Biological Skin Research Articles

A stretchable and self-healable all-in-one iontronic elastomer for luminescent caution and multiple perceptions

Mimicking the multi-functions of biological skin via ionic elastomers is of primary interest for flexible and wearable electronics. Herein, we present a facile all-in-one strategy for preparing highly stretchable and healable iontronic elastomer, being capable of luminescent caution and multimode perception. The all-in-one iontronic elastomer is composed of a phosphor-doped polydimethylsiloxane emitter sandwiched between two solid ionic gel conductors. The all-in-one iontronic elastomer is sensitive to variable stimuli, including tensile, pressure, temperature and liquid. In particular, it shows stable light emission even after stretching up to 250%, bending or twisting 180°, and cut:ting partially. Moreover, the all-in-one iontronic elastomer has been utilized for real-time monitoring of human joint motion and environmental change, as well as signal caution of wearable/portable display, suggesting great potential in personal health and safety care. A highly stretchable and healable all-in-one iontronic elastomer that enables functions such as strain, temperature, liquid sensor together with luminescence is developed. Moreover, the multifunctional all-in-one iontronic elastomer can be utilized for real-time monitoring of human joint motion and wearable/portable display. • A liquid free solid ionic gel (SIG) possesses excellent stretchable and self-healable property was prepared. • An all-in-one iontronic elastomer was prepared by stacking an electroluminescent layer between two SIGs. • The iontronic elastomer exhibits stable light emission under bending, twisting, stretching, or heat treatment states. • The iontronic elastomer was utilized for real-time monitoring of human joint motion and wearable/portable display.

730 Clinical utility of the portable pressure measuring device for garment therapy on burn scar

IntroductionThe experimenters developed a portable pressure measuring device using silicon piezoresistive pressure sensors. The purpose of this study was to determine the effectiveness of pressure garment therapy using proposed device with objective data obtained through a randomized controlled trial.MethodsPressure measurements were acquired through a readout circuit consisting of an analog-to-digital converter, a microprocessor, and a Bluetooth transmission module for wireless data transmission to an external device. This was a double-blinded, randomized, controlled trial in patients with hypertrophic scars. In the pressure monitoring group, garment pressures were monitored using the portable pressure measuring device, and the compression garment was adjusted so that the pressure was maintained at the therapeutic range of 15 – 25 mmHg. In the control group, non-surgical standard treatment of burn scars except for pressure monitoring was performed in the same manner.ResultsNo significant intergroup difference was noted at the initial evaluations (p >0.05) between two groups. The pre- to post-treatment change in the scar thickness (p=0.03) and erythema (p=0.03), more reductions were found in the pressure monitoring group than control group. There were no significant differences in the change measurements between the two groups for melanin levels (p=0.62) and transepidermal water loss (TEWL) (p=0.94). The changes (skin distensibility, biological skin elasticity, gross skin elasticity, and skin viscoelasticity) measured with the cutometer showed no significant differences between the two groups (p=0.87, p=0.32, p=0.37, and p=0.29, respectively).ConclusionsComplementary characteristics such as wireless transmission to an external device may allow burn patients to continuously wear the device for real-time measurements. A Portable pressure monitoring device is effective for significantly improving burn-associated scar characteristics.

Superstable and Intrinsically Self‐Healing Fibrous Membrane with Bionic Confined Protective Structure for Breathable Electronic Skin

AbstractConsiderable effort has been devoted to the fabrication of electronic skin that can imitate the self‐healing and sensing function of biological skin. Almost all self‐healing electronic skins are composed of airtight elastomers or hydrogels, which will cause skin inflammation. Fibrous membranes are ideal materials for preparing highly sensitive breathable electronic skins. However, the development of intrinsically self‐healing fibrous membranes with high stability is still a challenge. Here, a novel interface protective strategy is reported to develop intrinsically self‐healing fibrous membranes with a bionic confined structure for the first time, which were further assembled into an all‐fiber structured electronic skin through interfacial hydrogen bonding. The electronic skin is multifunctional with self‐powering, self‐healing, breathability, stretchability, and thermochromism functionalities, which is highly promising for application in intelligent wearable sensing systems.

Superstable and Intrinsically Self-Healing Fibrous Membrane with Bionic Confined Protective Structure for Breathable Electronic Skin.

Considerable effort has been devoted to the fabrication of electronic skin that can imitate the self-healing and sensing function of biological skin. Almost all self-healing electronic skins are composed of airtight elastomers or hydrogels, which will cause skin inflammation. Fibrous membranes are ideal materials for preparing highly sensitive breathable electronic skins. However, the development of intrinsically self-healing fibrous membranes with high stability is still a challenge. Here, a novel interface protective strategy is reported to develop intrinsically self-healing fibrous membranes with a bionic confined structure for the first time, which were further assembled into an all-fiber structured electronic skin through interfacial hydrogen bonding. The electronic skin is multifunctional with self-powering, self-healing, breathability, stretchability, and thermochromism functionalities, which is highly promising for application in intelligent wearable sensing systems.

Recent Advances in Electronic Skins with Multiple-Stimuli-Responsive and Self-Healing Abilities.

Wearable electronic skin (e-skin) has provided a revolutionized way to intelligently sense environmental stimuli, which shows prospective applications in health monitoring, artificial intelligence and prosthetics fields. Drawn inspiration from biological skins, developing e-skin with multiple stimuli perception and self-healing abilities not only enrich their bionic multifunctionality, but also greatly improve their sensory performance and functional stability. In this review, we highlight recent important developments in the material structure design strategy to imitate the fascinating functionalities of biological skins, including molecular synthesis, physical structure design, and special biomimicry engineering. Moreover, their specific structure-property relationships, multifunctional application, and existing challenges are also critically analyzed with representative examples. Furthermore, a summary and perspective on future directions and challenges of biomimetic electronic skins regarding function construction will be briefly discussed. We believe that this review will provide valuable guidance for readers to fabricate superior e-skin materials or devices with skin-like multifunctionalities and disparate characteristics.

The Role of Skin Substitutes in Acute Burn and Reconstructive Burn Surgery: An Updated Comprehensive Review.

Burns disrupt the protective skin barrier with consequent loss of cutaneous temperature regulation, infection prevention, evaporative losses, and other vital functions. Chronically, burns lead to scarring, contractures, pain, and impaired psychosocial well-being. Several skin substitutes are available and replace the skin and partially restore functional outcomes and improve cosmesis. We performed a literature review to update readers on biologic and synthetic skin substitutes to date applied in acute and reconstructive burn surgery. Improvement has been rapid in the development of skin substitutes in the last decade; however, no available skin substitute fulfills criteria as a perfect replacement for damaged skin.

An Adaptive Building Skin Concept Resulting from a New Bioinspiration Process: Design, Prototyping, and Characterization

Building envelopes can manage light, heat gains or losses, and ventilation and, as such, play a key role in the overall building performance. Research has been focusing on increasing their efficiency by proposing dynamic and adaptive systems, meaning that they evolve to best meet the internal and external varying conditions. Living organisms are relevant examples of adaptability as they have evolved, facing extreme conditions while maintaining stable internal conditions for survival. From a framework based on the inspiration of living envelopes such as animal constructions or biological skins, the concept of an adaptive envelope inspired by the Morpho butterfly was proposed. The system can manage heat, air, and light transfers going through the building and includes adaptive elements with absorption coefficients varying with temperature. This paper presents the developed framework that led to the final concept as well as the concept implementation and assessment. A prototype for heat and light management was built and integrated into a test bench. Measurements were performed to provide a first assessment of the system. In parallel, geometrical parametric models were created to compare multiple configurations in regards to indicators such as air, light, or heat transfers. One of the models provided light projections on the system that were compared with measurements and validated as suitable inputs in grey-box models for the system characterization.

Racial/ethnic differences in treatment efficacy and safety for moderate-to-severe plaque psoriasis: a systematic review.

Biologic medications have revolutionized treatment of psoriasis; however, there remains uncertainty in which medications should be used to maximize efficacy based on race/ethnicity. The purpose was to determine if efficacy of biological medications differs based on race/ethnicity. A systematic review identified all clinical trials focused on biologic treatment outcomes from inception of database until March 5th, 2021. Included studies provided data on racial/ethnic differences in biologic skin clearance efficacy using the Psoriasis Area and Severity Index (PASI) and "clear/almost clear" scores. There were 1220 studies identified, and 24 included in the review. The races/ethnicities included were Asian (n = 2740), White (n = 9745), Black (n = 138), and Latino (n = 728). Ixekizumab provided the highest "clear/almost clear" score (90.7%, 89.4%) and PASI 75 (98.8%, 96.6%) for Asian and Latino patients, respectively. Guselkumab had the highest "clear/almost clear" score for White (86.8%) patients, while Black patients had highest "clear/almost clear" (75.0%) and PASI 75 (91.7%) scores to brodalumab. Limitations included lack of studies reporting outcome data based on race/ethnicity and lack of patients of color within psoriasis clinical trials. For treatment of plaque psoriasis, there is evidence of differences in efficacy of biologics improving clinical disease severity between different races or ethnicities.

Elastic Tactile Sensor Skin on Double-Curved Surfaces for Robots and Wearables

Tactile perception is an important modality for dexterous manipulation, but faces unique challenges in that the sensor has to wrap around the system. Biological skin solves these problems extremely well. Not only can it detect contacts, but it also grows on complex three-dimensional shapes, stretches with underlying soft tissue and around joints, and leaves enough space inside for other organs. Previous artificial sensors could only achieve different subsets of these features. We present a novel tactile sensor skin which is completely made from elastic silicone rubber and can stretch to multiple times its original length without damage. It can be produced in three-dimensional double-curved shapes, is thin enough to accommodate other robot components or human body parts, and it can measure forces and locations of multiple simultaneous contacts. We develop production methods and material formulations, algorithms for computer-aided design, compact readout electronics using small, low-power FPGAs, firmware, and software.

A review of mechanochromic polymers and composites: From material design strategy to advanced electronics application

The design and fabrication of functional polymers with fascinating mechanochromic properties are of profound significance to their prospective applications, such as wearable electronic skin, smart screen, artificial muscle, encryption, and anti-counterfeiting devices. Drawn inspiration from color-changing properties of biological skins, numerous approaches, from molecular synthesis to special biomimicry engineering, have been employed to construct flexible stimuli-responsive materials with superior mechano-stimulated optical change performance. In this review, we highlight and discuss recent important progress in material structure design strategy for mechanochromic polymers and composites. These optical variations primarily originate from the force-induced molecular structure change, disruption of intermolecular interaction, evolution of physical photonic and morphological structure. Moreover, according to their respective structure-property relationships, their multifunctional applications in advanced electronics field are also demonstrated with representative examples. Furthermore, a summary and perspective regarding the existing challenges in this field will be discussed, aiming to provide valuable insight into their future developments. We believe this feature review will bring helpful guidance to readers for choosing effective chromogenic material design method to satisfy different application requirements.

Venous Leg Ulcers: Advanced Therapies and New Technologies.

The prevalence of venous leg ulcers (VLUs) differs between 1.5% and 3% in the general population. The challenge in treating VLUs is common recurrence. Moreover, VLUs can be resistant to healing, despite appropriate treatment. In these cases, advanced wound therapies should be considered. The number of new technologies, applied in VLUs treatment, has increased in the last years. These therapies include biophysical interventions such as ultrasound therapy, electrical stimulations, electromagnetic therapy, or phototherapy. Furthermore, stem cell therapies, biologic skin equivalents, platelet-rich plasma therapy, oxygen therapies, anti-TNF therapy, or negative pressure wound therapy are advanced venous ulcer therapeutic methods that may support the standard of care. Medical devices, such as a muscle pump activator, or intermittent pneumatic compression device, may be especially useful for specific subgroups of patients suffering from VLUs. Some of the above-mentioned technologies require broader evidence of clinical efficacy and are still considered experimental therapies in dermatology.

Properties and parameters for effective laser hair removal: A review

Because some people seek consultations for the removal of unwanted body hair, a permanent, safe, and non-invasive method of hair removal is needed. Laser hair removal has been a popular cosmetic procedure. It is a monthly treatment that may take up to ten sessions for permanent results. However, its efficacy varies due to the patient’s biological skin hair traits, the adjustment of the optimal parameters of the laser, and the protocols. The purpose of this review is to discuss the properties and parameters employed for laser hair removal. Once parameters for laser hair removal have been optimized, this treatment offers an effective and permanent solution for unwanted body hair.

Soft Elastomeric Capacitor for Strain and Stress Monitoring on Sutured Skin Tissues.

Sutures are ubiquitous medical devices for wound closures in human and veterinary medicine, and suture techniques are frequently evaluated by comparing tensile strengths in ex vivo studies. Direct and nondestructive measurement of tensile force present in sutured biological skin tissue is a key challenge in biomechanical fields because of the unique and complex properties of each sutured skin specimen and the lack of compliant sensors capable of monitoring large levels of strain. The authors have recently proposed a soft elastomeric capacitor (SEC) sensor that consists of a highly compliant and scalable strain gauge capable of transducing geometric variations into a measurable change in capacitance. In this study, corrugated SECs are used to experimentally characterize the inherent biomechanical properties of canine skin specimens. In particular, an SEC corrugated with a re-entrant hexagonal honeycomb pattern is studied to monitor strain and stresses for three specific suture patterns: simple interrupted, cruciate, and intradermal patterns. Stress is estimated using constitutive models based on the Fractional Zener and the Kelvin-Voigt models, parametrized using a particle swarm algorithm from experimental data and results from a validated finite element model. Results are benchmarked against findings from the literature and show that SECs are valuable for clinical evaluation of tensile force in biological skins. It was found that both the ranking of suture pattern performance and the sutured skin's Young's modulus using the proposed approach agreed with data reported in the literature and that the estimated stress at the suture level closely matched that of an approximate finite element model.

Photo‐Polymerization Induced Hierarchical Pattern via Self‐Wrinkling

AbstractHierarchical patterns are widely found on the biological skins in nature and can provide unique functions to surfaces such as wettability, optical, and adhesive properties. Herein, a facile and robust strategy to generate the self‐wrinkling pattern on the surface of the photo‐curing coating is proposed, which comprises a crosslinking monomer, photoinitiator, and fluorinated copolymer as additive. The fluorinated copolymer, which contains fluorocarbon chains possessing low surface‐energy, tertiary amine as coinitiator, and anthracene in the side chain, can self‐assemble to the top layer for constructing the gradient photo‐crosslinking system. Upon the irradiation of ultraviolet (UV) light, the mismatch of shrinkage caused by the gradient photo‐crosslinking leads to the formation of wrinkles, the morphology of which can be regulated by monomer proportion, the content of fluorinated copolymer, and the thickness of the film. Taking the spatiotemporal advantages of light, the hierarchical patterns of wrinkle are generated by programmed exposure with photomask, which has potential applications in anti‐counterfeiting and encapsulation of light‐emitting diode (LED) chip for displaying. This strategy provides a rapid and universal alternative method to fabricate a hierarchical pattern of the surface.

A numerical study of space‐fractional three‐phase‐lag bioheat transfer model during thermal therapy

AbstractPrediction of accurate temperature profile and control of temperature are two important factors to treat the cancerous cells effectively in the living tissue during thermal therapy. To deal with this, we have generated a space‐fractional mathematical model of bioheat transfer within the living skin tissue by using three‐phase‐lag constitutive relation. The present model with Dirichlet's boundary condition is investigated in the companionship of the metabolic and external heat source during the thermal therapy. Exponentially decaying (with position) laser heat source is used as an external heating source term. To find out the solution, the model is converted to an initial value problem by using a fractional backward finite difference scheme and then Runge–Kutta (4,5) scheme is applied for determining the temperature profile within the living biological skin tissue. The effect on the dimensionless temperature profile during thermal therapy due to variations in the value of parameters like an order of space‐fractional derivative, relaxation times, blood perfusion coefficient, rate of thermal conductivity, and the external laser heat source incorporated in the current bioheat transfer model is discussed graphically. Results obtained from the study are beneficial in the field of medicine, especially for oncologists.

Octabenzone Isolated from Saharan Myrtle Leaves (Myrtus nivellei)

Background: The Algerian Saharan plants are plants of terrestrial origin, which during their evolution have adapted to the Algerian south ecosystem. By their particular ecological and evolutionary position, it is possible that these endemic plants also selected specific secondary metabolites with original chemical and biological characteristics. Objective: Phytochemical investigation of ethyl acetate and n-butanol extracts of M. nivellei leaves. Methods: Air-dried and coarsely powdered leaves were macerated with 80% methanol. The methanol extract diluted with distilled water was successively extracted with hexane, ethyl acetate and n- BuOH. The ethyl acetate and n-butanol extracts were fractionated by sephadex (LH-20) column using MeOH as eluent. Fraction 1 from ethyl acetate extract was chromatographed by preparative TLC to give pure compound (1). Fractions 4 and 5 from n-butanol extract were chromatographed by RPHPLC over a C18 column using MeOH/H2O (4:6, v/v) as solvent system. Fraction 4 gave compounds 3 (1.5 mg) and 4 (1.1 mg), fraction 5 gave compound 2 (5.5 mg). Structural elucidation was established by a combination of one- and two-dimensional NMR techniques, and mass spectrometry. Results: The investigation of ethyl acetate and n-butanol extracts of M. nivellei leaves allowed the isolation for the first time of Octabenzone (1) which was never reported before along with three known flavonols, myricetin 3-O-β-D-(6”-galloyl)galactoside (2), quercetin 3-O-β-D-(6”- galloyl)galactoside (3) and myricetin 3-O-arabinoside (4). Conclusion: These results suggested that the leaves of M. nivellei stand as a promising natural source for sunscreen products such as octabenzone. In combination with its richness of phenolic compounds, these observations lead us toward further studies concerning M. nivellei biological activity against skin damages and skin cancer.

Engineering Bioactive Scaffolds for Skin Regeneration.

Large skin wounds pose a major clinical challenge. Scarcity of donor site and postsurgical scarring contribute to the incomplete or partial loss of function and aesthetic concerns in skin wound patients. Currently, a wide variety of skin grafts are being applied in clinical settings. Scaffolds are used to overcome the issues related to the misaligned architecture of the repaired skin tissues. The current review summarizes the contribution of biomaterials to wound healing and skin regeneration and addresses the existing limitations in skin grafting. Then, the clinically approved biologic and synthetic skin substitutes are extensively reviewed. Next, the techniques for modification of skin grafts aiming for enhanced tissue regeneration are outlined, and a summary of different growth factor delivery systems using biomaterials is presented. Considering the significant progress in biomaterial science and manufacturing technologies, the idea of biomaterial-based skin grafts with the ability for scarless wound healing and reconstructing full skin organ is more achievable than ever.

Identification of the thermo-physical properties of a stratified tissue. Adiabatic hypodermic wall

Biological living tissues possess thermophysical properties that are difficult to measure directly and their estimation is very important in order to decide the appropriate treatment procedure (e.g. place of inoculation and appropriate amount of drug dosage) in case an abnormality is detected. In the present paper, we numerically investigate, for the first time, the determination of several thermo-physical blood-tissue properties of a one-dimensional, multi-layered biological skin tissue subjected to external heating. In contrast to the usual parabolic model that assumes infinitely fast propagation of the heat signal, in the present paper, the bio-heat transfer in such a biological body is mathematically modelled by a hyperbolic partial differential equation, which takes into account that the thermal wave speed is finite. On the skin surface a convective boundary condition holds taking into account the heat exchange with the environment, whilst on the most inner wall of the tissue an adiabatic boundary condition applies. Then, in this framework, the piecewise constant thermo-physical properties of interest given by the thermal conductivity, heat capacity and blood perfusion rate are accurately and stably reconstructed from non-intrusive temperature measurements on the inner and outer boundaries of the multi-layered tissue by minimizing a weighted nonlinear least-squares objective function.

Biocompatible MXene/Chitosan-Based Flexible Bimodal Devices for Real-Time Pulse and Respiratory Rate Monitoring

Electronic skins, often with recognition and sensing capabilities that are beyond those associated with biological skin, provide important medical information for human health. However, how to make electronic skins with both tactile and touchless perceptions for applications in real-time health monitoring is a challenge due to biological complexity. Herein, flexible bimodal e-skins are demonstrated using a lamellated MXene/chitosan film as the kernel sensing layer. These biomimetic hybrid films show excellent biocompatibility in a cytotoxicity test, indicating a reduced risk of application in the human body. The flexible devices display two modes that can detect pressure (with a limit of detection (LoD) of 3 Pa, stability >3500 times, and response time of 143 ms) and humidity (stability >20 days). The bifunctional sensor can also be used in detecting and discriminating electrophysiological signals (including voice recognition, human pulses, and finger bending) and biochemical molecules (respiratory rate). This work may lead to the application of biocomposite materials in multifunctional flexible sensing technology.

638 Sleep and circadian markers of BMI in a diverse sample of 9-year old children from the Fragile Families Child and Wellbeing Study

Abstract Introduction Hispanic and Black school-age children from low-income communities experience disproportionate rates of obesity (26% Hispanic, 22% Black) compared to their White counterparts (14%). Sleep patterns and circadian regulation of biological markers are associated with BMI status. However, little is known about racial and ethnic disparities in circadian regulation among children of color. These suggest that it is important to investigate biological markers that could help delineate associations between sleep-circadian regulation and obesity among children of color. Serotonin transporter gene, a neurotransmitter associated with circadian rhythm regulation, has emerged as an important biological variable. In this study, we investigated whether this factor could serve as a proxy for studying associations of circadian rhythm regulation with weight status in this diverse sample. Methods Statistical analysis included descriptive and linear regression analysis of the wave 5, Year 9 cohort of the Fragile Families Child and Wellbeing Study dataset. Interviews were conducted with the participant child around their ninth birthday for data collection on home routines and other parent relationship and school connectedness variables. Biological variables were derived from saliva samples at Year 9 to assess telomere length and DNA methylation levels and changes. Variables of interest included sleep duration, sleep timing, and biological variables 5httlpr (insomnia and sleep quality), skin 2 (serotonin transporter), telomere length (stress) and rs9939609 (fat mass and obesity), with BMI as the outcome. Results The final sample of 466 children comprised 52% male were 9 years old. Participants’ race was: 35% White, 46% Black, 20% Hispanic, 4% Asian and 5% other. Median family income was $42,500. Sleep duration obtained from these children was negatively associated with BMI (β = -0.245 with p=0.022). We found that gk5stin212 (serotonin transporter gene) was positively associated with BMI (β = 0.991, p = 0.009), while no significant associations was found for genetic variable gk5stin210. Conclusion Circadian rhythm dysregulation may serve as a biological mechanism driving overweight or obesity among minority children. Lifestyle and behavioral interventions aimed at the family unit may be needed to modify household and environmental factors that affect circadian regulation among children. Support (if any) NIH (T32HL129953), K07AG052685, R01MD007716, R01HL142066, K01HL135452, R01HL152453