An innovative device for in vivo and in vitro study of fragrance evaporation after application on skin or model surfaces.

An original device has been developed to measure perfume release in the air above a surface. This device has proven its originality, effectiveness, and repeatability both in vitro on different types of model surfaces and in vivo directly on the skin of the forearm of volunteers. A perfume composed of eight fragrance molecules in ethanol was used to measure evaporation in the headspace with solid phase microextraction (SPME) and gas chromatography analysis. Temperature control, time effects, system dimensions, volume and seal integrity, and SPME optimizations were investigated for the measurement device and the analytical method setup. Finally, the system's effectiveness and modularity were demonstrated with evaporation studies carried out on four different surfaces: a chemically inert glass surface, the Strat-M® model, a perfume test strip, and the skin. This original device shows promising results in providing a better understanding of the evaporation phenomena of fragrance molecules and its link with the physicochemical properties of the skin.

Transdermal Minimally Invasive Optical Multiplex Detection of Protein Biomarkers by Nanopillars Array-Embedded Microneedles.

Biomarkers detection has become essential in medical diagnostics and early detection of life-threatening diseases. Modern-day medicine relies heavily on painful and invasive tests, with the extraction of large volumes of venous blood being the most common tool of biomarker detection. These tests are time-consuming, complex, expensive and require multiple sample manipulations and trained staff. The application of "intradermal" biosensors utilizing microneedles as minimally invasive sensing elements for capillary blood biomarkers detection has gained extensive interest in the past few years as a central point-of-care (POC) detection platform. Herein, we present a diagnosis paradigm based on vertically aligned nanopillar array-embedded microneedles sampling-and-detection elements for the direct optical detection and quantification of biomarkers in capillary blood. We present here a demonstration of the simple fabrication route for the creation of a multidetection-zone silicon nanopillar array, embedded in microneedle elements, followed by their area-selective chemical modification, toward the multiplex intradermal biomarkers detection. The utilization of the rapid and specific antibody-antigen binding, combined with the intrinsically large sensing area created by the nanopillar array, enables the simultaneous efficient ultrafast and highly sensitive intradermal capillary blood sampling and detection of protein biomarkers of clinical relevance, without requiring the extraction of blood samples for the ex vivo biomarkers analysis. Through preliminary in vitro and in vivo experiments, the direct intradermal in-skin blood extraction-free platform has demonstrated excellent sensitivity (low pM) and specificity for the accurate multiplex detection of protein biomarkers in capillary blood.

Quantitative estimation of optical properties in bilayer media within the subdiffusive regime using tilted fiber-optic probe diffuse reflectance spectroscopy, part 2: probe design, realization, and experimental validation.

Significance: Tissues like skin have a layered structure where each layer's optical properties vary significantly. However, traditional diffuse reflectance spectroscopy assumes a homogeneous medium, often leading to estimations that reflects the properties of neither layer. There's a clear need for probes that can precisely measure the optical properties of layered tissues. Aim: This paper aims to design a diffuse reflectance probe capable of accurately estimating the optical properties of bilayer tissues in the subdiffusive regime. Approach: Using Monte Carlo simulations, we evaluated key geometric factors-fiber placement, tilt angle, diameter, and numerical aperture-on optical property estimation, following the methodology in Part I. A robust design is proposed that balances accurate intrinsic optical property (IOP) calculations with practical experimental constraints. Results: The designed probe, featuring eight illumination and eight detection fibers with varying spacings and tilt angles. The estimation error of the IOP calculation for bilayer phantoms is less than 20% for top layers with thicknesses between 0.2 and 1.0 mm. Conclusion: Building on the approach from Part I and using a precise calibration, the probe effectively quantified and distinguished the IOPs of bilayer samples, particularly those relevant to early skin pathology detection and characterization.

Electrical Impedance Tomography-Based Electronic Skin for Multi-Touch Tactile Sensing Using Hydrogel Material and FISTA Algorithm.

Flexible electronic skin (e-skin) can enable robots to have sensory forms similar to human skin, enhancing their ability to obtain more information from touch. The non-invasive nature of electrical impedance tomography (EIT) technology allows electrodes to be arranged only at the edges of the skin, ensuring the stretchability and elasticity of the skin's interior. However, the image quality reconstructed by EIT technology has deteriorated in multi-touch identification, where it is challenging to clearly reflect the number of touchpoints and accurately size the touch areas. This paper proposed an EIT-based flexible tactile sensor that employs self-made hydrogel material as the primary sensing medium. The sensor's structure, fabrication process, and tactile imaging principle were elaborated. To improve the quality of image reconstruction, the fast iterative shrinkage-thresholding algorithm (FISTA) was embedded into the EIDORS toolkit. The performances of the e-skin in aspects of assessing the touching area, quantitative force sensing and multi-touch identification were examined. Results showed that the mean intersection over union (MIoU) of the reconstructed images was improved up to 0.84, and the tactile position can be accurately imaged in the case of the number of the touchpoints up to seven (larger than two to four touchpoints in existing studies), proving that the combination of the proposed sensor and imaging algorithm has high sensitivity and accuracy in multi-touch tactile sensing. The presented e-skin shows potential promise for the application in complex human-robot interaction (HRI) environments, such as prosthetics and wearable devices.

Signal Quality in Continuous Transcutaneous Bilirubinometry.

Bilirubin is a product of the metabolism of hemoglobin from red blood cells. Higher levels of bilirubin are a sign that either there is an unusual breaking down rate of red blood cells or the liver is not able to eliminate bilirubin, through bile, into the gastrointestinal tract. For adults, bilirubin is occasionally monitored through urine or invasive blood sampling, whilst all newborns are routinely monitored visually, or non-invasively with transcutaneous measurements (TcBs), due to their biological immaturity to conjugate bilirubin. Neonatal jaundice is a common condition, with higher levels of unconjugated bilirubin concentration having neurotoxic effects. Actual devices used in TcBs are focused on newborn populations, are hand-held, and, in some cases, operate in only two wavelengths, which does not necessarily guarantee reliable results over all skin tones. The same occurs with visual inspections. Based on that, a continuous bilirubin monitoring device for newborns is being developed to overcome visual inspection errors and to reduce invasive procedures. This device, operating optically with a mini-spectrometer in the visible range, is susceptible to patient movements and, consequently, to situations with a lower signal quality for reliable bilirubin concentration estimates on different types of skin. Therefore, as an intermediate development step and, based on skin spectra measurements from adults, this work addresses the device's placement status prediction as a signal quality indication index. This was implemented by using machine learning (ML), with the best performances being achieved by support vector machine (SVM) models, based on the spectra acquired on the arm and forehead areas.

Development and optical characterisation of agarose-based phantoms mimicking biological tissues for studies of light penetration in the brain.

Searching for materials that accurately mimic the optical properties of biological tissues is essential, particularly for transcranial photobiomodulation (PBM) research, where it is necessary to comprehend how light propagates through the head tissues. In this research, we characterised, in the 500-1200 nm range, the transmittance spectra of porcine tissues (skin, muscle, cranium, brain, and cerebellum) and different agarose-based phantoms. These phantoms were developed using different combinations of titanium dioxide (TiO2), India ink, organometallic compounds, and laser-ablated gold and zinc oxide nanoparticles. The surface and mechanical properties of these phantoms were also characterized. The results showed that an increased TiO2 concentration decreased the optical transmittance of the phantoms. However, when TiO2 was added to the India ink and laser-ablated nanoparticles' phantoms, not only did it reduce transmittance amplitude, but it also flattened its spectra. Comparing the phantoms and biological tissues' results, the spectral profiles of TiO2 samples appeared similar to those of muscle, skin, and brain/cerebellum; organometallic compounds replicated the skin and muscle curves; India ink emulated skin and cranium; and the laser-ablated nanoparticles mimicked the muscle. Although it was possible to establish qualitative similarities between the phantoms and the biological tissues' optical transmittance spectra, there is a need for further studies with different components' combinations to ascertain curves that more closely mimic the biological tissues.

Characteristics of the Integument of Phyllomedusa burmeisteri (Anura, Phyllomedusidae) and Boana semilineata (Anura, Hylidae) Males Can Contribute to Understanding its Relation to Habitat.

The integument of anurans plays vital physiological roles, crucial for understanding the species' survival in their environment. Despite its significance, there are few studies describing the cutaneous morphology of anurans from the Brazilian Atlantic Forest. This study aimed to characterize the integument of Phyllomedusa burmeisteri and Boana semilineata in males using microscopic and histochemical approaches. Histological sections were stained with various dyes, and additional fragments underwent electron microscopy and energy-dispersive X-ray spectroscopy. Results showed different projections on the dorsal and ventral regions of males from these species, without the Eberth-Katschenko layer. Differences in the arrangement of chromatophore cells in regions with varying solar incidence were observed in the spongy dermis. Various gland types were identified, aiding taxonomic differentiation and validation of behavioral data. Both species had seromucous and granular glands, while only P. burmeisteri displayed lipid glands. Histochemical analysis revealed higher production of polysaccharides and proteins, contributing to the integument's moisture and protection. Lipid secretions in P. burmeisteri helped waterproof the integument more effectively against desiccation. This study concludes that analyzing anuran integument provides valuable insights into their behavior, with integument composition potentially influenced by habitat choice among different species.

The effect of ceramides on skin absorption by Raman spectroscopy.

INTRODUCTION: Ceramides are essential epidermal constituents that play a critical role in skin moisturization treatment as a raw material in cosmetics formulation. Recently, ceramides have been known to be frequently applied in various cosmetic formulations. Despite ceramide's beneficial characteristics, academic research regarding ceramides and their skin absorption remains insufficient. Therefore, our study conducted clinical research employing Raman spectroscopy to investigate the effects of ceramides on skin absorption to enhance the understanding of ceramides' dermatological functionality and their topical application in cosmetics science. MATERIALS AND METHODS: Twenty healthy individuals with dry skin have participated in this clinical trial. In this double-arm designed trial, the test group received an investigational product with ceramides (5000 ppm) and a control group received an investigational product without the ceramides while all other components remained identical. The subjects visited the clinical research center and acclimatized for 30 min in constant humidity and temperature for equilibrium, subsequently conducting a measurement. Before the trial, the research subject's target site (lower arm area) was kept clean, devoid of any cosmetic administering 24 h before the trial when investigational product was topically applied. RESULTS: Our findings with Raman spectroscopy statistically demonstrate that skin absorption amount, speed and depth for both groups improved overall (p < 0.05) after administration of the investigational product. Notably, the test group received an investigational product with ceramides (5000 ppm) indicating superior effectiveness across all parameters compared to a control group from comparison analysis of each parameter (p < 0.05). CONCLUSION: This study concludes that ceramide-containing cosmetics provide a beneficial effect on skin absorption via visual and statistical results of Raman spectroscopy analysis.

Novel Cosmetic Ingredient CS-AA Polyion Complex and Skin Moisturizing Effect.

PURPOSE: The study explored the enhanced skin moisturizing capabilities and moisture retention effects achieved by forming a polyion complex using sulfated glycosaminoglycan (GAG), specifically chondroitin sulfate (CS), and amino acids (AA) such as glutamine (Q) and arginine (R). The overall hydration effect of this CS-AA complex was examined. METHODS: After analyzing the CS-AA polyion complex structure using spectroscopic methods, the ex vivo moisture retention ability was assessed under dry conditions using porcine skin samples. Additionally, the efficacy of the CS-AA polyion complex in reducing transepidermal water loss (TEWL) and improving skin hydration was evaluated on human subjects using a digital evaporimeter and a corneometer, respectively. RESULTS: Validating a systematic reduction in particle size, the following order was observed: CS > CS/AA simple mixture > CS-AA complex based on dynamic light scattering (DLS) and transmission electron microscopy (TEM) analysis. Furthermore, observations revealed that the CS-AA complex exhibits negligible surface charge. Additionally, Fourier-transform infrared spectroscopy (FT-IR) analysis demonstrated a distinct peak shift in the complex, confirming the successful formation of the CS-AA complex. Subsequently, the water-holding effect through porcine skin was assessed, revealing a notable improvement in moisture retention (weight loss) for the CS-Q complex: 40.6% (1 h), 20.5% (2 h), and 18.7% (4 h) compared to glycerin. Similarly, the CS-R complex demonstrated enhancements of 50.2% (1 h), 37.5% (2 h), and 33% (4 h) compared to glycerin. Furthermore, TEWL improvement efficacy on human skin demonstrated approximately 25% improvement for both the CS-Q complex and CS-R complex, surpassing the modest 12.5% and 18% improvements witnessed with water and glycerin applications, respectively. Finally, employing a corneometer, hydration changes in the skin were monitored over 4 weeks. Although CS alone exhibited nominal alterations, the CS-Q complex and CS-R complex showed a significant increase in moisture levels after 4 weeks of application. CONCLUSION: In this study, polyion complexes were successfully formed between CS, a sulfated GAG, and AA. Comparisons with glycerin, a well-known moisturizing agent, confirmed that the CS-AA complex exhibits superior moisturizing effects in various aspects. These findings suggest that the CS-AA complex is a more effective ingredient than CS or AA alone in terms of efficacy.

Polyurethane/Carbon Nanotube-Based ThermoSense Electronic Skin: Perception to Decision Making Aided by Internet of Things Brain.

Human skin has several receptors collaborating with the brain to provide appropriate "decisions" when applying stimuli. Several research articles state that biomimetic electronic skin (e-skin) is reportedly used for sensor-related applications and performs similarly to natural skin. However, research reporting the capability of the e-skin to make decisions and therefore react upon exposure to adverse conditions is still in its nascent stage. Herein, we report the development of an e-skin, ThermoSense, that can thermoregulate by making appropriate decisions. Thermoplastic polyurethane and multiwalled carbon nanotubes were used as the model composite. The heating and sensing capabilities of the optimized e-skin were studied in detail. In the study window, the e-skin demonstrated excellent electrothermal conversion efficiency by generating a temperature of 192 °C, consuming a power of 2.23 W. A finite element modeling (FEM) was adopted to determine the distribution of the filler in the case of the optimized e-skin and thus was used to probe the reason for the heating across the e-skin via mapping of the internal energy across the sample. FEM results and experimental findings are in strong agreement. Additionally, the e-skin demonstrated its capability to act as a thermal sensor with a 0.947% °C-1 sensitivity. To integrate the decision-making capabilities of the e-skin, an Internet of Things (IoT) brain console was made using the e-skin and electronic chips by leveraging More than Moore's concept. The IoT brain was automated with decision-making programming that was controllable via an in-house-developed mobile application. The console worked exclusively under simulated conditions. When there was a shift from the set point temperature, it started to heat. Postusage, the e-skin matrix was recycled, and the recycled e-skin demonstrated a marginal decrement in performance attributes. This study opens new avenues for developing decision-making e-skins for next-generation human-machine interphases.

Skin-interfaced microfluidic biosensors for colorimetric measurements of the concentrations of ketones in sweat.

Ketones, such as beta-hydroxybutyrate (BHB), are important metabolites that can be used to monitor for conditions such as diabetic ketoacidosis (DKA) and ketosis. Compared to conventional approaches that rely on samples of urine or blood evaluated using laboratory techniques, processes for monitoring of ketones in sweat using on-body sensors offer significant advantages. Here, we report a class of soft, skin-interfaced microfluidic devices that can quantify the concentrations of BHB in sweat based on simple and low-cost colorimetric schemes. These devices combine microfluidic structures and enzymatic colorimetric BHB assays for selective and accurate analysis. Human trials demonstrate the broad applicability of this technology in practical scenarios, and they also establish quantitative correlations between the concentration of BHB in sweat and in blood. The results represent a convenient means for managing DKA and aspects of personal nutrition/wellness.

Robust and Environmentally Friendly MXene-Based Electronic Skin Enabling the Three Essential Functions of Natural Skin: Perception, Protection, and Thermoregulation.

The development of electronic skin (e-skin) emulating the human skin's three essential functions (perception, protection, and thermoregulation) has great potential for human-machine interfaces and intelligent robotics. However, existing studies mainly focus on perception. This study presents a novel, eco-friendly, mechanically robust e-skin replicating human skin's three essential functions. The e-skin is composed of Ti3C2Tx MXene, polypyrrole, and bacterial cellulose nanofibers, where the MXene nanoflakes form the matrix, the bacterial cellulose nanofibers act as the filler, and the polypyrrole serves as a conductive "cross-linker". This design allows customization of the electrical conductivity, microarchitecture, and mechanical properties, integrating sensing (perception), EMI shielding (protection), and thermal management (thermoregulation). The optimal e-skin can effectively sense various motions (including minuscule artery pulses), achieve an EMI shielding efficiency of 63.32 dB at 78 µm thickness, and regulate temperature up to 129 °C in 30 s at 2.4 V, demonstrating its potential for smart robotics in complex scenarios.

A multiplex microbial profiling system for the identification of the source of body fluid and skin samples.

Determining the source of body fluids is crucial in forensic investigations, as it provides valuable information about suspects and the nature of the crime. Microbial markers that trace the source of tissues and body fluids based on site specificity and temporal stability are often used effectively for this purpose. In this study, a multiplex system comprising seven microbial markers (Finegoldia magna, Corynebacterium tuberculostearicum, Cutibacterium acnes, Haemophilus parainfluenzae, Streptococcus oralis, Prevotella melaninogenica and Faecalibacterium prausnitzii) was developed to distinguish between skin, saliva, and feces samples. Based on these markers, the system produces electropherograms that are specific for each sample type. We collected 492 samples from six different skin sites (palm, antecubital crease, inguinal crease, cheek, upper back, and toe web space), the buccal mucosa, and stool were collected to further test the system. Beta diversity analysis revealed distinct clustering among the three sample groups. Additionally, skin microenvironment cluster analysis was used to identify skin sites accurately. This analysis classified skin samples into four distinct microenvironments: dry, moist, oily, and foot. Finally, we established a machine learning prediction model based on random forest regression to identify the skin microenvironment, achieving an overall prediction accuracy of 79 %. The multiplex system developed in this study accurately identifies the sources of body fluids, and the skin microenvironment. These findings offer new insights into the application of microbial markers in forensic science.

Mineralized aggregates based on native protein phase transition for non-destructive diagnosis of seborrheic skin by surface-enhanced Raman spectroscopy.

The non-homeostasis of sebum secretion by the sebaceous glands in a complicated microenvironment dramatically impacts the skin health of many people in the world. However, the complexity and hydrophobicity of sebum mean a lack of diagnostic tools, which makes it challenging to determine the reason behind cortical imbalances. Herein, a biomimetic mineralized aggregates (PTL@Au and PTB@Au) strategy has been proposed, which could obtain molecular information about sebum by surface-enhanced Raman spectroscopy (SERS). The breaking of disulfide bonds leads to changes in hydrogen bonding, which transform the natural protein into amyloid-like phase transition protein with ß-sheets. It provides sites for the nucleation and crystallization of gold nanocrystals to build mineralized aggregates. The mineralized aggregates show robust adhesion stability at the interfaces of different materials through hydrogen bonding and electrostatic interactions. The stabilization, hydrophobicity (contact angle: 134°), and optical transmission (75%) of the structure could result in superior SERS performance for sebum analysis. It should be noted that this enables the sebum detection of clinical samples while ensuring safety. Such generalized bionic mineralization construction and diagnosis methods also serve as an advanced paradigm for a range of biomedical applications.

Exploring the bias: how skin color influences oxygen saturation readings via Monte Carlo simulations.

Significance: Our goal is to understand the root cause of reported oxygen saturation ( SpO 2 ) overestimation in heavily pigmented skin types to devise solutions toward enabling equity in pulse oximeter designs. Aim: We aim to gain theoretical insights into the effect of skin tone on SpO 2 - R curves using a three-dimensional, four-layer tissue model representing a finger. Approach: A finger tissue model, comprising the epidermis, dermis, two arteries, and a bone, was developed using a Monte Carlo-based approach in the MCmatlab software. Two skin tones-light and dark-were simulated by adjusting the absorption and scattering properties within the epidermal layer. Following this, SpO 2 - R curves were generated in various tissue configurations, including transmission and reflection modes using red and infrared wavelengths. In addition, the influence of source-detector (SD) separation distances on both light and dark skin tissue models was studied. Results: In transmission mode, SpO 2 - R curves did not deviate with changes in skin tones because both pulsatile and non-pulsatile terms experienced equal attenuation at red and infrared wavelengths. However, in reflection mode, measurable variations in SpO 2 - R curves were evident. This was due to differential attenuation of the red components, which resulted in a lower perfusion index at the red wavelength in darker skin. As the SD separation increased, the effect of skin tone on SpO 2 - R curves in reflection mode became less pronounced, with the largest SD separation exhibiting effects similar to those observed in transmission mode. Conclusions: Monte Carlo simulations have demonstrated that different light pathlengths within the tissue contribute to the overestimation of SpO 2 in people with darker skin in reflection mode pulse oximetry. Increasing the SD separation may mitigate the effect of skin tone on SpO 2 readings. These trends were not observed in transmission mode; however, further planned research using more complex models of the tissue is essential.

Skin-attachable Tb-MOF ratio fluorescent sensor for real-time detection of human sweat pH.

The pH of human sweat is highly related with a variety of diseases, whereas the monitoring of sweat pH still remains challenging for ordinary families. In this study, we developed a novel dual-emission Tb-MOF using DPA as the ligand and further designed and constructed a skin-attachable Tb-MOF ratio fluorescent sensor for real-time detection of human sweat pH. With the increased concentration of H+, the interaction of H+ with carbonyl organic ligand leads to the collapse of the Tb-MOF crystal structure, resulting in the interruption of antenna effect, and correspondingly increasing the emission of the ligand at 380 nm and decreasing the emission of the central ion Tb3+ at 544 nm. This Tb-MOF nanoprobe has a good linear response in the pH range of 4.12-7.05 (R2 = 0.9914) with excellent anti-interference ability. Based on the merits of fast pH response and high sensitivity, the nanoprobe was further used to prepare flexible wearable sensor. The wearable sensor can detect pH in the linear range of 3.50-6.70, which covers the pH range of normal human sweat (4.50-6.50). Subsequently, the storage stability and detection accuracy of the sensors were evaluated. Finally, the sensor has been successfully applied for the detection of pH in actual sweat samples from 21 volunteer and the real-time monitoring of pH variation during movement processing. This skin-attachable Tb-MOF sensor, with the advantages of low cost, visible color change and long shelf-life, is appealing for sweat pH monitoring especially for ordinary families.

A skin secretion metabolome analysis of the Greek Dodecanese Lycian salamanders: Preliminary evidence of dietary alkaloid sequestration in urodeles.

Lyciasalamandra species, like most amphibians, secrete a wide array of compounds from their granular and mucous skin glands, including the internally synthesized samandarine alkaloids, making their skin a complex organ performing a variety of functions. Lyciasalamandra helverseni and L. luschani basoglui are insular endemics of the Dodecanese islands of SE Greece, bearing distinct isolated populations, with well-documented phylogenetic profiles. Here, we employ a metabolomics approach, utilizing UPLC-ESI-HRMS/MS data of the skin secretions sampled from a number of specimens found in the islands of Karpathos, Kasos and Kastellorizo, in an effort to reveal aspects of their chemistry and diversity across populations. The results indicated statistically significant variation between all taxa examined, based on various secreted compounds. The underlying factors of variation highlighted by the multivariate analysis were differences in samandarine and other alkaloid content as well as in animal size. Metabolite annotation, based on dereplication tools and most importantly HRMS and HRMS/MS spectra, yielded a number of known samandarine alkaloids, reported for the first time in the currently studied Lyciasalamandra species. We also present documentation for novel members of the samandarine alkaloid family, as well as preliminary evidence for a possible dietary alkaloid sequestration. This work can set the basis for further research of this often-neglected endemic species of the Salamandridae, as well as the structural investigation of the samandarine alkaloid group.

Preliminary Studies about Valorization of Acmella oleracea Bioactive Content in Modern Dermato-Cosmetic Applications to Combat Skin Oxidative Stress.

The development of products with skin-protective effects has been driven by the increasing incidence of skin diseases that are exacerbated by increasing pollution, urbanization, poor living, working, fatigue, dietary habits, and general treatment. The ability of antioxidants to protect the skin from oxidative stress and its effects makes them one of the most important ingredients in today's cosmetics. This article aims first to characterize the plant extracts obtained from Acmella oleracea (A. oleracea) and then to evaluate the preliminary criteria for a new marketed product: the stability, antioxidant activity, and in vitro behavior of certain serums based on A. oleracea plant extract and hyaluronic acid. The extracts were obtained by liquid-solid extraction methods (maceration (M), ultrasound-assisted extraction (UEA), and a combined method between these two (UEA + M) using an aqueous solution of ethyl alcohol as the extraction solvent. The determination of the amounts of compounds with antioxidant activity highlighted the fact that the extract obtained from the whole plant of A. oleracea using maceration in conditions of S/L = 1:30, 20 days, and an extraction solvent percentage of 50% led to obtaining the highest amount of polyphenols (30.42 µg GAE/g), while using the combined UAE + M method under conditions of S/L = 1:30, 6 min + 20 days, and 50% extraction solvent led to obtaining the highest amount of flavonoids (32.88 mg QE/g). The tests performed on dermato-cosmetic serums based on the plant extract and multimolecular hyaluronic acid (HA) (1 HA with HMW-1.0 mDa-1.6 mDa; HA with LMW-10 kDa-200 kDa; and HA OLIGO, MW < 10 kDa) led to the conclusion that they exhibit structural stability, good shear behavior revealing a satisfactory texture, and high physical stability during storage. These results encourage the transition to in-depth testing, both microbiological and dermatological, as a final step in the consideration of a new commercial product.

Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions for transmittance pulse oximetry measurement.

Significance: Questions about the accuracy of pulse oximeters in measuring arterial oxygen saturation ( SpO 2 ) in individuals with darker skin pigmentation have resurfaced since the COVID-19 pandemic. This requires investigation to improve patient safety, clinical decision making, and research. Aim: We aim to use computational modeling to identify the potential causes of inaccuracy in SpO 2 measurement in individuals with dark skin and suggest practical solutions to minimize bias. Approach: An in silico model of the human finger was developed to explore how changing melanin concentration and arterial oxygen saturation ( SaO 2 ) affect pulse oximeter calibration algorithms using the Monte Carlo (MC) technique. The model generates calibration curves for Fitzpatrick skin types I, IV, and VI and an SaO 2 range between 70% and 100% in transmittance mode. SpO 2 was derived by inputting the computed ratio of ratios for light and dark skin into a widely used calibration algorithm equation to calculate bias ( SpO 2 - SaO 2 ). These were validated against an experimental study to suggest the validity of the Monte Carlo model. Further work included applying different multiplication factors to adjust the moderate and dark skin calibration curves relative to light skin. Results: Moderate and dark skin calibration curve equations were different from light skin, suggesting that a single algorithm may not be suitable for all skin types due to the varying behavior of light in different epidermal melanin concentrations, especially at 660 nm. The ratio between the mean bias in White and Black subjects in the cohort study was 6.6 and 5.47 for light and dark skin, respectively, from the Monte Carlo model. A linear multiplication factor of 1.23 and exponential factor of 1.8 were applied to moderate and dark skin calibration curves, resulting in similar alignment. Conclusions: This study underpins the careful re-assessment of pulse oximeter designs to minimize bias in SpO 2 measurements across diverse populations.

In vivo confocal Raman spectroscopy: The window into the skin.

Development of in vivo confocal Raman spectroscopy (ICRS) methodology over the last 20 years has enabled previously unavailable capability to acquire molecular concentration gradients across the stratum corneum (SC), at the micron level and in a clinical setting. Professor Tony Rawlings has been a driving force in SC research for over 30 years, working with a wide range of teams across the world. Because a detailed knowledge of skin biochemistry was key to interpreting ICRS-acquired molecular concentration gradients, the authors formed a close working relationship with Professor Rawlings during the development of ICRS. This article, therefore, presents a summary of this process and how challenges raised by application of ICRS were tackled, towards the goal of validating the technique for clinical skin measurement.

Le développement de la méthodologie de spectroscopie confocale Raman in vivo (In vivo Confocal Raman Spectroscopy, ICRS) au cours des 20 dernières années a permis d'acquérir des gradients de concentration moléculaire dans l'ensemble du stratum corneum (SC), au niveau du micron et dans un contexte clinique, ce qui était impossible auparavant. Le professeur Tony Rawlings joue un rôle moteur dans la recherche sur le SC depuis plus de 30 ans et travaille avec de nombreuses équipes à travers le monde. Étant donné qu'une connaissance détaillée de la biochimie cutanée était essentielle à l'interprétation des gradients de concentration moléculaire acquis par l'ICRS, les auteurs ont établi une relation de travail étroite avec le professeur Rawlings pendant le développement de l'ICRS. Cet article présente donc un résumé de ce processus et de la manière dont les défis soulevés par l'application de l'ICRS ont été abordés dans le but de valider la technique de mesure clinique de la peau.