Retinol and Oligopeptide-Loaded Lipid Nanocarriers as Effective Raw Material in Anti-Acne and Anti-Aging Therapies

Introduction

Harnessing the therapeutic potential of retinol and peptides in line with the current trend of “skin minimalism” is possible through the use of solid lipid nanoparticles (SLNs), colloidal carriers of active substances for topical application [1]. Lipid nanoparticles provide a delivery system for active compounds, increasing their bioavailability while controlling permeation and distribution in target tissues [2]. The biocompatibility and lack of toxicity of the aforementioned lipid carriers are primarily related to the structure of the lipid matrix, which undergoes enzymatic degradation to compounds naturally found in the human body [2].

Peptides used in cosmetics have a low molecular weight and are hydrophilic in nature [3]. Based on their structure and chain length, these compounds can be divided into oligopeptides, polypeptides, and proteins [4,5]. The study of Olejnik et al. [5] showed that the group of peptides used in cosmetics is also divided in terms of action and function concerning the skin–signal peptides, so-called neuropeptides, and carrier peptides. The oligopeptide (pentapeptide-18) used in the study belongs to the group of neurotransmitter inhibitor peptides, which in its action resembles the natural enkephalin pathway by affecting the reduction in acetylcholine release at the synapse in the nervous system [6,7]. Clinical studies indicate its broad anti-aging effect on the skin, including by reducing the depth of facial wrinkles [6].

Retinol, a compound from the retinoid group, shows analogous properties and structure characteristics of vitamin A [8]. Retinol is the primary biologically inactive form and must be converted to retinal and then to retinoic acid, which is the only biologically active form [9]. This process occurs in the cell and is associated with RBPs (retinoid binding proteins) [10,11]. The positive effects of retinol can be observed in all layers of the skin (collagen synthesis and regulation of sebaceous glands) [12].

The incorporation of retinol into a matrix of lipid nanoparticles may provide a solution to the problematic limitations of retinoids when they are used in cosmetic therapies. Wissing and Lasoń et al. [13,14] pointed out the contribution of solid lipid nanoparticles to the controlled release of active substances and to protecting them from chemical degradation; this includes retinol and peptides. Also emphasized are the occlusive properties of lipid nanoparticles, which increase skin hydration [15]. Ferreira et al. [16] further pointed out that retinoids delivered topically in the form of lipid nanoparticles are more stable and better tolerated by the skin. Anil and Kannan [17], on the other hand, stressed that the incorporation of peptides inside lipid nanoparticles provides better bioavailability, while Almeida et al. [18] pointed out the increased stability, prolonged release of peptides, and prevention of their degradation.

Nowadays, the cosmetic market offers many active substances dedicated to the care of aging skin, where ensuring an adequate level of hydration and effective antioxidant activity play an important role [19]. Among the most commonly used active compounds, in addition to the aforementioned retinol and peptides, are vitamin C [19,20] and glycolic acid [21]. These substances have an anti-aging effect through their antioxidant and exfoliating properties. On the other hand, in the case of acne-prone skin and skin with imperfections, chemical peels with the use of, among other components, mandelic and pyruvic acids, are considered to be the most effective. They have a beneficial effect on the regulation of the sebaceous glands, while also having an antibacterial effect, which are desired for the care of skin with acne problems [22,23].

The purpose of the study presented in this paper was to introduce the designed dispersion of lipid nanoparticles, i.e., solid lipid nanoparticles loaded with retinol and pentapeptide-18 (oligopeptide, Tyr-D-Ala-Gly-Phe-Leu), into semi-solid cosmetic preparations in the form of night face creams. The work included physicochemical characterization of the cosmetic products, and evaluation of their stability as well as their efficacy (in vivo studies). The novelty of this research lies in the combination of retinol and oligopeptide in a lipid carrier, which is a new solution unprecedented in the cosmetic market. An attempt was also made to verify the effectiveness of the anti-aging oligopeptide and the reduction in the irritant potential of retinol introduced into lipid carriers and used in anti-aging and anti-acne therapies.

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Materials

Lipid nanoparticles were produced by applying a high shear homogenization (HSH) method based on multiple emulsion (W/O/W) (Figure 1). The lipid phase (1.75 wt.%)—L-phosphatidylcholine (Sigma-Aldrich, Steinheim, Germany), Imwitor® 900 K (glyceryl monostearate; IOI Oleo GmbH, Hamburg, Germany), and hexadecyltrimethylammonium (CTAB; Chemat, Gdańsk, Poland)—was prepared first, and heated to the melting point of the lipid. The next step was to add 2.0 wt.% of retinol (DSM, Kaiseraugst, Switzerland) and then glycerol (Chempur, Piekary Śląskie, Poland). At the same time, an aqueous solution of Tween® 80 at a concentration of 3% w/w (polysorbate 80; Pol-Aura, Zawroty, Poland) was prepared with the addition of 0.1 wt.% sodium cholate (Acros Organics, Antwerp, Belgium). Leuphasyl® peptide (pentapeptide-18/Tyr-D-Ala-Gly-Phe-Leu; Lipotec, Barcelona, Spain), which was the internal aqueous phase, was added to the lipid phase (high shear homogenization, 8000 rpm/15 min–Ultra-Turrax® DI 25 Basic, IKA-Werke GmbH, Staufen im Breisgau, Germany). The final step was to add the resulting pre-emulsion to the previously prepared aqueous surfactant solution under continuous stirring.

Pawłowska, M.; Marzec, M.; Jankowiak, W.; Nowak, I. Retinol and Oligopeptide-Loaded Lipid Nanocarriers as Effective Raw Material in Anti-Acne and Anti-Aging Therapies. Life 2024, 14, 1212. https://doi.org/10.3390/life14101212

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