Photo‐control of biological systems with azobenzene polymers

Abstract

Azobenzene-containing polymers offer tremendous advantages and opportunities over other stimuli-responsive materials to interface with biology. Azobenzene's fast, reversible, and innocuous cis-trans geometrical isomerization can be leveraged into dramatic intra-and inter-molecular changes when incorporated in polymeric materials. Azobenzene use has grown from a colorant, through to optical storage materials, and most recently in a variety of biologically themed applications. This review highlights the broad impact this photo-switch has had in recent years and offers a snapshot of the research landscape at the interface between photochemistry and biology. From photo-reversible micelles and peptides to controlled drug release and sensing, the versatility of azobenzene makes it a favored photo-switch found in many emerging applications. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3058-3070 KEYWORDS: azo polymers; biological applications of polymers; photochemistry; photophysics; water-soluble polymers; stimuli-sensitive polymers; dyes/pigments INTRODUCTION Synthetic materials for interfacing with biology have been designed and synthesized for millennia; recently the complexity and capability of these systems has increased significantly. 1 Aided by our growing understanding of how biology interacts with artificial materials, researchers have now assembled a broad toolkit of materials and processes that allows us to fine-tune interactions at the interface, eliciting specific biological responses on demand. These methods of bio-control can be broadly categorized as either chemical (ligand presence, charge, surface groups) or material changes (stiffness, moisture content).

Controlling Motion at the Nanoscale: Rise of the Molecular Machines

“…The motion is linked to geometric changes in the molecules produced upon tautomeric transformation triggered by light absorption and consequent proton migration. Collective reorganization of the molecules within the lattice leads to small uniaxial cell expansion, which in turn results in bending of the crystal.While the workhorse of many photomechanical studies, the azobenzene chromophore, has been extensively probed as isolated molecules, on surfaces, in polymers, and within liquid crystals, it has been far less studied by the crystalline photomechanical community [223][224][225][226][227]. This is due, in part, to the sterically demanding trans to cis isomerization process which may beimpeded in a crystal.…”

Driving Cells with Light‐Controlled Topographies

“…[17] Light responsivity is typically obtained by dispersing or chemically binding photoactive units within the polymer network. [17] Light responsivity is typically obtained by dispersing or chemically binding photoactive units within the polymer network.…”

Photocontrolled micellar aggregation of amphiphilic DNA-azobenzene conjugates

“…Azobenzene is a ubiquitous chromophore with applications in both biological and materials science because little degradation occurs during photoisomerization and facile synthetic routes to derivatives exist [16][17][18]. Trans-azobenzene is more thermodynamically stable but can be converted to the cis isomer with UV irradiation (365 nm); cis-to-trans isomerization occurs thermally or by irradiation with visible light.…”