Stabilization of Niaouli essential oil-loaded gelatin nanofibers: characterization and in vitro evaluation

Niaouli essential oil (NEO), obtained from Melaleuca quinquenervia leaves, is a plant-derived active compound with high biological activity properties; however, its direct use is limited due to its hydrophobicity, volatility, and instability. In this study, biologically active and mechanically enhanced nanofiber-based drug delivery systems were developed by directly incorporating NEO into gelatin (G)-based electrospun nanofibers and enhancing their stability through chemical crosslinking with glutaraldehyde (GTA) vapor. In this context, electrospun nanofibers loaded with NEO concentrations of 1% (GN1), 5% (GN5), and 10% v/v (GN10). They were exposed to the vapor generated by the GTA solution for different durations (10, 30 min, 1 h, and 3 h), temperature settings (25 and 50 °C), and two different volumes (50 and 100 µL). Morphological analysis and water solubility tests were performed to determine the optimal crosslinking conditions. Subsequently, both GN1 and GN5 NEO-loaded nanofibers, crosslinked for 1 h and 3 h were comprehensively characterized in terms of morphology, chemical structure, wettability, mechanical strength, thermal stability, in vitro drug release behavior, and antimicrobial activity. Following 3 h of crosslinking, GN1_C3 nanofibers exhibited a rapid initial release (92% in ~ 120 h), while GN5_C3 nanofibers provided a slower, sustained release (75% in ~ 240 h). Biological evaluations using MTT assay, fluorescence microscopy, and SEM confirmed high cytocompatibility and effective support of L929 fibroblast adhesion and proliferation. Strong antibacterial activity was observed against S. aureus and E. coli for GN5_C3. To the best of our knowledge, this is the first study reporting the direct incorporation of NEO into electrospun nanofibers. The fabricated NEO-loaded and crosslinked nanofibers represent a platform for tissue engineering and antimicrobial applications due to their high biological and antimicrobial properties.