We herein report a new design route to stable, heterophase photocatalysts, which function as highly dispersible conjugated polymer nanoparticles and porous monoliths under visible light in aqueous ...medium. They were constructed by attachment of the ionic‐liquid species 1‐alkyl‐3‐vinylimidazolium bromide onto the side chains of a photoactive polymer. The structure configuration allows not only photocatalysis in aqueous environment but also a unique self‐initiation radical cross‐linking process to transform the water‐soluble photoactive polymer into a heterophase system, either as nanoparticles or a porous monolith. High photocatalytic activity and reusability of the heterophase system were demonstrated in the degradation of organic dyes and reduction of CrVI into CrIII in water under visible‐light irradiation.
Photoactive polymer‐based nanoparticles and porous materials were formed by the side‐product‐ and surfactant‐free self‐initiated cross‐linking of a conjugated polymer bearing vinylimidazolium side groups. The polymer acts as both a photosensitizer and a stabilizer for colloidal systems. The obtained cross‐linked polymers serve as efficient, recyclable, cost‐effective heterogeneous photocatalysts under visible‐light irradiation.
Despite multiple research approaches to prevent bacterial colonization on surfaces, device‐associated infections are currently responsible for about 50% of nosocomial infections in Europe and ...significantly increase health care costs, which demands development of advanced antibacterial surface coatings. Here, novel antimicrobial composite materials incorporating zinc oxide nanoparticles (ZnO NP) into biocompatible poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel layers are prepared by mixing the PNIPAAm prepolymer with ZnO NP, followed by spin‐coating and photocrosslinking. Scanning electron microscopy (SEM) characterization of the composite film morphology reveals a homogeneous distribution of the ZnO NP throughout the film for every applied NP/polymer ratio. The optical properties of the embedded NP are not affected by the matrix as confirmed by UV‐vis spectroscopy. The nanocomposite films exhibit bactericidal behavior towards Escherichia coli (E. coli) for a ZnO concentration as low as ≈0.74 μg cm−2 (1.33 mmol cm−3), which is determined by inductively coupled plasma optical emission spectrometry. In contrast, the coatings are found to be non‐cytotoxic towards a mammalian cell line (NIH/3T3) at bactericidal loadings of ZnO over an extended period of seven days. The differential toxicity of the ZnO/hydrogel nanocomposite thin films between bacterial and cellular species qualifies them as promising candidates for novel biomedical device coatings.
Novel antimicrobial composite materials incorporating zinc oxide nanoparticles into biocompatible poly(N‐isopropylacrylamide) hydrogel layers are prepared by simple film preparation from a mixture of both components in solution, followed by photocrosslinking. The nanocomposite films exhibit bactericidal behavior towards Escherichia coli (E. coli) while being non‐cytotoxic towards mammalian cells.
Herein, we report on the structural design principle of small‐molecule organic semiconductors as metal‐free, pure organic and visible light‐active photocatalysts. Two series of electron‐donor and ...acceptor‐type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C−H functionalization of electron‐rich heteroaromates with malonate derivatives. A mechanistic study of the light‐induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy‐band structure, the small‐molecule organic semiconductors could offer a new class of metal‐free and visible light‐active photocatalysts for chemical reactions.
Give and take: Small‐molecule organic semiconductor donor–acceptor systems with a tunable absorption range and defined energy‐band structure are designed as metal‐free, pure organic, visible‐light‐active photocatalysts to meet crucial requirements, such as absorption in the visible region, sufficient light‐generated redox potential, and long exciton lifetime.
Specifically designed and functionalized nanoparticles hold great promise for biomedical applications. Yet, the applicability of nanoparticles is critically predetermined by their surface ...functionalization. Here we demonstrate that amino-functionalized polystyrene nanoparticles (PS-NH(2)) of ∼100 nm in diameter, but not carboxyl- or nonfunctionalized particles, trigger NLRP3 inflammasome activation and subsequent release of proinflammatory interleukin 1β (IL-1β) by human macrophages. PS-NH(2) induced time-dependent proton accumulation in lysosomes associated with lysosomal destabilization, release of cathepsin B, and damage of the mitochondrial membrane. Accumulation of mitochondrial reactive oxygen species was accompanied by oxidation of thioredoxin, a protein playing a central role in maintaining the cellular redox balance. Upon oxidation, thioredoxin dissociated from the thioredoxin-interacting protein (TXNIP). Liberated TXNIP, in turn, interacted with the NLRP3 protein, resulting in a conformational change of the pyrin domain of the NLRP3 protein, as was predicted by molecular modeling. Consequently, this prompted assembly of the NLRP3 inflammasome complex with recruitment and activation of caspase-1, inducing IL-1β release by cleavage of pro-IL-1β. The central role of the NLRP3 inflammasome for cytokine production was confirmed by in vitro knockdown of NLRP3 and of the adaptor protein ASC, confirming that other inflammasomes were not activated by PS-NH(2). The PS-NH(2)-mediated proinflammatory macrophage activation could be antagonized by the radical scavenger N-acetyl-L-cysteine, which prevented mitochondrial damage, caspase-1 activation, and the subsequent release of IL-1β. Our study reveals the molecular mechanism of NLRP3 inflammasome activation by amino-functionalized nanoparticles and suggests a strategy as to how such adverse effects could be antagonized.
Nanoparticles of various shapes, sizes, and materials carrying different surface modifications have numerous technological and biomedical applications. Yet, the mechanisms by which nanoparticles ...interact with biological structures as well as their biological impact and hazards remain poorly investigated. Due to their large surface to volume ratio, nanoparticles usually exhibit properties that differ from those of bulk materials. Particularly, the surface chemistry of the nanoparticles is crucial for their durability and solubility in biological media as well as for their biocompatibility and biodistribution. Polystyrene does not degrade in the cellular environment and exhibits no short-term cytotoxicity. Because polystyrene nanoparticles can be easily synthesized in a wide range of sizes with distinct surface functionalizations, they are perfectly suited as model particles to study the effects of the particle surface characteristics on various biological parameters. Therefore, we have exploited polystyrene nanoparticles as a convenient platform to study bio-nano interactions. This review summarizes studies on positively and negatively charged polystyrene nanoparticles and compares them with clinically used superparamagnetic iron oxide nanoparticles.
Nanocarrier (NC)‐mediated drug delivery is widely researched in medicine but to date has not been used in agriculture. The first curative NC‐based treatment of the worldwide occurring grapevine trunk ...disease Esca, with more than 2 billion infected plants causing a loss yearly of $1.5 billion, is presented. To date, only repetitive spraying of fungicides is used to reduce chances of infection. This long‐term treatment against Esca uses minimal amounts of fungicide encapsulated in biobased and biodegradable lignin NCs. A single trunk injection of <10 mg fungicide results in curing of an infected plant. Only upon Esca infection, ligninolytic enzymes, secreted by the Esca‐associated fungi, degrade the lignin NC to release the fungicide. The specific antifungal activity is confirmed in vitro and in planta (in Vitis vinifera L. cv. ‘Portugieser’). All treated plants prove to exhibit significantly fewer symptoms several weeks after treatment, and their condition is monitored for 5 years (2014–2018), proving a long‐term curative effect of this NC treatment. This study proves the efficacy of this NC‐mediated drug delivery for agriculture, using a minimum amount of fungicides. It is believed that this concept can be extended to other plant diseases worldwide to reduce extensive spraying of agrochemicals.
A nanocarrier (NC)‐based treatment for grapevines, infected by the worldwide occurring trunk disease Esca, is developed. In contrast to extensive spraying, this long‐term effective treatment uses minimum amounts of fungicide encapsulated in biobased lignin NCs. The fungicide is released only on demand in case of infection due to ligninolytic enzymes, secreted by the Esca‐associated fungi, degrading the carrier matrix.
Dual‐Responsive Photocatalytic Polymer Nanogels Ferguson, Calum T. J.; Huber, Niklas; Landfester, Katharina ...
Angewandte Chemie International Edition,
July 29, 2019, Volume:
58, Issue:
31
Journal Article
Peer reviewed
Selective activation of photocatalysts under constant light conditions has recently been targeted to produce multi‐responsive systems. However, controlled activation, with easy recovery of the ...photocatalysts, induced by external stimuli remains a major challenge. Mimicking the responsiveness of biological systems to multiple triggers can offer a promising solution. Herein, we report dual‐responsive polymer photocatalysts in the form of nanogels consisting of a cross‐linked poly‐N‐isopropylacrylamide nanogel, copolymerised with a photocatalytically active monomer. The dual‐responsive polymer nanogels undergo a stark decrease in diameter with increasing temperature, which shields the photocatalytic sites, decreasing the activity. Temperature‐dependent photocatalytic formation of NAD+ in water demonstrates the ability to switch photocatalysis on and off. Moreover, the photocatalysed syntheses of several fine chemicals were carried out to demonstrate the utility of the designed material.
Responsive photocatalytic polymers: The inclusion of photocatalytic sites in a temperature‐responsive polymer nanogel network created a dual‐responsive polymer photocatalyst that can be utilised to selectively catalyse numerous reactions at specific temperatures.
Nanocarriers (NC) are very promising tools for cancer immunotherapy. Whereas conventional vaccines are based on the administration of an antigen and an adjuvant in an independent fashion, ...nanovaccines can facilitate cell-specific co-delivery of antigen and adjuvant. Furthermore, nanovaccines can be decorated on their surface with molecules that facilitate target-specific antigen delivery to certain antigen-presenting cell types or tumor cells. However, the target cell-specific uptake of nanovaccines is highly dependent on the modifications of the nanocarrier itself. One of these is the formation of a protein corona around NC after
administration, which may potently affect cell-specific targeting and uptake of the NC. Understanding the formation and composition of the protein corona is, therefore, of major importance for the use of nanocarriers in vaccine approaches. This Mini Review will give a short overview of potential non-specific interactions of NC with body fluids or cell surfaces that need to be considered for the design of NC vaccines for immunotherapy of cancer.
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