A comparison between silicone‐free and silicone‐based emulsions: Technological features and in vivo evaluation

Abstract

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.

In Situ Swelling Formulation of Glycerol-Monooleate-Derived Lyotropic Liquid Crystals Proposed for Local Vaginal Application

“…Before starting the analysis, the sample was placed into the instrument vial slot, where it was left to equilibrate at 37 ± 0.5 °C (operative temperature) for five minutes. The measurements were conducted for 3 h, during which time the integrated TurbiSoft software (Formulaction, L’Union, France) recorded alterations in delta-backscattering (ΔBS) and delta-transmission (ΔT) profiles as a function of time and vial height [ 48 ], ultimately determining the destabilization kinetic profile by measuring the Turbiscan stability index (TSI). TSI values were directly derived from a sophisticated formula by the software according to Equation (3), as previously reported [ 49 ]: where scan i (h) is the average of backscattering recorded at each time (i) of measurement, scan i−1 (h) is the average of backscattering for the i−1 time of measurement and H represents the sample height.…”

Olive Leaves and Citrus Peels: From Waste to Potential Resource for Cosmetic Products

“…The same protocol was performed to prepare emulsions in the presence of natural extracts. The formulations were kept at rest for 24 h at room temperature to ensure a suitable equilibration of the emulsions, and then all characterization studies were carried out as described below [33].…”

Synthesis of Vinyl-Containing Polydimethylsiloxane in An Active Medium

“…Polysiloxanes are extensively applied in many fields, including the cosmetic industry, electronics, biomedicine, artificial muscles, etc. [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Such a diversity of applications is owing to the unique properties of polysiloxanes: a wide range of working temperatures, weather resistance, inertness, hydrophobicity, chemical stability, low dielectric permittivity, etc.…”