Polymer-Based Module for NAD+ Regeneration with Visible Light.

The regeneration of enzymatic cofactors by cell-free synthetic modules is a key step towards producing a purely synthetic cell. Herein, we demonstrate the regeneration of the enzyme cofactor NAD+ by photo-oxidation of NADH under visible-light irradiation by using metal-free conjugated polymer nanoparticles. Encapsulation of the light-active nanoparticles in the lumen of polymeric vesicles produced a fully organic module able to regenerate NAD+ in an enzyme-free system. The polymer compartment conferred physical and chemical autonomy to the module, allowing the regeneration of NAD+ to occur efficiently, even in harsh chemical environments. Moreover, we show that regeneration of NAD+ by the photocatalyst nanoparticles can oxidize a model substrate, in conjunction with the enzyme glycerol dehydrogenase. To ensure the longevity of the enzyme, we immobilized it within a protective silica matrix; this yielded enzymatic silica nanoparticles with enhanced long-term performance and compatibility with the NAD+ -regeneration system.

Shaping the Assembly of Superparamagnetic Nanoparticles.

Superparamagnetism exists only in nanocrystals, and to endow micro/macro-materials with superparamagnetism, superparamagnetic nanoparticles have to be assembled into complex materials. Most techniques currently used to produce such assemblies are inefficient in terms of time and material. Herein, we used evaporation-guided assembly to produce superparamagnetic supraparticles by drying ferrofluid droplets on a superamphiphobic substrate in the presence of an external magnetic field. By tuning the concentration of ferrofluid droplets and controlling the magnetic field, barrel-like, cone-like, and two-tower-like supraparticles were obtained. These assembled supraparticles preserved the superparamagnetism of the original nanoparticles. Moreover, other colloids can easily be integrated into the ferrofluid suspension to produce, by co-assembly, anisotropic binary supraparticles with additional functions. Additionally, the magnetic and anisotropic nature of the resulting supraparticles was harnessed to prepare magnetically actuable microswimmers.

A Reversible Proton Generator with On/Off Thermoswitch.

A reversible polymer photoacid with a thermal on/off switch at physiological temperature able to trigger a large pH modulation of its environment is prepared. Light is used to control the acidity of the solution. Additionally, the temperature could be used to modulate the photoacid efficiency, practically turning on and off the ability of the polymer to produce protons. The behavior of this thermoresponsive photoacid copolymer is the result of the combined action of the temperature-responsive N-isopropylacrylamide and of a reversible photoacid monomer based on a spiropyran derivative. The acidification of the aqueous medium is activated by irradiation at λ = 460 nm. The reverse reaction is achieved by removing the light stimuli or by exposing the solution to UV-light. Increasing the temperature above the lower critical solution temperature of the copolymer deactivates the photoacid and irradiation at λ = 460 nm does not lead to the generation of protons or to any detectable change in the pH value of the solution. Hence, the addition of N-isopropylacrylamide as a comonomer acts as a thermal on/off switch for the photoacid and the coupling of temperature-and light-responsiveness in the polyphotoacids yields a "thermophotoacid".

Enhanced photoluminescence properties of a carbon dot system through surface interaction with polymeric nanoparticles.

HYPOTHESIS: Carbon dot systems are highly surface sensitive fluorescent nanomaterials. In the presence of specific molecules or ions, the fluorescence properties can be strongly influenced. Often their fluorescent properties are activated or strongly enhanced through passivation agents such as polymer coatings. While several passivating polymers have been directly attached to the carbon dot systems, the interaction of carbon dot systems with the polymer surface of colloids has not been investigated as a way to activate or enhance the photoluminescent properties. Here, we show for the first time that the interaction of carbon dot systems with polymer colloids can strongly enhance the fluorescent properties of the carbon dot systems. EXPERIMENTS: To introduce carbon dot - polymer nanoparticle interactions, carbon dots are either generated directly in a microwave assisted synthesis in the presence of negatively charged polystyrene nanoparticles (in situ) or synthesized in the microwave separately and mixed afterwards with polymer nanoparticles (mixing). For the carbon dot system synthesis, chitosan, 1,2-ethylenediamine, and acetic acid are used as precursors. The produced carbon dot - polymer nanoparticle system are characterized by scanning electron microscopy, transmission electron microscopy, and flow cytometry measurements, and their interaction is assessed by fluorescence spectroscopy and fluorescence lifetime measurements. FINDINGS: We show that depending on the synthesis route (in situ or mixing), the carbon dot systems are either covalently attached (in situ) or electrostatically bound (mixing) to the surface of the nanoparticles. Regardless of the preparation methods of the investigated carbon dot - polymer nanoparticle system and the interaction (chemical or physical) with the surface, the fluorescence intensity is strongly enhanced and the fluorescence lifetime prolonged. These findings indicate a stabilization of the radiative trap states of carbon dot systems through interaction with the surface of the particles.

Fibrous Nanozyme Dressings with Catalase-Like Activity for H2O2 Reduction To Promote Wound Healing.

The concentrations of the redox pair hydrogen peroxide (H2O2) and oxygen (O2) can promote or decelerate the progression and duration of the wound healing process. Although H2O2 can reach critically high concentrations and prohibit healing, a sufficient O2 inflow to the wound is commonly desired. Herein, we describe the fabrication and use of a membrane that can contemptuously decrease H2O2 and increase O2 levels. Therefore, hematite nanozyme particles were integrated into electrospun and cross-linked poly(vinyl alcohol) membranes. Within the dual-compound membrane, the polymeric mesh provides a porous scaffold with high water permeability and the nanozymes act as a catalyst with catalase-like activity that can efficiently convert H2O2 into O2, as shown by a catalase assay. When comparing the growth of fibroblasts at an H2O2 concentration of 50 µM, the growth was largely enhanced when applying the nanozyme dressing. Thus, application of the nanozyme dressing can significantly reduce the harmful effect of higher H2O2 concentrations. The described catalytic membranes could be used in the future to provide an improved environment for cell proliferation in wounds and thus applied as advanced wound healing dressings.

Multifunctional clickable and protein-repellent magnetic silica nanoparticles.

Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene functional groups on their surface as orthogonally addressable chemical functionalities. Simultaneously, a short-chain zwitterion is added to decrease the non-specific adsorption of biomolecules on the nanoparticles surface. The multifunctional particles display reduced protein adsorption after incubation in undiluted fetal bovine serum as well as in single protein solutions (serum albumin and lysozyme). Besides, the particles retain their capacity to selectively react with biomolecules. Thus, they can be covalently bio-functionalized with an antibody by means of orthogonal click reactions. These features make the described multifunctional silica nanoparticles a promising system for the study of surface interactions with biomolecules, targeting, and bio-sensing.

How morphology influences relaxivity - comparative study of superparamagnetic iron oxide-polymer hybrid nanostructures.

Superparamagnetic iron oxides (SPIOs) are widely used in MRI as T2 contrast agents, and interest is still growing. Here, the T2 relaxivity of three different SPIO-polymer hybrid morphologies, i.e. homogeneously distributed iron oxide within a polymer matrix, Janus-like nanoparticles and polymer nanocapsules containing iron oxides, is studied. Making use of calculations based on theory for agglomerated systems, the obtained T2 values could be predicted for all different morphologies, except for nanocapsules. Nanocapsules, in contrast to full spheres, allow for water exchange between encapsulated water and bulk water, and thus have two contributions to relaxivity. One originates from the capsules acting as a weakly magnetized cluster and the other stems from the individual SPIOs inside the capsule. Therefore, the relaxivities were also computed using an empirical equation found in the literature, which considers water exchange, resulting in a better T2 forecast for the nanocapsules. The presented study is the first example of a comparison between measured and calculated relaxivities of nanocapsules.

Ellipsoid-shaped superparamagnetic nanoclusters through emulsion electrospinning.

Ellipsoid-shaped nanoclusters composed of single superparamagnetic nanoparticles can be generated by emulsion electrospinning. Stretching and subsequent solvent evaporation of iron oxide loaded emulsion droplets during the emulsion electrospinning process enables the creation of such structures embedded in polymer nanofibers. Dissolution of the polymer fibers yields an aqueous dispersion of the inorganic clusters which are the first example of ellipsoid-shaped superparamagnetic nanoclusters with a high saturation magnetization (∼47 emu g(-1)).

Colloidal polymers with controlled sequence and branching constructed from magnetic field assembled nanoparticles.

The assembly of nanoparticles into polymer-like architectures is challenging and usually requires highly defined colloidal building blocks. Here, we show that the broad size-distribution of a simple dispersion of magnetic nanocolloids can be exploited to obtain various polymer-like architectures. The particles are assembled under an external magnetic field and permanently linked by thermal sintering. The remarkable variety of polymer-analogue architectures that arises from this simple process ranges from statistical and block copolymer-like sequencing to branched chains and networks. This library of architectures can be realized by controlling the sequencing of the particles and the junction points via a size-dependent self-assembly of the single building blocks.

Mass spectrometry and imaging analysis of nanoparticle-containing vesicles provide a mechanistic insight into cellular trafficking.

Rational design of nanocarriers for drug delivery approaches requires an unbiased knowledge of uptake mechanisms and intracellular trafficking pathways. Here we dissected these processes using a quantitative proteomics approach. We isolated intracellular vesicles containing superparamagnetic iron oxide polystyrene nanoparticles and analyzed their protein composition by label-free quantitative mass spectrometry. The proteomic snapshot of organelle marker proteins revealed that an atypical macropinocytic-like mechanism mediated the entry of nanoparticles. We show that the entry mechanism is controlled by actin reorganization, atypical macropinocytic signaling, and ADP-ribosylation factor 1. Additionally, our proteomics data demonstrated a central role for multivesicular bodies and multilamellar lysosomes in trafficking and final nanoparticle storage. This was confirmed by confocal microscopy and cryo-TEM measurements. By quantitatively analyzing the protein composition of nanoparticle-containing vesicles, our study clearly defines the routes of nanoparticle entry, intracellular trafficking, and the proteomic milieu of a nanoparticle-containing vesicle.

Tailor-made nanocontainers for combined magnetic-field-induced release and MRI.

The synthesis of a novel nanocapsule-based carrier system is described, possessing a triggered release in remote-controlled fashion upon application of an external magnetic field in combination with the possibility to use the capsules as contrast agents for magnetic resonance imaging (MRI). Therefore, polymeric nanocontainers containing a high amount of superparamagnetic MnFe2 O4 nanoparticles and a thermo-degradable shell are fabricated via a miniemulsion route. The process allows the facile encapsulation of hydrophilic compounds, as demonstrated for a model dye. Release of the encapsulated dye is achieved upon application of an external alternating magnetic field. While the magnetic nanoparticles here act as heat generators to stimulate the decomposition of the shell and subsequently a release of the payload, they additionally enable the use of the nanocapsules as imaging agents for MRI. Due to the encapsulated magnetic nanoparticles, the nanocapsules possess high r2 relaxivity values of 96-120 Hz mmol(-1) , which makes them suitable for MRI. In toxicity experiments, the nanocapsules show no cell toxicity up to fairly high concentrations (600 µg mL(-1) ). Due to their dual-functionality, the nanocapsules possess high potential as nanocarriers with combined magnetic-field-induced release capability and as contrast agents for MRI.

Drug delivery without nanoparticle uptake: delivery by a kiss-and-run mechanism on the cell membrane.

Nearly all concepts of nanocarriers as drug delivery devices rely on intracellular uptake. Instead, we demonstrate an alternative concept for rapid and specific delivery of cargo by nanoparticles to TIP47+/ADRP+ lipid droplets. The model can serve as a novel strategy for the non-invasive delivery of drugs by releasing hydrophobic cargo, in our case a model dye, through a kiss-and-run mechanism between nanoparticles and the cell membrane.

Well-defined nanofibers with tunable morphology from spherical colloidal building blocks.

From particles to fibers: Nanofibers with different morphologies and periodicities can be fabricated by supraparticular assembly of magnetic spherical nanoparticles. A linear sintering process is used to merge the assembled colloids together. The structure of the obtained fibers is controlled by the process parameters and the morphology of the spherical colloidal building blocks.