Photoactivated cell-killing amino-based flavylium compounds

Hélder Oliveira,Iva Fernandes,Victor De Freitas,Ana Rita Pereira,Paula Araújo,Nuno Mateus,Joana Oliveira

doi:10.1038/s41598-021-01485-y

Hélder Oliveira, Iva Fernandes + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-01485-y

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Abstract

Photodynamic therapy (PDT) is a well-established therapeutic for the treatment of different diseases. The growing interest of this technique required the development of new photosensitizers with better photo-features. This work reports the study of the potential of five nature-inspired amino-based flavylium compounds with different structural features as photosensitizers towards topical PDT. In terms of dark cytotoxicity the five pigments were tested towards confluent skin cells in both fibroblasts and keratinocytes. In the range of concentrations tested (6.3–100 μM), keratinocytes were more prone to growth inhibition and the IC50 values for 5OH4′NMe2, 7NEt2st4′NMe2 and 7NEt24′NH2 were determined to be 47.3 ± 0.3 μM; 91.0 ± 0.8 μM and 29.8 ± 0.8 μM, respectively. 7NEt24′NMe2, 7NEt2st4′NMe2 and 7NEt24′NH2 showed significant fluorescence quantum yields (from 3.40 to 20.20%) and production of singlet oxygen (1O2). These latter chromophores presented IC50 values of growth inhibition of keratinocytes between 0.9 and 1.5 µM, after 10 min of photoactivation with white light. This cellular damage in keratinocyte cells upon white light activation was accompanied with the production of reactive oxygen species (ROS). It was also found that the compounds can induce damage by either type I (ROS production) or type II (singlet oxygen) PDT mechanism, although a higher cell survival was observed in the presence of 1O2 quenchers. Overall, a structure–activity relationship could be established, ranking the most important functional groups for the photoactivation efficiency as follows: C7-diethylamino > C4′-dimethylamino > C2-styryl.

Highlights

Photodynamic therapy (PDT) is a well-established therapeutic for the treatment of different diseases
While most flavylium cation no longer exist at these pH values, the introduction of amino groups in adequate positions of the 2-phenyl-1-benzopyrylium core delocalizes the positive charge of the pyrylium ring and extends the pH range of the flavylium stability to the neutral region (Fig. S5)[23]
Three compounds with 2-phenyl-1-benzopyrilium core were synthesized including 5-hydroxy-4′-(dimethylamino)-benzopyrylium (5OH4′NMe2); 7-diethylamino-4′dimethylamino-benzopyrylium (7NEt24′NMe2) and 7-diethylamino-4′-amino-benzopyrylium (7NEt24′NH2). Besides this chemical stability improvement associated with the inclusion of amino groups, another explored possible strategy to achieve colour and stability at the same time is the extension of the π conjugation of the flavylium by introducing a double bond between ring C and ring B as in 2-styryl-1-benzopyrylium

Summary

Introduction

Photodynamic therapy (PDT) is a well-established therapeutic for the treatment of different diseases. Pounds were incubated during 4 h at different concentrations (applied concentration) with HaCaT proliferating cells, they were removed and replaced with fresh medium, and after that, plates were either irradiated with white light with a total energy of 6.6 J cm−2 or maintained in the dark at room temperature during the corresponding time of irradiation.

Results

Conclusion