Layers Of Skin Tissue Research Articles

Degree of sulfation of freeze-dried calcium alginate sulfate scaffolds dramatically influence healing rate of full-thickness diabetic wounds.

Diabetic foot ulcer (DFU) is a chronic and non-healing wound in all age categories with a high prevalence and mortality in the world. An ideal wound dressing for DFU should possess the ability of adsorbing high contents of exudate and actively promote wound healing. Here, we introduced the calcium alginate sulfate as a new biomaterial appropriate for use in wound dressing to promote the healing of full-thickness ulcers in a diabetic mouse model. In this regard, alginate sulfate (Alg-S) solutions with different degree of substitution (DS) of 0.2, 0.5, and 0.9 were synthesized, freeze-dried, crosslinked by calcium cations, purified by washing and refreeze-dried. Primary analyses including swelling ratio, porosity content and mechanical properties revealed that all Alg-S scaffolds possess necessities for use as a wound dressing. After confirming the cytocompatibility of both alginate and alginate sulfate-based scaffolds by MTT assay, they were used as wound dressing for healing of full-thickness ulcers in diabetic mice. The results of wound healing process confirmed that calcium alginate sulfate scaffolds can heal the wounds faster than both alginate-treated and non-treated wounds. Furthermore, the histological analyses of healed tissues reveled normal regeneration of the skin tissue layers and collagen deposition similar to the healthy tissue.

Fabrication and Dielectric Validation of an Arm Phantom for Electromyostimulation.

Electromyostimulation (EMS) is an up-and-coming training method that demands further fundamental research regarding its safety and efficacy. To investigate the influence of different stimulation parameters, electrode positions and electrode sizes on the resulting voltage in the tissue, a tissue mimicking phantom is needed. Therefore, this study describes the fabrication of a hydrogel arm phantom for EMS applications with the tissue layers of skin, fat, blood and muscle. The phantom was dielectrically validated in the frequency range of 20 Hz to 100 Hz. We also conducted electromyography (EMG) recordings during EMS on the phantom and compared them with the same measurements on a human arm. The phantom reproduces the dielectric properties of the tissues with deviations ranging from 0.8% to more than 100%. Although we found it difficult to find a compromise between mimicking the permittivity and electrical conductivity at the same time, the EMS-EMG measurements showed similar waveforms (1.9-9.5% deviation) in the phantom and human. Our research contributes to the field of dielectric tissue phantoms, as it proposes a multilayer arm phantom for EMS applications. Consequently, the phantom can be used for initial EMS investigations, but future research should focus on further improving the dielectric properties.

Honeybee stinger-based biopsy needle and influence of the barbs on needle forces during insertion/extraction into the iliac crest: A multilayer finite element approach

Bone marrow biopsy (BMB) needles are frequently used in medical procedures, including extracting biological tissue to identify specific lesions or abnormalities discovered during a medical examination or a radiological scan. The forces applied by the needle during the cutting operation significantly impact the sample quality. Excessive needle insertion force and possible deflection might cause tissue damage, compromising the integrity of the biopsy specimen. The present study aims at proposing a revolutionary bioinspired needle design that will be utilized during the BMB procedure. A non-linear finite element method (FEM) has been used to analyze the insertion/extraction mechanisms of the honeybee-inspired biopsy needle with barbs into/from the human skin-bone domain (i.e., iliac crest model). It can be seen from the results of the FEM analysis that stresses are concentrated around the bioinspired biopsy needle tip and barbs during the needle insertion process. Also, these needles reduce the insertion force and reduce the tip deflection. The insertion force in the current study has been reduced by 8.6% for bone tissue and 22.66% for skin tissue layers. Similarly, the extraction force has been reduced by an average of 57.54%. Additionally, it has been observed that the needle-tip deflection got reduced from 10.44 mm for a plain bevel needle to 6.3 mm for a barbed biopsy bevel needle. According to the research findings, the proposed bioinspired barbed biopsy needle design could be utilized to create and produce novel biopsy needles for successful and minimally invasive piercing operations.

In-silico investigation of intratumoural magnetic hyperthermia for breast cancer therapy using FePt or FeCrNbB magnetic nanoparticles

In this work, we conduct a numerical study on magnetic nanoparticle hyperthermia for the treatment of a breast tumour. The geometry of the problem is comprised of a deformed ellipsoidal tumour region, a healthy glandular tissue region, a fat tissue layer and a skin tissue layer. An aqueous suspension of magnetic nanoparticles (FeCrNbB or FePt) is directly injected into the breast tumour using a syringe. The perfusion of blood through the tissue regions is modelled using the Darcy-Brinkman-Forchheimer equation, and the shear-thinning behaviour of blood is described by the Carreau–Yasuda model. The transport and deposition of nanoparticles within the tissues, the temperature distribution during therapy, and the survival rates of healthy cells and cancer cells are also considered. The governing equations with their associated initial and boundary conditions are solved using the finite element method, and the solution algorithm developed in FreeFEM++ was validated against results from the existing literature. Subsequently, the influence of the nanoparticle solid volume fraction, injection time, and magnetic field amplitude and oscillation frequency on the velocity, temperature, nanoparticle concentration distribution, duration required for effective hyperthermia, and thermal damage to healthy tissues was examined. The numerical results reveal that the cell damage is greater in skin tissue than the healthy gland and fat tissues. For small injection time (tinj=0.4), the healthy gland tissue damage is greater for FePt nanoparticles than FeCrNbB nanoparticles. However, this trend is reversed for larger injection times (tinj=0.5, 0.6). For small magnetic field frequency (ω=5×104, 105), the maximum tissue temperature is higher with FePt nanoparticles than FeCrNbB nanoparticles, but a reversal in trend occurs for larger values of ω (ω=2×105). The findings show that the time duration required for effective magnetic hyperthermia and thermal damage to the healthy tissue regions is reduced with increased injected nanoparticle volume fraction, duration of nanoparticle injection, and the amplitude and frequency of the alternating magnetic field. Moreover, the effective hyperthermia duration and the healthy tissue damage are less for FePt nanoparticles than FeCrNbB nanoparticles.

Hydrogel/Nanofiber Composite Wound Dressing Optimized for Skin Layer Regeneration through the Mechanotransduction-Based Microcellular Environment.

Wound dressings have been designed to provide the optimal environment to fibroblasts, keratinocytes, and macrophages to promote wound healing while inhibiting potential microbial infection. Gelatin methacrylate (GelMA) is a photopolymerizable hydrogel with a gelatin backbone that contains natural cell binding motifs such as arginine-glycine-aspartic acid (RGD) and MMP-sensitive degradation sites, making it an ideal material for wound dressing. However, GelMA alone is unable to stably protect the wound and regulate cellular activities due to its weak mechanical properties and nonmicropatterned surface, limiting its application as a wound dressing. Herein, we report the development of a hydrogel-nanofiber composite wound dressing utilizing GelMA and poly(caprolactone) (PCL)/gelatin nanofiber, which can systematically manage the skin regeneration process with an enhanced mechanical property and micropatterned surface. GelMA sandwiched between electrospun aligned and interlaced nanofibers that mimic epidermis and dermis layers, respectively, increased the stiffness of the resulting hydrogel composite with a comparable swelling rate as GelMA. Fabricated hydrogel composite was determined to be biocompatible and nontoxic. In addition to the beneficial effect of GelMA in accelerating wound healing, subsequent histological analysis revealed upregulated re-epithelialization of granulation tissue and deposition of mature collagen. Hydrogel composite interacted with fibroblasts to regulate their morphology, proliferation, and collagen synthesis, as well as the expression of α-SMA, TGF-β, and collagen I and III during the wound healing process both in vitro and in vivo. Taken together, we propose hydrogel/nanofiber composite as a wound dressing of the next generation that can induce skin tissue layer regeneration beyond the basic wound closure promotion of present dressings.

Dynamic interaction of injected liquid jet with skin layer interfaces revealed by microsecond imaging of optically cleared ex vivo skin tissue model

BackgroundNeedle-free jet injection (NFJI) systems enable a controlled and targeted delivery of drugs into skin tissue. However, a scarce understanding of their underlying mechanisms has been a major deterrent to the development of an efficient system. Primarily, the lack of a suitable visualization technique that could capture the dynamics of the injected fluid–tissue interaction with a microsecond range temporal resolution has emerged as a main limitation. A conventional needle-free injection system may inject the fluids within a few milliseconds and may need a temporal resolution in the microsecond range for obtaining the required images. However, the presently available imaging techniques for skin tissue visualization fail to achieve these required spatial and temporal resolutions. Previous studies on injected fluid–tissue interaction dynamics were conducted using in vitro media with a stiffness similar to that of skin tissue. However, these media are poor substitutes for real skin tissue, and the need for an imaging technique having ex vivo or in vivo imaging capability has been echoed in the previous reports.MethodsA near-infrared imaging technique that utilizes the optical absorption and fluorescence emission of indocyanine green dye, coupled with a tissue clearing technique, was developed for visualizing a NFJI in an ex vivo porcine skin tissue.ResultsThe optimal imaging conditions obtained by considering the optical properties of the developed system and mechanical properties of the cleared ex vivo samples are presented. Crucial information on the dynamic interaction of the injected liquid jet with the ex vivo skin tissue layers and their interfaces could be obtained.ConclusionsThe reported technique can be instrumental for understanding the injection mechanism and for the development of an efficient transdermal NFJI system as well.

Fabrication and characterization of bilayer scaffolds - nanocellulosic cryogels - for skin tissue engineering by co-culturing of fibroblasts and keratinocytes

This study focuses on developing a microarchitectural bilayer structure for stimulating the two top layers of skin tissue (epidermis and dermis) fabricated using a one-step freeze-drying method. Cellulose nanofibers (CNFs) and poly (vinyl) alcohol (PVA) were used as a biocompatible scaffolding material, and the composition was designed in such a way that it provides physical and biological property attributes. In this work, scaffolding materials with integrated layer structures and well interconnected and open pore structures were obtained. This bilayer structure had porosity with a pore size of 19.72 μm and 90.71 μm for the simulation of the epidermis and dermis, respectively. The production and expression of laminin, collagen IV, and keratin 10 proteins in the bilayer cryogel scaffolds obtained from the immunofluorescence study were 49.7 %, 63.8 %, and 49.3 %, respectively. The extracellular matrix (ECM) was produced in each scaffold layer. The observations confirmed that the porosity and pore size of both N1 and N2 layers were appropriate for the fibroblast and keratinocyte cells, respectively. H&E stained cross-sections of bilayer cryogel scaffolds illustrated epidermal and dermal layers produced by co-culturing keratinocytes and fibroblasts. Based on the results, the bilayer CNF/PVA scaffold can be used in skin tissue engineering applications. However, more experiments and in vivo evaluations are needed to express this conclusion more accurately.

Regulatory mechanism of deferoxamine on macrophage polarization and wound healing in mice with deep tissue injury

Regulatory mechanism of deferoxamine on macrophage polarization and wound healing in mice with deep tissue injury

Understanding Formulation and Temperature Effects on Dermal Transport Kinetics by IVPT and Multiphysics Simulation

It is often unclear how complex topical product formulation factors influence the transport kinetics through skin tissue layers, because of multiple confounding attributes. Environmental factors such as temperature effect are also poorly understood. In vitro permeation testing (IVPT) is frequently used to evaluate drug absorption across skin, but the flux results from these studies are from a combination of mechanistic processes. Two different commercially available formulations of oxybenzone-containing sunscreen cream and continuous spray were evaluated by IVPT in human skin. Temperature influence between typical skin surface temperature (32°C) and an elevated 37°C was also assessed. Furthermore, a multiphysics-based simulation model was developed and utilized to compute the flux of modeled formulations. Drug transport kinetics differed significantly between the two drug products. Flux was greatly influenced by the environmental temperature. The multiphysical simulation results could reproduce the experimental observations. The computation further indicated that the drug diffusion coefficient plays a dominant role in drug transport kinetics, influenced by the water content which is also affected by temperature. The in vitro testing and bottom-up simulation shed insight into the mechanism of dermal absorption kinetics from dissimilar topical products.

Multidrug Idebenone/Naproxen Co-loaded Aspasomes for Significant in vivo Anti-inflammatory Activity.

The use of proper nanocarriers for dermal and transdermal delivery of anti‐inflammatory drugs recently gained several attentions in the scientific community because they pass intact and accumulate payloads in the deepest layers of skin tissue. Ascorbyl palmitate‐based vesicles (aspasomes) can be considered a promising nanocarrier for dermal and transdermal delivery due to their skin whitening properties and suitable delivery of payloads through the skin. The aim of this study was the synthesis of multidrug Idebenone/naproxen co‐loaded aspasomes for the development of an effective anti‐inflammatory nanomedicine. Aspasomes had suitable physicochemical properties and were safe in vivo if topically applied on human healthy volunteers. Idebenone/naproxen co‐loaded aspasomes demonstrated an increased therapeutic efficacy of payloads compared to the commercially available Naprosyn® gel, with a rapid decrease of chemical‐induced erythema on human volunteers. These promising results strongly suggested a potential application of Idebenone/naproxen multidrug aspasomes for the development of an effective skin anti‐inflammatory therapy.

Spectral-based estimation of components concentration in skin tissue layers with independence of shading via optical modeling of skin tissue

Spectral-based estimation of components concentration in skin tissue layers with independence of shading via optical modeling of skin tissue

Effect of Rectus Plication during Abdominoplasty on the Mechanical Power and Airway Pressures: Comparison of Two Ventilatory Strategies

Background: Abdominoplasty is a commonly requested procedure for aesthetic improvement of the affected soft tissue layers of skin, fat, and muscle through the slightest incision feasible. The degree of plicature generates an increase in intraabdominal pressure that causes an increase in intrathoracic pressure. Pressure, volume, flow, and respiratory rate are components of a unique physical variable, the mechanical power (MP), and is an integrated variable linked to most factors related to postoperative pulmonary complications. Purpose: To assess the effect of rectus plication (RP) during abdominoplasty on lung pressures and the contribution to increasing the MP. Method: A open-label study was conducted at TJ Plast Advanced Center for Plastic Surgery in Tijuana, México, from September 2021 to May 2022. The study included forty-six female patients subjected to abdominoplasty or liposuction with abdominoplasty. After the induction of general anesthesia and neuromuscular blockade, they were allocated into two groups: Group 1 pressure control ventilation-volume guaranteed (PCV-VG) and Group 2 volume control ventilation (VCV). Respiratory pressures and MP were assessed before and after RP. Results: During VCV, patients had a greater increase in peak pressure (PIP) (P 0.000). Plateau pressure (Pplat) increased 1.78 ± 0.35 cmH2O in group 2 after RP (P = 0.001). MP had a greater increase in group 2 after RP (P 0.01). Conclusion: This prospective study showed that RP is related to an increase in PIP and Pplat and an increase in the MP better controlled with PCV-VG ventilation.

126 Lipidomic analysis of tissue layers in healthy skin

The skin consists of multiple tissue layers harboring distinct compartments of lipid metabolism. Because of limitations in separating and homogenizing skin tissue layers and given technological advances in mass spectrometry, there is a need for precise dissection of the microanatomy of skin combined with quantitative assessment of lipid distribution by employing state of the art technology. The aim of this project is to analyze lipid profiles by Liquid Chromatography - Mass Spectrometry (LC-MS) to detect lipid alterations in healthy skin.

Dispersion profile of a needle-free jet injection depends on the interfacial property of the medium.

Injections into or through the skin are common drug or vaccine administration routes, which can be achieved with conventional needles, microneedles, or needle-free jet injections (NFJI). Understanding the transport mechanism of these injected fluids is critical for the development of effective drug administration devices. NFJI devices are distinct from traditional injection techniques by their route and time scale, which relies on a propelled microjet with sufficient energy to penetrate the skin surface and deliver the drug into the targeted region. The injected fluid interacts with multiple skin tissue layers and interfaces, which implies that the corresponding injection profile is dependent on their mechanical properties. In this study, we address the lack of fundamental knowledge on the impact of these interfaces on the injection profiles of NFJI devices.

Impact of the mechanical properties of penetrated media on the injection characteristics of needle-free jet injection

Needle-free jet injection systems are characterized by the increased drug delivery efficacy over conventional needle-based injection systems and have become a viable alternative. The majority of previous studies have investigated underlying mechanisms of needle-free jet injection systems with an emphasis on the fluid dynamics of the propelled microjet without considering the influence of an injected medium on the penetration and dispersion of the microjet. Unlike the injected fluid introduced directly into a target region of the skin tissue through a hollow needle, the fluid microjet produced by a needle-free injector has to work through multiple skin tissue layers and interfaces having different mechanical properties. Here we evaluated injection characteristics in two hydrogel media having similar stiffness controlled precisely but different pore size and hence different fracture toughness. High-speed imaging data showed that the fracture toughness of the medium influenced the penetration mechanism of the injected microjet, whereas viscoelastic and poroelastic characteristics of the medium determined the final attainable injection profiles. The injection profiles were also dependent on the type and depth of the interface between the layers of two media, where tight and loose interfaces can have different effects on the distribution of injected drug as the injected fluid prefers the path having the least resistance. Our findings would improve the present understanding of needle-free jet injection systems and could help to develop more effective drug delivery systems.

NUMERICAL ANALYSIS OF HEAT TRANSFER IN MULTILAYERED SKIN TISSUE EXPOSED TO 5G MOBILE COMMUNICATION FREQUENCIES

Rapid growth in wireless communications has triggered the advent of 5G mobile communication systems. The use of millimeter waves (30-300 GHz) in 5G system has generated global concern about its biological safety. In present paper, we have numerically analyzed the heat transfer in a 3D multilayered skin tissue exposed to 5G frequencies. The numerical scheme comprises coupling of solution of Maxwell's equation of wave propagation within tissue to Pennes’ bioheat equation. Temperature variations are analyzed at 28 GHz, 38 GHz, and 60 GHz. Additionally, electric field and specific absorption rate distribution are also studied. Highest values of electric field and specific absorption rateare estimated in epidermis layer of skin tissue. For all considered frequencies, highest transient temperature (37.36°C) is predicted in subcutaneous fat layer of the skin. However, the steady state temperature is nearly same as core body temperature (37°C). The results show that 5G mobile phones do not cause any thermal damage to the skin tissue and can be considered safe.

Evaluation of Acute Dermal Irritation, Sensitization and Acute Dermal Toxicity of Leather Cream in Laboratory Animals

Unused leather products attract fungal invasion and deteriorate the product lifespan. The development of antifungal leather cream/polish can solve this array considered that the prepared formulation is skin friendly. Possible adhesion of leather cream to the skin may provide a route for entry of hazardous and harmful ingredients. In this study, leather cream prepared in the laboratory and a marketed product of leather cream were tested for acute dermal irritation in rabbits, skin sensitization in guinea pigs, and acute dermal toxicity in rats. Draize dermal irritation scoring system was used to examine the condition of erythema and edema in rabbits at intervals of 24, 48 and 72 hours. Percentage sensitization rate, sensitization grade, sensitization classifications were accessed in guinea pigs after 24 hours of dermal exposure. Rats were observed daily for 14 days to detect any signs of irritation, change in general behavior, toxicity, morbidity and mortality. Histological examination of rat’s skin was performed at the end of the study. No any kind of dermal responses or any observable signs of systemic toxicity were detected in rabbits treated with either of the leather cream samples. No sensitization, erythema or edema was observed in guinea pigs. In the case of rats, the skin was normal with negative signs of toxicity, erythema or edema. Histological study also failed to show any damage in skin tissue layers of rats applied with test materials. The result provides a base for development of anti-fungal leather cream/polish which can enhance the life of leather and avoid the fungal invasion upon storing for a period of time. © 2020 iGlobal Research and Publishing Foundation. All rights reserved.

Role of skin tissue layers and ultra-structure in transcutaneous electrical stimulation including tDCS

Background. During transcranial electrical stimulation (tES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), current density concentration around the electrode edges that is predicted by simplistic skin models does not match experimental observations of erythema, heating, or other adverse events. We hypothesized that enhancing models to include skin anatomical details, would alter predicted current patterns to align with experimental observations. Method. We develop a high-resolution multi-layer skin model (epidermis, dermis, and fat), with or without additional ultra-structures (hair follicles, sweat glands, and blood vessels). Current flow patterns across each layer and within ultra-structures were predicted using finite element methods considering a broad range of modeled tissue parameters including 78 combinations of skin layer conductivities (S m–1): epidermis (standard: 1.05 × 10−5; range: 1.05 × 10−6 to 0.465); dermis (standard: 0.23; range: 0.0023 to 23), fat (standard: 2 × 10−4; range: 0.02 to 2 × 10−5). The impact of each ultra-structures in isolation and combination was evaluated with varied basic geometries. An integrated final model is then developed. Results. Consistent with prior models, current flow through homogenous skin was annular (concentrated at the electrode edges). In multi-layer skin, reducing epidermis conductivity and/or increasing dermis conductivity decreased current near electrode edges, however no realistic tissue layer parameters produced non-annular current flow at both epidermis and dermis. Addition of just hair follicles, sweat glands, or blood vessels resulted in current peaks around each ultrastructure, irrespective of proximity to electrode edges. Addition of only sweat glands was the most effective approach in reducing overall current concentration near electrode edges. Representation of blood vessels resulted in a uniform current flow across the vascular network. Finally, we ran the first realistic model of current flow across the skin. Conclusion. We confirm prior models exhibiting current concentration near hair follicles or sweat glands, but also exhibit that an overall annular pattern of current flow remains for realistic tissue parameters. We model skin blood vessels for the first time and show that this robustly distributes current across the vascular network, consistent with experimental erythema patterns. Only a state-of-the-art precise model of skin current flow predicts lack of current concentration near electrode edges across all skin layers.

526 Computational modeling of two methods of histologic embedding during Mohs micrographic surgery

Skin cancer is the most common malignancy in the United States. Mohs micrographic surgery (MMS) combines surgical excision with oriented microscopic evaluation to provide the highest cure rate for non-melanoma skin cancers. Despite a theoretical 100% margin assessment, the recurrence rate for large skin cancers is as high as 41%. One potential reason for high recurrence rates is unanticipated tissue deformation during histologic processing. Two methods of embedding are the glass-slide and the heat sink embedding method. In the glass-slide method, tissue is manipulated onto a two-dimensional surface and then immobilized by freezing. In the heat sink method, tissue is applied to a frozen two-dimensional surface that immobilizes the tissue on contact. Despite new techniques for studying tissue biomechanics, few biomechanical studies have been applied to dermatology nor MMS. We propose computational modeling of excised skin tissue to describe deformations that arise during MMS tissue processing. We hypothesize that the model of skin tissue embedded with the glass-slide will reveal distinct strain patterns relative to the heat sink embedded tissue. An anisotropic Prandtl-Reuss elastoplastic material model was applied to assess Young’s modulus, Poisson’s ratio, and yield stress. The three-dimensional shape of a Mohs layer of skin tissue was created with a mesh of hexahedral elements as a three-dimensional solid. Force parameters were collected with a microscopic cantilever force indenter on fresh skin tissue to define the strain on the elements. Different types of strain, including normal and von Mises effective strain were assessed. The models support our hypothesis of distinct strain patterns for the two embedding methods. Further modeling is needed to define the clinical scenarios that would be negatively impacted by these differences.

NANO FAT COMBINED WITH PLATELET RICH PLASMA INJECTION VERSUS NANO FAT INJECTION ALONE IN THE TREATMENT OF ATROPHIC SCAR

Background: An atrophic scar is an indented scar that heals below the normal layer of skin tissue. Atrophic scars form when the skin is unable to regenerate tissue. As a result, it leaves behind imbalanced scarring. Objective: To evaluate the efficacy and safety of the autologous emulsified fat transfer with or without platelet rich plasma in the treatment of atrophic scar. Patients and methods: This study was carried out at Dermatology Department, Al-HusseinUniversityHospital, Faculty of Medicine, Al-AzharUniversity. This study included 60 patients with atrophic scar divided into 2 equal groups: group (A) treated with nanofat and platelet rich plasma, and group (B) treated with nanofat only. Scar in both groups caused by different etiological factors, their ages ranged from 19 to 59 years with 40 males and 20 females on a period from March 2019 to December 2019. Results: No significant differences between group A and group B after treatment, revealing that the corner stone of significance created by nanofat injection including adipose derived stem cells and growth factors without obvious clinical and statistical significance of additional platelet rich plasma. Conclusion: Nanofat injection has been shown to have beneficial effects in the treatment of atrophic scar, wrinkles, and skin discolorations, being highly effective in improving the height and pliability of all scars with mild improvement in pigmentation and vascularities, addition of platelet rich plasma to nanofat showed the same result which treated.