Molecular and supramolecular characterization of Ni(II)/losartan hydrophobic nanoprecipitate

Synthesis of a chitosan nanoparticle suspension and its protective effects against enamel demineralization after an in vitro cariogenic challenge

Objective

Our study aims to synthesize, characterize, and determine the effects of a ChNPs suspension on human enamel after cariogenic challenge via pH-cycling.

Methodology

ChNPs were synthesized by ion gelation and characterized by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. Forty enamel blocks were divided into four groups (n=10/group): (i) ChNPs suspension; (ii) chitosan solution; (iii) 0.05% sodium fluoride (NaF) solution; and (iv) distilled water. Specimens were exposed to cariogenic challenge by cycling in demineralization solution (3 h) and then remineralized (21h) for 7 days. Before each demineralization cycle, the corresponding solutions were passively applied for 90 s. After 7 days, specimens were examined for surface roughness (Ra) and Knoop hardness (KHN) before and after the cariogenic challenge; % KHN change (variation between initial and final hardness), and surface topography by an optical profilometer. The data were analyzed by repeated-measures ANOVA, One-way ANOVA, and Tukey tests (α=0.05).

Results

TEM images showed small spherical particles with diameter and zeta potential values of 79.3 nm and +47.9 mV, respectively. After the challenge, all groups showed an increase in Ra and a decrease in KHN values. Optical profilometry indicated that ChNPs- and NaF-treated specimens showed uneven roughness interspersed with smooth areas and the lowest %KHN values.

Conclusion

The ChNPs suspension was successfully synthesized and minimized human enamel demineralization after a cariogenic challenge, showing an interesting potential for use as an oral formulation for caries prevention.

Hydrophobic Nanoprecipitates of β-Cyclodextrin/Avermectins Inclusion Compounds Reveal Insecticide Activity against Aedes aegypti Larvae and Low Toxicity against Fibroblasts

In the present work, hydrophobic nanoprecipitates (HNPs) of inclusion complexes formed between β-cyclodextrin (βCD) and the avermectins (AVMs) named eprinomectin (EPRI) and ivermectin (IVER) were synthesized and characterized, and their larvicidal activity against Aedes aegypti and human safety against fibroblasts were evaluated. Initially, thermogravimetric analysis/differential thermal analysis data revealed that inclusion increased the thermal stability of AVMs in the presence of βCD. Nuclear magnetic resonance experiments and density functional theory calculations pointed out the inclusion of the benzofuran ring of the two AVMs in the βCD cavity. Isothermal titration calorimetry experiments allowed identification of different binding constants for EPRI/βCD ( K_b = 1060) and βCD/IVER ( K_b = 1700) systems, despite the structural similarity. Dynamic light scattering titrations of AVMs' dimethyl sulfoxide solution in βCD aqueous solution demonstrated that the formed HNPs have lower sizes in the presence of βCD. Finally, the inclusion of EPRI in βCD increased its larval toxicity and reduced its human cytotoxicity, while for IVER/βCD no beneficial effect was observed upon inclusion. These results were rationalized in terms of structural differences between the two molecules. Finally, the EPRI/βCD complex has great potential as an insecticide against A. aegypti larvae with high human safety.