Electrostatic binding of substituted metal phthalocyanines to enterobacterial cells: Its role in photodynamic inactivation

Abstract

The effect of ionic substituents in zinc and aluminum phthalocyanine molecules and of membrane surface charge on the interaction of dyes with artificial membranes and enterobacterial cells, as well as on photosensitization efficiency was studied. It has been shown that increasing the number of positively charged substituents enhances the extent of phthalocyanine binding to Escherichia coli cells. This, along with the high quantum yield of singlet oxygen generation, determines efficient photodynamic inactivation of Gram-negative bacteria by zinc and aluminum octacationic phthalocyanines. The effect of Ca2+ and Mg2+ cations and pH on photodynamic inactivation of enterobacteria in the presence of octacationic zinc phthalocyanine has been studied. It has been shown that effects resulting in lowering negative charge on outer membrane protect bacteria against photoinactivation, which confirms the crucial role in this process of the electrostatic interaction of the photosensitizer with the cell wall. Electrostatic nature of binding is consistent with mainly electrostatic character of dye interactions with artificial membranes of different composition. Lower sensitivity of Proteus mirabilis to photodynamic inactivation, compared to that of E. coli and Salmonella enteritidis, due to low affinity of the cationic dye to the cells of this species, was found.

Mitochondria-targeted antioxidants as highly effective antibiotics

“…To further confirm that AcrAB-TolC was a transporter for ethidium and SkQ1, we applied fluorescence correlation spectroscopy (FCS) for measuring ethidium accumulation in E. coli cells 43–45 . FCS measures fluctuations in the emission signal of a small number of fluorescent molecules diffusing into and out of the focus volume of an excitation laser.…”

The Photosensitizer Octakis(cholinyl)zinc Phthalocyanine with Ability to Bind to a Model Spike Protein Leads to a Loss of SARS-CoV-2 Infectivity In Vitro When Exposed to Far-Red LED

“…Cationic water-soluble zinc phthalocyanines with a high quantum yield of singlet oxygen production are powerful photoantimicrobials against a broad spectrum of pathogens, including enveloped viruses [13][14][15][16][17][18][19][20]. In this study, we used an octacationic derivative, octakis(cholinyl)zinc phthalocyanine (Zn-PcChol 8+ ), and LED with the emission maximum at 692 nm to inactivate infectivity of SARS-CoV-2 tested in Vero E6 cell cultures.…”

Turning Photons into Drugs: Phthalocyanine‐Based Photosensitizers as Efficient Photoantimicrobials

“…As a result of electrostatic repulsion molecules having negatively charged substituents, such as zinc octacarboxyphthalocyanine ( Φ Δ =0.57) have almost no affinity to bacterial cells. By comparison, zinc octakis(pyridiniomethyl) phthalocyanine ( Φ Δ =0.45), which has an identical central atom and a similar Φ Δ, does have photobactericidal activity, indicating that the positive charge at the macrocycle periphery crucially affects E. coli photoinactivation [51] …”