ABSTRACT
The fungus Aspergillus parasiticus is a contaminant in agricultural crops and its eradication involves the indiscriminate use of harmful synthetic pesticides. In the search for antifungal agents of natural origin, chitosan (Q) and capsaicin (C) are coupled in the form of nanoparticles (Np), which can possess a direct application under specific conditions. Due to their small size, Np can cross through the cell wall, taking the cells into a pro-oxidant environment known as "oxidative stress", which presents when the reactive oxygen species (ROS) surpass the number of antioxidants in the cell. In the present investigation, nanoparticles of chitosan (Np Q) and nanoparticles of chitosan-capsaicin (Np QC) with an average diameter of 44.8 ± 20.6 nm and 111.1 ± 14.1 nm, respectively, were synthesized, and there was a zeta potential of + 25.6 ± 0.7 mV and + 26.8 ± 6.1 mV, respectively. The effect of the concentration of Np Q (A, B, C, and D), of Np QC (A, B, C, and D), and capsaicin in a solution (control) was evaluated on the viability of the spores, the accumulation of intracellular ROS, and the morphometric changes of A. parasiticus. Acute toxicity of the Np was determined utilizing bioassays with Artemia salina, and acute phytotoxicity was evaluated in lettuce seeds (Lactuca sativa). According to ROS results, capsaicin (control) did not induce oxidative stress in the cell; otherwise, it was observed to have an elevated (p < 0.05) accumulation of ROS when the concentration of Np Q increased. For both, Np Q and Np QC, an inverse physiological pattern relating spore viability and ROS accumulation in the fungus was found; the viability of spores decreased as the ROS accumulation increased. The spore viability of A. parasiticus diminished upon increasing the concentration of chitosan (0.3−0.4 mg/mL) in the Np, while the intracellular accumulation of ROS increased proportionally to the concentration of the nanomaterials in the treatments of Np Q and Np QC. On the other hand, Np QC presented a lower (p < 0.05) toxicological effect in comparison with Np Q, which indicates that the incorporation of bioactive compounds, such as capsaicin, into nanoparticles of chitosan is a strategy that permits the reduction of the toxicity associated with nanostructured materials.
ABSTRACT
Engineering of multifunctional drug nanocarriers combining stability and good release properties remains a great challenge. In this work, natural polymers κ-carrageenan (κ-CAR) and chitosan (CS) were deposited onto olive oil nanoemulsion droplets (NE) via layer-by-layer (LbL) self-assembly to study the release mechanisms of the anti-inflammatory diflunisal (DF) as a lipophilic drug model. The nano-systems were characterized by dynamic light scattering (DLS), zeta potential (ζ-potential) measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS) and Fourier transform infrared spectroscopy (FTIR) to confirm the NE-coating with polymer layers. In addition, kinetic release studies of DF were developed by the dialysis diffusion bag technique. Mathematical models were applied to investigate the release mechanisms. The results showed that stable and suitably sized nanocapsules (~300 nm) were formed. Also, the consecutive adsorption of polyelectrolytes by charge reversal was evidenced. More interestingly, the drug release mechanism varied depending on the number of layers deposited. The nanosized systems containing up to two layers showed anomalous transport and first order kinetics. Formulations with three and four layers exhibited Case II transport releasing diflunisal with zero order kinetics. Hence, our results suggest that these polyelectrolyte nanocapsules have great potential as a multifunctional nanocarrier for drug delivery applications.
