Novel Anthracene-Appended Calix[4]triazacrown-5 as an Effective Fluorescence Probe for Co2+ and Hazardous Cr2O7 2- Ions.

A new calix[4]triazacrown-5-derived fluorescence chemosensor (AntUr-AzClx) at cone conformation was synthesized to afford an effective fluorescent probe, which enables an enhancement in the fluorescence intensity specifically in the presence of Co2+ metal ions as well as a turnoff response for hazardous dichromate anions. 1H-NMR, 13C-NMR, ESI-MS, and elemental analysis techniques were used to characterize the structure of the anthracene-appended calix[4]triazacrown-5 (AntUr-AzClx). The metal ion-binding ability of AntUr-AzClx was evaluated against Co2+, Ba2+, Ni2+, Pb2+, and Zn2+ ions. On the basis of various metal ion recognition phenomena, AntUr-AzClx exhibited outstanding selectivity for only the Co2+ ion among other metal ions. Also, the calix[4]triazacrown-5-derived fluorescence chemosensor showed high sensitivity towards the Co2+ ion with a very low limit of detection (LOD) 0.142 µmol L-1. In addition, anion binding abilities of AntUr-AzClx against various anions such Cr2O7 2-, HCO3 -, CO3 2-, NO3 -, SO3 2-, SO4 2-, N3 -, F-, and I- demonstrated that AntUr-AzClx enables selective and highly sensitive detection of the Cr2O7 2- anion with an excellent LOD of 4.182 nmol L-1 in DMF/PBS (1/1, v/v; pH: 7.05). Furthermore, the calix[4]triazacrown-5-derived fluorescence chemosensor displayed a significant sensing behavior to detect the presence of dichromate anions even in real samples.

Silver Nanoparticles Improve Fluorophore Photostability: Application to a Hypericin Study.

Protection against the negative effects of solar radiation involves using cosmetics with a UV filter, but visible radiation can also have negative effects. We use dietary supplements and take medications; unfortunately, many of them contain substances that degrade under the influence of visible light, which transform into chemical compounds harmful to health. Manufacturers often include information on the prohibition of exposure to sunlight on the packaging, but consumers often do not read the product leaflet. The solution to this problem may be the addition of silver particles to preparations. In the presented article, we proposed the use of silver nanoparticles to reduce the photobleaching and photoreaction of fluorophore, while increasing the fluorescence intensity. For our research, we used a compound that is particularly sensitive to radiation: hypericin.

Baicalein Targets MAPK9 to Induce Apoptosis of Hepatocellular Carcinoma Cells.

Hepatocellular carcinoma (HCC) is a significant global health concern. However, there are limited effective treatments available for it. The use of natural products in the management and treatment of HCC is gaining more attention. Baicalein is a flavonoid compound that has been reported to have antitumor activities in HCC. However, the direct binding targets of baicalein are still unknown. Therefore, we used the DNA-programmed affinity labeling method to identify the target of baicalein and validated its function in HCC cells. We set blank and competitive DNA probes as negative controls. The results showed that baicalein had 136 binding targets, of which 13 targets were differently expressed in HCC tissues. The enriched cellular process of these targets was apoptosis, which involved MAPK9. We tested the binding affinity of baicalein with MAPK9 as 89.7 nM (Kd) by surface plasmon resonance and analyzed the binding sites by virtual docking. Notably, the binding of baicalein with MAPK9 increased the protein levels of MAPK9 itself and the related downstream apoptosis signaling, triggering the apoptosis of HCC cells. However, the inhibitor of MAPK9, SP600125, blocked the baicalein-induced apoptosis, and the amounts of MAPK9 and downstream molecules were also decreased, indicating that baicalein acted through MAPK9 to induce apoptosis of HCC cells. In conclusion, we used the DNA-programmed affinity labeling method to identify the direct-binding target MAPK9 of baicalein and validated its function in baicalein-induced apoptosis of HCC cells, which would be helpful to understand and use baicalein in HCC therapy.

Regioselective photocyclodimerization of 2-anthracenecarboxylic acid through ATP hydrolysis-driven conformational change using simulation prediction-designed GroEL mutant.

GroEL, a chaperone protein responsible for peptide and denatured protein folding, undergoes substantial conformational changes driven by ATP binding and hydrolysis during folding. Utilizing these conformational changes, we demonstrated the GroEL-mediated regioselective photocyclodimerization of 2-anthracenecarboxylic acid (AC) using ATP hydrolysis as an external stimulus. We designed and prepared an optimal GroEL mutant to employ in a docking simulation that has been actively used in recent years. Based on the large difference in the motif of hydrogen bonds between AC and GroEL mutant compared with the wild-type, we predicted that GroELMEL, in which the 307‒309th amino acid residues were mutated to Ala, could alter the orientation of bound AC in GroEL. The GroELMEL-mediated photocyclodimerization of AC can be used for regioselective inversion upon ATP addition to a moderate extent.

Induction of Paraptotic Cell Death in Cancer Cells by Triptycene-Peptide Hybrids and the Revised Mechanism of Paraptosis II.

In previous work, we reported on iridium(III) (Ir(III)) complex-peptide hybrids as amphiphilic conjugates (IPH-ACs) and triptycene-peptide hybrids as amphiphilic conjugates (TPH-ACs) and found that these hybrid compounds containing three cationic KK(K)GG peptide units through C6-C8 alkyl linkers induce paraptosis II, which is one of the nonapoptotic programmed cell death (PCD) types in Jurkat cells and different from previously reported paraptosis. The details of that study revealed that the paraptosis II induced by IPH-ACs (and TPH-ACs) proceeds via a membrane fusion or tethering of the endoplasmic reticulum (ER) and mitochondria, and Ca2+ transfer from the ER to mitochondria, which results in a loss of mitochondrial membrane potential (ΔΨm) in Jurkat cells. However, the detailed mechanistic studies of paraptosis II have been conducted only in Jurkat cells. In the present work, we decided to conduct mechanistic studies of paraptosis II in HeLa-S3 and A549 cells as well as in Jurkat cells to study the general mechanism of paraptosis II. Simultaneously, we designed and synthesized new TPH-ACs functionalized with peptides that contain cyclohexylalanine, which had been reported to enhance the localization of peptides to mitochondria. We found that TPH-ACs containing cyclohexylalanine promote paraptosis II processes in Jurkat, HeLa-S3 and A549 cells. The results of the experiments using fluorescence Ca2+ probes in mitochondria and cytosol, fluorescence staining agents of mitochondria and the ER, and inhibitors of paraptosis II suggest that TPH-ACs induce Ca2+ increase in mitochondria and the membrane fusion between the ER and mitochondria almost simultaneously, suggesting that our previous hypothesis on the mechanism of paraptosis II should be revised.

In Vitro Photoselective Gene Transfection of Hepatocellular Carcinoma Cells with Hypericin Lipopolyplexes.

The lipopolyplex, a multicomponent nonviral gene carrier, generally demonstrates superior colloidal stability, reduced cytotoxicity, and high transfection efficiency. In this study, a new concept, photochemical reaction-induced transfection, using photosensitizer (PS)-loaded lipopolyplexes was applied, which led to enhanced transfection and cytotoxic effects by photoexcitation of the photosensitizer. Hypericin, a hydrophobic photosensitizer, was encapsulated in the lipid bilayer of liposomes. The preformed nanosized hypericin liposomes enclosed the linear polyethylenimine (lPEI)/pDNA polyplexes, resulting in the formation of hypericin lipopolyplexes (Hy-LPP). The diameters of Hy-LPP containing 50 nM hypericin and 0.25 µg of pDNA were 185.6 ± 7.74 nm and 230.2 ± 4.60 nm, respectively, measured by dynamic light scattering (DLS) and atomic force microscopy (AFM). Gel electrophoresis confirmed the encapsulation of hypericin and pDNA in lipopolyplexes. Furthermore, in vitro irradiation of intracellular Hy-LPP at radiant exposures of 200, 600, and 1000 mJ/cm2 was evaluated. It demonstrated 60- to 75-fold higher in vitro luciferase expression than that in nonirradiated cells. The lactate dehydrogenase (LDH) assay supported that reduced transfection was a consequence of photocytotoxicity. The developed photosensitizer-loaded lipopolyplexes improved the transfection efficiency of an exogenous gene or induced photocytotoxicity; however, the frontier lies in the applied photochemical dose. The light-triggered photoexcitation of intracellular hypericin resulted in the generation of reactive oxygen species (ROS), leading to photoselective transfection in HepG2 cells. It was concluded that the two codelivered therapeutics resulted in enhanced transfection and a photodynamic effect by tuning the applied photochemical dose.

On the discrepancy between crossovers of solubility in supercritical carbon dioxide and retention in supercritical fluid chromatography.

Various crossover phenomena are immanent to supercritical fluids due to multidirectional temperature effects in highly compressible supercritical fluid media. Solubility crossover, i.e. controversial effect of temperature on solubility at different pressures, is probably the most well-known among them. A curious discrepancy in upper crossover pressure values between solubility in supercritical carbon dioxide and retention in supercritical fluid chromatography with pure CO2 as an eluent was unexpectedly observed for several non-polar compounds on different stationary phases. In some cases, retention crossover was found to happen at pressures almost twice as high as pressures for solubility crossover for the same compound. Retention data for three solutes with known solubility crossovers: anthracene, benzoic acid and vanillin, were collected at different pressures and temperatures for several stationary phases. The existence of upper retention crossovers, i.e. such pressure values beyond which temperature increase starts decreasing retention, were registered for all solute-sorbent combinations. Using known thermodynamic models of temperature effect on retention in supercritical fluid chromatography and on solubility in supercritical carbon dioxide, possible reasoning for the observed discrepancies is discussed. Major contribution of the balance between adsorption and partition retention mechanisms in defining retention crossover values is hypothesized.

Effects of Ring Functionalization in Anthracene-Based Cyclophanes on the Binding Properties Toward Nucleotides and DNA.

Supramolecular recognition of nucleobases and short sequences is an emerging research field focusing on possible applications to treat many diseases. Controlling the affinity and selectivity of synthetic receptors to target desired nucleotides or short sequences is a highly challenging task. Herein, we elucidate the effect of substituents in the phenyl ring of the anthracene-benzene azacyclophane on the recognition of nucleoside triphosphates (NTPs) and double-stranded DNA. We show that introducing phenyl rings increases the affinity for NTPs 10-fold and implements groove and intercalation binding modes with double-stranded DNA. NMR studies and molecular modeling calculations support the ability of cyclophanes to encapsulate nucleobases as part of nucleotides.

A versatile sensor capable of ratiometric fluorescence detection of trace water and turn-on detection of Cu2+ modulating the binding interaction of a Cu(II) complex with BSA and DNA complemented by docking studies.

A fluorescent molecule, pyridine-coupled bis-anthracene (PBA), has been developed for the selective fluorescence turn-on detection of Cu2+. Interestingly, the ligand PBA also exhibited a red-shifted ratiometric fluorescence response in the presence of water. Thus, a ratiometric water sensor has been utilized as a selective fluorescence turn-on sensor for Cu2+, achieving a 10-fold enhancement in the fluorescence and quantum yield at 446 nm, with a lower detection limit of 0.358 µM and a binding constant of 1.3 × 106 M-1. For practical applications, sensor PBA can be used to detect Cu2+ in various types of soils like clay soil, field soil and sand. The interaction of the PBA-Cu(II) complex with transport proteins like bovine serum albumin (BSA) and ct-DNA has been investigated through fluorescence titration experiments. Additionally, the structural optimization of PBA and the PBA-Cu(II) complex has been demonstrated by DFT, and the interaction of the PBA-Cu(II) complex with BSA and ct-DNA has been analyzed using theoretical docking studies.

Mechanism of non-phenolic substrate oxidation by the fungal laccase Type 1 copper site from Trametes versicolor: the case of benzo[a]pyrene and anthracene.

Laccases (EC 1.10.3.2) are multicopper oxidases with the capability to oxidize diverse phenolic and non-phenolic substrates. While the molecular mechanism of their activity towards phenolic substrates is well-established, their reactivity towards non-phenolic substrates, such as polycyclic aromatic hydrocarbons (PAHs), remains unclear. To elucidate the oxidation mechanism of PAHs, particularly the activation mechanism of the sp2 aromatic C-H bond, we conducted a density functional theory investigation on the oxidation of two PAHs (anthracene and benzo[a]pyrene) using an extensive model of the T1 copper catalytic site of the fungal laccase from Trametes versicolor.

A spermine-responsive supramolecular chemotherapy system constructed from a water-soluble pillar[5]arene and a diphenylanthracene-containing amphiphile for precise chemotherapy.

Stimuli-responsive supramolecular chemotherapy, particularly in response to cancer biomarkers, has emerged as a promising strategy to overcome the limitations associated with traditional chemotherapy. Spermine (SPM) is known to be overexpressed in certain cancers. In this study, we introduced a novel supramolecular chemotherapy system triggered by SPM. The system featured pyridine salts of a diphenylanthracene derivative (PyEn) and a complementary water-soluble pillar[5]arene (WP5C5) with long alkyl chains. The diphenylanthracene unit of PyEn is effectively encapsulated within the long alkyl chains of WP5C5, resulting in a substantial reduction in the cytotoxicity of PyEn towards normal cells. The therapeutic effect of PyEn is selectively triggered intracellularly through SPM, leading to the endosomal release of PyEn and concurrent in situ cytotoxicity. This supramolecular chemotherapy system exhibits notable tumor inhibition against SPM-overexpressed cancers with reduced side effects on normal tissues. The supramolecular strategy for intracellular activation provides a novel tool with potential applications in chemotherapeutic interventions, offering enhanced selectivity and reduced cytotoxicity to normal cells.

Construction and synergistic anti-tumor study of a tumor microenvironment-based multifunctional nano-drug delivery system.

To solve the problems existing in the clinical application of hypericin (Hyp) and tirapazamine (TPZ), a nano-drug delivery system with synergistic anti-tumor functions was constructed using mesoporous silica nanoparticles (MSN) and sodium alginate (SA). The system exhibited excellent stability, physiological compatibility and targeted drug release performance in tumor tissues. In the in vitro and in vivo experiments, Hyp released from MSN killed tumor cells through photodynamic therapy (PDT). The degree of hypoxia in the tumor tissue site was exacerbated, enabling TPZ to fully exert its anti-tumor activity. Our studies suggested that the synergistic effects between the components of the nano-drug delivery system significantly improve the anti-tumor properties of Hyp and TPZ.

A series of anthracene-derived dyes for Cu2+-assisted CO sensing and bio-imaging: synthesis, performance, and mechanism.

Endogenous CO acts as an important messenger for signal transduction and therapeutic effect in the human body. Fluorescent imaging appears to be a promising method for endogenous CO recognition, but traditional luminescent probes based on Pd-complexes suffered from defects of high cost. In this work, four anthracene-derived dyes having an = N-N = group were synthesized for Cu2+-assisted CO sensing. Their molecular structure, photophysical performance and spectral response to Cu2+ and CO were analyzed in detail. The optimal probe showed good selectivity and quenching effect to Cu2+, with PLQY (photoluminescence quantum yield) decreased from 0.33 to 0.04. The quenching mechanism was found as a static quenching mechanism by forming a non-fluorescent complex with Cu2+ (stoichiometric ratio = 1:1), as revealed by single crystal, EPR (electron paramagnetic resonance), and XPS (X-ray photoelectron spectroscopy) analysis. Such quenching effect could be reversed by CO, showing recovered fluorescence, with PLQY recovered to 0.32 within 328 s. Discussion on cellular endogenous CO imaging was included as well.

Fluorescence lifetime nanothermometer based on the equilibrium formation of anthracene AIE-excimers in living cells.

The effective measurement of temperature in living systems at the nano and microscopic scales continues to be a challenge to this day. Here, we study the use of 2-(anthracen-2-yl)-1,3-diisopropylguanidine, 1, as a nanothermometer based on fluorescence lifetime measurements and its bioimaging applications. In aqueous solution, 1 is shown in aggregated form and the equilibrium between the two main aggregate types (T-shaped and π-π) is highly sensitive to the temperature. The heating of the medium shifts the equilibrium toward the formation of highly emissive T-shaped aggregates. This species shows a high fluorescence emission and a long lifetime in comparison with the π-π aggregates and the freé monomer. A linear relationship between the fluorescence lifetime and the temperature both in aqueous solution and in a synthetic intracellular buffer was found. Fluorescence lifetime imaging microscopy (FLIM) also showed a linear relationship between lifetime and temperature with an excellent sensitivity in MCF7 breast cancer cells, which opens the door for its potential use as FLIM nanothermometer in the biomedical field.

Unraveling the structure-chirality sensing relationship between achiral anthracene-based tetracationic nanotubes and nucleosides in aqueous host-guest complexation.

In biological systems, nucleosides play crucial roles in various physiological processes. In this study, we designed and synthesized four achiral anthracene-based tetracationic nanotubes (1-4) as artificial hosts and chiroptical sensors for nucleosides in aqueous media. Notably, different nanotubes exhibit varied chirality sensing on circular dichroism (CD)/circularly polarized luminescence (CPL) spectra through the host-guest complexation, which prompted us to explore the factors influencing their chiroptical responses. Through systematic host-guest experiments, the structure-chirality sensing relationship between achiral anthracene-based tetracationic nanotubes and nucleosides in the host-guest complexation was unraveled. Firstly, the CD response originates from the anthracene rings situated at the side-wall position, resulting from the right-handed (P)- or left-handed (M)-twisted conformation of the macrocyclic structure. Secondly, the CPL signal is influenced by the presence of anthracene rings at the linking-wall position, which results from intermolecular chiral twisted stacking between these anthracene rings. Therefore, these nanotubes can serve as chiroptical sensor arrays to enhance the accuracy of nucleotide recognition through principal component analysis (PCA) analysis based on the diversified CD spectra. This study provides insights for the construction of adaptive chirality from achiral nanotubes with dynamic conformational nature and might facilitate further design of chiral functional materials for several applications.

Carbohydrate-Functionalized Anthracene Carboximides as Multivalent Ligands and Bio-Imaging Agents.

Anthracene carboximides (ACIs) conjugated with gluco-, galacto- and mannopyranosides are synthesized, by glycosylation of N-hydroxyethylanthracene carboximide acceptor with glycosyl donors. Glycoconjugation of anthracene carboximide increases the aq. solubility by more than 3-fold. The glycoconjugates display red-shifted absorption and emission, as compared to anthracene. Large Stokes shift (λabs/λem=445/525 nm) and high fluorescence quantum yields (Φ) of 0.86 and 0.5 occur in THF and water, respectively. The ACI-glycosides undergo facile photodimerization in aqueous solutions, leading to the formation of the head-to-tail dimer, as a mixture of syn and anti-isomers. Solution phase and solid-state characterizations by dynamic light scattering (DLS), microscopic imaging by atomic force (AFM) and transmission electron (TEM) microscopies reveal self-assembled vesicle structures of ACI glycosides. These self-assembled structures act as multivalent glycoclusters for ligand-specific lectin binding, as evidenced by the binding of Man-ACI to Con A, by fluorescence and turbidity assays. The conjugates do not show cellular cytotoxicity (IC50) till concentrations of 50 µM with HeLa and HepG2 cell lines and are cell-permeable, showing strong fluorescence inside the cells. These properties enable the glycoconjugates to be used in cell imaging. The non-selective cellular uptake of the glycoconjugates suggests a passive diffusion through the membrane.

Photodynamic antibacterial research on hypericin-loaded PEGylated mesoporous silica delivery system.

In this study, a novel drug delivery system (MSN-PEG-Hypericin) was successfully fabricated using tetraethyl orthosilicate and 3-aminopropyltriethoxysilane as raw materials, and the PEGylation of the prepared aminated mesoporous silica and grafting of hypericin onto the carrier were further conducted to obtain MSN-PEG-Hypericin. The successful preparation of MSN-PEG-Hypericin was characterized by several physical-chemical techniques. Furthermore, the MSN-PEG-Hypericin system increased the ability of hypericin to generate reactive oxygen species (ROS) in vitro. The cytotoxicity assay and hemolysis analysis showed that MSN-PEG-Hypericin had good biocompatibility. For antibacterial studies, the irradiation time and incubation time of photodynamic therapy (PDT) for S. aureus and E. coli were respectively 8 min and 8 h, and the concentrations of hypericin were 2.5 and 5 µg/mL. The result of triphenyl tetrazolium chloride assay indicated that MSN-PEG-Hypericin had stronger photodynamic antibacterial activity than free hypericin, and S. aureus was more sensitive to PDT than E. coli, which was related to their cell structural differences. The antibacterial mechanism study indicated that the generated ROS could destroy the bacterial structures and cause bacterial death due to the leakage of the contents. The MSN-PEG-Hypericin system prepared in this study had potential application prospects in the antibacterial field.

Ultrasmall Single-Chain Nanoparticles Derived from Amphiphilic Alternating Copolymers.

The collapse or folding of an individual polymer chain into a nanoscale particle gives rise to single-chain nanoparticles (SCNPs), which share a soft nature with biological protein particles. The precise control of their properties, including morphology, internal structure, size, and deformability, are a long-standing and challenging pursuit. Herein, a new strategy based on amphiphilic alternating copolymers for producing SCNPs with ultrasmall size and uniform structure is presented. SCNPs are obtained by folding the designed alternating copolymer in N,N-dimethylformamide (DMF) and fixing it through a photocatalyzed cycloaddition reaction of anthracene units. Molecular dynamics simulation confirms the solvophilic outer corona and solvophobic inner core structure of SCNPs. Furthermore, by adjusting the length of PEG units, precise control over the mean size of SCNPs is achieved within the range of 2.8 to 3.9 nm. These findings highlight a new synthetic strategy that enables enhanced control over morphology and internal structure while achieving ultrasmall and uniform size for SCNPs.

Photodegradation enhances the toxic effect of anthracene on skin.

Anthracene, a polycyclic aromatic hydrocarbon (PAH), is a widespread environmental pollutant that poses potential risks to human health. Exposure to anthracene can result in various adverse health effects, including skin-related disorders. Photo exposure sufficiently removes the anthracene from the environment but also generates more degradation products which can be more toxic. The goal of this study was to assess the change in anthracene dermotoxicity caused by photodegradation and understand the mechanism of this change. In the present study, over 99.99% of anthracene was degraded within 24 h of sunlight exposure, while producing many intermediate products including 9,10-anthraquinone and phthalic acid. The anthracene products with different durations of photo exposure were applied to 2D and 3D human keratinocyte cultures. Although the non-degraded anthracene significantly delayed the cell migration, the cell viability and differentiation decreased dramatically in the presence of the photodegraded anthracene. Anthracene photodegradation products also altered the expression patterns of a number of inflammation-related genes in comparison to the control cells. Among these genes, il1a, il1b, il8, cxcl2, s100a9, and mmp1 were upregulated whereas the tlr4 and mmp3 were downregulated by the photodegraded anthracene. Topical deliveries of the photodegraded and non-degraded anthracene to the dorsal skin of hairless mice showed more toxic effects by the photodegraded anthracene. The 4-hour photodegradation products of anthracene thickened the epidermal layer, increased the dermal cellularity, and induced the upregulation of inflammatory markers, il1a, il1b, s100a9, and mmp1. In addition, it also prevented the production of a gap junction protein, Connexin-43. All the evidence suggested that photodegradation enhanced the toxicities of anthracene to the skin. The 4-hour photodegradation products of anthracene led to clinical signs similar to acute inflammatory skin diseases, such as atopic and contact dermatitis, eczema, and psoriasis. Therefore, the potential risk of skin irritation by anthracene should be also considered when an individual is exposed to PAHs, especially in environments with strong sunlight.

Brain-Targeted Black Phosphorus-Based Nanotherapeutic Platform for Enhanced Hypericin Delivery in Depression.

Depression is a significant global health concern that remains inadequately treated due to the limited effectiveness of conventional drug therapies. One potential therapeutic agent, hypericin (HYP), is identified as an effective natural antidepressant. However, its poor water solubility, low bioavailability, and limited ability to penetrate the brain parenchyma have hindered its clinical application. To address these shortcomings and enhance the therapeutic efficacy of HYP, it is loaded onto black phosphorus nanosheets (BP) modified with the neural cell-targeting peptide RVG29 to synthesize a nanoplatform named BP-RVG29@HYP (BRH). This platform served as a nanocarrier for HYP and integrated the advantages of BP with advanced delivery methods and precise targeting strategies. Under the influence of 808 nm near-infrared irradiation (NIR), BRH effectively traversed an in vitro BBB model. In vivo experiments validated these findings, demonstrating that treatment with BRH significantly alleviated depressive-like behaviors and oxidative stress in mice. Importantly, BRH exhibited an excellent safety profile, causing minimal adverse effects, which highlighted its potential as a promising therapeutic agent. In brief, this novel nanocarrier holds great promise in the development of antidepressant drugs and can create new avenues for the treatment of depression.