**1. Introduction**

Fungi are ubiquitous microorganisms that can colonize several natural environments, equipped with enzymatic machinery enabling the degradation of various types of materials and matrices [1]. Members of the genus *Aspergillus*, such as *A. fumigatus* and *A. flavus*, together with *Penicillium rubens*, can be isolated from indoor environments and can colonize and damage cellulolytic substrates such as archival documents and books [2,3]. The fungi of the genus *Cladosporium* are well known as phytopathogenic microorganisms able to infect different kinds of plants [4]. *Penicillium citrinum* is recognized mainly as a citrus fruit pathogen, but occasionally it also occurs in tropical spices and cereals [5]. Other fungi, such as members of the genera *Geotrichum*, *Mucor* and *Fusarium*, can be isolated from various foods where they can release dangerous mycotoxins [6,7].

There are fungi typically from soil, such as *Purpureocillium* and *Exophiala*, and certain types of them can successfully inhabit stones and be responsible for bioweathering phenomena [1,8]. Different species, mainly belonging to the phylum Basidiomycota, are considered

**Citation:** Kapustová, M.; Granata, G.;Napoli, E.; Puškárová, A.; Buˇcková, M.; Pangallo, D.; Geraci, C. Nanoencapsulated Essential Oils with Enhanced Antifungal Activity for Potential Application on Agri-Food, Material and Environmental Fields. *Antibiotics* **2021**, *10*, 31. https://doi.org/ 10.3390/antibiotics10010031

Received: 6 November 2020 Accepted: 24 December 2020 Published: 1 January 2021

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to be wood-decay fungi such as *Pleurotus eryngii*, *Bjerkandera adusta* and *Phanerochaete chrysosporium* [9]. The wood-decay fungi can also lead to the biodeterioration of wood components commonly used in construction and may impose serious problems on building stability [10]. Finally, many of the fungi mentioned above can cause various fastidious health complications and, in some cases, also serious pathogenicity [11]. Therefore, it is necessary to implement a series of precautions for their control and inhibition on various kinds of surfaces (especially in an indoor environment) and in food processing.

Over the decades, the massive use of synthetic antifungal products induced resistance phenomena in a large number of fungal species. In this direction, the use of substances derived from plants, such as essential oils, can be considered a valid alternative that better meets the wishes of consumers increasingly oriented toward natural remedies [12]. Essential oils (EOs) are phytocomplexes obtained from aromatic plants by hydrodistillation or steam distillation. Their chemical composition is very complex due the presence of a large variety of volatile compounds, mainly terpenes. Monoterpenes and sesquiterpenes are present in the form of hydrocarbons, alcohols, aldehydes, ketones, esters, ethers, peroxides and phenols. Phenylpropane derivatives occur less frequently than the aforesaid terpenes [13]. The EO chemical composition is influenced by the geographical position, environment condition, stage of ripening and extraction technique. More than half of the essential oils from Lamiaceae family plants have good antifungal activity (minimum inhibitory concentrations (MICs) < 1000 μg/mL) [14]. As reported by Rao et al. [15], terpenes and terpenoids are known to exhibit intense antifungal activity. Their action mechanism is multitarget and does not favor the appearance of resistance fungal strains [16,17].

Unfortunately, EOs are lipophilic compounds, easily degradable by the effects of oxygen, light, moisture and temperature. Nanoencapsulation is a valid strategy to overcome these obstacles. This technology allows for the protection the essential oils from thermal and photodegradation phenomena, increasing their solubility in aqueous environments, masking their flavor and improving their bioaccessibility and bioavailability [18]. The subcellular size and relative larger surface area per unit volume enhances EO concentration in the zone where the microorganisms are preferentially located, such as water-rich phases or liquid–solid interfaces [19].

The nanocapsules, prepared by interfacial deposition of the preformed polymer (nanoprecipitation), represent an effective method to obtain robust nanosystems suitable (by a feasible scale-up process) for applications in various fields, ranging from medicine, health and agri-food to the environment [20]. In these systems, the EO is located in the inner core, surrounded by a polymeric wall.

In this study, nanocapsules based on the biodegradable and biocompatible poly(<sup>ε</sup>caprolactone) (PCL) polymer were prepared. The nanocapsules were loaded with commercial EOs of *Origanum vulgare* (OV) and *Thymus capitatus* (TC), both having known antifungal activity [21–23]. The antifungal ability of the encapsulated and free EOs were assayed against a panel of fourteen different fungi belonging to the Ascomycota and Basidiomycota phyla. These fungi are usually responsible for the biodeterioration and biodegradation of different materials and for the contamination of food, causing damage to human health.

The aim of this work is the preparation of aqueous, ecofriendly nanosuspensions with effective and broad-spectrum antifungal activity for potential applications on different natural matrices and materials.
