Electrospun Eco-Friendly Materials Based on Poly(3-hydroxybutyrate) (PHB) and TiO₂ with Antifungal Activity Prospective for Esca Treatment

Esca is a type of grapevine trunk disease that severely affects vine yield and longevity. Phaeomoniella chlamydospora (P. chlamydospora) is one of the main fungi associated with esca. The aim of the present study was to obtain eco-friendly materials with potential antifungal activity against P. chlamydospora based on biodegradable and biocompatible poly(3-hydroxybutyrate) (PHB), nanosized TiO₂-anatase (nanoTiO₂), and chitosan oligomers (COS) by conjunction of electrospinning and electrospraying. One-pot electrospinning of a suspension of nanosized TiO₂ nanoparticles in PHB solution resulted in materials in which TiO₂ was incorporated within the fibers (design type "in"). Simultaneous electrospinning of PHB solution and electrospraying of the dispersion of nanosized TiO₂ in COS solution enabled the preparation of materials consisting of PHB fibers on which TiO₂ was deposited on the fibers' surface (design type "on"). Several methods including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), thermogravimetric analyses (TGA) and water contact angle were utilized to characterize the obtained materials. The incorporation of nanoTiO₂ in the PHB fibers, as well as nanoTiO₂ deposition onto the surface of the PHB fibers resulted in increased roughness and hydrophobicity of the obtained composite fibrous materials. Moreover, TiO₂-on-PHB fibrous material exhibited complete inhibition of fungal growth of P. chlamydospora. Therefore, the obtained eco-friendly fibrous materials based on PHB and nanoTiO₂ are promising candidates for protection against esca in agriculture.