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. 2022 Nov 15;14(22):4936.
doi: 10.3390/polym14224936.

Porphyrin Polymers Bearing N, N'-Ethylene Crosslinkers as Photosensitizers against Bacteria

Sofía C Santamarina  1 , Daniel A Heredia  1 , Andrés M Durantini  1 , Edgardo N Durantini  1
Affiliations

Porphyrin Polymers Bearing N, N'-Ethylene Crosslinkers as Photosensitizers against Bacteria

Sofía C Santamarina et al. Polymers (Basel). .

Abstract

The appearance of microbes resistant to antibiotics requires the development of alternative therapies for the treatment of infectious diseases. In this work two polymers, PTPPF16-EDA and PZnTPPF16-EDA, were synthesized by the nucleophilic aromatic substitution of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin and its Zn(II) complex with ethylenediamine, respectively. In these structures, the tetrapyrrolic macrocycles were N,N'-ethylene crosslinked, which gives them greater mobility. The absorption spectra of the polymers showed a bathochromic shift of the Soret band of ~10 nm with respect to the monomers. This effect was also found in the red fluorescence emission peaks. Furthermore, both polymeric materials produced singlet molecular oxygen with high quantum yields. In addition, they were capable of generating superoxide anion radicals. Photodynamic inactivation sensitized by these polymers was tested in Staphylococcus aureus and Escherichia coli bacteria. A decrease in cell viability greater than 7 log (99.9999%) was observed in S. aureus incubated with 0.5 μM photosensitizer upon 30 min of irradiation. Under these conditions, a low inactivation of E. coli (0.5 log) was found. However, when the cells were treated with KI, the elimination of the Gram-negative bacteria was achieved. Therefore, these polymeric structures are interesting antimicrobial photosensitizing materials for the inactivation of pathogens.

Keywords: antimicrobial; photodynamic inactivation; polymer; porphyrin; singlet oxygen.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Synthesis of TPPF20 and ZnTPPF20. Reagents and conditions: (a) BF3·Et2O, DCM, r.t., 40 h; (b) DDQ, DCM, r.t., 2 h, 35%; (c) Zn(CH3COO)2, DCM/methanol, 4 h, 95%.
Scheme 2
Scheme 2
Synthesis of PTPPF16-EDA and PZnTPPF16-EDA. Reagents and conditions: (a) EDA, dimethylformamide, r.t., 72 h, (b) 80 °C 4 h.
Figure 1
Figure 1
SEM images of (A) PTPPF16-EDA and (B) PZnTPPF16-EDA polymeric materials deposited as a film, scale bar 20 µm.
Figure 2
Figure 2
UV-visible absorption of (A) TPPF20 (solid line) and PTPPF16-EDA (dashed line) and (B) ZnTPPF20 (solid line) and PZnTPPF16-EDA (dashed line) in DMF.
Figure 3
Figure 3
Fluorescence emission spectra of (A) TPPF20 (solid line) and PTPPF16-EDA (dashed line) and (B) ZnTPPF20 (solid line) and PZnTPPF16-EDA (dashed line) in DMF (λexc = 424 nm).
Scheme 3
Scheme 3
Photodecomposition of DMA mediated by O2(1Δg) to produce 9,10-endoperoxide.
Figure 4
Figure 4
First-order plots for the photooxidation of DMA sensitized by PTPPF16-EDA (▼), PZnTPPF16-EDA (▲) and ZnTMP (●) in DMF, λirr = 424 nm (0.34 mW/cm2).
Scheme 4
Scheme 4
Reduction of NBT mediated by O2•− to produce diformazan.
Figure 5
Figure 5
Detection of O2•− by the NBT method as an increase in the absorption at 560 nm sensitized by PTPPF16-EDA (▼) and PZnTPPF16-EDA (▲) in DMF irradiated with white light (44 mW/cm2), [NBT] = 0.2 mM and [NADH] = 0.5 mM. Control of NBT + NADH without PS (●).
Figure 6
Figure 6
Survival of S. aureus (~107 CFU/mL) treated with 0.5 µM (▼) PTPPF16-EDA and (▲) PZnTPPF16-EDA for 30 min at 37 °C in the dark and irradiated with white light (90 mW/cm2) for different times. Irradiated control: culture without PS (●) (* p < 0.05 compared with control).
Figure 7
Figure 7
Survival of E. coli (~107 CFU/mL) treated with 0.5 µM (▼) PTPPF16-EDA or (▲) PZnTPPF16-EDA for 30 min at 37 °C in the dark and irradiated with white light (90 mW/cm2) for different times. Cells incubated with 100 mM KI for 20 min at 37 °C in the dark prior to PDI treatments with (▽) PTPPF16-EDA or (△) PZnTPPF16-EDA. Irradiated controls: culture without PS (●) and culture treated with 100 mM KI without PS (O) (* p < 0.05 compared with control).
Figure 8
Figure 8
Absorption spectra of (A) PTPPF16-EDA and (B) PZnTPPF16-EDA containing 100 mM KI in DMF/10% after different irradiation times (Δt = 10 min, solid lines) with white light (44 mW/cm2) and Lugol’s solution (dashed line). Inset: changes in absorbance at 360 nm after different irradiation times.
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