Improving Riparin-A Dissolution through a Laponite Based Nanohybrid

(1) Background: Riparin-A presents several pharmacological activities already elucidated, such as antimicrobial modulator, antileishmania, anxiolytic, anti-inflammatory, antinociceptive, and antioxidant. Even with important bioactive effects, the applicability of Riparin-A is limited due to its low solubility in water, impairing its dissolution in biological fluids. Thus, the objective of this study was to develop a nanohybrid based on Riparin-A and Laponite to obtain a better dissolution profile and evaluate its cytotoxic potential. (2) Methods: The formation of a hybrid system was highlighted by X-ray powder diffraction, infrared spectroscopy, and thermal analysis. Solubility, dissolution, and cytotoxicity studies were performed; (3) Results: An increase in the solubility and aqueous dissolution rate of Riparin-A was observed in the presence of clay. Diffractometric analysis of the hybrid system suggests the amorphization of Riparin-A, and thermal analyses indicated attenuation of decomposition and melting of the Riparin-A after interaction with clay. Furthermore, the nanosystem did not exhibit cytotoxic activity on normal and tumorigenic lines. (4) Conclusions: These results are promising for the development of the Riparin-A/Laponite nanosystem for therapeutic purposes, suggesting an increase in the range of possible routes of administration and bioavailability of this bioactive compound.

Changes in Optical Properties upon Dye-Clay Interaction: Experimental Evaluation and Applications

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

Adsorption-desorption of anthocyanins from jambolan (Syzygium cumini) fruit in laponite® platelets: Kinetic models, physicochemical characterization, and functional properties of biohybrids

This study aims to develop and characterize biohybrids (BH) based on anthocyanins (ACNs) from jambolan (Syzygium cumini) and laponite® (Lap). ACNs from jambolan fruit were extracted using an acidified water solution at pH 1. ACNs were recovered from extract using Lap as adsorbent between 5 °C and 40 °C. There was no significant effect (p > 0.05) of the temperature on the adsorption process of ACNs. Thus, the process was classified as physical adsorption in heterogeneous sites where ACNs were stabilized by means of van der Waals force, π - π force, and hydrogen bonding on the Lap surface. After adsorption, the BH powder appeared to have an amorphous structure and red color. However, the color changed at pH ≥ 7. In addition, the obtained BH showed antioxidant properties and high stability when exposed to visible light irradiation. This research reports new information about the valorization and application of ACNs from jambolan for food industrial applications.

Combination of adsorption and heterogeneous photo-Fenton processes for the treatment of winery wastewater

The performance of both adsorption and heterogeneous photo-Fenton processes, combined for the first time for the treatment of a real winery wastewater (WW), was evaluated under different operational conditions. A Portuguese natural Ca-smectite (Ca-Sm) was applied in both processes, however, with different purposes: (1) as an adsorbent, which reveals great capacity to retain organic acids, and (2) as catalyst support for the production of an iron-based catalyst (Fe-Sm). Both Ca-Sm and Fe-Sm materials were characterized by XRD, FTIR, low temperature N₂ adsorption isotherms, and SEM-EDX. The adsorption process was investigated under different experimental conditions, namely, different pH, adsorbent dosages, and different concentrations of the organic contaminant. The adsorption isotherm was successfully described by Jovanovich isothermal model (R² = 0.990), which predicted a maximum adsorption capacity of 161 mg C/g. Regarding to the heterogeneous photo-Fenton process, the higher TOC removal percentage obtained (78.7% - 240 min) was achieved at pH 4.0, with a H₂O₂ concentration of 98 mM and a catalyst dosage (S:L, solid:liquid ratio) corresponding to 6.00 g/L (UV-C). As a result, the combination of both treatment processes, using the optimized conditions, allowed a total TOC removal of 90%, where the initial TOC₀ (825 mg C/L) was reduced by 54%, through the adsorption process, and by 36% by means of heterogeneous photo-Fenton process [TOC₀ = 825 mg C/L (1) - TOC_f-ads = 380 mg C/L (2) - TOC_f-pF = 81 mg C/L (3)].

New Organic/Inorganic Pigments Based on Azo Dye and Aluminum-Magnesium Hydroxycarbonates with Various Mg/Al Ratios

This study set out to investigate the impact of aluminum-magnesium hydroxycarbonates (LHs) with various Mg/Al ratios on the formation of hybrid pigments. The colorants were also evaluated for their flame-retardant properties. In the first part of the study, the hybrid pigments were submitted to comprehensive characterization using time-of-flight secondary ion mass spectrometry (TOF-SIMS), ²⁷Al solid-state nuclear magnetic resonance (NMR) spectroscopy, powder X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and N₂ adsorption as well as scanning and transmission electron microscopy (SEM/STEM). The relationship between the Mg/Al ratios of the LH carriers and the formation of lake pigments was explored. The TOF-SIMS spectrum of LH modified with azo chromophore (AC) showed an intense peak for the C₁₉H₁₅O₅N₂Mg⁺ ion, confirming metal-dye interactions. Incorporation of the organic colorant into the LH host enhanced its resistance to dissolution in organic solvent (butyl acetate), as well as improving its color stability under elevated temperatures. The second part of the study evaluated the flammability of ethylene-norbornene (EN) composites, in which the pigments had been applied as colorants. Cone calorimetry revealed that addition of the organic-inorganic pigments resulted in a substantial improvement of the flame retardancy, reflected by the decreased values of the heat release rate (HRR_MAX) and total heat release parameter (THR) of the EN composites in comparison to a neat sample (unfilled EN).