Enhanced photocatalytic and antibacterial activity of acridinium-grafted g-C3N4 with broad-spectrum light absorption for antimicrobial photocatalytic therapy

As a metal-free polymeric photocatalyst, graphitic carbon nitride (g-C₃N₄) has attracted great attention owing to its high stability and low toxicity. However, g-C₃N₄ suffers from low light harvesting ability which limits its applications in antimicrobial photocatalytic therapy (APCT). Herein, acridinium (ADN)-grafted g-C₃N₄ (ADN@g-C₃N₄) nanosheets are prepared via covalent grafting of ADN to g-C₃N₄. The obtained ADN@g-C₃N₄ exhibits a narrow optical band gap (2.12 eV) and a wide optical absorption spectrum (intensity a.u. > 0.30) ranging from ultraviolet to near-infrared region. Moreover, ADN@g-C₃N₄ would produce reactive oxygen species (ROS) under light irradiation to exert effective sterilization and biofilm elimination activities against both gram-negative and gram-positive bacteria. Molecular dynamics simulation reveals that the ADN@g-C₃N₄ may move toward, tile and insert the bacterial lipid bilayer membrane through strong van der Waals and electrostatic interaction, decreasing the order parameter of the lipid while increasing the conducive of ROS migration, inducing ADN@g-C₃N₄ with improved antimicrobial and antibiofilm performance. Moreover, ADN@g-C₃N₄ could efficiently eradicate oral biofilm on artificial teeth surfaces. This work may provide a broad-spectrum light-induced photocatalytic therapy for preventing and treating dental plaque diseases and artificial teeth-related infections, showing potential applications for intractable biofilm treatment applications. An acridinium-grafted g-C₃N₄ (ADN@g-C₃N₄) with a narrow band gap and broad-spectrum light absorption was synthesized. The narrow optical band gap and improved electrostatic interaction with bacterial lipid bilayer membrane of ADN@g-C₃N₄ strengthened the ROS generation and facilitated the diffusion of ROS to bacteria surface, leading to enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation. STATEMENT OF SIGNIFICANCE: An acridinium-grafted g-C₃N₄ (ADN@g-C₃N₄) with a narrow band gap and broad-spectrum light absorption was developed as an antimicrobial photocatalytic therapy agent. The ADN@g-C₃N₄ exhibited enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation, showing potential applications for intractable biofilm treatment.

Combinatorial delivery of doxorubicin and acridine orange by gold core silica shell nanospheres functionalized with poly(ethylene glycol) and 4-methoxybenzamide for cancer targeted therapy

Combinatorial therapies based on the simultaneous administration of multiple drugs can lead to synergistic effects, increasing the efficacy of the cancer therapy. However, it is crucial to develop new delivery systems that can increase the drugs' therapeutic selectivity and efficacy. Gold core silica shell (AuMSS) nanoparticles present physicochemical properties that allow their simultaneous application as drug delivery and imaging agents. Herein, poly(ethylene glycol) was modified with 4-methoxybenzamide and 3-(triethoxysilyl)propyl isocyanate (TPANIS) to create a novel surface functionalization capable of improving the colloidal stability and specificity of AuMSS nanospheres towards cancer cells. Moreover, a dual drug combination based on Doxorubicin (DOX) and Acridine orange (AO) was characterized and administered using the AuMSS-TPANIS nanospheres. The obtained results show that the DOX:AO drug combination can mediate a synergistic therapeutic effect in both HeLa and MCF-7 cells, particularly at the 2:1, 1:1, and 1:2 ratios. Additionally, the TPANIS functionalization increased the AuMSS nanospheres colloidal stability and selectivity towards MCF-7 cancer cells (overexpressing sigma receptors). Such also resulted in an enhanced cytotoxic effect against MCF-7 cells when administering the DOX:AO drug combination with the AuMSS-TPANIS nanospheres. Overall, the obtained results confirm the therapeutic potential of the DOX:AO drug combination as well as the targeting capacity of AuMSS-TPANIS, supporting its application in the cancer-targeted combinatorial chemotherapy.

Amino-isocyanoacridines: Novel, Tunable Solvatochromic Fluorophores as Physiological pH Probes

Amino-isocyanoacridines (ICAAcs), as first members of their class, turned out to be a novel, multifunctional acridine orange (AO) type dye family with a number of additional favorable properties. They have enhanced solvatochromic emission range, low quantum yields (ΦF = 2.9-0.4%) in water, reduced basicity (pKa = 7.05-7.58), and their optical behavior could be fine-tuned by complexation with Ag(I) ions, too. Based on both their vibronic absorption and the charge transfer bands, ICAAcs can be applied as stable pH-probes with great precision (2-3% error) in the physiological pH range of 6-8 using UV-vis and fluorescence detection. The dyes are also able to sense pH change in different microenvironments, such as the Stern layer, as it was demonstrated on sodium lauryl sulfate micelles. The optical behavior of the ICAAc derivatives is discussed based on high-level quantum chemical calculations. All three dyes are well-applicable with conventional epifluorescence imaging. Furthermore, at the blue excitation, diMICAAc is optimally suited as a whole-cell probe for both the conventional microscopic and the laser-illumination studies, like flow- and imaging cytometric, or confocal laser-scanning microscopic examinations.

To Loop or Not to Loop: Influence of Hinge Flexibility on Self-Assembly Outcomes for Acridine-Based Triazolylpyridine Chelates with Zinc(II), Iron(II), and Copper(II)

Coordination-driven self-assembly has been established as an effective strategy for the efficient construction of intricate architectures in both natural and artificial systems, for applications ranging from gene regulation to metal-organic frameworks. Central to these systems is the need for carefully designed organic ligands, generally with rigid components, that can undergo self-assembly with metal ions in a predictable manner. Herein, we report the synthesis and study of three novel organic ligands that feature 3,6-disubstituted acridine as a rigid spacer connected to two 2-(1,2,3-triazol-4-yl)pyridine "click" chelates through hinges of the same length but differing flexibility. The flexibility of these "three-atom" hinges was modulated by i) moving from secondary to tertiary amide functional groups and ii) replacing an sp² amide carbon with an sp³ methylene carbon. In an effort to understand the role of hinge flexibility in directing self-assembly into mononuclear loops or dinuclear cylinders, the impact of these changes on self-assembly outcomes with zinc(II), iron(II), and copper(II) ions is described.

Excimer Emission of Acridine Orange Adsorbed on Gadolinium-Yttrium Orthovanadate Nanoparticles

Studying the complexes of inorganic nanoparticles - organic dye molecules is of great importance for their theranostics application. In this paper, we report gadolinium-yttrium orthovanadate nanoparticles (VNPs) - Acridine Orange (AO) complex formation in water solutions. To study the interactions between VNPs and AO, the methods of steady-state and time-resolved spectroscopy were used. It was shown that in aqueous solutions containing VNPs, AO aggregation takes place with a sandwich-like stacking of AO molecules in the near-surface layer of VNPs. The VNPs-AO complex formation causes significant changes in the AO fluorescence spectrum, namely, the appearance of a new broad, structureless band in the long-wavelength spectral edge, which was not observed in AO spectrum in a pure water solution. By analyzing of the absorption, fluorescence excitation spectra and fluorescence decay, the static excimer origin of the long-wavelength fluorescence band has been established.

Synthesis, spectroscopic studies and biological evaluation of acridine derivatives: The role of aggregation on the photodynamic efficiency

Two new photoactive compounds (1 and 2) derived from the 9-amidoacridine chromophore have been synthesized and fully characterized. Their abilities to produce singlet oxygen upon irradiation have been compared. The synthesized compounds show very different self-aggregating properties since only 1 present a strong tendency to aggregate in water. Biological assays were conducted with two cell types: hepatoma cells (Hep3B) and human umbilical vein endothelial cells (HUVEC). Photodynamic therapy (PDT) studies carried out with Hep3B cells showed that non-aggregating compound 2 showed photoxicity, ascribed to the production of singlet oxygen, being aggregating compound 1 photochemically inactive. On the other hand suspensions of 1, characterized as nano-sized aggregates, have notable antiproliferative activity towards this cell line in the dark.

Valproic Acid Induces Endocytosis-Mediated Doxorubicin Internalization and Shows Synergistic Cytotoxic Effects in Hepatocellular Carcinoma Cells

Valproic acid (VPA), a well-known histone deacetylase (HDAC) inhibitor, is used as an anti-cancer drug for various cancers, but the synergistic anti-cancer effect of VPA and doxorubicin (DOX) combination treatment and its potential underlying mechanism in hepatocellular carcinoma (HCC) remain to be elucidated. Here, we evaluate the mono- and combination-therapy effects of VPA and DOX in HCC and identify a specific and efficient, synergistic anti-proliferative effect of the VPA and DOX combination in HCC cells, especially HepG2 cells; this effect was not apparent in MIHA cells, a normal hepatocyte cell line. The calculation of the coefficient of drug interaction confirmed the significant synergistic effect of the combination treatment. Concurrently, the synergistic apoptotic cell death caused by the VPA and DOX combination treatment was confirmed by Hoechst nuclear staining and Western blot analysis of caspase-3 and poly (ADP-ribose) polymerase (PARP) activation. Co-treatment with VPA and DOX enhanced reactive oxygen species (ROS) generation and autophagy, which were clearly attenuated by ROS and autophagy inhibitors, respectively. Furthermore, as an indication of the mechanism underlying the synergistic effect, we observed that DOX internalization, which was induced in the VPA and DOX combination-treated group, occurred via by the caveolae-mediated endocytosis pathway. Taken together, our study uncovered the potential effect of the VPA and DOX combination treatment with regard to cell death, including induction of cellular ROS, autophagy, and the caveolae-mediated endocytosis pathway. Therefore, these results present novel implications in drug delivery research for the treatment of HCC.