Application of biophysical and skin imaging techniques to evaluate the film‐forming effect of cosmetic formulations

Evaluation of the hydrating benefits of a cationic hyaluronic acid: From biological evaluation to consumer home use trial

Active ingredients are often assessed based on physiological measurements, but innovative technologies to measure skin sensations can provide a holistic volunteer assessment of the use of an ingredient. In this paper, the hydrating benefits of a cationic hyaluronic acid (HA) were evaluated alongside clinical biometrics and innovative cognitive measurements to determine how biological benefits correlated with volunteers' feelings and perceptions of hydration. The results demonstrated that cationic HA provides hydrating benefits at the clinical level due to its film-forming properties. Through the use of innovative behavioural measurement tools, we were able to show that these outcomes are perceived by naïve consumers in real-life conditions. In addition, the benefits of cationic HA reported by users were in accordance with the mental representation they had related to the use of HA, thus the product achieved complete sensorial embodiment. We can conclude that the combination of clinical evaluations and home use trials consolidates product assessment when seeking to measure consumer satisfaction with proven biological benefits.

Development and Efficacy Evaluation of Innovative Cosmetic Formulations with Caryocar brasiliense Fruit Pulp Oil Encapsulated in Freeze-Dried Liposomes

Encapsulation and drying technologies allow the engineering of innovative raw materials from plant biodiversity, with potential applications in pharmaceutical and cosmetic fields. Lipid-based nanoencapsulation stands out for its efficiency, ease of production, and versatility in encapsulating substances, whether hydrophilic or lipophilic. This work aimed at encapsulating pequi oil in liposomes and freeze-dried liposomes to enhance its stability and functional benefits, such as skin hydration and anti-aging effects, for use in innovative cosmetic formulations. Pequi oil-extracted from the Caryocar brasiliense fruit pulp, a plant species from Brazilian plant biodiversity-is rich in secondary metabolites and fatty acids. Liposomes and dried liposomes offer controlled production processes and seamless integration into cosmetic formulations. The physicochemical analysis of the developed liposomes confirmed that the formulations are homogeneous and electrokinetically stable, as evidenced by consistent particle size distribution and zeta potential values, respectively. The gel-type formulations loaded with the dried liposomes exhibit enhanced skin hydration, improved barrier function, and refined microrelief, indicating improvements in skin conditions. These results highlight the potential of dried liposomes containing pequi oil for the development of innovative cosmeceutical products. This research contributes to the valorization of Brazilian biodiversity by presenting an innovative approach to leveraging the dermatological benefits of pequi oil in cosmetic applications.

Methods for skin image analysis and their applications in dermatology and cosmetic research: a comprehensive review

INTRODUCTION

In recent years, several non-invasive imaging methods have been introduced to facilitate studies in dermatology and cosmetic research, almost completely replacing invasive methods such as biopsy. Imaging devices have proven to be useful tools in skin analysis and therapy monitoring. This review aimed to investigate the most recent studies in cosmetic dermatology the imaging technology and methods that are being used to assess skin characteristics and summarize its fundamentals, possible applications, advantages, and limitations, and to give a future perspective to the clinical trials.

EVIDENCE ACQUISITION

For that, a literature review was carried out in the main scientific database platforms and the studies associating skin image analysis with dermatology and cosmetic research were selected and discussed.

EVIDENCE SYNTHESIS

It was possible to infer that skin image analyses are not only practical and effective, but have also become increasingly essential for the skin sciences. The in vivo and real-time image analyses allow a more complete evaluation and the follow-up of the same region for different periods. It was also possible to observe that macroscopic, microscopic, and mesoscopic imaging methods are complementary, allowing different approaches in the same study.

CONCLUSIONS

These technologies are expected to evolve more and more quickly in the near future.

Film-Forming, Moisturizing, and Sensory Properties of a Cosmetic Formulation Containing Tara Gum and Brazilian Berry Extracts

The development of cosmetic formulations with moisturizing and film-forming properties has been very important to help keep skin physiology and protection. In this context, this study aimed to develop a cosmetic formulation containing Tara gum and Brazilian berry extract and evaluate its physical-mechanical, film-forming, and sensory properties. A gel formulation was developed based on Tara gum added to Plinia cauliflora extract and was characterized by its spreadability profile and sensory properties. A clinical study was carried out with ten participants to evaluate the skin microrelief, stratum corneum water content, transepidermal water loss (TEWL), and skin morphological characteristics by reflectance confocal microscopy (RCM) before and after 2 h of application of the formulations. The formulation with Brazilian berry significantly decreased the work of shear parameter, which can be correlated with improved spreadability in the sensory analysis. The clinical study showed that both formulations improved skin hydration and reduced the TEWL. The RCM imaging analysis showed the visible film on the skin surface, a decrease in the size of furrows, an increase in the reflectance of the interkeratinocytes, and reflectance of the stratum corneum for both formulations. These results were more pronounced for the formulation containing Brazilian berry. The Tara gum in the gel formulation promoted the formation and visualization of a polymeric net on the stratum corneum surface, demonstrated by the images obtained from RCM. However, the formulation added with the Brazilian berry extract improved the skin microrelief, honeycomb pattern of the epidermis, and skin hydration in deeper layers of the epidermis.

In vivo transepidermal water loss: Validation of a new multi-sensor open chamber water evaporation system Tewameter TM Hex

BACKGROUND

Instrumentation technology for transepidermal water loss measurements has not been substantially modified since its introduction by Nilsson in 1977. Recent progress in sensor development allowed a new sensor arrangement using a matrix of 30 sensors. Raw measurement values are processed with spatial statistical analysis. We aimed to compare the new, multi-sensor probe (Tewameter TM Hex) with the established Tewameter TM 300 probe and to gain reference data for the new parameters of transepidermal energy loss and water vapor concentration on skin.

MATERIAL AND METHODS

Baseline measurements and repeated measurements on the volar forearm and assessment on eight different anatomical locations were performed on 24 healthy volunteers (both gender) with the TM Hex and the TM 300.

RESULTS

A significant correlation (p < 0.001; R-coefficient = 0.9) between TM Hex and the TM 300 with a low coefficient of variance (CV) 11% for TM Hex and 19% for TM 300, could be assessed. The CV ranged between 7% (right inner upper arm) and 14% (palms). Average transepidermal heat loss ranged from 12 W/m2 on the lower leg to 38.8 W/m2 on the palm.

CONCLUSION

The correlation between TM Hex and TM 300 along with the robustness of the measurements with the TM Hex shows that the new probe for assessment of epidermal barrier function is comparable to the TM 300. In most conditions, TM Hex provides more accurate measurements than TM 300. New parameters open the field to studying skin's water and energy balance.

Development of multifunctional sunscreens: Evaluation of physico-mechanical and film-forming properties

The exposome consists of several factors such as solar radiation and pollution, which can provoke skin damage and lead to premature skin aging. Thus, the use of multifunctional sunscreens is critical in order to prevent this damage. In addition, film formation is very important to reach the expected SPF. Within this context, the objective of the present study was to develop and evaluate the in vivo SPF, sensory, physico-mechanical, and film-forming properties of sunscreens containing a biopolymer from Tara and red algae. A clinical study of the film-forming effect and of skin hydration was performed by instrumental measurements and by biophysical and skin imaging techniques. The SPF of both formulations, with or without the biopolymer, was 45.6. This result was 10.09% higher than expected. higher than expected. However, the sunscreen added to the biopolymer showed better sensory and texture properties, significantly increased skin hydration and reduced transepidermal water loss. The film-forming property was observed by the analysis of Reflectance Confocal Microscopy images 2, 4, and 6 h after formulation application, and this result was more pronounced for the sunscreen added to the biopolymer. Thus, the film-forming property of the biopolymer was important for prolonging the skin barrier function due to film formation and to obtain more effective and multifunctional sunscreens that provide longer protection.

Evaluation of Morphological and Structural Skin Alterations on Diabetic Subjects by Biophysical and Imaging Techniques

Diabetes causes increased production of advanced glycation end products (AGEs), which may lead to irreversible damage to collagen fibers, and early and more accentuated signs of skin aging. Thus, the objective of this study was to evaluate diabetic skin's mechanical and morphological characteristics and compare these to healthy skin. Twenty-eight female participants aged between 39 and 55 years were enrolled: half had type 2 diabetes, and the others were healthy. Wrinkles, transepidermal water loss (TEWL), stratum corneum water content, skin color, elasticity, morphological and structural characteristics of epidermis and dermis echogenicity were evaluated using biophysical and skin imaging techniques. Higher TEWL values were observed in participants with diabetes, who also showed lower skin elasticity and wrinkles with greater volume, area, and depth. In addition, the Reflectance Confocal Microscopy (RCM) imaging analysis showed that all participants with diabetes presented polycyclic papillae and deformed and amorphous collagen fibers. The obtained data showed significant differences between healthy and diabetic skin and could help develop more specific topical treatments to improve the treatment of skin conditions in people with diabetes. Finally, RCM is an advanced imaging technique that allows for a more profound analysis of diabetic skin, which could assist in the evaluation of dermocosmetic treatments to improve the skin alterations caused by this disease.

Application of a Reflectance Confocal Microscopy Imaging Analysis Score for the Evaluation of Non-Melanogenic Changes in Male Photoaged Skin

The photoaging process is characterized by skin changes due to ultraviolet radiation exposure and is the principal environmental factor affecting skin aging. Reflectance confocal microscopy permits noninvasive skin imaging to understand how the photoaging process may change skin. Since men do not habitually use a sunscreen, the application of skin imaging techniques is important to understand the influence of sunlight on their skin health. The aim of this study was to develop a score based on RCM imaging analyses to evaluate the morphological and structural changes of the photoaged skin according to literature data. The score was applied in order to determine possible correlations between chronological aging and sunscreen use behavior among men. Thus, 40 men aged 18 to 50 years were recruited, images from the frontal region of their skin were obtained and the score was applied. It was observed that habits are more important than age for the skin photoaging process. Men with photoprotection habits showed overall better skin morphological and structural characteristics regardless of age, demonstrating that sun protection behavior is a major key factor in the understanding of photoaging, so that men should be encouraged to start the use of cosmetic products and to perform selfcare.

Simultaneous Physico-Mechanical and In Vivo Assessment towards Factual Skin Performance Profile of Topical Polymeric Film-Forming Systems

Topical film-forming systems (FFS) change drastically after solvent displacement, therefore indicating their skin metamorphosis/transformation as a property of special regulatory and research interest. This paper deals with the lack of suitable characterization techniques, suggesting a set of methods able to provide a comprehensive notion of FFS skin performance. After screening the physico-chemical, mechanical and sensory properties of FFS and resulting films, an elaborate three-phase in vivo study was performed, covering skin irritation, friction and substantivity. Upon removal of 24-hour occlusion, no significant change in erythema index was observed, while the film-former type (cellulose ether, acrylate and/or vinyl polymer) affected transepidermal water loss (TEWL); hydrophobic methacrylate copolymer-based samples decreased TEWL by 40–50%, suggesting a semi-occlusive effect. Although both the tribological parameters related to the friction coefficient and the friction curve’s plateau provided valuable data, their analysis indicated the importance of the moment the plateau is reached as the onset of the secondary formulation, while the tertiary state is still best described by the completion of the film’s drying time. The final part of the in vivo study proved the high in-use substantivity of all samples but confirmed the optimal 4:1 ratio of hydrophobic cationic and hydrophilic polymers, as indicated during early physico-mechanical screening.

Eco-friendly sunscreen formulation based on starches and PEG-75 lanolin increases the antioxidant capacity and the light scattering activity in the visible light

Most modern sunscreens contain physical filters, which scatter the sunlight, increasing the photons' pathway in the upper stratum corneum. This effect can lead to a better efficacy of the UV filters and improve the diffuse reflection. However, the addition of nanosized inorganic UV filters reduces the antioxidant capacity of sunscreen formulations. Two cream formulations (F1, F2) which differ in the ingredient PEG75 Lanolin (F2), have been characterized for their radical protection factor (RPF) and their optical properties in vitro using electron paramagnetic resonance (EPR) spectroscopy and UV/VIS spectrometry. The RPF for PEG-75 Lanolin was also determined. Furthermore, their radical protection properties were analyzed on porcine skin ex vivo after visible light irradiation by EPR. The structure of each formulation in the skin surface was determined by reflectance confocal microscopy in vivo. The addition of lanolin increased the reflectance and reduced the transmittance for visible light, improving the scattering drastically. Besides, the antioxidant capacity was also increased for F2, something unpublished until now. F1 presented a lower scattering provided by starches. The sunscreens showed high scattering properties and antioxidant capacity, especially for F2, which presented the lowest radical formation in the skin model. These results are consistent with the RPF measurements where F2 has a higher RPF value (193 ± 3 × 10¹⁴ radicals/mg) than F1 (155 ± 4 × 10¹⁴ radicals/mg) and for PEG-75 Lanolin (37 ± 1 × 10¹⁴ radicals/mg). The combination of starches and PEG-75 Lanolin is the first solution to provide both, light scattering and antioxidant capacity, in sunscreens.

Stratum corneum occlusion induces water transformation towards lower bonding state: a molecular level in vivo study by confocal Raman microspectroscopy

OBJECTIVE

It is conventionally understood that occlusive effects are the retention of excessive water in the stratum corneum (SC), the increase of SC thickness (swelling) and a decrease of the transepidermal water loss. However, the influence of occlusion on water binding properties in the SC is unknown.

METHODS

The action of plant-derived jojoba and almond oils, as well as mineral-derived paraffin oil and petrolatum topically applied on human skin, is investigated in vivo using confocal Raman microspectroscopy. To understand the oils' influence on the SC on the molecular level, the depth-dependent hydrogen bonding states of water in the SC and their relationship to the conformation of keratin, concentration of natural moisturizing factor (NMF) molecules and lipid organization were investigated.

RESULTS

A significant SC swelling was observed only in petrolatum-treated skin. The water concentration was increased in oil-treated skin in the intermediate SC region (40-70% SC depth). Meanwhile, the amount of free, weakly and tightly bound water increased, and strongly bound water decreased in the uppermost SC region (0-30% SC depth). The NMF concentration of oil-treated skin was significantly lower at 50-70% SC depth. The lateral organization of lipids in oil-treated skin was lower at 0-30% SC depth. The secondary structure of keratin was changed towards an increase of β-sheet content in mineral-derived oil-treated skin and changed towards an increase of α-helix content in plant-derived oil-treated skin.

CONCLUSION

The occlusive properties can be summarized as the increase of free water and the transformation of water from a more strongly to a more weakly hydrogen bonding state in the uppermost SC, although some oils cause insignificant changes of the SC thickness. The accompanied changes in the keratin conformation at the intermediate swelling region of the SC also emphasize the role of keratin in the SC's water-transporting system, that is the water in the SC transports intercellularly and intracellularly in the intermediate swelling region and only intercellularly in the uppermost non-swelling region. Bearing this in mind, almond, jojoba and paraffin oils, which are not occlusive from the conventional viewpoint, have an occlusion effect similar to petrolatum on the SC.