Infections caused by invasive fungal biofilms have been widely associated with high morbidity and mortality rates, mainly due to the advent of antibiotic resistance. Moreover, fungal biofilms impose an additional challenge, leading to multidrug resistance. This fact, along with the contamination of medical devices and the limited number of effective antifungal agents available on the market, demonstrates the importance of finding novel drug candidates targeting pathogenic fungal cells and biofilms. In this context, an alternative strategy is the use of antifungal peptides (AFPs) against fungal biofilms. AFPs are considered a group of bioactive molecules with broad-spectrum activities and multiple mechanisms of action that have been widely used as template molecules for drug design strategies aiming at greater specificity and biological efficacy. Among the AFP classes most studied in the context of fungal biofilms, defensins, cathelicidins and histatins have been described. AFPs can also act by preventing the formation of fungal biofilms and eradicating preformed biofilms through mechanisms associated with cell wall perturbation, inhibition of planktonic fungal cells’ adhesion onto surfaces, gene regulation and generation of reactive oxygen species (ROS). Thus, considering the critical scenario imposed by fungal biofilms and associated infections and the application of AFPs as a possible treatment, this review will focus on the most effective AFPs described to date, with a core focus on antibiofilm peptides, as well as their efficacy in vivo, application on surfaces and proposed mechanisms of action.

Diverse peptides have been evaluated for their activity against pathogenic microorganisms. Here, five mastoparan variants were designed based on mastoparan-L, among which two (R1 and R4) were selected for in-depth analysis. Mastoparan-L (parent/control), R1, and R4 inhibited susceptible/resistant bacteria at concentrations ranging from 2 to 32 μM, whereas only R1 and R4 eradicated Pseudomonas aeruginosa biofilms at 16 μM. Moreover, the toxic effects of mastoparan-L toward mammalian cells were drastically reduced in both variants. In skin infections, R1 at 64 μM was the most effective variant, reducing P. aeruginosa bacterial counts 1000 times on day 4 post-infection. Structurally, all of the peptides showed varying levels of helicity and structural stability in aqueous and membrane-like conditions, which may affect the different bioactivities observed here. By computationally modifying the physicochemical properties of R1 and R4, we reduced the cytotoxicity and optimized the therapeutic potential of these mastoparan-like peptides both in vitro and in vivo.