Photoinactivation of Planktonic and Biofilm Forms of Escherichia coli through the Action of Cationic Zinc(II) Phthalocyanines

Abstract

Novel water‐soluble zinc(II) phthalocyanines (ZnPc) peripherally substituted with 4‐dimethylaminopyridine (DMAP) units (ZnPc 1–2) and the corresponding quaternized derivatives (ZnPc 1 a–2 a) were synthesized and their photodynamic inactivation (PDI) efficiency against a Gram‐negative bacterium, a recombinant bioluminescent Escherichia coli strain either in planktonic or biofilm form, was investigated. The analysis of the photophysical properties revealed that the increase in the number of DMAP units on ZnPc shifted the absorption and emission band in aqueous media to the red region. The presence of multi‐positive charges on ZnPc derivatives prevented aggregation and enhances the solubility in aqueous media. The quaternized derivatives ZnPc 1 a and 2 a displayed good stability and promising efficacy to generate singlet oxygen (1O2). The affinity of the amphiphilic ZnPc 1–2 and quaternized ZnPc 1 a–2 a to planktonic bacterial cells corresponded to an average uptake of ∼106 PS molecules.CFU−1. The PDI assays conducted with planktonic cells and biofilms of E. coli show that irradiation with red or white light (150 mW.cm−2) in the presence of 20 μM of ZnPc derivatives caused an effective inactivation. ZnPc 1 a and ZnPc 2 a exhibited the highest inactivation efficiency, particularly of the planktonic form, causing a 5 log‐scale (99.99 %) reduction in bioluminescence. The inactivation factor for biofilms was 99 % (2 log). ZnPc 1 a and ZnPc 2 a can be regarded as promising photosensitizers for the photodynamic inactivation of Gram‐negative bacteria.

Selective Detection of Trinitrophenol by Amphiphilic Dimethylaminopyridine-Appended Zn(II)phthalocyanines at the Near-Infrared Region

“…Photostability, stability, photobleaching, and singlet oxygen studies were carried out as described in the literature. 32 Thin films of ZnPcs were prepared by a spin-coating method by dissolving 1 mg of compound in 200 μL, which was spin-coated on the quartz substrate. Thin films were annealed at 70 °C overnight and stored in the vacuum desiccator.…”

Antimicrobial Photodynamic Therapy in the Control of COVID-19

“…(AMD). Additionally, in the last few years, the approach has been shown to be highly effective against all types of microorganisms, such as Gram-positive and Gram-negative bacteria, fungi, parasites, and viruses [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], a group to which the causative agent of COVID-19 belongs. This broad-spectrum activity will clearly be useful in the treatment of emerging infectious diseases, such as COVID-19 [21,33].…”

Amphiphilic tricationic Zn(II)phthalocyanine provides effective photodynamic action to eradicate broad-spectrum microorganisms

“…Furthermore, tetracationic and amphiphilic phthalocyanines demonstrated to be efficient in the photoinactivation of microorganisms [54,55]. Quaternized phthalocyanines proved high PDI efficiency due to the peripheral positive charges of the ammonium groups that lead to consistent electrostatic interactions with the negative groups at the cell wall of Gram-negative bacteria [56]. In the present case, for prokaryotic cells Gram-positive bacteria were more susceptible compared to Gram-negative ones to photodynamic activity sensitized by (NCH 3 ) 3 ZnPc 3+ .…”