolecular interaction is designed in molecular level, which can address the coharvest of photon energy and low-grade heat energy at room temperature. Such PPCMs gain the total gravimetric energy density up to 131.18 J g^-1 by charging solid sample and 160.50 J g^-1 by charging solution. Notably, the molar isomerization enthalpy upgrades by a factor of up to 2.4 compared to azobenzene. The working mechanism is explained by the computational studies. All the stored energy can release out as heat under Vis light, causing a fast surface temperature rise. This study demonstrates a new molecular designing strategy for developing azobenzene-based PPCMs with high gravimetric energy density by improving the photon energy storage.

Thermodynamic stability of cis-azobenzene containing DNA materials based on van der Waals forces

Taking advantage of van der Waals forces, an azobenzene-containing surfactant with a stable cis-state was designed and synthesized to fabricate photoresponsive DNA material. The reported DNA material exhibited reversible liquid crystalline-to-isotropic liquid transition under UV/Vis illuminations via the trans-cis isomerization of azobenzene. It also gained the ability to maintain the isotropic liquid state after UV light had ceased thanks to the thermodynamic stability of the cis-isomer of the azobenzene-containing surfactant. This work provides a design strategy for fabricating photoresponsive phase-change biomaterials.

Photoregulative phase change biomaterials showing thermodynamic and mchanical stabilities

Azobenzenes are great photochromic molecules for switching the physical properties of various materials via trans-cis isomerization. However, the UV light resulted cis-azobenzene is metastable and thermodynamically gets back to trans-azobenzene after ceasing UV irradiation, which causes an unwanted property change of azobenzene-containing materials. Additionally, thermal and mechanical conditions would accelerate this process dramatically. In this present work, a new type of azobenzene-containing surfactant is designed for the fabrication of photoresponsive phase change biomaterials. With a "locked" cis-azobenzene conformation, the resulting biomaterials could maintain their disordered state after ceasing UV light, which exhibit great resistance to thermal and piezo conditions. Interestingly, the "locked" cis-azobenzene could be unlocked by Vis light in high efficiency, which opens a new way for the design of phase change materials only responding to light. By showing stable cis-azobenzene maintained physical state, the newly fabricated biomaterials provide new potential for the construction of advanced materials, like self-healing materials, with less use of long time UV irradiation for maintaining their disordered states.