Inverted methoxypyridinium phthalocyanines for PDI of pathogenic bacteria

Abstract

Phthalocyanines (Pc) are photoactive molecules that can absorb and emit light in a large range of the UV-Vis spectrum with recognized potential for medical applications. Considering the biomedical applications an important limitation of these compounds is their low solubility in water. The use of suitable pyridinium groups on Pc is a good strategy to solve this drawback and to make them more effective to photoinactivate Gram-negative bacteria via a photodynamic inactivation (PDI) approach. Herein, an easy synthetic access to obtain inverted tetra- and octa-methoxypyridinium phthalocyanines (compounds 5 and 6) and also their efficiency to photoinactivate a recombinant bioluminescent strain of Escherichia coli is described. The obtained results were compared with the ones obtained when more conventional thiopyridinium phthalocyanines (compounds 7 and 8) were used. This innovative study comparing thiopyridinium and inverted methoxypyridinium moieties on cationic Pc is reported for the first time taking into account the efficiency of singlet oxygen ((1)O2) generation, water solubility and uptake properties.

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

“…Tetra‐cationic thio‐pyridinium ZnPcs were able to cause a 5.0 log of reduction on the viability of a recombinant bioluminescent strain of E. coli . Similarly, inverted tetra‐ and octa‐methoxypyridinium ZnPcs showed 4.1 log of bioluminescence emission reduction against the same recombinant bioluminescent strain of E. coli and under similar PDI conditions . Tri‐ and tetra‐cationic pyridyloxy In(III)Pc cause reductions of ∼8.5 log in E. coli .…”

“…688 nm along with a broad shoulder peak until ca . 840 nm probably due to the presence of aggregates . In addition, ZnPc 2 shows the Q‐band slightly redshifted in comparison to ZnPc 1 .…”

Antimicrobial photodynamic therapy against Staphylococcus aureus using zinc phthalocyanine and zinc phthalocyanine-integrated TiO2 nanoparticles

“…Studies in the literature have shown that cationic charges of PSs are more effective [21][22][23]. In addition, this accumulation occurs faster in microbial cells and could selectively bind to these microorganisms while PS accumulation is slow in normal mammalian cells [24].…”

Evaluation of meso-substituted cationic corroles as potential antibacterial agents

“…The results obtained with macrocycles such as porphyrins, (Alves et al 2015), phthalocyanines (Dei et al 2006, Pereira et al 2012, Ryskova et al 2013, Lourenço et al 2015, Marciel et al 2017 or porphycenes (Xavier et al 2010, RuizGonzález et al 2015, Masiera et al 2017) are particularly relevant. The discovery that positively charged PS at physiological pH values promote the photoinactivation of microbial cells, namely of antibiotic resistant Gram-negative bacteria has stimulated the development of new useful cationic PS for PDI.…”

“…(Lim et al 2012, Hwang et al 2012, Agadjanian et al 2009, Cardote et al 2012, Iglesias et al 2015, Barata et al 2013, Preuß et al 2014, Pohl et al 2014. According to that and following our interest in the development of tetrapyrrolic macrocycles with antibacterial activity, (Alves et al 2009, 2014b, Carvalho et al 2009, Costa et al 2012, Pereira et al 2012, Gomes et al 2013, Mesquita et al 2014a, b, Simões et al 2016, Lourenço et al 2015, Rocha et al 2015, Batalha et al 2015, Moura et al 2016, Castro et al 2017 we decided to synthesize the cationic corrole derivatives 2b and 3b and to study, for the first time, their efficiency in the PDI of Gram-negative bacteria. Herein, the synthesis, structural characterisation, photophysical properties (absorbance and singlet oxygen generation) and biological activity of the new cationic corroles against the naturally bioluminescent bacterium Allivibrio fischeri (A. fischeri) will be reported.…”