Propolis, known for its immunological and therapeutic properties due to flavonoids and phenolic acids, has been used in alternative medicine for many years. In Ecuador, the commercialization of stingless bee honey has been increasing recently, although the physical-chemical and biological characteristics of honey from each species are unknown due to their different behaviors and diets. The objective of this research was to synthesize chitosan nanoparticles by encapsulating commercial honey (NPMC), honey (NPMA), and propolis (NPP) from Tetragonisca angustula by ionic gelation and glutaraldehyde cross-linking. The polymeric nanoparticles were structurally characterized (TGA and FT-IR), and their antimicrobial activity against E. coli and S. aureus, cytotoxicity, and controlled release were evaluated in two phases at different pH levels, one gastric (pH 1.8) and intestinal (pH 7.4). FT-IR analysis of the polymeric nanoparticles revealed the presence of hydroxyl and alkyl groups. NPMA and NPP showed characteristic vibrations of flavonoids and C=O, regardless of the molecular weight of chitosan. In the TGA, the NPMC had decomposition efficiencies of 97.22% (LMW) and 92.10% (HMW). Propolis nanoparticles achieved encapsulation efficiencies of 94.31% and 89.21%. NPPA (HMW-chitosan-based nanoparticles encapsulating propolis from stingless bees) was the most effective against S. aureus. NPPB (LMW-chitosan-based nanoparticles encapsulating propolis from stingless bees) at 10 μg/mL showed higher cytotoxicity than NPMAA (HMW-chitosan-based nanoparticles encapsulating honey from stingless bees). In summary, propolis nanoparticles maintained efficiencies above 76%, while NPMC and NPMA exhibited loading capacities greater than 27%. In contrast, formulations with high molecular weight chitosan showed slightly lower values, although these differences were not statistically significant.

Keratoconus is an eye disease that distorts the shape of the cornea. This study aimed to analyze the effect of an increase in intraocular pressure applied to eyes with different severity of keratoconus disease using patient-specific models. Finite element models of the normal eye, eye with keratoconus, and eye with keratoglobus were constructed. The loading conditions considered the intraocular pressure increment as well as their physiological intraocular pressure. The analysis was performed with distinct materials for normal and keratoconic eyes. The finite element analysis revealed differences in the three models in terms of their deformation and maximum principal stress, and differences were observed in corneal curvature and thickness. These findings could enhance research in the biomechanical area, leading to more successful treatment options and a more individualized approach in the field of practical ophthalmology. Further investigation with larger sample sizes and more precise data on eye material would allow us to evaluate whether these disparities could inform the diagnosis of keratoconus.

Chitosan (CS) is one of the most studied natural polymers in biomaterials because its extraction from the exoskeletons of crustaceans such as shrimp and crabs is not too complex or expensive. Additionally, this polysaccharide has hydroxyl and primary amino functional groups in its structure, making it particularly useful for interacting with other compounds, mainly in acidic media. Polyvinylpyrrolidone (PVP), like chitosan, has antibacterial properties and biocompatibility with living tissue, which has made these two biopolymers the object of study for the development of new materials with desired properties and in the design of drug delivery systems (DDS). Both materials can form films and gels; however, one advantage of PVP compared to CS is its solubility in water. Another essential feature of these biopolymers is their ability to form complexes with synthetic drugs and natural products, which makes them especially useful in the design of DDS. This review presents the main characteristics of these biopolymers and addresses the possibility of combining them to develop materials and DDS that provide individual characteristics to improve their physical, chemical, and biological properties.