Resveratrol encapsulation in high molecular weight chitosan-based nanogels for applications in ocular treatments: Impact on human ARPE-19 culture cells.

Oxidative stress and inflammation play a pivotal role in ocular diseases. Resveratrol (RSV) is a natural bioactive that has recently attracted attention due to it potent antioxidant and anti-inflammatory properties. However, RSV presents poor aqueous solubility and chemical instability. Besides, effective drug delivery to the posterior segment of the eye is challenge. Nanotechnology emerges as a possible solution to improve both limitations. Here, we developed and characterized nanogels (NG) based on high molecular weight chitosan (HCS) crosslinked with sodium tripolyphosphate. The distribution size of NG presented a major population around 140 nm with a ζ-potential value of 32 ± 2 mV. TEM and AFM images showed that NG exhibited a rounded morphology. RSV encapsulation efficiency was 59 ± 1%. Photodegradation experiments showed that HCS by its own protects RSV from UV light-induced degradation. Biocompatibility assays revealed that NG were not cytotoxic neither inflammatory in human retinal pigment epithelial cells (ARPE-19), which constitutes the outer blood-retinal barrier. After cellular internalization, we report an endo-lysosomal escape of NG, which is crucial for efficient nanocarriers delivery systems. In conclusion, we envision that HCS based NG could constitute novel carriers for RSV, opening the possibility of its application in ocular diseases.

Structural characterization of nanoemulsions stabilized with sodium caseinate and of the hydrogels prepared from them by acid-induced gelation.

Hydrogels obtained by acidification with glucono-δ-lactone (GDL), starting from nanoemulsions formulated with different concentrations of sodium caseinate (1-4 wt%) or 4 wt% sodium caseinate and sucrose (2-8 wt%), were prepared with the aim of quantifying structural parameters of both, initial nanoemulsions and hydrogels after 2.5 h of GDL addition, using the Guinier-Porod (GP) or the generalized GP models. Gelation process was followed by performing in situ temperature-controlled X-ray small angle scattering experiments (SAXS) using synchrotron radiation. In nanoemulsions, the calculated radius of gyration for oil nanodroplets (Rg oil ) decreased with increasing protein concentration and for the 4 wt% protein nanoemulsion, with increasing sucrose content. Calculated values of Rg oil were validated correlating them with experimental Z-average values as measured by dynamic light scattering (DLS). For hydrogels, radii of gyration for the sphere equivalent to the hydrogel scattering object (R gsph ) were close to 3 nm while correlation distances among building blocks (R g2 ) were dependent on formulation. They increased with increasing contents of sodium caseinate and sucrose. R g2 parameter linearly correlated with hydrogel strength (G' ∞ ): a more connected nanostructure led to a stronger hydrogel.