Heavy-atom-free π-twisted photosensitizers for fluorescence bioimaging and photodynamic therapy.

As the field of preclinical research on photosensitizers (PSs) for anticancer photodynamic therapy (PDT) continues to expand, a focused effort is underway to develop agents with innovative molecular structures that offer enhanced targeting, selectivity, activation, and imaging capabilities. In this context, we introduce two new heavy-atom-free PSs, DBXI and DBAI, characterized by a twisted π-conjugation framework. This innovative approach enhances the spin-orbit coupling (SOC) between the singlet excited state (S1) and the triplet state (T1), resulting in improved and efficient intersystem crossing (ISC). Both PSs are highly effective in producing reactive oxygen species (ROS), including singlet oxygen and/or superoxide species. Additionally, they also demonstrate remarkably strong fluorescence emission. Indeed, in addition to providing exceptional photocytotoxicity, this emissive feature, generally lacking in other reported structures, allows for the precise monitoring of the PSs' distribution within specific cellular organelles even at nanomolar concentrations. These findings underscore the dual functionality of these PSs, serving as both fluorescent imaging probes and light-activated therapeutic agents, emphasizing their potential as versatile and multifunctional tools in the field of PDT.

Effects of Erucamide on Fiber "Softness": Linking Single-Fiber Crystal Structure and Mechanical Properties.

Erucamide is known to play a critical role in modifying polymer fiber surface chemistry and morphology. However, its effects on fiber crystallinity and mechanical properties remain to be understood. Here, synchrotron nanofocused X-ray Diffraction (nXRD) revealed a bimodal orientation of the constituent polymer chains aligned along the fiber axis and cross-section, respectively. Erucamide promoted crystallinity in the fiber, leading to larger and more numerous lamellae crystallites. The nXRD nanostructual characterization is complemented by single-fiber uniaxial tensile tests, which showed that erucamide significantly affected fiber mechanical properties, decreasing fiber tensile strength and stiffness but enhancing fiber toughness, fracture strain, and ductility. To correlate these single-fiber nXRD and mechanical test results, we propose that erucamide mediated slip at the interfaces between crystallites and amorphous domains during stress-induced single-fiber crystallization, also decreasing the stress arising from the shear displacement of microfibrils and deformation of the macromolecular network. Linking the single-fiber crystal structure with the single-fiber mechanical properties, these findings provide the direct evidence on a single-fiber level for the role of erucamide in enhancing fiber "softness".

A new G-quadruplex-specific photosensitizer inducing genome instability in cancer cells by triggering oxidative DNA damage and impeding replication fork progression.

Photodynamic therapy (PDT) ideally relies on the administration, selective accumulation and photoactivation of a photosensitizer (PS) into diseased tissues. In this context, we report a new heavy-atom-free fluorescent G-quadruplex (G4) DNA-binding PS, named DBI. We reveal by fluorescence microscopy that DBI preferentially localizes in intraluminal vesicles (ILVs), precursors of exosomes, which are key components of cancer cell proliferation. Moreover, purified exosomal DNA was recognized by a G4-specific antibody, thus highlighting the presence of such G4-forming sequences in the vesicles. Despite the absence of fluorescence signal from DBI in nuclei, light-irradiated DBI-treated cells generated reactive oxygen species (ROS), triggering a 3-fold increase of nuclear G4 foci, slowing fork progression and elevated levels of both DNA base damage, 8-oxoguanine, and double-stranded DNA breaks. Consequently, DBI was found to exert significant phototoxic effects (at nanomolar scale) toward cancer cell lines and tumor organoids. Furthermore, in vivo testing reveals that photoactivation of DBI induces not only G4 formation and DNA damage but also apoptosis in zebrafish, specifically in the area where DBI had accumulated. Collectively, this approach shows significant promise for image-guided PDT.

Arabidopsis thaliana Zn2+-efflux ATPases HMA2 and HMA4 are required for resistance to the necrotrophic fungus Plectosphaerella cucumerina BMM.

Zinc is an essential nutrient at low concentrations, but toxic at slightly higher ones. It has been proposed that hyperaccumulator plants may use the excess zinc to fend off pathogens and herbivores. However, there is little evidence of a similar response in other plants. Here we show that Arabidopsis thaliana leaves inoculated with the necrotrophic fungus Plectosphaerella cucumerina BMM (PcBMM) accumulate zinc and manganese at the infection site. Zinc accumulation did not occur in a double mutant in the zinc transporters HEAVY METAL ATPASE2 and HEAVY METAL ATPASE4 (HMA2 and HMA4), which has reduced zinc translocation from roots to shoots. Consistent with a role in plant immunity, expression of HMA2 and HMA4 was up-regulated upon PcBMM inoculation, and hma2hma4 mutants were more susceptible to PcBMM infection. This phenotype was rescued upon zinc supplementation. The increased susceptibility to PcBMM infection was not due to the diminished expression of genes involved in the salicylic acid, ethylene, or jasmonate pathways since they were constitutively up-regulated in hma2hma4 plants. Our data indicate a role of zinc in resistance to PcBMM in plants containing ordinary levels of zinc. This layer of immunity runs in parallel to the already characterized defence pathways, and its removal has a direct effect on resistance to pathogens.

Nickel Poisoning of a Cracking Catalyst Unravelled by Single-Particle X-ray Fluorescence-Diffraction-Absorption Tomography.

Ni contamination from crude oil in the fluid catalytic cracking (FCC) process is one of the primary sources of catalyst deactivation, thereby promoting dehydrogenation-hydrogenation and speeding up coke growth. Herein, single-particle X-ray fluorescence, diffraction and absorption (µXRF-µXRD-µXAS) tomography is used in combination with confocal fluorescence microscopy (CFM) after thiophene staining to spatially resolve Ni interaction with catalyst components and study zeolite degradation, including the processes of dealumination and Brønsted acid sites distribution changes. The comparison between a Ni-lean particle, exposed to hydrotreated feedstock, and a Ni-rich one, exposed to non-hydrotreated feedstock, reveals a preferential interaction of Ni, found in co-localization with Fe, with the γ-Al2 O3 matrix, leading to the formation of spinel-type hotspots. Although both particles show similar surface zeolite degradation, the Ni-rich particle displays higher dealumination and a clear Brønsted acidity drop.

Localization and Speciation of Iron Impurities within a Fluid Catalytic Cracking Catalyst.

Fluid catalytic cracking is a chemical conversion process of industrial scale. This process, utilizing porous catalysts composed of clay and zeolite, converts heavy crude-oil fractions into transportation fuel and petrochemical feedstocks. Among other factors iron-rich reactor and feedstream impurities cause these catalyst particles to permanently deactivate. Herein, we report tomographic X-ray absorption spectroscopy measurements that reveal the presence of dissimilar iron impurities of specific localization within a single deactivated particle. Whereas the iron natural to clay in the composite seems to be unaffected by operation, exterior-facing and feedstream-introduced iron was found in two forms. Those being minute quantities of ferrous oxide, located near regions of increased porosity, and impurities rich in Fe3+ , preferentially located in the outer dense part of the particle and suggested to contribute to the formation of an isolating amorphous silica alumina envelope.