A Pluronic F127/Carbopol 974P Nanogel Provides a Water-Dispersible Formulation of Duguetia stelechantha Essential Oil for Developmental Safety Assessment in Zebrafish Embryos.

Polymeric nanogels are attractive biomaterial platforms for preparing aqueous dispersions of hydrophobic bioactive compounds, including essential oils. However, incorporating chemically complex, terpene-rich oils into these polymeric systems may modify their supramolecular organization, colloidal behavior, and biological responses. Such physicochemical changes do not, by themselves, demonstrate controlled release or quantitative delivery performance. Here, we developed and characterized a Pluronic F127/Carbopol 974P nanogel incorporating a nominal concentration of 1% (w/w) Duguetia stelechantha essential oil droplets (EODs) and evaluated the developmental safety profile of the complete formulation using zebrafish (Danio rerio) embryos as a vertebrate screening model. Chemical analysis showed that EODs were dominated by sabinene (41.44%), terpinen-4-ol (17.61%), and spathulenol (9.21%). The optimized EOD-incorporated nanogel (nGDs) provided a homogeneous aqueous dispersion of the hydrophobic oil, whereas FTIR, DSC, DLS, SEM, and AFM revealed formulation-dependent differences in spectral behavior, thermal transitions, hydrodynamic parameters, dried-sample morphology, and apparent nanomechanical properties. These differences are compatible with non-covalent association and changes in polymer organization but do not establish molecular localization or a specific self-assembly mechanism. The nominal oil content should not be interpreted as an experimentally determined encapsulation efficiency or analytical loading capacity. Exposure to nGDs at 50-200 μg mL-1 induced concentration-dependent developmental toxicity, including increased mortality, altered hatching, reduced spontaneous tail coiling, cardiac impairment, and morphological abnormalities. In contrast, the oil-free polymeric matrix did not reproduce the toxicity profile observed for nGDs, indicating that the carrier alone did not account for the adverse responses induced by the complete formulation. These findings characterize the developmental safety profile of nGDs as a water-dispersible formulation designed for biological application without the addition of an organic cosolvent or another external dispersing vehicle. Without a free-EOD comparator, the results cannot determine whether formulation modified the intrinsic toxicity of the oil.