The effect of silanization assisted nanoparticle hydrophobicity on emulsion stability through droplet size distribution analysis

Quercetin encapsulation and release using rapid CO2-responsive rosin-based surfactants in Pickering emulsions

Emulsion-based delivery systems are extensively employed for encapsulating functional active ingredients, protecting them from degradation, and enhancing bioavailability and release efficiency. Here, a CO2-responsive surfactant synthesized from rosin displays rapid responsiveness to CO2 at room temperature, transitioning reversibly switches between active and inactive states multiple times. The dual tertiary amines on the rosin rigid structure contributes to its CO2 sensitivity. When in its active cationic form, in conjunction with silica nanoparticles, it exhibits desired Pickering emulsification performance across various oil phases. In the Pickering emulsion loaded with quercetin, the encapsulation efficiency and loading efficiency reached 80.50% and 0.69%, respectively, with stability lasting at least 30 days. The system provides robust protection for quercetin against external factors, such as UV and heat, revealing sustained release effects. This study investigated the potential of using rosin-based CO2-responsive surfactants alongside nanoparticles to design stable Pickering emulsion systems for active substance encapsulation and sustained release.

Oleic acid decorated kraft lignin as a hydrophobic and functional filler of cellulose acetate films

The packaging industry has primarily been dominated by single-use, petrochemical-sourced plastic materials despite their short-term use. Their leakage into the ecosystem after their use poses substantial environmental concerns. As a result, compostable and renewable packaging material alternatives are garnering significant attention. Cellulose acetate is a derivative of cellulose that exhibits excellent tensile properties, transparency, melt processability, and intermediate compostability. However, its application in the food packaging industry is limited due to its hygroscopic behavior and lack of dimensional stability. This study investigated using lignin (pristine and esterified) as a functional additive of cellulose acetate. The effect of varying concentrations of pristine kraft and oleic acid functionalized lignin in the cellulose acetate matrix and its effect on the resulting film's mechanical, morphological, viscoelastic, and water barrier properties were explored. Comprehensive characterization of the thermomechanical processed lignin-cellulose acetate sheets revealed reduced moisture absorption, improved UV and moisture barrier, and enhanced tensile properties with melt processability. Overall, the studied films could have appealing properties for food and other packaging applications, thus, serving as eco-friendly and sustainable alternatives to conventional petroleum-derived packing materials.

Esterification of lignin with long chain fatty acids for the stabilization of oil-in-water Pickering emulsions

Pickering emulsions offer numerous advantages over conventional surfactant-stabilized emulsion systems, including lower loading levels and enhanced long-term stability. Through both organic and inorganic Pickering emulsifying particles exist, more efforts are being invested in devising renewable, biodegradable, and non-toxic alternatives to conventional Pickering emulsifiers. In this study, the use of lignin (unmodified and esterified) specimens as an effective alternative to conventional Pickering emulsifiers was investigated. Hexanoyl chloride, decanoyl chloride, and palmitoyl chloride esterified lignin specimens were produced and their employability as Pickering emulsifiers was studied. The effects of varying the concentrations of lignin (unmodified and esterified specimens) and pH of the dispersion medium on the stability of the produced Pickering emulsions were explored. Comprehensive characterization of the esterified lignin stabilized Pickering emulsions exhibited enhanced stability, and smaller average oil droplet size, resulting in stable Pickering emulsions with high zeta potential and better flow properties. Overall, the studied esterified lignin specimens can have appealing applications in various Pickering emulsion systems, as a nontoxic and sustainable alternative to conventional emulsifiers.

A comparison between silicone free and silicone-based emulsions: technological features and in vivo evaluation

Objective

Nowadays, the use of silicones in cosmetic formulation is still controversial, given that “natural” or “biodegradable” components are preferred. Often, the exclusion and/or the discrimination of these excipients from cosmetic field are unmotivated because all things cannot be painted with the same brush. Hence, we want to bring to light and underline the advantages of including silicones in cosmetic emulsions, refuting and debunking some myths related to their use.

Methods

Silicone‐free and silicone‐based emulsions were obtained within an easy homogenization process. Droplet size distribution was assessed by laser diffraction particle size analyser Mastersizer 2000™, and by optical microscopy. The long‐time stability profiles were investigated thanks to the optical analyser Turbiscan® Lab Expert. Diffusing wave spectroscopy (DWS) by Rheolaser Master™ and frequency sweep measurements by Kinexus® Pro Rotational Rheometer were carried out to assess a full rheological characterization. In vivo studies were carried out by the evaluation of Trans Epidermal Water Loss (TEWL) over time on healthy human volunteers. A skin feeling rating was collected from the same volunteers by questionnaire.

Results

From size distribution analysis, a better coherence of data appeared for silicone‐based emulsion, as the size of the droplets was kept unchanged after 1 month, as well as the uniformity parameter. Morphological investigation confirmed a homogenous droplet distribution for both samples. Silicones enhanced the viscosity, compactness and strength of the cream, providing a suitable stability profile both at room temperature and when heated at 40°C. The solid‐like viscoelastic behaviour was assessed in the presence of dynamic oscillatory stresses. The monitoring of TEWL over time demonstrated non‐occlusive properties of emulsions containing silicones, the values of which were comparable to the negative control. Silicone‐based emulsions gained higher scores from the volunteers in silkiness, freshness and softness features, while lower scores were obtained in greasiness compared to silicone‐free emulsions. No cases of irritation were recorded by the candidates.

Conclusion

The presence of specific silicones inside a cosmetic product improved its technological characteristics. The rheological identity and the stability feature showed the real suitability of prepared emulsion as a cosmetic product. Moreover, this study demonstrated that silicone‐based emulsions are safe for the skin and did not cause skin occlusion. Improved skin sensations are registered by potential consumers when silicones are included in the formulation.

Examining the role of salinity on the dynamic stability of Pickering emulsions

HYPOTHESIS

The effect of salinity on Pickering emulsion stability to coalescence under dynamic forces present during flow in porous media for applications including enhanced oil recovery is poorly understood. Recent work suggests the absence of significant electrostatic repulsion in brine prompts unattached particles to assemble into inter-droplet networks that increase emulsion stability. We hypothesize that emulsions stabilized by nanoparticles coated with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) will generate particle networks in brine and exhibit greater stability to coalescence than in deionized water (DI).

EXPERIMENTS

We stabilized decane-in-water emulsions with GLYMO-coated silica nanoparticles at various particle concentrations using brine and DI as the aqueous phase. We imaged the emulsions to calculate droplet diameters, then centrifuged the emulsions and weighed the volume of decane released to determine the extent of coalescence. We compared these measurements to evaluate the effect of salinity on emulsion stability.

FINDINGS

Emulsions demonstrate greater dynamic stability and smaller droplet diameters with increasing nanoparticle concentration and salinity. Controlling for differences in droplet size, we observe that brine reduces the emulsion coalescence rate by a factor of 78 ± 23 relative to DI. This difference supports and quantifies past work suggesting that unattached nanoparticles aggregate in brine and increase overall emulsion stability, whereas nanoparticles in DI remain separated.

Methyl-grafted silica nanoparticle stabilized water-in-oil Pickering emulsions with low-temperature stability

HYPOTHESIS

The viscosity of water-in-oil Pickering emulsions may dramatically increase upon cooling. The solvation of the long-chain alkyl groups grafted on the particles stabilizer is the likely cause of the strong dependence of rheological property on temperature. Thus, we hypothesize that silica nanoparticles (NPs) grafted with short-chain alkyl groups can stabilize Pickering emulsions, yielding weakly temperature-dependent rheological property.

EXPERIMENTS

Using alkyl-grafted (methyl, octyl, and octadecyl) silica NPs as emulsifiers, the rheological properties and microstructure of the water-in-oil Pickering, as well as the solvation of the silica NPs, were studied using diffusing-wave spectroscopy microrheology measurements, confocal laser scanning microscopy, and low-field nuclear magnetic resonance measurements.

FINDINGS

The use of methyl- and octadecyl-grafted silica NPs, which have almost identical optimum contact angles, to stabilize emulsions dramatically reduced the effect of cooling on the viscosity. Moreover, the emulsions stabilized by these methyl-grafted silica NPs exhibited nearly constant rheological properties as the temperature decreased from 75 to 5 °C. The nearly constant rheological properties are attributed to the nearly constant solvation in this temperature range. These materials have potential applications in the cosmetics and petroleum industries.

Utility of Pickering emulsions in improved oral drug delivery

Pickering emulsions are surfactant-free emulsions stabilized by solid particles. Their unique structure endows them with good stability, excellent biocompatibility, and environmental friendliness. Pickering emulsions have displayed great potential in oral drug delivery. Several-fold increases in the oral bioavailability or bioaccessibility of poorly soluble drugs, such as curcumin, silybin, puerarin, and rutin, were achieved by using Pickering emulsions, whereas controlled release was found for indomethacin and caffeine. The shell of the interfacial particle stabilizers provides enhanced gastrointestinal stability to the cargos in the oil core. Here, we also discuss general considerations concerning particle stabilizers and design strategies to control lipid digestion.