Abstract
(1) Background: Acne is a widespread skin disease, especially among adolescents. Following the COVID-19 pandemic and the use of masks, the problem has been affecting a greater number of people, and the attention of the skin care beauty routine cosmetics has been focused on the “Maskne”, caused by the sebum excretion rate (SER) that stimulates microbial proliferation. (2) Methods: the present study was focused on the rheological characterization and quality assurance of the preservative system of an anti-acne serum. The biological effectiveness (cytotoxicity—skin and eye irritation—antimicrobial, biofilm eradication and anti-inflammatory activity) was evaluated in a monolayer cell line of keratinocytes (HaCaT) and on 3D models (reconstructed human epidermis, RHE and human reconstructed corneal epithelium, HCE). The Cutibacterium acnes, as the most relevant acne-inducing bacterium, is chosen as a pro-inflammatory stimulus and to evaluate the antimicrobial activity of the serum. (3) Results and Conclusions: Rheology allows to simulate serum behavior at rest, extrusion and application, so the serum could be defined as having a solid-like behavior and being pseudoplastic. The preservative system is in compliance with the criteria of the reference standard. Biological effectiveness evaluation shows non-cytotoxic and irritant behavior with a good antimicrobial and anti-inflammatory activity of the formulation, supporting the effectiveness of the serum for acne-prone skin treatment.
Highlights
Acne is a chronic pilosebaceous inflammatory disease most often, but, seen in adolescents
The increase in the shear rate influences the viscosity of the serum, which decreases as a consequence of the destruction and deformation of its internal structure
The shear thinning behaviour becomes essential for a serum during its spreading because the cosmetic should be evenly spread on the skin in order to guarantee a homogeneous and complete absorption of the product [18]
Summary
Acne is a chronic pilosebaceous inflammatory disease most often, but , seen in adolescents. The outer surface of adult skin is colonized by resident microflora, normal flora or indigenous microbiota that represents an integral part of the innate immune system. The indigenous microbiota of the skin is considered a potential source of infection, when there is a skin injury or a disruption to the skin’s normal microbiological balance [4]. The Grampositive, anaerobic, aerotolerant, bacillus-shaped C. acnes bacterium is a major resident of the human skin microbiota and the most frequent cause of opportunistic infection with an optimal growth according to skin environmental conditions, temperature ranging from 31 to 37 ◦C and pH ranging between 4.2 and 7.9 [5,6]. Microbial over-colonization in the SG and biofilm organization are involved in the inflammatory cascade interacting with Toll-like receptor (TLR) and stimulating androgen secretion. The presence of C. acnes bacteria promotes the formation of propionic and acetic acid, the release of extracellular enzymatic products such as proteases, lipases, and hyaluronidases inducing irritation, inflammation and efflux of inflammatory mediators as IL-1α and IL-8 in dermis and surrounding tissues via TLR2 [10,11]
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