Cutaneous Bioavailability Research Articles

Modern topical drugs-new developments in galenics and pharmacology

The importance of topically applied pharmaceuticals, especially for the treatment of dermatological diseases, is still essential. Thanks to detailed knowledge of the organisation and function of the physicochemical barrier of the skin, new galenic concepts have increasingly been developed to market maturity in recent years. Colloidal drug carrier systems in particular, but also targeted physicochemical modifications of matrices are used to optimise the cutaneous bioavailability of topically applied drugs. In addition, new molecules are increasingly becoming available for the development of these preparations or drugs known from systemic therapy are being formulated into topicals. Against this background, dermatopharmacology is also developing more and more into ahighly specialised science in this area, which is producing innovative concepts for the therapy of special indications. In addition to the classic small-molecule drugs, biotechnological molecules are increasingly finding their way into application, so that amodern age of dermatopharmacology has dawned, which will open up previously unimagined possibilities for topical therapy now and in the coming years.

Intravenous treatment of calcinosis cutis with sodium thiosulfate - A case series.

Calcinosis cutis is defined as the deposition of calcium salts in the skin. The dystrophic form is the most common and usually occurs in chronic inflammatory processes associated with collagenoses. Therapeutic options include surgical excision as well as a few pharmacological treatments. Overall, the evidence for the known therapeutic interventions is very limited and there is a lack of valid recommendations. Intravenous sodium thiosulfate has been used successfully in the treatment of calciphylaxis. In our case series, five patients with dystrophic calcinosis cutis received intravenous sodium thiosulfate for at least six cycles on five consecutive days per month, with single doses of 12.5g and 25.0g, respectively. A reduction in the calcified lesions could not be proven with certainty, but stable disease conditions were achieved. Intravenous sodium thiosulfate may counteract the progression of calcinosis cutis. The successful use of epicutaneously applied sodium thiosulfate, as described in the literature, suggests that a higher cutaneous bioavailability can be achieved to exert a lytic effect on calcinosis cutis. This is further supported by the reported efficacy of high-dose sodium thiosulfate in the treatment of calciphylaxis.

Topical Semisolid Drug Product Critical Quality Attributes with Relevance to Cutaneous Bioavailability and Pharmacokinetics: Part I—Bioequivalence of Acyclovir Topical Creams

PurposeTo develop a toolkit of test methods for characterizing potentially critical quality attributes (CQAs) of topical semisolid products and to evaluate how CQAs influence the rate and extent of active ingredient bioavailability (BA) by monitoring cutaneous pharmacokinetics (PK) using an In Vitro Permeation Test (IVPT).MethodsProduct attributes representing the physicochemical and structural (Q3) arrangement of matter, such as attributes of particles and globules, were assessed for a set of test acyclovir creams (Aciclostad® and Acyclovir 1A Pharma) and compared to a set of reference acyclovir creams (Zovirax® US, Zovirax® UK and Zovirax® Australia). IVPT studies were performed with all these creams using heat-separated human epidermis, evaluated with both, static Franz-type diffusion cells and a flow through diffusion cell system.ResultsA toolkit developed to characterize quality and performance attributes of these acyclovir topical cream products identified certain differences in the Q3 attributes and the cutaneous PK of acyclovir between the test and reference sets of products. The cutaneous BA of acyclovir from the set of reference creams was substantially higher than from the set of test creams.ConclusionsThis research elucidates how differences in the composition or manufacturing of product formulations can alter Q3 attributes that modulate myriad aspects of topical product performance. The results demonstrate the importance of understanding the Q3 attributes of topical semisolid drug products, and of developing appropriate product characterization tests. The toolkit developed here can be utilized to guide topical product development, and to mitigate the risk of differences in product performance, thereby supporting a demonstration of bioequivalence (BE) for prospective topical generic products and reducing the reliance on comparative clinical endpoint BE studies.

In Vitro-In Vivo Correlation of Buprenorphine Transdermal Systems Under Normal and Elevated Skin Temperature.

Application of external heat using a heating pad over buprenorphine transdermal system, Butrans® has been shown to increase systemic levels of buprenorphine in human volunteers. The purpose of this study was to perform in vitro permeation studies at normal as well as elevated temperature conditions to evaluate the correlation of in vitro data with the existing in vivo data. In vitro permeation tests (IVPT) were performed on human skin from four donors. The IVPT study design was harmonized to a previously published clinical study design and skin temperature was maintained at either 32 ± 1°C or 42 ± 1°C to mimic normal and elevated skin temperature conditions, respectively. IVPT studies on human skin were able to demonstrate heat induced enhancement in flux and cumulative amount of drug permeated from Butrans® which was reasonably consistent with the corresponding enhancement observed in vivo. Level A in vitro-in vivo correlation (IVIVC) was established using unit impulse response (UIR) based deconvolution method for both baseline and heat arms of the study. The percent prediction error (%PE) calculated for AUC and Cmax values was less than 20%. The studies indicated that IVPT studies performed under the same conditions as those of interest in vivo may be useful for comparative evaluation of the effect of external heat on transdermal delivery system (TDS). Further research may be warranted to evaluate factors, beyond cutaneous bioavailability (BA) assessed using an IVPT study, that can influence plasma exposure in vivo for a given drug product.

Biocompatible gliadin-sericin complex colloidal particles used for topical delivery of the antioxidant phloretin

Oxidative stress caused by environmental exposures results in numerous skin diseases. Phloretin (PHL) is often used to relieve various skin symptoms, however, precipitation or crystallization of PHL in aqueous systems limits its ability to diffuse through the stratum corneum, making it difficult to exert effect at the target. To address this challenge, we herein report a method for the generation of core–shell nanostructure (G-LSS) via the growth of sericin crust around gliadin nanoparticle as a topical nanocarrier of PHL to improve its cutaneous bioavailability. Physicochemical performance, morphology, stability, and antioxidant activity of the nanoparticles were characterized. G-LSS-PHL exhibited uniformed spherical nanostructures with the robust encapsulation on PHL (∼90 %). This strategy protected PHL from UV-induced degradation, facilitating to inhibit erythrocyte hemolysis and quench free radicals in a dose-dependent manner. Transdermal delivery experiments and porcine skin fluorescence imaging indicated that G-LSS facilitated the penetration of PHL across the epidermis layer of skin to reach deep-seated sites, and promoted cumulative turnover of PHL with a 2.0-fold increase. Cell cytotoxicity and uptake assay confirmed that as-prepared nanostructure was nontoxic to HSFs, and promoted cellular absorption of PHL. Therefore, this work opened up new promising avenues for developing robust antioxidant nanostructure for topical applications.

Permethrin Steal Effect by Unmasked Corneocytic Keratin in Topical Therapy of Scabies

Introduction: The use of epicutaneously applied permethrin in the treatment of common scabies is considered to be the first-line therapy. Due to increasing clinical treatment failure, the development of genetic resistance to permethrin in Sarcoptes scabiei var. hominis has been postulated. In addition, metabolic resistance and pharmacokinetic limitations by parasitic digestion and reactive thickening of stratum corneum are suspected to cause a reduction in cutaneous bioavailability. Methods: Since lipophilic permethrin is known to form hydrophobic interactions with proteins via van der Waals interactions, a similar interaction was assumed and investigated for permethrin and the protein keratin. Using keratin particles extracted from animal material, a model for hyperkeratotic and parasitic digested scabies skin was developed. Using fluorescence-labeled keratin and ³H-permethrin, their interaction potential was validated by loading and unloading experiments. Additionally, the impact of keratin to permethrin penetration was investigated based on an in vitro model using Franz diffusion cells. Results: For the first time, keratin particles were introduced as a model for dyskeratotic skin, as we were able to show, the keratin particles’ interaction potential with permethrin but no penetration behavior into the stratum corneum. Moreover, comparative penetration experiments of a reference formulation with and without added keratin or keratin-adherent permethrin showed that keratin causes a steal effect for permethrin, leading to a relevant reduction in cutaneous bioavailability in the target compartment. Conclusion: The results provide further evidence for a relevant pharmacokinetic influencing factor in the epicutaneous application of permethrin and a rationale for the necessity of keratolytic pretreatment in hyperkeratotic skin for the effective use of topical permethrin application in scabies.

Supersaturation as a Galenic Concept for Improving the Cutaneous Bioavailability of Drugs in Topical Therapy.

The essential force that allows an epicutaneously applied drug to penetrate the skin is mediated by diffusion. The physicochemical properties of the skin tissue at the site of application and the concentration gradient of the dissolved drug between the vehicle and the stratum corneum are decisive here. One way to specifically improve these diffusion conditions is to use supersaturation. This uses the physical principle of the difference between the solubility curve and precipitation curve (Ostwald-Miers range). During the conversion of the application vehicle into the segregation vehicle, supersaturation of the dissolved drug substance in a solvent is achieved by evaporation, e.g., of a solubilizer. In principle, the change in solubility can also be achieved by heating and then cooling a solution. This principle has already been realized in a formulation of a fixed combination of calcipotriol and betamethasone dipropionate, two lipophilic drugs susceptible to hydrolysis, and is available on the market as a spray foam.

Therapeutic peculiarities in diseases of the nipple skin

Die Mamillenregion ist durch besondere anatomische Verhältnisse charakterisiert und lässt sich aus dermatologischer Perspektive in Brusthaut, Haut des Brustwarzenhofes (Areola) und Haut der Brustwarze (Papilla mammae) unterteilen. Im klinischen Zusammenhang sind die Brustwarzen häufig während der Stillzeit durch mechanische Beanspruchung, Milieuänderung mit Mazeration durch den Milchfluss sowie durch mikrobielle Erreger alteriert. Zudem besteht hier die Gefahr der Entwicklung einer Mastitis puerperalis. Außerhalb der Schwangerschaft und Stillzeit finden sich gelegentlich an der Mamillenhaut Ekzemerkrankungen, häufig bei atopischer Disposition (atopisches Mamillenekzem) oder als irritatives Kontaktekzem („joggers nipple“). Seltener werden allergische Kontaktekzeme auf Konservierungsstoffe von Topika oder Metallen (Piercings) beobachtet. Auch im Rahmen einer Skabiesinfestation wird eine Beteiligung der Mamillen, insbesondere bei Frauen, regelmäßig beobachtet. Von großer klinischer Bedeutung sind seltene, präinvasive Läsionen eines Mammakarzinoms oder der Morbus Paget der Mamille vom extramammären Typ. Durch die besonderen anatomischen Gegebenheiten ist es naheliegend, dass bei der Anwendung von Topika sich auch spezifische Penetrationsbedingungen ableiten. Experimentelle Untersuchungen an Humanhaut ex vivo legen nahe, dass in Abhängigkeit von der Molmasse und der Löslichkeit des Arzneistoffs sowie des eingesetzten Vehikelsystems eine deutliche Zunahme der kutanen Bioverfügbarkeit, insbesondere an der Brustwarze selbst durch den transpapillären Diffusionsweg, auftreten kann. Dies sollte insbesondere bei der topischen Anwendung von Arzneistoffen mit bekanntem dosisabhängigem Nebenwirkungspotenzial (z. B. Glukokortikoiden) beachtet werden. Allerdings fehlt dafür bisher eine klinische Evidenz.

Simultaneous Delivery of Econazole, Terbinafine and Amorolfine with Improved Cutaneous Bioavailability: A Novel Micelle-Based Antifungal “Tri-Therapy”

Lack of accurate diagnosis and the use of formulations designed to address the poor aqueous solubility of antifungal agents, but not optimized for delivery, contribute to unsatisfactory outcomes for topical treatment of cutaneous mycoses. The objective of this study was to develop a micelle-based antifungal formulation containing econazole (ECZ), terbinafine (TBF) and amorolfine (AMF) using D-α-tocopheryl polyethylene glycol succinate (TPGS) for simultaneous cutaneous delivery of three agents with complementary mechanisms of action. The antifungal “tri-therapy” micelle-based formulation containing 0.1% ECZ, 0.1% TBF and 0.025% AMF had a drug loading 10-fold lower than the “reference” marketed formulations (Pevaryl®, 1% ECZ; Lamisil®, 1% TBF; Loceryl®, 0.25% AMF). Finite dose application of the micelle-based formulation for 6 h resulted in a statistically equivalent deposition of ECZ (p > 0.05) and TBF (p > 0.05) from the 2 systems, and a 2-fold higher accumulation of AMF (p = 0.017). Antifungal concentrations above MIC80 against Trichophyton rubrum were achieved in each skin layer with the “tri-therapy”, which also exhibited a preferential deposition of each antifungal agent in pilosebaceous unit (PSU)-containing biopsies as compared with PSU-free biopsies (p < 0.05). A planned clinical study will test whether these promising results translate to improved therapeutic outcomes in vivo.

An eco-friendly zein nanoparticle as robust cosmetic ingredient ameliorates skin photoaging

Zein colloidal particles, which have generally regarded as safe (GRAS) status, have been routinely used in formulations of oral nutraceuticals but not in skin care products. Herein, we constructed for the first time zein-based topical vehicles to address skin photoaging. To this end, we fabricated a new type of eco-friendly nanoparticles by co-assembling zein with hyaluronic acid (HA), a cell-specific molecule, to encapsulate hydrophobic tetrahydrocurcumin (THC) with an aim to improve its cutaneous bioavailability. Impressively, the prepared nanoparticles could increase the solubility of THC in water by 72.84 times, and were stable at pH 4–10. In particular, the topical delivery systems were effective in UVB-induced cell and animal photoaging models, and were able to restore the accumulation of matrix metalloproteinase-1 (MMP-1) and inflammatory factors to the normal levels at the selected conditions. In addition, the biotransformation of THC in HaCaT cells was observed and clarified. This strategy may open up new promising avenues for developing innovative nanocosmetics containing anti-photoaging ingredient.

Polymeric micelle formulations for the cutaneous delivery of sirolimus: A new approach for the treatment of facial angiofibromas in tuberous sclerosis complex

Facial angiofibromas are benign tumors characteristic of tuberous sclerosis complex. The disease involves the mTOR pathway and the cutaneous manifestation responds to topical treatment with sirolimus (SIR). However, there are no approved topical SIR products and extemporaneous formulations have been sub-optimal. The aims of this study were (i) to develop aqueous formulations of SIR loaded in polymeric micelles prepared using D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and (ii) to use the cutaneous biodistribution method, in conjunction with a new statistical approach, to investigate the feasibility of SIR delivery to the viable epidermis. Optimized micelle solutions and hydrogels (0.2%) were developed and stable at 4 °C for at least 6 and 3 months, respectively. Cutaneous delivery experiments (infinite and finite dose) using porcine skin demonstrated that both formulations increased SIR cutaneous bioavailability as compared to the control (ointment 0.2%). Moreover, studies with the micellar hydrogel 0.2% demonstrated SIR deposition in the viable epidermis with no transdermal permeation. These encouraging results confirmed that polymeric micelles enabled development of aqueous SIR formulations capable of targeted epidermal delivery. Furthermore, the cutaneous biodistribution provided a detailed insight into drug bioavailability in the different skin compartments that could complement/explain clinical observations of formulation efficacy.

Influence of keratolytics on cutaneous pharmacokinetics of glucocorticoids.

Keratolytics are often used to accelerate and improve the therapeutic response of hyperkeratotic dermatoses. Keratolytics are a chemically inhomogeneous group of substances and substance mixtures that clinically lead to a decrease in symptoms of a cornification disorder, but mediate different effects. Thus, keratolytic, keratoplastic, keratoemulsifying and keratodiluting effects are distinguished. The physicochemical effects or pharmacological efficacy of the respective keratolytics result in different mechanism as well as risks with regard to local or systemic compatibility. Until now, only little attention has been paid upon selection of keratolytics to the immediate consequences regarding diffusion conditions and pharmacokinetics of sequentially applied topicals, in particular of glucocorticoids. This paper deals with the influence of keratolytics on the penetration-time profile of betamethasone dipropionate in sequential application. For this purpose, cutaneous bioavailability was investigated with the Franz chamber test using a tritium-labeled drug depending on the previous application of a keratolytic agent. Comparative data analyses were performed. It was shown that keratoplastic substances significantly promote diffusion of the glucocorticoid. Keratoemulsifying substance mixtures exert no relevant effects in this regard, while keratodiluting substance mixtures inhibit penetration. The targeted selection of a keratolytic can optimize the therapeutic effect and influence the bioavailability of sequentially applied topicals.

Methotrexate-Loaded Nanostructured Lipid Carrier Gel Alleviates Imiquimod-Induced Psoriasis by Moderating Inflammation: Formulation, Optimization, Characterization, In-Vitro and In-Vivo Studies.

IntroductionMethotrexate exhibits poor cutaneous bioavailability and systemic side effects on topical administration, so there is an unmet need for a novel carrier and its optimized therapy. Methotrexate-loaded nanostructured lipid carriers (MTXNLCs) were formulated and characterized to determine in vitro drug release and evaluate the role of MTXNLC gel in the topical treatment of psoriasis.MethodsA solvent diffusion technique was employed to prepare MTXNLCs, which was optimized using 32 full factorial designs. The mean diameter and surface morphology of MTXNLCs was evaluated. The crystallinity of lyophilized MTXNLCs was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD). MTXNLCs were integrated in 1% w/w Carbopol 934 P gel base, and in vitro skin deposition studies in human cadaver skin (HCS) were carried out.ResultsThe optimized MTXNLCs were rod-shaped, with an average particle size of 253 ± 8.65 nm, a zeta potential of −26.4±0.86 mV, and EE of 54.00±1.49%. DSC and XRD data confirmed the formation of NLCs. Significantly higher deposition of MTX was found in HCS from MTXNLC gel (71.52 ±1.13%) as compared to MTX plain gel (38.48±0.96%). In vivo studies demonstrated significant improvement in therapeutic response and reduction in local side effects with MTXNLCs-loaded gel in the topical treatment of psoriasis. Anti-psoriatic efficacy of MTXNLCs 100 ug/cm2 compared with plain MTX gel was evaluated using imiquimod (IMQ)-induced psoriasis in BALB/c mice. The topical application of MTXNLCs to the mouse ear resulted in a significant reduction of psoriatic area and severity index, oxidative stress, inflammatory cytokines like TNF-α, IL-1β, and IL-6 and IMQ-induced histopathological alterations in mouse ear samples.ConclusionDeveloped formulation of MTXNLC gel demonstrated better anti-psoriatic activity and also displayed prolonged and sustained release effect, which shows that it can be a promising alternative to existing MTX formulation for the treatment of psoriasis.

Topical delivery of Tacrolimus using liposome containing gel: An emerging and synergistic approach in management of psoriasis

Psoriasis is a chronic relapsing inflammatory and hyperproliferative skin disease affecting quality of life. It affects an estimated 8 million Americans and more than 125 million people worldwide. The estimated cost to treat psoriasis in USA is over 13 billion US dollars per year. Treatment of psoriasis may include topical steroid-sparing agent, topical corticosteroids, phototherapy or biologics. Tacrolimus has 10-fold greater immunosuppressive activity than the ciclosporin A which has been recommended for effective treatment of psoriasis. However, it has been widely investigated using conventional formulation approaches which limit its clinical outcomes. It has poor cutaneous bioavailability when administered topically using conventional delivery approach, thus it has poor efficacy against the psoriasis. Low aqueous solubility and high degradation of Tacrolimus make it difficult to formulate as a liquid preparation. Moreover, Tacrolimus has narrow therapeutic index and thus it is essential to prevent its possible toxic effects when a modified release dosage form is administered. The present hypothesis aims to put forward to incorporate Tacrolimus into a novel lipid based nanocarrier system, which would be further loaded into a hydrogel base and evaluated for its target specific topic delivery. Due to the structural similarity of the lipid nanocarriers and skin, these vesicles would target the skin tissues effectively and treat psoriasis with minimum or no side effects. Thus, the proposed formulation would be a considerable value addition to the current therapeutic approaches used for psoriasis management.

Cutaneous Biodistribution: A High-Resolution Methodology to Assess Bioequivalence in Topical Skin Delivery.

A draft guideline from the European Medicines Agency (EMA) highlights the need for methods to assess the quality/equivalence of topical drug formulations. The “cutaneous biodistribution method”, which provides insight into a drug’s spatial distribution in the epidermis/dermis, was used to compare cutaneous bioavailability of econazole nitrate (ECZ) from a reference medicinal product (RMP) and two approved bioequivalent generic creams under finite dose conditions. Statistically significant differences between the ECZ biodistributions from the RMP/Generics were determined and used with acceptance criteria based on those from the EMA to evaluate bioequivalence. In porcine skin, ECZ deposition in total skin, epidermis, upper and lower dermis from Generic 1 was within the acceptance interval, contrary to Generic 2, which was marginally below it. For human skin, Generic 1 deposition was marginally above the acceptance interval and not bioequivalent. The results were consistent with those using the EMA’s acceptance intervals using the ratio of the mean ECZ depositions of Generic 1 and the RMP. Differences identified using this data-rich technique may not translate to observable differences in clinical efficacy; however, generics with non-statistically different biodistributions to the RMP should have a comparable clinical effect. The cutaneous biodistribution method could benchmark the development of topical generic products.

Self-assembled mPEG-hexPLA polymeric nanocarriers for the targeted cutaneous delivery of imiquimod

mPEG-hexPLA micelles have shown their ability to improve delivery and cutaneous bioavailability of a wide range of poorly water soluble and lipophilic molecules. Although poorly water soluble, imiquimod (IMQ) is only moderately lipophilic and it was decided to investigate whether mPEG-hexPLA polymeric micelles could be used as a drug delivery system for this “less than ideal” candidate for encapsulation. Nanosized IMQ micelles (dn = 27 nm) were formulated and characterized. Moreover, the innovative use of size exclusion chromatography allowed the exact drug localization inside the formulation to be determined; it appeared that the use of acetic acid to solubilize IMQ led to a higher IMQ content outside the micelle than inside. IMQ micelles (0.05%) were formulated in a gel using carboxymethyl cellulose (CMC). In vitro application of this formulation to porcine and human skin led to promising delivery results. IMQ deposition in human skin was 1.4 ± 0.4 µg/cm2 while transdermal permeation was only 79 ± 19 ng/cm2: the formulation displayed >17-fold selectivity for cutaneous deposition over transdermal permeation. The optimized 0.05% gel significantly outperformed Aldara® cream (containing 5% IMQ) formulation in terms of delivery efficiency to human skin (2.85 ± 0.74% vs 0.04 ± 0.01%). Despite IMQ being only partially incorporated in the micelles, the biodistribution profile showed that the optimized 0.05% gel delivered as much as 518.2 ± 173.3 ng/cm2 (1.04 ± 0.35% of the applied dose) to the viable epidermis and 236.4 ± 88.2 ng/cm2 (0.47 ± 0.18% of the applied dose) to the upper dermis where the target antigen presenting cells reside. In contrast, for Aldara® cream, the delivery efficiencies in those layers were less than 0.02%. The optimal 0.05% gel thus allowed therapeutically relevant drug levels to be achieved in target tissues despite a 100-fold dose reduction.

In vivo assessment and prediction of topical bioavailability of iodiconazole, a new triazole antifungal agent

Objective To assess the in vivo cutaneous bioavailability of iodiconazole in a topical formulation. Methods Iodiconazole cream was topically administrated to the ventral forearms of 10 healthy volunteers for 1 hour, and the excess formulation was removed. The stratum corneum (SC) at the application sites was tape-stripped immediately or at different time points, quantified gravimetrically, and extracted for analysis. Together with concomitant transepidermal water loss (TEWL) measurement, SC drug concentration-depth profiles were reproducibly determined and fitted mathematically to obtain the SC-vehicle partition coefficient (K) and a first-order rate constant (D/L2) related to iodiconazole diffusivity. The main pharmacokinetic parameters were calculated by Drug and Statistics software. With these parameters, the uptake of iodiconazole of time into SC was assessed. The variation of iodiconazole concentrations in stratum corneum post-removal of the formulation was also investigated. Results The mean values of K and D/L2 of 10 healthy volunteers were (0.13 ± 0.07) and (0.15 ± 0.08) /hour, respectively. The classic lag-time for diffusion (Tlag) across the SC varied from 0.52 hours to 2.28 hours. The mean value of time to reach steady-state transport (Tss) was (3.74 ± 1.69) hours. The mean values of the elimination half-life (t1/2) and the elimination rate constant (Kel) of 10 healthy volunteers were (8.47 ± 5.36) hours and (0.11 ± 0.05) /hour, respectively. Conclusions After topical application, iodiconaole penetrated into the SC rapidly and maintained a high concentration at the target site. The results of this study can provide reliable evidences for the clinical medication and the design of following phase Ⅱ study for iodiconazole. Key words: Dermatopharmacokinetics; Bioavailability; Tape stripping; Stratum corneum; Skin absorption; Iodiconazole

Development of a method for quantitative determination of the cytotoxic agent piplartine (piperlongumine) in multiple skin layers.

This study reports the development of a simple and reproducible method, with high rates of recovery, to extract the cytotoxic agent piplartine from skin layers, and a sensitive and rapid UV-HPLC method for its quantification. Considering the potential of piplartine for topical treatment of skin cancer, this method may find application for formulation development and pharmacokinetics studies to assess cutaneous bioavailability. Porcine skin was employed as a model for human tissue. Piplartine was extracted from the stratum corneum (SC) and remaining viable skin layers (VS) using methanol, vortex homogenization and bath sonication, and subsequently assayed by HPLC using a C18 column, and 1:1 (v/v) acetonitrile-water (adjusted to pH 4.0 with acetic acid 0.1%) as mobile phase. The quantification limit of piplartine was 0.2 μg/mL (0.6 μm), and the assay was linear up to 5 μg/mL (15.8 μm), with within-day and between-days assay coefficients of variation and relative errors <15%. Piplartine recovery from SC and VS varied from 86 to 96%. The method was suitable to assay samples from skin penetration studies, enabling detection of differences in cutaneous delivery in different skin compartments resulting from treatment with various formulations and time periods.

The effect of aging on vasomotion responses to varying rates of local heating.

We compared the cutaneous microvascular vasomotion responses of 8 young (23 ± 1 yr) and 8 older (68 ± 2 yr) adults in the forearm and leg using laser‐Doppler fluxmetry (LDF) and wavelet analysis to investigate endothelial, neurogenic, and myogenic activity. We measured cutaneous microvascular responses at uncontrolled basal temperature (27 ± 2.2 °C), controlled basal temperature (33 °C), and initial vasodilation (onset of heating), and sustained vasodilation, at 42 and 44 °C, in response to both a slow (0.1 °C · 10 s‐1) and a fast (0.5 °C · 10 s‐1) local heating protocol. At baseline (no heating), there were no differences between the groups (all P &gt; 0.05). At a controlled local temperature of 33 °C (thermoneutral), neurogenic activity was higher in the leg of the young compared to the older group (P = 0.04). Following the initiation of the heating protocols, the young participants responded with higher neurogenic activity in the forearm compared to the older group during fast local heating (P = 0.03), but not in response to slow local heating (P &gt; 0.05). In the leg, the young group had higher endothelial nitric oxideindependent activity compared to the older group (P = 0.01) for both heating protocols. The young group also had an increase in endothelial nitric oxide‐dependent activity during the slow protocol (P &lt; 0.001), while the older cohort experienced increases in neurogenic (P = 0.02) and myogenic (P = 0.04) activity. Following 35 min at 42 °C, neurogenic activity was significantly increased in the leg of the older group compared to the young group during the slow heating protocol (P = 0.02). Furthermore, after increasing local temperature from 42 to 44 °C, the older adults had higher endothelial nitric oxide‐independent activity (P = 0.04) in the forearm of the fast protocol while the young subjects had higher neurogenic activity (P = 0.04). Neurogenic activity in the leg of the older group was increased (P = 0.02) during the fast protocol at 44 °C. These results suggest that regional differences in the response to local heating persist with age and that the primary mechanisms responsible for vasodilation caused by local heating are diminished with age; however, overall vasodilation is offset by the other mechanisms. Moreover, our results suggest that as we age the reliance on endothelial activity shifts from endothelial nitric oxide‐dependent to endothelial nitric oxide‐independent mechanisms. These data suggest that the cutaneous bioavailability of nitric oxide is diminished with age.Support or Funding InformationBall State University SPA Fellows StipendThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Synthesis of poly(lactide-co-glycerol) as a biodegradable and biocompatible polymer with high loading capacity for dermal drug delivery.

Due to the low cutaneous bioavailability of tacrolimus (TAC), penetration enhancers are used to improve its penetration into the skin. However, poor loading capacity, non-biodegradability, toxicity, and in some cases inefficient skin penetration are challenging issues that hamper their applications for the dermal TAC delivery. Here we present poly(lactide-co-glycerol) (PLG) as a water soluble, biodegradable, and biocompatible TAC-carrier with high loading capacity (14.5% w/w for TAC) and high drug delivery efficiencies into the skin. PLG was synthesized by cationic ring-opening copolymerization of a mixture of glycidol and lactide and showed 35 nm and 300 nm average sizes in aqueous solutions before and after loading of TAC, respectively. Delivery experiments on human skin, quantified by fluorescence microscopy and LC-MS/MS, showed a high ability for PLG to deposit Nile red and TAC into the stratum corneum and viable epidermis of skin in comparison with Protopic® (0.03% w/w, TAC ointment). The cutaneous distribution profile of delivered TAC proved that 80%, 16%, and 4% of the cutaneous drug level was deposited in the stratum corneum, viable epidermis, and upper dermis, respectively. TAC delivered by PLG was able to efficiently decrease the IL-2 and TSLP expressions in human skin models. Taking advantage of the excellent physicochemical and biological properties of PLG, it can be used for efficient dermal TAC delivery and potential treatment of inflammatory skin diseases.