Researchers develop alternative lipid nanoparticles for skin hydration
10 Jul 2023 --- In their latest research, scientists from the Universidade Lusófona’s Research Center for Biosciences & Health Technologies in Portugal and the University of Alcalá in Spain aimed to develop solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) based on stearic acid and glyceryl distearate.
The research, published in Cosmetics, investigates blends of stearic acid, glyceryl distearate (Precirol ATO 5), Capryol 90 and Tween 80, which were probed to prepare the SLN and NLC. These lipid nanoparticles were further characterized according to particle size, polydispersity index, pH and viscosity.
Using stearic acid in SLN and NLC increases the flexibility of the lipid matrix and creates an opportunity to incorporate a higher quantity of actives. This inexpensive lipid could provide additional benefits, replenishing stratum corneum (SC), the outermost layer of the skin barrier, and fatty acids to promote skin barrier preservation.
The results of the efficacy studies demonstrated a threefold increase in hydration after applying lipid nanoparticles. The increase has been attributed to the occlusive properties of the SLN and NLC formulations, which can form a film on the skin surface with the consequent decrease in cutaneous transepidermal water loss (TEWL), which hydrates the SC.
Lipid depletion
The SC is mainly composed of ceramides, fatty acids, and cholesterol in a lipid extracellular matrix. Depletions or disturbances in the SC lipids occur because of environmental, occupational and physical factors, such as age, humidity and temperature, or contact with detergents.
In this context, a direct relationship between the severity of a skin condition and the degree of lipid imbalance in the SC has been established.
Dysregulation of the epidermal barrier function can lead to various skin diseases, which severely impact the quality of life, flag the researchers.
Accelerated and long-term stability tests were performed for 90 days and in vivo assays to evaluate safety and efficacy.
In vivo, biocompatibility tests conducted in human volunteers showed no negative impact of the formulations when applied openly or under occlusion. Efficacy studies with the most stable nanoparticles made of glyceryl distearate (Precirol ATO 5) showed increased skin hydration.
Nanoparticle potential
Studies demonstrated a triple increase in hydration.
The nanoparticles developed in this study have shown potential for cosmetic use and the blend of lipids provides good biocompatibility and moisturizing properties, according to the researchers.
Lipid nanoparticles show promising results in improving the penetration of bioactive molecules in cosmetic applications. Their hydrophobic nature facilitates their passage through this skin layer.
These nanoparticles are used more often in the cosmetic industry due to their controlled release of active substances on the skin surface. However, the release of the molecules of interest encapsulated in these nanosystems depends on the type of matrix and their location in that matrix.
SLN and NLC are particularly popular because they enable the transport of hydrophilic and lipophilic substances, have a biocompatible and biodegradable nature, increase the solubility of the incorporated compounds, display low toxicity, allow a controlled release of the actives and can be used easily in large-scale production.
According to the researchers, nanoparticle design can still be streamlined, especially to reduce formulation costs, boost stability and widen cosmetic applicability. These lipids can form a protective hydrophobic layer that reduces water loss and increases skin hydration.
Stability and compatibility
The study evidences the advantages of using Precirol ATO 5 instead of stearic acid to produce lipid nanoparticles for cutaneous applications with suitable stability, skin compatibility and moisturizing properties.
The work provides a comprehensive analysis of the stability of the developed nanoparticles over three months, filling a “critical knowledge gap” left by previous studies that either incompletely described stability results or omitted them altogether.
The lipid nanoparticles made of Precirol ATO 5 displayed superior physicochemical properties for skin applications, with a good performance in accelerated and long-term stability studies for at least one month.
Further studies need to be conducted using a quality-by-design approach to fine-tune the lipid/surfactant blend, load active compounds into these nanoparticles, and further evaluate their cosmetic benefits.
In recent regulatory developments surrounding nanoparticles for cosmetics, the EU’s Scientific Committee on Consumer Safety revised its guidance on the safety assessment of nanomaterials in cosmetics for the second time.
Meanwhile, nanoparticles like silver and zinc oxide, used in cosmetics, may have access to the brain and bypass its blood-brain barrier, which can negatively affect cellular function and brain health, finds Dr. Eugenia Valsami-Jones, chair in environmental nanoscience at the University of Birmingham, UK.
By Inga de Jong
