The molecular arrangement of ceramides in the unit cell of the long periodicity phase of stratum corneum models shows a high adaptability to different ceramide head group structures.

The stratum corneum (SC) lipid matrix, composed primarily of ceramides (CERs), cholesterol and free fatty acids (FFA), has an important role for the skin barrier function. The presence of the long periodicity phase (LPP), a unique lamellar phase, is characteristic for the SC. Insight into the lipid molecular arrangement within the LPP unit cell is imperative for understanding the relationship between the lipid subclasses and the skin barrier function.

Effect of sphingosine and phytosphingosine ceramide ratio on lipid arrangement and barrier function in skin lipid models.

The lipids in the uppermost layer of the skin, the stratum corneum (SC), play an important role in the skin barrier function. The three main subclasses in the SC lipid matrix are ceramides (CER), cholesterol, and free fatty acids. In inflammatory skin diseases, such as atopic dermatitis and psoriasis, the SC lipid composition is modulated compared to the composition in healthy SC.

Phytosphingosine ceramide mainly localizes in the central layer of the unique lamellar phase of skin lipid model systems.

Understanding the lipid arrangement within the skin's outermost layer, the stratum corneum (SC), is important for advancing knowledge on the skin barrier function. The SC lipid matrix consists of ceramides (CERs), cholesterol, and free fatty acids, which form unique crystalline lamellar phases, referred to as the long periodicity phase (LPP) and short periodicity phases. As the SC lipid composition is complex, lipid model systems that mimic the properties of native SC are used to study the SC lipid organization and molecular arrangement.

Engineering of an automated nano-droplet dispensing system for fabrication of antigen-loaded dissolving microneedle arrays.

Dissolving microneedle arrays (dMNAs) are promising devices for intradermal vaccine delivery. The aim of this study was to develop a reproducible fabrication method for dMNAs based on an automated nano-droplet dispensing system that minimizes antigen waste. First, a polymer formulation was selected to dispense sufficiently small droplets (<18 nL) that can enter the microneedle cavities (base diameter 330 µm).

Improved organotypic skin model with reduced quantity of monounsaturated ceramides by inhibiting stearoyl-CoA desaturase-1.

Full thickness models (FTM) are 3D in vitro skin cultures that resemble the native human skin (NHS) to a great extent. However, the barrier function of these skin models is reduced. The skin barrier is located in the stratum corneum (SC) and consists of corneocytes embedded in a lipid matrix.

Skin barrier lipid enzyme activity in Netherton patients is associated with protease activity and ceramide abnormalities.

Individuals with Netherton syndrome (NTS) have increased serine protease activity, which strongly impacts the barrier function of the skin epidermis and leads to skin inflammation. Here, we investigated how serine protease activity in NTS correlates with changes in the stratum corneum (SC) ceramides, which are crucial components of the skin barrier. We examined two key enzymes involved in epidermal ceramide biosynthesis, β-glucocerebrosidase (GBA) and acid-sphingomyelinase (ASM).

Diphtheria toxoid dissolving microneedle vaccination: Adjuvant screening and effect of repeated-fractional dose administration.

In this study the effect of repeated-fractional intradermal administration of diphtheria toxoid (DT) compared to a single administration in the presence or absence of adjuvants formulated in dissolving microneedles (dMNs) was investigated. Based on an adjuvant screening with a hollow microneedle (hMN) system, poly(I:C) and gibbsite, a nanoparticulate aluminum salt, were selected for further studies: they were co-encapsulated with DT in dMNs with either a full or fractional DT-adjuvant dose. Sharp dMNs were prepared regardless the composition and were capable to penetrate the skin, dissolve within 20 min and deposit the intended antigen-adjuvant dose, which remained in the skin for at least 5 h.

Skin of atopic dermatitis patients shows disturbed β-glucocerebrosidase and acid sphingomyelinase activity that relates to changes in stratum corneum lipid composition.

Patients with Atopic Dermatitis (AD) suffer from inflamed skin and skin barrier defects. Proper formation of the outermost part of the skin, the stratum corneum (SC), is crucial for the skin barrier function. In this study we analyzed the localization and activity of lipid enzymes β-glucocerebrosidase (GBA) and acid sphingomyelinase (ASM) in the skin of AD patients and controls.

Hyaluronan molecular weight: Effects on dissolution time of dissolving microneedles in the skin and on immunogenicity of antigen.

Biomaterials used as matrix for dissolving micro needles (dMNs) may affect the manufacturing process as well as the potency of the active pharmaceutical ingredient, e.g. the immunogenicity of incorporated vaccine antigens.

The effects of LXR agonist T0901317 and LXR antagonist GSK2033 on morphogenesis and lipid properties in full thickness skin models.

Full thickness models (FTMs) are 3D-cultured human skin models that mimic many aspects of native human skin (NHS). However, their stratum corneum (SC) lipid composition differs from NHS causing a reduced skin barrier. The most pronounced differences in lipid composition are a reduction in lipid chain length and increased monounsaturated lipids.

Selectivity in cornified envelop binding of ceramides in human skin and the role of LXR inactivation on ceramide binding.

The cornified lipid envelope (CLE) is a lipid monolayer covalently bound to the outside of corneocytes and is part of the stratum corneum (SC). The CLE is suggested to act as a scaffold for the unbound SC lipids. By profiling the bound CLE ceramides, a new subclass was discovered and identified as an omega-hydroxylated dihydrosphingosine (OdS) ceramide.

Compromising human skin in vivo and ex vivo to study skin barrier repair.

Ex vivo regenerated stratum corneum (SC) after tape-stripping can be used as a model to study the barrier function of compromised skin. Yet, details about how close the regenerated SC model mimics the lipid properties (e.g.

Hypercholesterolemia in young adult APOE mice alters epidermal lipid composition and impairs barrier function.

Long-term exposure to hypercholesterolemia induces the development of skin xanthoma's characterized by the accumulation of lipid-laden foam cells in humans and in mice. Early skin changes in response to hypercholesterolemia are however unknown. In this study, we investigated the skin lipid composition and associated barrier function in young adult low-density lipoprotein receptor knockout (LDLR) and apolipoprotein E knockout (APOE) mice, two commonly used hypercholesterolemic mouse models characterized by the accumulation of apolipoprotein B containing lipoproteins.

Hyaluronan-based dissolving microneedles with high antigen content for intradermal vaccination: Formulation, physicochemical characterization and immunogenicity assessment.

The purpose of this study was to optimize the manufacturing of dissolving microneedles (dMNs) and to increase the antigen loading in dMNs to investigate the effect on their physicochemical properties. To achieve this, a novel single-array wells polydimethylsiloxane mold was designed, minimizing antigen wastage during fabrication and achieving homogeneous antigen distribution among the dMN arrays. Using this mold, hyaluronan (HA)-based dMNs were fabricated and tested for maximal ovalbumin (OVA) content.

Immunogenicity of diphtheria toxoid and poly(I:C) loaded cationic liposomes after hollow microneedle-mediated intradermal injection in mice.

In this study, we aimed to investigate the immunogenicity of cationic liposomes loaded with diphtheria toxoid (DT) and poly(I:C) after hollow microneedle-mediated intradermal vaccination in mice. The following liposomal formulations were studied: DT loaded liposomes, a mixture of free DT and poly(I:C)-loaded liposomes, a mixture of DT-loaded liposomes and free poly(I:C), and liposomal formulations with DT and poly(I:C) either individually or co-encapsulated in the liposomes. Reference groups were DT solution adjuvanted with or without poly(I:C) (DT/poly(I:C)).

Development of PLGA nanoparticle loaded dissolving microneedles and comparison with hollow microneedles in intradermal vaccine delivery.

Skin is an attractive but also very challenging immunisation site for particulate subunit vaccines. The aim of this study was to develop hyaluronan (HA)-based dissolving microneedles (MNs) loaded with PLGA nanoparticles (NPs) co-encapsulating ovalbumin (OVA) and poly(I:C) for intradermal immunisation. The NP:HA ratio used for the preparation of dissolving MNs appeared to be critical for the quality of MNs and their dissolution in ex vivo human skin.

Altered lipid properties of the stratum corneum in Canine Atopic Dermatitis.

Skin barrier disruption plays a role in the pathogenesis of atopic dermatitis (AD) in humans. However, little is known about skin barrier (dys-) function in Canine Atopic Dermatitis. The properties of lipids located in the outermost layer of the skin, the stratum corneum (SC) are considered to be important for the barrier.

Intradermal vaccination with hollow microneedles: A comparative study of various protein antigen and adjuvant encapsulated nanoparticles.

In this study, we investigated the potential of intradermal delivery of nanoparticulate vaccines to modulate the immune response of protein antigen using hollow microneedles. Four types of nanoparticles covering a broad range of physiochemical parameters, namely poly (lactic-co-glycolic) (PLGA) nanoparticles, liposomes, mesoporous silica nanoparticles (MSNs) and gelatin nanoparticles (GNPs) were compared. The developed nanoparticles were loaded with a model antigen (ovalbumin (OVA)) with and without an adjuvant (poly(I:C)), followed by the characterization of size, zeta potential, morphology, and loading and release of antigen and adjuvant.

Diphtheria toxoid and N-trimethyl chitosan layer-by-layer coated pH-sensitive microneedles induce potent immune responses upon dermal vaccination in mice.

Dermal immunization using antigen-coated microneedle arrays is a promising vaccination strategy. However, reduction of microneedle sharpness and the available surface area for antigen coating is a limiting factor. To overcome these obstacles, a layer-by-layer coating approach can be applied onto pH-sensitive microneedles.

Altered expression of epidermal lipid bio-synthesis enzymes in atopic dermatitis skin is accompanied by changes in stratum corneum lipid composition.

Background: The barrier dysfunction in atopic dermatitis (AD) skin correlates with stratum corneum (SC) lipid abnormalities including reduction of global lipid content, shorter ceramide (CER) as well as free fatty acid (FFA) chain length and altered CER subclass levels. However, the underlying cause of these changes in lipid composition has not been fully investigated.

Aim: We investigated whether the expression of CER and FFA biosynthesis enzymes are altered in AD skin compared with control skin and determine whether changes in enzyme expression can be related with changes in lipid composition.

Repeated fractional intradermal dosing of an inactivated polio vaccine by a single hollow microneedle leads to superior immune responses.

The purpose of this study was to investigate the effect of various repeated fractional intradermal dosing schedules of inactivated polio vaccine serotype 1 (IPV1) on IPV1-specific IgG responses in rats. By utilizing an applicator that allowed for precisely controlled intradermal microinjections by using a single hollow microneedle, rats were immunized intradermally with 5 D-antigen units (DU) of IPV1 at 150μm skin depth. This dose was administered as a bolus, or in a repeated fractional dosing schedule: 4 doses of 1.

Quantitative analysis of ceramides using a novel lipidomics approach with three dimensional response modelling.

In the outermost layer of the skin, the stratum corneum (SC), ceramides form a diverse and essential pool of lipids. Due to their diversity and the limited availability of synthetic standards it is challenging to quantitatively analyse all SC ceramides independently. We aim to perform a detailed analysis of ceramides on SC harvested from in vivo and ex vivo skin, therefore, a LC/MS method was developed in which all steps from sample acquisition until data analysis were examined and optimized.

IgG-loaded hyaluronan-based dissolving microneedles for intradermal protein delivery.

Dissolving microneedles are an attractive approach for non-invasive delivery of drugs via the skin, particularly when the doses are in the microgram or low-milligram range. The aim of the study was to develop hyaluronan-based, monoclonal IgG-loaded microneedles for intradermal delivery enabling efficient penetration and rapid dissolution in the skin while preserving protein stability. Microscopic analysis showed successful preparation of sharp microneedles with the tip length of ~280 μm and with up to 10% (w/w) of IgG content.