A Porphyrin-Faced Zn8L6 Cage for Selective Oxidation of C(sp3)-H Bonds and Sulfides

Catalytic oxidation of benzyl C-H bonds and sulfides from fuel oils stands as an attractive proposition in the quest for clean energy, yet their simultaneous oxidation with a singular, economically friendly catalyst is not well established. In this work, the combination of a cobalt(II) porphyrin ligand with 2-pyridinecarboxaldehyde and ZnII yielded a Zn8L6 cage (Co cube). The three-dimensional conjugated structure effectively enhances energy transfer efficiency, enabling the Co cube to show a good ability to activate oxygen under light conditions for photooxidation. Moreover, this catalytic system demonstrates high selectivity for the photocatalytic oxidation of C(sp3)-H bonds and sulfides, employing the Co cube as a single component catalyst, molecular oxygen as the oxidant, and activating oxygen into 1O2 under mild reaction conditions. This provides significant insights for organic synthesis and future design of photocatalysts with complex molecular components.

Singlet oxygen production of Zn-Ag-In-S quantum dots for photodynamic treatment of cancer cells and bacteria

Zn-Ag-In-S (ZAIS) quantum dots (QDs) were synthesized with various Ag-to-In ratios and used as novel photosensitizers for photodynamic therapy (PDT) on cancer cell inhibition and bacterial sterilization, and their structural, optical, and photodynamic properties were investigated. The alloyed QDs displayed a photoluminescence quantum yield of 72% with a long fluorescence lifetime of 5.3 μs when the Ag-to-In ratio was 1:3, suggesting a good opportunity as a dual functional platform for fluorescence imaging and PDT. The ZAIS QDs were then coated with amphiphilic brush copolymer poly(maleic anhydride-alt-1-octadecene) (PMAO) before application. The 1O2 quantum yield of the ZAIS/PMAO was measured to be 8%, which was higher than previously reported CdSe QDs and comparable to some organic photosensitizers. Moreover, the ZAIS QDs showed excellent stability in aqueous and biological media, unlike organic photosensitizers that tend to degrade over time. The in vitro PDT against human melanoma cell line (A2058) and Staphylococcus aureus shows about 30% inhibition rate upon 20 min light irradiation. Cell staining images clearly demonstrated that co-treatment with ZAIS QDs and light irradiation effectively killed A2058 cells, demonstrating the potential of ZAIS QDs as novel and versatile photosensitizers for PDT in cancer and bacterial treatment, and provides useful information for future designing of QD-based photosensitizers.

Porphyrin-Schiff Base Conjugates Bearing Basic Amino Groups as Antimicrobial Phototherapeutic Agents

New porphyrin–Schiff base conjugates bearing one (6) and two (7) basic amino groups were synthesized by condensation between tetrapyrrolic macrocycle-containing amine functions and 4-(3-(N,N-dimethylamino)propoxy)benzaldehyde. This approach allowed us to easily obtain porphyrins substituted by positive charge precursor groups in aqueous media. These compounds showed the typical Soret and four Q absorption bands with red fluorescence emission (Φ_F ~ 0.12) in N,N-dimethylformamide. Porphyrins 6 and 7 photosensitized the generation of O₂(¹Δ_g) (Φ_Δ ~ 0.44) and the photo-oxidation of L-tryptophan. The decomposition of this amino acid was mainly mediated by a type II photoprocess. Moreover, the addition of KI strongly quenched the photodynamic action through a reaction with O₂(¹Δ_g) to produce iodine. The photodynamic inactivation capacity induced by porphyrins 6 and 7 was evaluated in Staphylococcus aureus, Escherichia coli, and Candida albicans. Furthermore, the photoinactivation of these microorganisms was improved using potentiation with iodide anions. These porphyrins containing basic aliphatic amino groups can be protonated in biological systems, which provides an amphiphilic character to the tetrapyrrolic macrocycle. This effect allows one to increase the interaction with the cell wall, thus improving photocytotoxic activity against microorganisms.

Recent progress in sono-photodynamic cancer therapy: From developed new sensitizers to nanotechnology-based efficacy-enhancing strategies

Many sensitizers have not only photodynamic effects, but also sonodynamic effects. Therefore, the combination of sonodynamic therapy (SDT) and photodynamic therapy (PDT) using sensitizers for sono-photodynamic therapy (SPDT) provides alternative opportunities for clinical cancer therapy. Although significant advances have been made in synthesizing new sensitizers for SPDT, few of them are successfully applied in clinical settings. The anti-tumor effects of the sensitizers are restricted by the lack of tumor-targeting specificity, incapability in deep intratumoral delivery, and the deteriorating tumor microenvironment. The application of nanotechnology-based drug delivery systems (NDDSs) can solve the above shortcomings, thereby improving the SPDT efficacy. This review summarizes various sensitizers as sono/photosensitizers that can be further used in SPDT, and describes different strategies for enhancing tumor treatment by NDDSs, such as overcoming biological barriers, improving tumor-targeted delivery and intratumoral delivery, providing stimuli-responsive controlled-release characteristics, stimulating anti-tumor immunity, increasing oxygen supply, employing different therapeutic modalities, and combining diagnosis and treatment. The challenges and prospects for further development of intelligent sensitizers and translational NDDSs for SPDT are also discussed.

Synthesis, anticancer evaluation and molecular docking studies of methotrexate's novel Schiff base derivatives against malignant glioma cell lines

Recent years have witnessed advancement in cancer research that has led to the development of improved cytotoxic therapies with reduced side effects. Methotrexate (MTX) is a commonly used anticancer drug having robust activity, but with serious side effects. Several derivatives of MTX have been reported by modification at different sites to reduce its side effects and enhance efficacy. The current work describes the development of active MTX Schiff base derivatives by treating MTX with several aldehydes viz 2-chlorobenzaldehyde, 3-nitrobenzaldehyde, 5-chloro-2-hydroxybenz-aldehyde, 2-hydroxy-5-nitrobenzaldehyde, 2-thiocarboxyaldehyde, trans-2-pentenal and glutaraldehyde. Newly synthesized derivatives were evaluated for their anticancer potential against human malignant glioma U87 (MG-U87) cell lines at different concentrations of 200 μM, 100 μM, 50 μM, 25 μM, 12.5 μm, 6.25 μm and 0 μM. MTX derivatives with 2-Chlorobenzaldehyde (IC₅₀ ∼100 μM), 2-Thiocarboxyaldehyde (IC₅₀ <200 μM) and 2- Pentenal (IC₅₀ ∼250 μM) showed much better activity at 100 µM compared to 400 µM concentration of MTX. Molecular docking studies were performed that showed a good correlation with the results obtained from in vitro experiments. The excellent agreement between molecular modeling and growth inhibition assay shows that the binding mode hypothesis is justly close to the experimentally biological values, therefore, may prove helpful for further lead optimization and clinical trials.Communicated by Ramaswamy H. Sarma.

Pre-Polymerization Enables Controllable Synthesis of Nanosheet-Based Porphyrin Polymers towards High-Performance Li-Ion Batteries

The precise regulation of nucleation growth and assembly of polymers is still an intriguing goal but an enormous challenge. In this study, we proposed a pre-polymerization strategy to regulate the assembly and growth of polymers by facilely controlling the concentration of polymerization initiator, and thus obtained two kinds of different nanosheet-based porphyrin polymer materials using tetrakis-5,10,15,20-(4-aminophenyl) porphyrin (TAPP) as the precursor. Notably, due to the π-π stacking and doping of TAPP during the preparation process, the obtained PTAPP-nanocube material exhibits a high intrinsic bulk conductivity reaching 1.49×10^-4  S m^-1 . Profiting from the large π-conjugated structure of porphyrin units, closely stacked layer structure and excellent conductivity, the resultant porphyrin polymers, as electrode materials for lithium ion batteries, deliver high specific capacity (≈650 mAh g^-1 at the current density of 100 mA g^-1 ), excellent rate performance and long-cycle stability, which are among the best reports of porphyrin polymer-based electrode materials for lithium-ion batteries, to the best of our knowledge. Therefore, such a pre-polymerization approach would provide a new insight for the controllable synthesis of polymers towards custom-made architecture and function.

Efficacy of Novel Schiff base Derivatives as Antifungal Compounds in Combination with Approved Drugs Against Candida Albicans

BACKGROUND

The increasing incidence of fungal infections, especially caused by Candida albicans, and their increasing drug resistance has drastically increased in recent years. Therefore, not only new drugs but also alternative treatment strategies are promptly required.

METHODS

We previously reported on the synergistic interaction of some azole and non-azole compounds with fluconazole for combination antifungal therapy. In this study, we synthesized some non-azole Schiff-base derivatives and evaluated their antifungal activity profile alone and in combination with the most commonly used antifungal drugs- fluconazole (FLC) and amphotericin B (AmB) against four drug susceptible, three FLC resistant and three AmB resistant clinically isolated Candida albicans strains. To further analyze the mechanism of antifungal action of these compounds, we quantified total sterol contents in FLC-susceptible and resistant C. albicans isolates.

RESULTS

A pyrimidine ring-containing derivative SB5 showed the most potent antifungal activity against all the tested strains. After combining these compounds with FLC and AmB, 76% combinations were either synergistic or additive while as the rest of the combinations were indifferent. Interestingly, none of the combinations was antagonistic, either with FLC or AmB. Results interpreted from fractional inhibitory concentration index (FICI) and isobolograms revealed 4-10-fold reduction in MIC values for synergistic combinations. These compounds also inhibit ergosterol biosynthesis in a concentration-dependent manner, supported by the results from docking studies.

CONCLUSION

The results of the studies conducted advocate the potential of these compounds as new antifungal drugs. However, further studies are required to understand the other mechanisms and in vivo efficacy and toxicity of these compounds.