Different Layers Of Skin Research Articles

Building Affordable, Durable, Medium-fidelity Ballistic Gel Phantoms for Ultrasound-guided Nerve Block Training.

Ultrasound phantoms - alternatives to live human tissue - give learners the opportunity to practice ultrasound-guided regional anesthesia without introducing undue risk to patients. Gelatin-based phantoms provide educators with durable and reusable task trainers; however, commercially available gel-based phantoms are expensive. Here, we investigate the production of durable, low-cost, ballistic gel-based ultrasound phantoms for median, femoral, suprainguinal fascia iliaca plane, and serratus anterior plane nerve blocks, as well as a methodology for producing a phantom for any ultrasound-guided nerve block procedure. Computer-aided design (CAD) software was utilized to design four phantoms replicating the anatomy of median, femoral, suprainguinal fascia iliaca plane, and serratus anterior plane nerve blocks, including relevant landmarks and tissue planes. Plastic models of the desired tissue planes were 3D printed and used to create silicone molds. Ballistic gel was melted and mixed with flour and dye to create a liquid, echogenic ballistic gel, which was poured into the silicone molds. Vessels were simulated by creating negative space in the ballistic gel using metal rods. Nerves were simulated using yarn submerged in ultrasound gel. Simulated bones were designed using CAD and 3D printed. Ballistic gel is a versatile, durable medium that can be used to simulate a variety of tissues and can be melted and molded into any shape. Under ultrasound, these phantoms provide realistic tissue planes that represent the borders between different layers of skin, muscle, and fascia. The echogenicity of the muscle tissue layers, nerves, vessels, and bones is realistic, and bones have significant posterior shadowing as would be observed in a human subject. These phantoms cost $200 each for the first phantom and $60 for each subsequent phantom. These phantoms require some technical skill to design, but they can be built for just 4% of the cost of their commercial counterparts.

Deep skin homogeneity and light diffusion: An accelerated Monte Carlo model for invivo skin characterization and consumer perception.

The appearance of healthy and youthful skin is related to many factors of the skin optical properties as perceived by our visual sense. The optics of light travelling through human tissues has been extensively investigated in the field of biomedical applications, including the experimental characterization and modelling of skin optics and the propagation of light such as lasers through the layers. This work presents an innovative approach to probe deep skin by means of spectrally and spatially resolved light diffusion in the different layers of skin. Dual hyperspectral measurements of the panellist's skin are performed invivo on subjects to obtain reflectance and light diffusion spectra. Both are simultaneously fitted by a GPU-accelerated Monte Carlo model to obtain skin optical parameters as a function of depth. The results show a clear correlation between deep skin light diffusion at wavelengths above 590 nm and the subject age, which indicates a progressive degradation of skin homogeneity with age. The effect of this orange-red light diffusion background is to alter the colour tone of the skin. A skincare product is used to show that the warmer skin colour tone is clearly perceivable to consumers when evaluating facial images with and without the product. The product effect also correlates well with hyperspectral measurements. Lastly, this innovative approach demonstrates a first step in real-time skin characterization for consumers and opens the door to customized cosmetic solutions for individual needs.

A new strategy to treat Pseudomonas aeruginosa infected burn wounds: Antimicrobial cocktails as potent topical therapy

Burn insults are traumatic as they inflict intense damage on different layers of skin and other organic body tissues, causing alterations in host's immune system, thereby, impairing the wound healing process. Weakened immune system and damaged natural cutaneous barrier opens a doorway for microorganisms to inhabit and infect burn wounds, lengthening hospital stays, and escalating the mortality rates. The most prominent burn wound infection-causing bacteria is Pseudomonas aeruginosa, which is accountable for higher mortality rates and is most ubiquitous among all the other burn wound pathogens because of its inclination to flourish in the moist environment causing invasive infections and selective advantage to grow within burn wound exudates. Due to the alarming rise in multi-drug resistance, the conventional therapy to treat burn insults and subsequent infections involving surgical removal of devitalized tissue, flushing wound site with normal saline, and employment of antibiotics topically is rendered ineffective suppressing physicians in their treatment choices and resulting in adverse outcomes observed in burn units. Despite advancements in the burn care field, rising drug resistance and its related consequences is necessitating vigorous research to devise an antimicrobial therapy targeting three broad areas collectively, for instance, P. aeruginosa infection management, immunomodulation, and wound healing. Hence, we propose formulating an antimicrobial cocktail exhibiting anti-infective, immunomodulatory, and wound healing properties having potential to improve survival rates among the P. aeruginosa infected burn populations, owning to its simple and easy application in resource-limited settings.

Investigation on the skin penetration of synthetic amorphous silica (SAS) used in cosmetic products

Synthetic amorphous silica (SAS) is used as additive in a variety of industrial applications for many decades and has been approved to be used in food, food contact materials, pharmaceuticals, and cosmetics. Due its internal structure, SAS is considered as a nanomaterial, thus it is affected by a general safety discussion. Based on the production process, SAS for cosmetic application is a nanomaterial by the EU Recommendation, although it was not considered as such, because the solely size-dependent definitions of the term “nanomaterial” emerged in recent times first in Recommendation 2011/696/EU. Therefore, former physicochemical and toxicological evaluations of SAS were already performed on nanomaterials, however, without being addressed as such. Safety concerns can only emerge if two criteria, (toxicological) hazard and exposure towards the substance is fulfilled at the same time. In case of SAS, the Scientific Committee on Consumer Safety (SCCS) challenged provided data to be insufficient to draw a conclusion regarding the safety of SAS and thus, requested further investigations, in particular by exploring skin penetration of particulate SAS.Investigation of specific particulate substances in skin penetration tests is an analytical challenge. The number of available analytical techniques that are capable to detect nanomaterials in complex matrices, like receptor fluids from skin penetration testing, are limited and still emerging. In the new studies, a comprehensive set of analytical techniques were used to investigate the skin penetration potential of SAS. Particle-sensitive, element and particle-specific combinations of techniques and different sample preparation procedures, that respected the particulate nature of SAS, were used to detect SAS in receptor fluids directly. In addition, electron microscopic techniques were used to examine different layers of skin to detect adsorbed SAS.The combination of Asymmetric Flow Field-Flow Fractionation (AF4) in combination with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for examination of receptor fluids and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM/EDX) for examination of skin itself, were identified as suitable techniques for the detection of SAS in skin penetration tests. Data from literature was used to compare the results of the studies with the outcome of other test systems (other particles, other techniques). Both, the test results, and literature evaluation led to the conclusion, that SAS does not penetrate skin. Based on this outcome and local and systemic dermal toxicity review of SAS, it can be concluded that dermal application of SAS in cosmetic formulations is negligible.

Asymmetric Electrospun Nanofiber Composed Of Polycaprolactone, Chitosan, and Curcumin To Promote Chronic Wound Healing

Chronic wounds are a growing medical issue around the world, with 2.4 - 4.5 million people afflicted in the United States alone. The condition currently makes up 2-3% of healthcare costs for developed countries, and this number is expected to increase as chronic wound-causing problems, like diabetes, grow in prevalence. Due to the lack of effective wound dressings, chronic wounds face a higher risk for bacterial infection and express high morbidity and mortality rates. Many current dressings are homogeneous and fail to account for the complexities of the different layers of skin. Alternatively, asymmetric electrospun nanofibers have a bilayer design that corresponds to the skin’s dermis and epidermis. We intend to demonstrate that an asymmetric electrospun nanofiber composed of polycaprolactone (PCL), chitosan (CS), and curcumin (Cur) can be utilized as a chronic wound dressing. These three biodegradable and biocompatible components were applied in an asymmetric design to mimic the protective epidermis and porous dermis. Upon electrospinning our asymmetric nanofiber and running it through a scanning electron microscope, we found that our hydrophobic PCL layer had a low porosity (52.16%) and thin nanofibers (281.82 nm), while our hydrophilic PCL/CS/Cur layer had a high porosity (61.18%) and thick nanofibers (425.54 nm). Our asymmetric nanofiber was also more effective at resisting bacterial permeation than the homogeneous PCL nanofiber. Our results highlight the superiority of asymmetric membranes for resisting bacterial infection and suggest that with further experimentation, we can establish our nanofiber as a viable wound dressing.

Assessing Skin Healing and Angiogenesis of Deep Burns in Vivo Using Two-Photon Microscopy in Mice

Prevalent methods for monitoring burn injuries and testing drug efficacies rely on fixed tissue sections. However, this may leave out cellular details in the living state. In vivo assessments of burn healing has been long sought after and are of scientific and clinical interest. Nicotinamide adenine dinucleotide (phosphate) (NAD(P)H), collagen, and melanin are endogenous fluorescent molecules and their signals can be captured by two-photon microscopy (TPM), therefore providing information on epidermal histological features and collagen growth in real-time. In addition, TMP imaging on exogenous fluorescent substances provides a basis for detecting blood vessels. In this work, two-photon microscopy was used to capture the exogenous fluorescent substances and endogenous fluorescent molecules at different times to assess and track burn healing in vivo. Combining TPM imaging and morphological characteristics, proliferation and differentiation of the keratinocytes in different layers of skin, collagen contents, and angiogenesis were identified and quantified. The TPM monitoring method provides an effective tool to systemically evaluate skin healing of deep burns in vivo.

Analysis of the Effects of Hyperthermia with Magnetic Nanoparticles on Cancer Tissues

Introduction: Hyperthermia is one of the noninvasive methods of treating cancer. In this method, heat can be generated in several methods. One of these methods is injecting magnetic nanoparticles as a solution into the tumor site and place it in a magnetic field. Methods: The study was analytical one, modeling was performed using computational methods, and in vitro experimental data were used as the boundary conditions. The problem was solved with a geometry consisting of different layers of skin, adjacent tissue, tumor and injection site and assuming axial symmetry. The problem was solved with a geometry consisting of different layers of skin, the adjacent tissue, the tumor and the injection site and assuming axial symmetry. The effect of different injection sites, effect of performing two injections with a smaller volume comparing with an injection with a large volume, and finally the effect of the injected solution on the temperature distribution of the tumor was investigated. Results: Results showed that injections with a smaller volume of solution in different sites would have better results, so that more parts of the tumor would reach to a temperature above 42°c, which is the temperature needed for having cancer cells died. Injection with the temperature of 37°c would be more effective than injection at room temperature and reached the desired temperature in less time. Conclusion: According to the novelty of this investigation in assuming data from empirical experiments on the solution containing cobalt ferrite nanoparticles coated with polyethylene glycol as the boundary condition of the problem in modeling, the study is an important step in a more precise prediction of the clinical conditions occurring through using these methods of hyperthermia.

Curcumin-Loaded Nanoemulsion for Better Cellular Permeation

Curcumin nanoemulsion was prepared using coconut oil, Tween 80 (surfactant) and polyethylene glycol (co-solvent) with the addition of honey and glycerol as additives. The nanoemulsion was optimized and systematically characterized for transdermal delivery. Small particle size (15.92 nm), low polydispersity index (0.17) and slight acidic (pH 4.18) curcumin nanoemulsion was obtained without any chemical degradation based on the Fourier transform infrared (FTIR) spectrum. The incorporation of curcumin inside nanoglobul improved curcumin stability and skin permeability. Its high permeability can be seen from Nile dyed curcumin in different layers of skin through fluorescent imaging. The release kinetic of curcumin followed the Higuchi model, which explains why the skin permeation was a Fickian diffusion-controlled process because the Korsmeyer constant was proven to be 0.3 (<0.5). Nanoencapsulation slightly decreased the antioxidant capacity of curcumin for about 7.9% compared to its free counterpart. It showed low cytotoxicity (EC50 2.3552 µg/mL) to human skin fibroblasts. Cell death was noticed at a high concentration (2.5 µg/mL) of treatment. Curcumin was also found to promote wound closure at low concentration 0.1563 µg/mL and was comparable with the performance of ascorbic acid based on scratch assay. Therefore, this nutritious curcumin nanoemulsion is a promising transdermal delivery system for topical application.

Lipid Vesicles and Nanoparticles for Non-invasive Topical and Transdermal Drug Delivery.

The delivery of drugs, via different layers of skin, is challenging because it acts as a natural barrier and exerts hindrance against molecules to permeate into or through it. To overcome such obstacles, different noninvasive methods, like vehicle-drug interaction, modifications of the horny layer and nanoparticles have been suggested. The aim of the present review is to highlight some of the non-invasive methods for topical, diadermal and transdermal delivery of drugs. Special emphasis has been made on the information available in numerous research articles that put efforts in overcoming obstacles associated with barrier functions imposed by various layers of skin. Advances have been made in improving patient compliance that tends to avoid hitches involved in oral administration. Of particular interest is the use of lipid-based vesicles and nanoparticles for dermatological applications. These particulate systems can effectively interact and penetrate into the stratum corneum via lipid exchange and get distributed in epidermis and dermis. They also have the tendency to exert a systemic effect by facilitating the absorption of an active moiety into general circulation.

Boronic Acid-Functionalized Two-Dimensional MoS2 at Biointerfaces.

While noncovalent interactions at two-dimensional nanobiointerfaces are extensively investigated, less knowledge about covalent interactions at this interface is available. In this work, boronic acid-functionalized 2D MoS2 was synthesized and its covalent multivalent interactions with bacteria and nematodes were investigated. Polymerization of glycidol by freshly exfoliated MoS2 and condensation of 2,5-thiophenediylbisboronic acid on the produced platform resulted in boronic acid-functionalized 2D MoS2. The destructive interactions between 2D MoS2 and bacteria as well as nematodes were significantly amplified by boronic acid functional groups. Because of the high antibacterial and antinematodal activities of boronic acid-functionalized 2D MoS2, its therapeutic efficacy for diabetic wound healing was investigated. The infected diabetic wounds were completely healed 10 days after treatment with boronic acid-functionalized 2D MoS2, and a normal structure for recovered tissues including different layers of skin, collagen, and blood vessels was detected.

Assessment of Laser Effects on Skin Rejuvenation.

Laser skin resurfacing has changed the approach of facial skin rejuvenation over the past decade. This article evaluates the laser effects on skin rejuvenation by the assessment of laser characteristics and histological and molecular changes, accompanied by the expression of proteins during and after laser-assisted rejuvenation of skin. It is important to note that different layers of skin with different cells are normally exposed to the sun's UV radiation which is the most likely factor in aging and damaging healthy skin. To identify the expression of proteins, using validated databases and reviewing existing data could reveal altered proteins which could be analyzed and mapped to investigate their expression and their different effects on cell biological responses. In this regard, proteomics data can be used for better investigation of the changes in the proteomic profile of the treated skin. Different assessments have revealed the survival and activation of fibroblasts and new keratinocytes with an increase of collagen and elastin fibers in the dermis and the reduction of matrix metalloproteinases (MMPs) and heat shock proteins (HSPs) as a result of different low-power laser therapies of skin. There are a wide range of biological effects associated with laser application in skin rejuvenation; therefore, more safety considerations should be regarded in the application of lasers in skin rejuvenation.

Assessment of Drug Flow Rate in Skin Cancer Therapy for Enhancing the Drug Delivery System.

The major impact in the clinical field is the harm posed by cancer. One most common type of cancer occurs in the skin. Though the conventionally existing modalities are successful in some cases, there is a need for new sensible methods to detect tumors at their initial stage. In accordance to these reasons and in addition to the incapability of the drugs to cross cellular barriers in skin the conventional administration methods are often compromised. To eradicate these problems the research work aims to develop the electrical analogue of skin involving layers like dermis, subcutaneous tissues, bones and muscular layers. The mathematical model has been developed to determine the electrical network of skin. The response of different skin layers are analyzed through simulation studies. It is observed that the cells present in each layer absorbs some amount of drug and let out the remaining to the neighboring layers. Further to minimize the diffusion rate of the drug a conventional controller has been incorporated and the results are analyzed by the contrast of the absorption and diffusion capacities for different layers of skin.

Bioengineered smart trilayer skin tissue substitute for efficient deep wound healing.

Skin substitutes for deep wound healing require meticulous designing and fabrication to ensure proper structural and functional regeneration of the tissue. Range of physical and mechanical properties conducive for regeneration of different layers of skin is a prerequisite of an ideal scaffold. However, single or bilayer substitutes, lacking this feature, fail to heal full thickness wound. Complete scar free regeneration of skin is still a big challenge. This study reports fabrication of a trilayer scaffold, from biodegradable polymers that can provide the right ambience for simultaneous regeneration of all the three layers of skin. The scaffold was developed through optimization of different fabrication techniques, namely, casting, electrospinning and lyophilisation, for obtaining a tailored trilayer structure. It has mechanical strength similar to skin layers, can maintain a porosity-gradient and provides microenvironments suitable for simultaneous regeneration of epidermis, dermis and hypodermis. A co-culture model, of keratinocytes and dermal fibroblasts, confirms the efficiency of the scaffold in supporting proliferation and differentiation of different types of cells, into organized tissue. The scaffold showed improved and expedited wound healing in-vivo. Taken together, these compelling evidences successfully established the engineered trilayer scaffold as a promising template for skin tissue regeneration in case of deep wound.

Vehiculation of Active Principles as a Way to Create Smart and Biofunctional Textiles.

In some specific fields of application (e.g., cosmetics, pharmacy), textile substrates need to incorporate sensible molecules (active principles) that can be affected if they are sprayed freely on the surface of fabrics. The effect is not controlled and sometimes this application is consequently neglected. Microencapsulation and functionalization using biocompatible vehicles and polymers has recently been demonstrated as an interesting way to avoid these problems. The use of defined structures (polymers) that protect the active principle allows controlled drug delivery and regulation of the dosing in every specific case. Many authors have studied the use of three different methodologies to incorporate active principles into textile substrates, and assessed their quantitative behavior. Citronella oil, as a natural insect repellent, has been vehicularized with two different protective substances; cyclodextrine (CD), which forms complexes with it, and microcapsules of gelatin-arabic gum. The retention capability of the complexes and microcapsules has been assessed using an in vitro experiment. Structural characteristics have been evaluated using thermogravimetric methods and microscopy. The results show very interesting long-term capability of dosing and promising applications for home use and on clothes in environmental conditions with the need to fight against insects. Ethyl hexyl methoxycinnamate (EHMC) and gallic acid (GA) have both been vehicularized using two liposomic-based structures: Internal wool lipids (IWL) and phosphatidylcholine (PC). They were applied on polyamide and cotton substrates and the delivery assessed. The amount of active principle in the different layers of skin was determined in vitro using a Franz-cell diffusion chamber. The results show many new possibilities for application in skin therapeutics. Biofunctional devices with controlled functionality can be built using textile substrates and vehicles. As has been demonstrated, their behavior can be assessed using in vitro methods that make extrapolation to their final applications possible.

CHEMICAL PENETRATION ENHANCERS FOR TRANSDERMAL DRUG DELIVERY SYSTEM

In present scenario more than 70% of the drugs that are taken by oral route are found to be less effective as desired, to overcome this constraint Transdermal drug delivery system has emerged as an innovative area of research, this system helps in delivering the drugs and macromolecules through skin into systemic circulation. At present, the worldwide market of Transdermal patch has reached 2 billion pounds. Many drugs like Estrogen, Progestrone, Nitroglycerine, Clonodine etc. are fabricated in form of Transdermal patches due to its ability to deliver the drug in non-invasive manner and also to overcome the problems associated with oral route. Although the Transdermal patches deliver the drug at predetermined rate1, the partitioning of drug from the system to the skin and then penetration through different layers of skin can be altered by adding penetration enhancers that can be physical or chemical in nature. This article deals with the role of different chemicals that can be used as penetration enhancer.
 Keywords: Penetration enhancer, Layer of skin, Fatty alcohol and glycol

Evidence for dietary time series in layers of cetacean skin using stable carbon and nitrogen isotope ratios.

Stable isotope analysis integrates diet information over a time period specific to the type of tissue sampled. For metabolically active skin of free-ranging cetaceans, cells are generated at the basal layer of the skin and migrate outward until they eventually slough off, suggesting potential for a dietary time series. Skin samples from cetaceans were analyzed using continuous-flow elemental analyzer isotope ratio mass spectrometry. We used ANOVAs to compare the variability of δ13 C and δ15 N values within and among layers and columns ("cores") of the skin of a fin, humpback, and sperm whale. We then used mixed-effects models to analyze isotopic variability among layers of 28 sperm whale skin samples, over the course of a season and among years. We found layer to be a significant predictor of δ13 C values in the sperm whale's skin, and δ15 N values in the humpback whale's skin. There was no evidence for significant differences in δ15 N or δ13 C values among cores for any species. Mixed-effects models selected layer and day of the year as significant predictors of δ13 C and δ15 N values in sperm whale skin across individuals sampled during the summer months in the Gulf of Alaska. These results suggest that skin samples from cetaceans may be subsampled to reflect diet during a narrower time period; specifically different layers of skin may contain a dietary time series. This underscores the importance of selecting an appropriate portion of skin to analyze based on the species and objectives of the study.

A CFA-Induced Model of Inflammatory Skin Disease in Miniature Swine.

Similarities between porcine and human skin make the pig an ideal model for preclinical studies of cutaneous inflammation and wound healing. Complete Freund's adjuvant (CFA) has been used to induce inflammation and to study inflammatory pain in several animal models. Here, we evaluated the inflammation caused by CFA injected in different layers of skin and subcutaneous (SC) tissue in a large-animal model. The degree of inflammation was evaluated at early and late time points by visual inspection and histopathologic analysis. In addition, the side effects of CFA injections were evaluated based on clinical findings, behavioral changes, physiologic state, and (histo)pathologic lesions. Pigs were injected with CFA at the back of the neck's skin at different depths. All animals showed histologic signs of inflammation at the injection site. Animals injected SC did not show any signs of pain or distress (loss of appetite, abnormal behavior) and did not require pain medication. Inflammation was followed by measuring the area of induration beneath the skin. Animals injected into the dermis and/or epidermis demonstrated a severe inflammatory response on the skin surface with massive swelling, redness within 12hrs of CFA injection, and severe skin necrosis within a week, preventing accurate induration measurements. In contrast to animals injected SC, animals receiving intradermal and/or intraepidermal injection of CFA showed signs of distress requiring pain medication. Conclusion. SC injection of CFA in swine induces an inflammatory response that can be measured accurately by induration without causing unnecessary discomfort, providing a useful preclinical large-animal model of inflammatory skin disease.

Digital Photography: a Tool for Nursing on the Assessment of Pressure Lesions

This work sought to assess the inter-observer agreement among expert nurses by using digital photographs and between these experts and the nursing registries in the electronic clinical record in the identification and degree of PL. This was an observational study, including 225 photographic records (184 patients, 97 with pressure lesion and 128 registries without lesion) randomly selected from the total of photographs registered in the PENFUP clinical trial (without lesion). Three expert evaluators assessed said photographs in masked manner. The notes from nursing of patients included related with the description of PL were evaluated. The Kappa index was calculated along with the composite agreement ratio for each evaluation. Good agreement was observed among expert evaluators of photographic records on the presence of PL and between good-moderate for the degree of PL (I-II). Likewise, upon evaluating the agreement between the nursing registries of PL and the photographic assessment of the three expert evaluators of the same areas, good agreement was observed to determine the presence of PL and moderate agreement for the degrees of PL. Photographic records are a tool that permits recognizing the types of wounds, as well as the visualization of the different layers of skin injured. The study highlights the importance of assessment and validation by experts, given that it permits identifying existing problems that can lead to the underestimation or overestimation of PL when conducted by a single caregiver.

Comparison between high-frequency ultrasonography and histological assessment reveals weak correlation for measurements of scar tissue thickness

ObjectiveCurrent methods for evaluating scar tissue volume following burns have shortcomings. The Vancouver Burn Scar scale is subjective, leading to a high variability in assessment. Although histological assessment via punch biopsy can discriminate between the different layers of skin, such an approach is invasive, inefficient, and detrimental to patient experience and wound healing. This study investigates the accuracy of high-frequency ultrasonography, a non-invasive alternative to histology, for measuring dermal and epidermal thickness in scar tissue. MethodsScar thicknesses of 10 patients following burns were assessed using a 2-D high-frequency ultrasound probe. The scars were then biopsied using a circular 4mm punch biopsy for histological assessment. Dermal, epidermal, and total thickness of the scar tissue was measured using ultrasound and histology, and correlations between the two measurements were calculated. ResultsThere was not a strong correlation between ultrasound measurement and histological analysis for epidermal, dermal, and total thickness (Spearman’s rank correlation of −0.1223, −0.6242, and −0.6242) of scar tissue. ConclusionsMeasurements of scar thickness using high-frequency ultrasonography did not recapitulate the in vivo dermal, epidermal and total thickness. Based on these findings, strategies for further optimization of 2-D ultrasonography is discussed before clinical and research use.

The Effect of Particle Size on the Deposition of Solid Lipid Nanoparticles in Different Skin Layers: A Histological Study.

In the present study the effect of particle size, as a substantial parameters in skin penetration, on the deposition depth and rate of SLNs in different layers of skin was explored. SLNs in different particle size ranges (80, 333 and 971 nm) made of Precirol as solid lipid were prepared using hot melt homogenization technique and pigmented by Rhodamine B to be able to be tracked in the skin under inspection of fluorescent microscopy. After 0.5 h, 3 h, 6 h and 24 h of SLNs administration on rat skin, animals were sacrificed and exercised skins were sliced by a freeze microtome. SLNs were monitored in the skin structure under fluorescence microscope. The size of SLNs played a crucial role in the penetration to deep skin layers. The sub100 nm size range of SLNs showed the most promising skin penetration rate and depth mainly via hair follicles. The results of the present study indicated that the selection of an appropriate size of particles may be a valuable factor impacting the therapeutic outcomes of dermal drug administration.