Potent Antimicrobial Chloroindium(III) Phthalocyanine Sensitizer Targeting Drug-Resistant Microbes: Physicochemical, Photobiological Validation and DFT Insights.

Background/

Objectives

An evaluation of the sensitizing properties of chloroindium(III) phthalocyanine complex (InPc) bearing 4-sulfonylphenoxy groups was performed.

Methods

The ability to form singlet oxygen under light exposure was assessed, and the quantum yield ΦΔ was calculated to be 0.82 ± 0.04. Under ultrasound exposure of the sensitizer (1 MHz, 3 W, 40% duty cycle), significant 1,3-diphenylisobenzofuran decomposition was observed.

Results

Moreover, the macrocycle was assigned to be a moderate-high photo- and sonostable sensitizer. Density functional theory studies supported experimental results, suggesting the InPc to be a good photochemical agent. From the global reactivity parameters analysis, it can be suggested that InPc would interact easily with electron-excess species, such as various free radicals, in the solution phase, and should also be able to interact with electrophilic species.

Conclusions

Studied InPc revealed high photodynamic antimicrobial activity and reached >4 log10 reduction in microbial growth against methicillin-resistant Staphylococcus aureus, and 4.08 ± 0.29 log10 against Candida albicans resistant to fluconazole (for dosimetry of 100 μM and 50 J/cm2). Interestingly, the photosensitizer studied was inactive against extended-spectrum β-lactamase-producing Escherichia coli.