Durable and biocompatible superhydrophobic surfaces are of significant potential use in biomedical applications. Here, a nonfluorinated, elastic, superhydrophobic film that can be used for medical wound dressings to enhance their hemostasis function is introduced. The film is formed by titanium dioxide nanoparticles, which are chemically crosslinked in a poly(dimethylsiloxane) (PDMS) matrix. The PDMS crosslinks result in large strain elasticity of the film, so that it conforms to deformations of the substrate. The photocatalytic activity of the titanium dioxide provides surfaces with both self‐cleaning and antibacterial properties. Facile coating of conventional wound dressings is demonstrated with this composite film and then resulting improvement for hemostasis. High gas permeability and water repellency of the film will provide additional benefit for medical applications.
The concentrations of the redox pair hydrogen peroxide (HO) and oxygen (O) can promote or decelerate the progression and duration of the wound healing process. Although HO can reach critically high concentrations and prohibit healing, a sufficient O inflow to the wound is commonly desired. Herein, we describe the fabrication and use of a membrane that can contemptuously decrease HO and increase O 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 HO into O, as shown by a catalase assay. When comparing the growth of fibroblasts at an HO 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 HO 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.
A three-component nanocapsule-based system allows monitoring the health cycle of coatings via autonomous visual highlighting of damages and reversible erasing through healing.
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.
Electrospun polymer mats are widely used in tissue engineering, wearable electronics, and water purification. However, in many environments, the polymer nanofibers prepared by electrospinning suffer from biofouling during long-term usage, resulting in persistent infections and device damage. Herein, we describe the fabrication of polymer mats with CeO 2−x nanorods that can prevent biofouling in an aqueous environment. The embedded CeO 2−x nanorods are functional mimics of natural haloperoxidases that catalyze the oxidative bromination of Br − and H 2 O 2 to HOBr. The generated HOBr, a natural signaling molecule, disrupted the bacterial quorum sensing, a critical step in biofilm formation. The polymer fibers provide porous structures with high water wettability, and the embedded cerium oxide nanozymes act as a catalyst that can efficiently trigger oxidative bromination, as shown by a haloperoxidase assay. Additionally, the embedded nanozymes enhance the mechanical property of polymer mats, as shown by a single-fiber bending test using atomic force microscopy. We envision that the fabricated polymer mats with CeO 2−x nanorods may be used to provide mechanically robust coatings with antibiofouling properties.
One
of the dreams of nanotechnology is to create tiny objects,
nanobots, that are able to perform difficult tasks in dimensions and
locations that are not directly accessible. One basic function of
these nanobots is motility. Movements created by self-propelled micro-
and nanovehicles are usually dependent on the production of propellants
from catalytic reactions of fuels present in the environment. Developing
self-powered nanovehicles with internally stored fuels that display
motion regulated by external stimuli represents an intriguing and
challenging alternative. Herein, a one-step preparation of fuel-containing
nanovehicles that feature a motion that can be regulated by external
stimuli is reported. Nanovehicles are prepared via a sol–gel process confined at the oil/water interface of
miniemulsions. The nanovehicles display shapes ranging from mushroom-like
to truncated cones and a core–shell structure so that the silica
shell acts as a hull for the nanovehicles while the core is used to
store the fuel. Azo-based initiators are loaded in the nanovehicles,
which are activated to release nitrogen gas upon increase of temperature
or exposure to UV light. Enhanced diffusion of nanovehicles is achieved
upon decomposition of the fuel.
We study the effect
of entanglements on the glass transition of
high molecular weight polymers, by the comparison of single-chain
nanoparticles (SCNPs) and equilibrated melts of high-molecular weight
polystyrene of identical molecular weight. SCNPs were prepared by
electrospraying technique and characterized using scanning electron
microscopy and atomic force microscopy techniques. Differential scanning
calorimetry, Brillouin light spectroscopy, and rheological experiments
around the glass transition were compared. In parallel, entangled
and disentangled polymer melts were also compared under cooling from
molecular dynamics simulations based on a bead-spring polymer model.
While experiments suggest a small decrease in the glass transition
temperature of films of nanoparticles in comparison to entangled melts,
simulations do not observe any significant difference, despite rather
different chain conformations.
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