Photoreversible Soft Azo Dye Materials: Toward Optical Control of Bio‐Interfaces

Abstract

systems interact with artificial materials, researchers have now assembled a versatile toolkit of materials and processes that allows one to fine-tune interactions at the interface, tailoring specific biological responses on demand. These strategies for biocontrol can be broadly categorized as chemical (charge, ligand presence, surface groups), material changes (moisture content, stiffness), or morphological changes (molecular orientation, surface topography, or mechanical actuation). Rational design of materials for biological interface applications has a unique set of challenges due to the unique requirements of a wide range of biological systems, since different tissues present specific compositions, with their own elasticity, structural organization, and triggering mechanisms. Even within a single organ or tissue, mechanical properties can vary widely depending on the region. A recent study of viscoelasticity in live mouse brain tissue for example found a tenfold difference within the brain depending on the region and morphological structure studied. [2] However, most biological tissues are far less stiff, and far more viscoelastic than typical artificial materials employed at their interface, especially early artificial cell culture materials, which can be much stiffer than in vivo extracellular matrix by many orders of magnitude. [3] In vivo, cells interface with a surrounding microenvironment consisting of an intricate macromolecular network of proteins and sugars swollen in an aqueous media gel. Therefore, the interaction between cells and the extracellular matrix (ECM) in the body is complex and involves a variety of cues related to topography, chemical markers, protein composition, solubility factors, and mechanical properties such as stiffness and elasticity (Figure 1a). [4] Yet much research over the past decades was focused on studying in vitro the effects of each of these signals on cell behavior, with a particular interest on the chemical factors, whereas only recently more advanced biomaterials with controlled physicomechanical properties have been developed, such as those with tunable and variable stiffness, alignment and orientation of key functional groups, and mechanical actuation. There is a large range of stiffness in human tissue, where bone (≈100 GPa) is nine orders of magnitude harder than brain tissue (≈0.1 kPa). [4] Therefore, biomaterial researchers assume a complex task of providing materials and processing technologies for controlling stiffness and micro-and nanostructures in Photoreversible optically switchable azo dye molecules in polymer-based materials can be harnessed to control a wide range of physical, chemical, and mechanical material properties in response to light, that can be exploited for optical control over the bio-interface. As a stimulus for reversibly influencing adjacent biological cells or tissue, light is an ideal triggering mechanism, since it can be highly localized (in time and space) for precise and dynamic control over a biosystem, and low-power visible light...

Deterministic Realization of Quasicrystal Surface Relief Gratings on Thin Azopolymer Films

“…The light‐structured azopolymer surfaces have already found applications in several scientific and technological areas including photonics, [ 13,23,31 ] wettability [ 32–34 ] and adhesion [ 35–38 ] among the others. However, their use as widespread photolithographic platform is hindered by the absence, despite significant theoretical efforts, [ 39–43 ] of quantitative models able to predict the geometry and the amount of surface deformation from the knowledge of material parameters and illumination distribution.…”

Azobenzene-based sinusoidal surface topography drives focal adhesion confinement and guides collective migration of epithelial cells

“…Azobenzene-containing amorphous thin films can be topographically patterned using light stimulus inducing cyclic and reversible photoisomerization of the azobenzenes 41 . Such surface microtopographies have recently been successfully implemented in single cell studies, highlighting the remarkable potential of azobenzene-containing materials in devising stimuli-responsive biointerfaces 35,49 . We used a glass-forming DR1-containing material (DR1-glass, Fig.…”

Light‐Controlled Regioselective Synthesis of Fullerene Bis‐Adducts

“…Compound E ‐ 4 shows the typical absorption spectrum of azobenzene derivatives: [22a–f] a weak n ‐π* band centered at 450 nm, with a molar absorption coefficient ( ϵ ) of 500 m −1 cm −1 , and a more intense π‐π* band in the UV region, with maximum at 322 nm and an ϵ of 22 000 m −1 cm −1 (Figure S15). Irradiation of E ‐ 4 at 313 nm or 365 nm produces a strong decrease in the UV absorption and an increase of the n ‐π* band (see Figure 2 a), which can be ascribed to an E → Z isomerization, until a photostationary state (PSS) is achieved.…”