Nanocarriers for intracellular delivery of molecular payloads triggered by visible light.

Stimuli-responsive nanocontainers have emerged as promising vehicles to deliver molecular payloads into the cytosol of cells in a spatially, temporally and dosage-controlled manner. These nanocontainers respond to a specific type of stimulus such as a change in redox status, enzymatic activity, pH, heat, light, and others. In this work, we introduce photoresponsive nanocontainers based on the self-assembly of vesicles with surface-confined cyclodextrin-adamantane host-guest chemistry.

Sonochemical Nitroxide-Mediated Polymerization: Harnessing Sonochemistry for Polymer Synthesis.

In polymer science, mechanochemistry is emerging as a powerful tool for materials science and molecular synthesis, offering novel avenues for controlled polymerization and post-synthetic modification. Building upon the previous research, nitroxide-mediated polymerization (NMP) is merged with mechanochemistry through the design of nitroxide-based mechanophore macroinitiators, pioneering the first instance of a sonochemical nitroxide-mediated-type polymerization. As NMP usually requires high temperatures, this study demonstrates that a sonochemical NMP-type process allows polymerization under reduced temperatures down to 55 °C.

ToF-SIMS Investigation of Environmental Effects on Analyte Migration in Matrix Coatings for Mass Spectrometry Imaging Using a Newly Developed Vapor Deposition System.

High resolution mass spectrometry images are of increasing importance in biological applications, such as the study of tissues and single cells. Two promising techniques for this are matrix-enhanced secondary ion mass spectrometry (ME-SIMS) and matrix-assisted laser desorption/ionization (MALDI). For both techniques, the sample of interest must be coated with a matrix prior to analysis, and analytes must migrate into the matrix.

Surface Tension Manipulation with Visible Light through Sensitized Disequilibration of Photoswitchable Amphiphiles.

Azoarene isomerization lies at the heart of numerous applications, from catalysis or energy storage to photopharmacology. While efficient switching between their E and Z isomers predominantly relies on UV light, a recent study by Klajn and co-workers introduced visible light sensitization of E azoarenes and their subsequent isomerization as a tool coined disequilibration by sensitization under confinement (DESC) to obtain high yields of the Z isomer. This host-guest approach is, however, still constrained to minimally substituted azoarenes with limited applicability in advanced molecular systems.

Photoresponsive Block Copolymer Nanostructures through Implementation of Arylazopyrazoles.

Responsive nanomaterials that can undergo reversible changes in morphology are interesting for the development of functional materials that interact with and respond to their environment. Amphiphilic block copolymers are well-known for their ability to create a wide range of supramolecular nanostructures in solution. Arylazopyrazoles (AAPs) are versatile molecular photoswitches, which change their configuration and hydrophobicity upon irradiation with UV light (365 nm, isomer, less hydrophobic) and green light (520 nm, isomer, more hydrophobic).

Functional Linkers Support Targeting of Multivalent Tweezers to Taspase1.

Taspase 1 is a unique protease not only pivotal for embryonic development but also implicated in leukemias and solid tumors. As such, this enzyme is a promising while still challenging therapeutic target, and with its protein structure featuring a flexible loop preceding the active site a versatile model system for drug development. Supramolecular ligands provide a promising complementary approach to traditional small-molecule inhibitors.

Multi-Stimuli-Responsive Water-Dispersible Magnetite Nanoparticles Using Arylazopyrazole-Modified Polymer Ligands.

In order to design new nanomaterials with improved functionalities, magnetite nanoparticles (MNP) modified with arylazopyrazole (AAP) molecular photoswitches are presented. Water dispersibility is achieved by using poly(acrylic acid) (pAA) as a multidentate ligand, which is modified with AAP by amide coupling. The polymer ligand stabilizes the MNP, allows for - isomerization of the photoswitch, and provides pH responsiveness.

Unravelling Competitive Interactions between Polymer Side Chains and End Groups with β-Cyclodextrin.

This study investigates unexpected competitive host-guest interactions of β-cyclodextrin (β-CD), which can occur with polymers in aqueous solution, using the examples of the two polymers poly(oligo(ethylene glycol) methyl ether methacrylate) and poly(glycerol mono methacrylate). Systematic structural modifications of the polymer provide insight into the host-guest interaction with β-CD and the competition between side chains and end groups such as hydrophobic end groups remaining from reversible addition fragmentation chain transfer polymerization or intentionally implemented molecular recognition units such as arylazopyrazole photoswitches.

Arylazopyrazoles for Conjugation by CuAAC Click Chemistry.

Molecular photoswitches are increasingly being implemented in bioactive compounds and responsive materials. For this purpose, photoswitches must be coupled to a wide variety of substrates and scaffolds. We present a library of "clickable" arylazopyrazoles (AAPs), which can be conjugated by Cu-catalyzed alkyne azide cycloaddition (CuAAC).

Photoswitching of arylazopyrazoles upon S (nπ*) excitation studied by transient absorption spectroscopy and molecular dynamics.

Arylazopyrazoles (AAPs) are an important class of molecular photoswitches with high photostationary states (PSS) and long thermal lifetimes. The ultrafast photoisomerization of four water-soluble arylazopyrazoles, all of them featuring an -dimethylated pyrazole ring, is studied by narrowband femtosecond transient absorption spectroscopy and molecular dynamics simulations. Upon S (nπ*) photoexcitation of the planar -isomers (-AAPs), excited-state bi-exponential decays with time constants in the 220-440 fs range and in the 1.

Stiffness Modulation and Pulsatile Release in Dual Responsive Hydrogels.

Inspired by nature, self-regulation can be introduced in synthetic hydrogels by incorporating chemo-mechanical signals or coupled chemical reactions to maintain or adapt the material's physico-chemical properties when exposed to external triggers. In this work, we present redox and light dual stimuli responsive hydrogels capable of rapidly adapting the polymer crosslinking network while maintaining hydrogel stability. Upon irradiation with UV light, polymer hydrogels containing redox responsive disulfide crosslinks and light responsive ortho-nitrobenzyl moieties show a release of payload accompanied by adaptation of the hydrogel network towards higher stiffness due to in situ crosslinking by S-nitrosylation.

Calamitic Liquid Crystals for Reversible Light-Modulated Phase Regulation Based on Arylazopyrazole Photoswitches.

Invited for the cover of this issue are the groups of Kentaro Tanaka at Nagoya University and Bart Jan Ravoo at the University of Münster. The image depicts the photoisomerization of a mesogen upon irradiation with different wavelengths of light. Read the full text of the article at 10.

Calamitic Liquid Crystals for Reversible Light-Modulated Phase Regulation Based on Arylazopyrazole Photoswitches.

The design of responsive liquid crystals enables a diversity of technological applications. Especially photochromic liquid crystals gained a lot of interest in recent years due to the excellent spatiotemporal control of their phase transitions. In this work we present calamitic light responsive mesogens based on a library of arylazopyrazole photoswitches.

Matrix-Enhanced SIMS: The Influence of Primary Ion Species and Cluster Size on Ion Yield and Ion Yield Enhancement of Lipids.

Time-of-flight secondary ion mass spectrometry is one of the most promising techniques for label-free analysis of biomolecules with nanoscale spatial resolution. However, high-resolution imaging of larger biomolecules such as phospholipids and peptides is often hampered by low yields of molecular ions. Matrix-enhanced SIMS (ME-SIMS), in which an organic matrix is added to the sample, is one promising approach to enhancing the ion yield for biomolecules.

Water-Soluble Arylazoisoxazole Photoswitches.

Azoheteroarenes are emerging as powerful alternatives to azobenzene molecular photoswitches. In this study, water-soluble arylazoisoxazole photoswitches are introduced. UV/vis and NMR spectroscopy revealed moderate to very good photostationary states and reversible photoisomerization between the E- and Z-isomers over multiple cycles with minimal photobleaching.

Multi-responsive Electropolymer Surface Coatings Based on Azo Molecular Switches and Carbazoles: Light, pH, and Electrochemical Control of Z→E Isomerization in Thin Films.

Light-responsive surfaces are attracting increasing interest, not least because their physicochemical properties can be selectively and temporally controlled by a non-invasive stimulus. Most existing immobilization strategies involve the chemical attachment of light-responsive moieties to the surface, although this approach often suffers from a low surface concentration of active species or a high inhomogeneity of applied coatings. Herein, electropolymerization of carbazoles as a facile and rapid approach for preparing light-responsive azo-based surface coatings is presented.

Selective Removal of Gold: N-Heterocyclic Carbenes as Positive Etch Resists on Planar Gold Surfaces.

N-Heterocyclic carbene (NHC)-modified planar gold surfaces (NHC@Au) were found to be more susceptible toward wet chemical etching than undecorated surface areas. Site-selective decoration of NHCs on Au was achieved by microcontact printing (μCP) of the NHC precursors 1,3-bis(diisopropylphenyl)imidazol-3-ium hydrogen carbonate (IPr(H)[HCO]) or 1,3-dimethylbenzimidazol-3-ium hydrogen carbonate (BIMe(H)[HCO]). Strikingly, BIMe@Au showed concentration-dependent etching behavior, tunable from a positive resist to a negative resist.

Rapid and reversible optical switching of cell membrane area by an amphiphilic azobenzene.

Cellular membrane area is a key parameter for any living cell that is tightly regulated to avoid membrane damage. Changes in area-to-volume ratio are known to be critical for cell shape, but are mostly investigated by changing the cell volume via osmotic shocks. In turn, many important questions relating to cellular shape, membrane tension homeostasis and local membrane area cannot be easily addressed because experimental tools for controlled modulation of cell membrane area are lacking.

Azoheteroarene and Diazocine Molecular Photoswitches: Self-Assembly, Responsive Materials and Photopharmacology.

Aromatic units tethered with an azo (-N=N-) functionality comprise a unique class of compounds, known as molecular photoswitches, exhibiting a reversible transformation between their E- and Z-isomers in response to photo-irradiation. Photoswitches have been explored extensively in the recent past to prepare dynamic self-assembled materials, optoelectronic devices, responsive biomaterials, and more. Most of such materials involve azobenzenes as the molecular photoswitch and to date, SciFinder lists more than 7000 articles and 1000 patents.

Arylazopyrazole-Modified Thiolactone Acrylate Copolymer Brushes for Tuneable and Photoresponsive Wettability of Glass Surfaces.

Photoswitches have long been employed in coatings for surfaces and substrates to harness light as a versatile stimulus to induce responsive behavior. We previously demonstrated the viability of arylazopyrazole (AAP) as a photoswitch in self-assembled monolayers (SAMs) on silicon and glass surfaces for photoresponsive wetting applications. We now aim to transfer the excellent photophysical properties of AAPs to polymer brush coatings.

Light-Responsive Conductive Surface Coatings on the Basis of Azidomethyl-PEDOT Electropolymer Films.

The design of responsive coatings has gained increasing attention recently, with light-responsive interfaces receiving particular appreciation, as their surface properties can be modulated with excellent spatiotemporal control. In this article, we present light-responsive conductive coatings acquired through a copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction between electropolymerized azide-functionalized poly(3,4-ethylenedioxythiophene) () and arylazopyrazole ()-bearing alkynes. The UV/vis and X-ray photoelectron spectroscopy (XPS) data indicate a successful post-modification, supporting a covalent attachment of moieties to .

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography.

Nanoparticles offer unique physical and chemical properties. Dip pen nanolithography of nanoparticles enables versatile patterning and nanofabrication with potential application in electronics and sensing, but is not well studied yet. Herein, the patterned deposition of various nanoparticles onto unmodified silicon substrates is presented.

Influence of Matrix p on Molecular Ion Formation in Matrix-Enhanced Secondary-Ion Mass Spectrometry.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is one of the most important techniques for chemical imaging of nanomaterials and biological samples with high lateral resolution. However, low ionization efficiency limits the detection of many molecules at low concentrations or in very small volumes. One promising approach to increasing the sensitivity of the technique is by the addition of a matrix that promotes ionization and desorption of important analyte molecules.

Versatile Surface Patterning with Low Molecular Weight Photoswitches.

Surface patterning of functional materials is a key technology in various fields such as microelectronics, optics, and photonics. In micro- and nanofabrication, polymers are frequently employed either as photoreactive or thermoresponsive resists that enable further fabrication steps, or as functional adlayers in electronic and optical devices. In this article, a method is presented for imprint lithography using low molecular weight arylazoisoxazoles photoswitches instead of polymer resists.

Reversible, Red-Shifted Photoisomerization in Protonated Azobenzenes.

Azobenzenes are among the best-studied molecular photoswitches and play a key role in the search for red-shifted photoresponsive materials for extended applications. Currently, most approaches deal with aromatic substitution patterns to achieve visible light application, on occasion paired with protonation to yield red-shifted absorption of the azonium species. Appropriate substitution patterns are essential to stabilize the latter approach, as conventional acids are known to induce a fast - to -conversion.