Optimal axial alkylpyridinium-bonded tricationic P-porphyrin in photodynamic inactivation of Escherichia coli
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Alkylpyridinium (Apy)-bonded porphyrins have received considerable attention as singlet-oxygen (1O2) sensitizers for photodynamic inactivation (PDI). It is expected that the introduction of Apy makes porphyrins water-soluble and enhances the affinity of porphyrins to DNA. Here, we focused on Apy-bonded P-porphyrins that were prepared through the modification of axial ligands of meso-tetraphenylporphyrinatophosphorus by the Apy’s group and linkers. These water-soluble porphyrins (1) were applied to sensitize the inactivation of Escherichia coli under visible-light irradiation, since there are only few 1O2 sensitizers that can efficiently inactivate E. coli at low concentrations. The PDI activities were evaluated using the half-life (T1/2 in min) of E. coli and the minimum effective concentrations ([P]) of the porphyrin sensitizers. It was found that the PDI activity towards E. coli depends on the alkyl chain length of Apy. The [P] value for E. coli was optimized to be 0.25 μM of bis[5-(3- ethyl-1-pyridinio)-3-oxapentyloxo]tetraphenylporphyrinatophosphorus dibromide chloride (1b). Since the previous results on the optimized [P] value for S. cerevisiae was 50 nM for 1b, it was found that the [P] value for E. coli was larger than that for S. cerevisiae.
KeywordsPhotoinactivation P-porphyrins Alkylpyridinium Escherichia coli
This research was supported by a Grant-in-Aid for Scientific Research (C) (16K05847) from the Japan Society for the Promotion of Science (JSPS).
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Conflict of interest
The authors declare that they have no conflict of interest.
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