Photodynamic Inactivation of Antibiotic-Resistant and Sensitive Aeromonas hydrophila with Peripheral Pd(II)- vs. Zn(II)-Phthalocyanines

A dew-responsive pectin-based herbicide for enhanced photodynamic inactivation

5-aminolevulinic acid (5-ALA) has been fully demonstrated as a biodegradable, without resistance, and pollution-free pesticide. However, the lack of targeting and the poor adhesion result in a low utilization rate, limiting its practical application. Herein, a dew-responsive polymer pro-pesticide Pec-hyd-ALA was successfully synthesized by grafting 5-ALA onto the pectin (PEC) backbone via acid-sensitive acylhydrazone bonds. When the pro-pesticide is exposed to acid dew on plant surfaces at night, 5-ALA is released and subsequently converted to photosensitize (Protoporphyrin IX, PpIX)in plant cells, leading to its accumulation and promoting photodynamic inactivation (PDI). An inverted fluorescence microscope has verified the accumulation of tetrapyrrole in plant cells. In addition, the highly bio-adhesive PEC backbone effectively improved the wetting and retention of 5-ALA on leaves. The pot experiment also demonstrated the system's control effect on barnyard grass. This work provides a promising approach to improving the herbicidal efficacy of 5-ALA.

Natural Sunlight-Mediated Emodin Photoinactivation of Aeromonas hydrophila

Aeromonas hydrophila can be a substantial concern, as it causes various diseases in aquaculture. An effective and green method for inhibiting A. hydrophila is urgently required. Emodin, a naturally occurring anthraquinone compound, was exploited as a photo-antimicrobial agent against A. hydrophila. At the minimum inhibitory concentration of emodin (256 mg/L) to inactivate A. hydrophilia in 30 min, an 11.32% survival rate was observed under 45 W white compact fluorescent light irradiation. In addition, the antibacterial activity under natural sunlight (0.78%) indicated its potential for practical application. Morphological observations demonstrated that the cell walls and membranes of A. hydrophila were susceptible to damage by emodin when exposed to light irradiation. More importantly, the photoinactivation of A. hydrophila was predominantly attributed to the hydroxyl radicals and superoxide radicals produced by emodin, according to the trapping experiment and electron spin resonance spectroscopy. Finally, a light-dependent reactive oxygen species punching mechanism of emodin to photoinactivate A. hydrophila was proposed. This study highlights the potential use of emodin in sunlight-mediated applications for bacterial control, thereby providing new possibilities for the use of Chinese herbal medicine in aquatic diseases prevention.

The role and molecular mechanism of flgK gene in biological properties, pathogenicity and virulence genes expression of Aeromonas hydrophila

Aeromonas hydrophila is a highly pathogenic aquatic resident bacterium that can cause co-morbidity in aquatic animals, waterfowl, poultry, and humans. Flagellum is the motility organ of bacteria important for bacterium tissue colonization and invasion. The flgK gene encodes a flagellar hook protein essential for normal flagellar formation. In order to explore the role of flgK in A. hydrophila, a flgK gene mutant strain of A. hydrophila (∆flgK-AH) was constructed using an efficient suicide plasmid-mediated homologous recombination method, and gene sequencing confirmed successful mutation of the flgK gene. The biological properties, pathogenicity and virulence genes expression were compared. The results showed that there was no significant difference in the growth, hemolytic, and swarming abilities, but the swimming and biofilm formation abilities of ∆flgK-AH were significantly reduced and the transmission electron microscope (TEM) results showed that the ∆flgK-AH strain did not have a flagellar structure. The median lethal dose (LD50) value of the ∆flgK-AH in Carassius auratus was 1.47-fold higher than that of the wild-type strain (WT-AH). The quantitative real-time PCR results showed that only the expression level of the lapA gene was up-regulated by 1.47 times compared with the WT-AH, while the expression levels of other genes were significantly down-regulated. In conclusion, flgK gene mutant led to a decline in the pathogenicity possibly by reducing swimming and biofilm formation abilities, these biological properties might result from the down-regulated expression of flagellate and pilus-related genes.

Cobalamin (Vitamin B12) in Anticancer Photodynamic Therapy with Zn(II) Phthalocyanines

Photodynamic therapy (PDT) is a curative method, firstly developed for cancer therapy with fast response after treatment and minimum side effects. Two zinc(II) phthalocyanines (3ZnPc and 4ZnPc) and a hydroxycobalamin (Cbl) were investigated on two breast cancer cell lines (MDA-MB-231 and MCF-7) in comparison to normal cell lines (MCF-10 and BALB 3T3). The novelty of this study is a complex of non-peripherally methylpyridiloxy substituted Zn(II) phthalocyanine (3ZnPc) and the evaluation of the effects on different cell lines due to the addition of second porphyrinoid such as Cbl. The results showed the complete photocytotoxicity of both ZnPc-complexes at lower concentrations (<0.1 μM) for 3ZnPc. The addition of Cbl caused a higher phototoxicity of 3ZnPc at one order lower concentrations (<0.01 μM) with a diminishment of the dark toxicity. Moreover, it was determined that an increase of the selectivity index of 3ZnPc, from 0.66 (MCF-7) and 0.89 (MDA-MB-231) to 1.56 and 2.31, occurred by the addition of Cbl upon exposure with a LED 660 nm (50 J/cm²). The study suggested that the addition of Cbl can minimize the dark toxicity and improve the efficiency of the phthalocyanines for anticancer PDT applications.

Photodynamic Therapy

In 1903, Von Tappeiner and Jesionek [...].

The identification of polyvalent protective immunogens and immune abilities from the outer membrane proteins of Aeromonas hydrophila in fish

Among aquaculture vaccines, polyvalent vaccines (for immunoprotection against multiple bacterial species) are more efficient and can better avoid bacterial resistance and antibiotic residues in fish. Here, 15 outer membrane proteins (OMPs) of Aeromonas hydrophila were cloned and purified, and mouse antisera were prepared. Passive immunization to Carassius auratus showed that four OMPs sera (OmpW, OmpAII, P5, and AHA2685) and the entire OMPs serum held effective immunoprotection against A. hydrophila infection. Furthermore, the active immunization of four OMPs to C. auratus showed that OmpW, OmpAII, P5, and AHA2685 held effective immunoprotection against A. hydrophila, and OmpW held active cross-protection against Vibrio alginolyticus. The mechanisms of these four candidate vaccines in triggering immune responses were subsequently explored. They all could activate innate immune responses in active immunization, down-regulate (p < 0.05) the inflammation-related genes expression to reduce the inflammatory reaction induced by A. hydrophila, and down-regulate (p < 0.05) antioxidant-related factors to reduce the antioxidant reaction for bacterial infection. Noteablely, the four OMPs had protective abilities on kidney and spleen tissues of C. auratus after challenged with A. hydrophila and V. alginolyticus by histopathological observation. Collectively, our results identify OmpW as a polyvalent vaccine candidate, and OmpAII, P5, and AHA2685 as vaccine candidates against A. hydrophila infection in fish.

Palladium Phthalocyanines Varying in Substituents Position for Photodynamic Inactivation of Flavobacterium hydatis as Sensitive and Resistant Species

Antimicrobial photodynamic therapy (aPDT) has been considered as a promising methodology to fight the multidrug resistance of pathogenic bacteria. The procedure involves a photoactive compound (photosensitizer), the red or near infrared spectrum for its activation, and an oxygen environment. In general, reactive oxygen species are toxic to biomolecules which feature a mechanism of photodynamic action. The present study evaluates two clinical isolates of Gram-negative Flavobacteriumhydatis (F. hydatis): a multidrug resistant (R) and a sensitive (S) strain. Both occur in farmed fish, leading to the big production losses because of the inefficacy of antibiotics. Palladium phthalocyanines (PdPcs) with methylpyridiloxy groups linked peripherally (pPdPc) or non-peripherally (nPdPc) were studied with full photodynamic inactivation for 5.0 µM nPdPc toward both F. hydatis, R and S strains (6 log), but with a half of this value (3 log) for 5.0 µM pPdPc and only for F. hydatis, S. In addition to the newly synthesized PdPcs as a "positive control" was applied a well-known highly effective zinc phthalocyanine (ZnPcMe). ZnPcMe showed optimal photocytotoxicity for inactivation of both F. hydatis R and S. The present study is encouraging for a further development of aPDT with phthalocyanines as an alternative method to antibiotic medication to keep under control the harmful pathogens in aquacultures' farms.