Evaluation of the antibacterial activity of gallic acid anchored phthalocyanine-doped silica nanoparticles towards Escherichia coli and Staphylococcus aureus biofilms and planktonic cells

In this work, we have described the synthesis of phthalocyanine complexes Zn(II) tetrakis 4-(5-formylpyridin-2-yl)oxy) phthalocyanine (2), Zn(II) tetrakis-1-butyl-4-(2-(6- (tetra-phenoxy)pyridin-3-yl) vinyl)pyridin-1-ium phthalocyanine (3) and Zn(II) tetrakis 1-butyl-5-(2-(1-butylpyridin-1-ium-4-yl)vinyl)-2-(tetra-phenoxy)pyridin-1-ium phthalocyanine (4). The effect of a varying number of charges when the Pc complexes are alone or grafted in gallic acid (GA) tagged silica nanoparticles on photodynamic antimicrobial chemotherapy (PACT) is investigated toward Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli) in both planktonic and biofilm forms. Complex 4, bearing a total of 8 cationic charges, displayed the highest activity with log CFU values of 8.60 and 6.42 against E.coli and S.aureus biofilms, respectively. The surface stability of E.coli and S.aureus biofilms in the presence of 4 and its conjugate was analysed using cyclic voltammetry. Scanning electron microscopy (SEM) and Raman spectra are also used to study the conformational and biochemical changes within biofilm upon subjecting them to PACT.

The implications of Ortho-, Meta- and Para- Directors on the In-Vitro Photodynamic Antimicrobial Chemotherapy Activity of Cationic Pyridyl-dihydrothiazole Phthalocyanines

Cationic Zn phthalocyanine complexes derived by alkylation reaction of tetra-(pyridinyloxy) phthalocyanines at the ortho, meta, and para positions to form Zn (II) Tetrakis 3-(4-(2-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (2), Zn (II) Tetrakis 3-(4-(3-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (4) and Zn (II) Tetrakis 3-(4-(4-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (6). The photophysicochemical behaviours of the Pc complexes are assessed. The meta and para-substituted complexes demonstrate high singlet oxygen quantum yields. The cationic Pcs demonstrate good planktonic antibacterial activity towards Staphylococcus aureus and Escherichia coli with the highest log reduction values of 9.29 and 8.55, respectively. The cationic complexes also demonstrate a significant decrease in the viability of in vitro biofilms after photo-antimicrobial chemotherapy at 100 µM for both Staphylococcus aureus and Escherichia coli biofilms.

Synthesis, theoretical calculations and laser flash photolysis studies of selected amphiphilic porphyrin derivatives used as biofilm photodegradative materials

Two positively charged metalloporphyrins were synthesized and theoretical studies were carried out. The complexes efficiently eradicated S. aureus and E. coli bacterial cells at 415 nm.

Detonation nanodiamonds-phthalocyanine photosensitizers with enhanced photophysicochemical properties and effective photoantibacterial activity

The nanophotosensitizers based on acetophenoxy tetrasubstituted metallophthalocyanines (MPc) and detonation nanodiamonds (DNDs) were successfully formed and their photophysicochemical properties were determined. The zinc(II)Pc and indium(III)Pc complexes along with their nanoconjugates were found to have high singlet oxygen quantum yields (0.72 - 0.84) associated with the heavy central metal effect. The ability of the functional groups present on the DNDs to bind to the bacteria cell and the improved solubility of the nanoconjugates due to DNDs resulted in effective photodynamic antimicrobial therapy (PACT) activity against S. aureus planktonic cells, with the highest log reduction of 9.72 ± 0.02 for the conjugate of InPc conjugate with DNDs after 30 min irradiation. PACT studies were investigated at a dose of 10 μg/mL for each sample. The results suggest that the readily synthesized nanoconjugates can be used as appropriate PACT agents.

A search for enhanced photodynamic activity against Staphylococcus aureus planktonic cells and biofilms: the evaluation of phthalocyanine-detonation nanodiamond-Ag nanoconjugates

The present work reports on the synthesis and characterization of novel zinc (2) and indium (3) 2-amino-4-bromophenoxy substituted phthalocyanines (Pcs) along with the self-assembled nanoconjugates formed viaπ-π stacking interaction onto detonation nanodiamonds (DNDs) to form 2@DNDs and 3@DNDs. 2@DNDs and 3@DNDs were covalently linked to chitosan-silver mediated nanoparticles (CSAg) to form 2@DNDs-CSAg and 3@DNDs-CSAg nanoconjugates. High singlet oxygen quantum yields in DMSO of 0.69 and 0.72 for Pcs alone and 0.90 and 0.92 for 2@DNDs-CSAg and 3@DNDs-CSAg, respectively, were obtained. The photodynamic antimicrobial chemotherapy (PACT) activity of both phthalocyanines and nanoconjugates was tested against planktonic cells and biofilms of S. aureus. 2@DNDs-CSAg and 3@DNDs-CSAg caused effective killing with a log reduction of 9.74. In addition, PACT studies on single-species S. aureus biofilms were carried out with log reduction values of 5.12 and 5.27 at 200 μg mL^-1 for 2@DNDs-CSAg and 3@DNDs-CSAg, respectively.

Synergistic anti-inflammatory activities of a new flavone and other flavonoids from Tephrosia hildebrandtii vatke

A new flavone, named hildeflavone (1) along with 7 other known flavonoids were isolated from the aerial parts of Tephrosia hildebrandtii Vatke. Their characterisation was based on NMR and MS data analysis. The anti-inflammatory properties of the crude extract, isolated compounds and combination of the compounds were investigated in lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs). Treatment of the LPS-stimulated PBMCs with the isolated flavonoids at a concentration of 100 µM significantly reduced the production of interleukins (IL-1β, IL-2 and IL-6), interferon-gamma (IFN-γ), granulocyte macrophage-colony stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF-α). It was also found that the combination of a flavone and flavanones exhibited remarkable synergistic anti-inflammatory effects on the production of the cytokines.