2-Hydroxychalcone as a Potent Compound and Photosensitizer Against Dermatophyte Biofilms

Abstract

Dermatophytes, fungi that cause dermatophytosis, can invade keratinized tissues in humans and animals. The biofilm-forming ability of these fungi was described recently, and it may be correlated with the long treatment period and common recurrences of this mycosis. In this study, we evaluated the anti-dermatophytic and anti-biofilm activity of 2-hydroxychalcone (2-chalcone) in the dark and photodynamic therapy (PDT)-mediated and to determine its mechanism of action. Trichophyton rubrum and Trichophyton mentagrophytes strains were used in the study. The antifungal susceptibility test of planktonic cells, early-stage biofilms, and mature biofilms were performed using colorimetric methods. Topographies were visualized by scanning electron microscopy (SEM). Human skin keratinocyte (HaCat) monolayers were also used in the cytotoxicity assays. The mechanisms of action of 2-chalcone in the dark and under photoexcitation were investigated using confocal microscopy and the quantification of ergosterol, reactive oxygen species (ROS), and death induction by apoptosis/necrosis. All strains, in the planktonic form, were inhibited after treatment with 2-chalcone (minimum inhibitory concentration (MIC) = 7.8-15.6 mg/L), terbinafine (TRB) (MIC = 0.008–0.03 mg/L), and fluconazole (FLZ) (1–512 mg/L). Early-stage biofilm and mature biofilms were inhibited by 2-chalcone at concentrations of 15.6 mg/L and 31.2 mg/L in all tested strains. However, mature biofilms were resistant to all the antifungal drugs tested. When planktonic cells and biofilms (early-stage and mature) were treated with 2-chalcone-mediated PDT, the inhibitory concentrations were reduced by four times (2–7.8 mg/L). SEM images of biofilms treated with 2-chalcone showed cell wall collapse, resulting from a probable extravasation of cytoplasmic content. The toxicity of 2-chalcone in HaCat cells showed higher IC50 values in the dark than under photoexcitation. Further, 2-chalcone targets ergosterol in the cell and promotes the generation of ROS, resulting in cell death by apoptosis and necrosis. Overall, 2-chalcone-mediated PDT is a promising and safe drug candidate against dermatophytes, particularly in anti-biofilm treatment.

Synthesis and Evaluation of the Antifungal and Toxicological Activity of Nitrofuran Derivatives

“…P. brasiliensis was kept in Fava-Netto medium at 37 °C for 96 h [ 61 ]. The strains of Trichophyton were kept in malt extract agar (malt extract (Kasvi, São José do Pinhais, Paraná, Brazil): 2%; peptone from animal tissue (Sigma-Aldrich, Milano, Italy): 2%; glucose (Synth, Diadema, São Paulo, Brazil): 2%; agar (Kasvi, São José do Pinhais, Paraná, Brazil: 2%), pH 5.7, and incubated at 28 °C for 7 days or until sporulation [ 35 , 38 ].…”

“…and 48 h ( C. neoformans ). A visual and colorimetric readout was performed with 0.03% resazurin (Sigma-Aldrich, Milano, Italy) [ 38 , 61 , 62 ]. Quality control was performed with C. krusei ATCC 6258 strains, using the drug AmB.…”

“…These mycoses affect about 20 to 25% of the world’s human population [ 8 , 37 ]. Trichophyton rubrum and T. mentagrophytes are the most prevalent [ 37 , 38 ]. The usual treatment is carried out with drugs from the family of azoles and allylamines.…”

“…The usual treatment is carried out with drugs from the family of azoles and allylamines. However, prolonged treatment time, recurrent infections, and frequent reports of resistant strains to conventional drugs are the main limitations in the treatment of these mycoses [ 38 , 39 , 40 ].…”

Nitric Oxide-Releasing Nanoparticles Are Similar to Efinaconazole in Their Capacity to Eradicate Trichophyton rubrum Biofilms

“…While typically involving the stratum corneum in healthy individuals, follicular and dermal invasion can occur in various clinical scenarios, such as immunosuppression, and can be a portal for polymicrobial infections (de Sousa Mda et al, 2015;Gupta et al, 2017;Pereira, 2021). The ability of these fungi to form biofilms has been widely studied in recent years (Costa-Orlandi et al, 2014;Brilhante et al, 2017;Costa-Orlandi et al, 2017;Danielli et al, 2017;Chen et al, 2019;Costa-Orlandi et al, 2020;Garcia et al, 2020;Bila et al, 2021). Biofilm formation by dermatophytes, especially in the setting of onychomycosis (Burkhart et al, 2002;Gupta et al, 2016;Lipner and Scher, 2019;Gupta and Foley, 2019), further complicates and limits current treatment strategies, as they are highly resistant to antimicrobials (Ramage et al, 2012).…”