Revisiting the Effect of Aging on the Transport of Molecules through the Skin.

Both intrinsic and extrinsic aging lead to a series of morphological changes in the skin including the flattening of the dermal-epidermal junction, increased stratum corneum dryness, reduction in sebaceous gland activity and enzyme activity as well as atrophy of blood vessels. In this study, the impact of these changes on the transport of molecules through the skin was revised. The increase in the number of transdermal formulations on the market in recent decades and life expectancy represent the main reasons for an in-depth discussion of this topic. Furthermore, elderly subjects have often been excluded from clinical trials due to polypharmacy, raising concerns in terms of efficacy and safety. In this way, ex vivo and in vivo studies comparing the transport of molecules through the mature and young skin were analyzed in detail. The reduced water content in mature skin had a significant impact on the transport rate of hydrophilic molecules. The lower enzymatic activity in aged skin, in turn, would explain changes in the activation of prodrugs. Interestingly, greater deposition of nanoparticles was also found in mature skin. In vivo models should be prioritized in future experimental studies as they allow to evaluate both absorption and metabolism simultaneously, providing more realistic information.

Development of a novel human stratum corneum mimetic phospholipid -vesicle-based permeation assay models for in vitro permeation studies.

OBJECTIVES: To develop and evaluate a novel human stratum corneum (SC) mimetic phospholipid vesicle-based permeation assay (PVPASC) model for in vitro permeation studies. SIGNIFICANCE: Due to the increasing restrictions on the use of human and animal skins, artificial skin models have attracted substantial interest in pharmaceuticals and cosmetic industries. In this study, a modified PVPASC model containing both SC lipids and proteins was developed. METHODS: The PVPASC model was optimized by altering the lipid composition and adding keratin in the formulation of large liposomes. The barrier properties were monitored by measuring the electrical resistance (ER) and permeability of Rhodamine B (RB). The modified PVPASC model was characterized in terms of the surface topography, solvent influence and storage stability. The permeation studies of the active components in Compound Nanxing Zhitong Plaster (CNZP) were performed to examine the capability of PVPASC in the application of skin penetration. RESULTS: The ER and Papp values of RB obtained from the optimized PVPASC model indicated a similar barrier property to porcine ear skin. Scanning electron microscope analysis demonstrated a mimic 'brick-and-mortar' structure. The PVPASC model can be stored for three weeks at -20 °C, and withstand the presence of different receptor medium for 24 h. The permeation studies of the active components demonstrated a good correlation (r2 = 0.9136) of Papp values between the drugs' permeation through the PVPASC model and porcine ear skin. CONCLUSION: Keratin contained composite phospholipid vesicle-based permeation assay models have been proven to be potential skin tools in topical/transdermal permeation studies.

Parafilm® M and Strat-M® as skin simulants in in vitro permeation of dissolving microarray patches loaded with proteins.

In vitro permeation studies play a crucial role in early formulation optimisation before extensive animal model investigations. Biological membranes are typically used in these studies to mimic human skin conditions accurately. However, when focusing on protein and peptide transdermal delivery, utilising biological membranes can complicate analysis and quantification processes. This study aims to explore Parafilm®M and Strat-M® as alternatives to dermatomed porcine skin for evaluating protein delivery from dissolving microarray patch (MAP) platforms. Initially, various MAPs loaded with different model proteins (ovalbumin, bovine serum albumin and amniotic mesenchymal stem cell metabolite products) were prepared. These dissolving MAPs underwent evaluation for insertion properties and in vitro permeation profiles when combined with different membranes, dermatomed porcine skin, Parafilm®M, and Strat-M®. Insertion profiles indicated that both Parafilm®M and Strat-M® showed comparable insertion depths to dermatomed porcine skin (in range of 360-430 µm), suggesting promise as membrane substitutes for insertion studies. In in vitro permeation studies, synthetic membranes such as Parafilm®M and Strat-M® demonstrated the ability to bypass protein-derived skin interference, providing more reliable results compared to dermatomed neonatal porcine skin. Consequently, these findings present valuable tools for preliminary screening across various MAP formulations, especially in the transdermal delivery of proteins and peptides.

Dose-dependent effect on skin permeation of polar and non-polar compounds.

The study of the relationship between the amount of drug applied to the skin and fraction of drug absorbed can improve our understanding of finite-dose percutaneous absorption in the development of topical products and risk assessment of hazardous chemical exposure. It has been previously shown that an increase in the dose applied to the skin leads to a decrease in the fraction of drug permeated the skin (dose-dependent effect). The objective of this research was to examine the dose-dependent effect using permeants of varying physiochemical properties. The dose-dependent effect was studied using human epidermal membrane under finite dose conditions in Franz diffusion cell with model permeants at doses ranging from 0.1 to 200 µg. The dose-dependent effect was evident with model permeants caffeine, corticosterone, dexamethasone, and estradiol, consistent with the relationship of decreasing fraction of dose permeated the skin at increasing the applied dose. However, no significant dose-dependent effect was observed for the polar model permeants urea, mannitol, tetraethyl ammonium, and ethylene glycol, suggesting different transport mechanisms for these permeants. It was also found that, at relatively high doses, estradiol, dexamethasone, and corticosterone could increase the permeation of polar and lipophilic permeants, which could counter the dose-dependent effect under the conditions studied.

Metamorphosis of Topical Semisolid Products-Understanding the Role of Rheological Properties in Drug Permeation under the "in Use" Condition.

When developing topical semisolid products, it is crucial to consider the metamorphosis of the formulation under the "in use" condition. Numerous critical quality characteristics, including rheological properties, thermodynamic activity, particle size, globule size, and the rate/extent of drug release/permeation, can be altered during this process. This study aimed to use lidocaine as a model drug to establish a connection between the evaporation and change of rheological properties and the permeation of active pharmaceutical ingredients (APIs) in topical semisolid products under the "in use" condition. The evaporation rate of the lidocaine cream formulation was calculated by measuring the weight loss and heat flow of the sample using DSC/TGA. Changes in rheological properties due to metamorphosis were assessed and predicted using the Carreau-Yasuda model. The impact of solvent evaporation on a drug's permeability was studied by in vitro permeation testing (IVPT) using occluded and unconcluded cells. Overall, it was found that the viscosity and elastic modulus of prepared lidocaine cream gradually increased with the time of evaporation as a result of the aggregation of carbopol micelles and the crystallization of API after application. Compared to occluded cells, the permeability of lidocaine for formulation F1 (2.5% lidocaine) in unoccluded cells decreased by 32.4%. This was believed to be the result of increasing viscosity and crystallization of lidocaine instead of depletion of API from the applied dose, which was confirmed by formulation F2 with a higher content of API (5% lidocaine) showing a similar pattern, i.e., a 49.7% reduction of permeability after 4 h of study. To the best of our knowledge, this is the first study to simultaneously demonstrate the rheological change of a topical semisolid formulation during volatile solvent evaporation, resulting in a concurrent decrease in the permeability of API, which provides mathematical modelers with the necessary background to build complex models that incorporate evaporation, viscosity, and drug permeation in the simulation once at a time.

Chitin-Glucan Complex Hydrogels: Physical-Chemical Characterization, Stability, In Vitro Drug Permeation, and Biological Assessment in Primary Cells.

Chitin-glucan complex (CGC) hydrogels were fabricated by coagulation of the biopolymer from an aqueous alkaline solution, and their morphology, swelling behavior, mechanical, rheological, and biological properties were studied. In addition, their in vitro drug loading/release ability and permeation through mimic-skin artificial membranes (Strat-M) were assessed. The CGC hydrogels prepared from 4 and 6 wt% CGC suspensions (Na51*4 and Na51*6 hydrogels, respectively) had polymer contents of 2.40 ± 0.15 and 3.09 ± 0.22 wt%, respectively, and displayed a highly porous microstructure, characterized by compressive moduli of 39.36 and 47.30 kPa and storage moduli of 523.20 and 7012.25 Pa, respectively. Both hydrogels had a spontaneous and almost immediate swelling in aqueous media, and a high-water retention capacity (>80%), after 30 min incubation at 37 °C. Nevertheless, the Na51*4 hydrogels had higher fatigue resistance and slightly higher-water retention capacity. These hydrogels were loaded with caffeine, ibuprofen, diclofenac, or salicylic acid, reaching entrapment efficiency values ranging between 13.11 ± 0.49% for caffeine, and 15.15 ± 1.54% for salicylic acid. Similar release profiles in PBS were observed for all tested APIs, comprising an initial fast release followed by a steady slower release. In vitro permeation experiments through Strat-M membranes using Franz diffusion cells showed considerably higher permeation fluxes for caffeine (33.09 µg/cm2/h) and salicylic acid (19.53 µg/cm2/h), compared to ibuprofen sodium and diclofenac sodium (4.26 and 0.44 µg/cm2/h, respectively). Analysis in normal human dermal fibroblasts revealed that CGC hydrogels have no major effects on the viability, migration ability, and morphology of the cells. Given their demonstrated features, CGC hydrogels are very promising structures, displaying tunable physical properties, which support their future development into novel transdermal drug delivery platforms.

Curcumin-loaded microemulsion: formulation, characterization, and in vitro skin penetration.

OBJECTIVE: Formulation of curcumin in a microemulsion with a high loading capacity and that favors its penetration into the skin. SIGNIFICANCE: Take advantage of the properties of microemulsions to promote the penetration of curcumin into the skin, with the aim of enhancing its therapeutic effects. METHODS: Curcumin was formulated in microemulsions based on oleic acid (oil phase), Tween® 80 (surfactant), and Transcutol® HP (cosurfactant). The microemulsion formation area was mapped by constructing pseudo-ternary diagrams for surfactant:co-surfactant ratios 1:1, 1:2, and 2:1. Microemulsions were characterized through measurements of specific weight, refractive index, conductivity, viscosity, droplet size, and in vitro skin permeation studies. RESULTS: Nine microemulsions were prepared and characterized, showing clear, stable formulations with globule size dependent on the proportion of the components. The microemulsion with the highest loading capacity (60 mg/mL), based on Tween® 80, Transcutol® HP, oleic acid, and water (40:40:10:10) was able to penetrate the viable epidermis, finding a total amount of curcumin in the receptor medium at 24 h of 10.17 ± 9.7 µg/cm2. The distribution of curcumin in the skin, visualized by confocal laser scanning microscopy, showed that the maximum amount was located between 20 and 30 µm. CONCLUSION: The inclusion of curcumin in a microemulsion allows its passage into and through the skin. The localization of curcumin, especially in the viable epidermis, would be important for those cases where local conditions are sought to be treated.

Fabrication and Evaluation of Matrix Type Novel Transdermal Patch Loaded with Tramadol Hydrochloride.

Objectives: Transdermal drug delivery as a novel drug delivery system has become a major research interest to the scientists for its controlled drug release and improved patient compliance. This study was conducted to develop an optimized transdermal patch of tramadol hydrochloride using an appropriate amount of suitable polymers. It was also planned to control the drug permeation rate from the device to achieve a sustained release pattern. Materials and Methods: Several numbers of formulations were prepared by altering the amount of excipients. Physicochemical and biopharmaceutical parameters were checked to get the optimized formulation with desired characteristics. Results: Fourier transform infrared spectroscopy results displayed no abnormal peaks and hence concluded that the drug and polymers were compatible with each other. The minimum standard deviation values of different physicochemical parameters assured that the method of preparation was skilled to develop patches with least intra-batch variability. A higher percentage of hydroxypropyl methylcellulose (HPMC) resulted in the greater tensile strength, moisture content and water vapor transmission rate of the patches. A high folding endurance value (>200) indicated the flexibility of the prepared patches and their integrity to the skin. The transdermal patches coded as F26 containing only HPMC polymer demonstrated the desired drug permeation rate (65.51%) within 12 hours through ex vivo permeation studies. Conclusion: The formulation coded as F26 was found to be the most optimized patch as it exhibited sustained drug permeation rate followed by higuchi diffusion kinetics, that also confirmed the capability of the formulation to exhibit matrix type drug delivery.

Contact lenses for pravastatin delivery to eye segments: Design and in vitro-in vivo correlations.

Oral administration of cholesterol-lowering statins, HMG-CoA reductase inhibitors, is associated with beneficial effects on eye conditions. This work aims to design contact lenses (CLs) that can sustainedly deliver pravastatin and thus improve the ocular efficacy while avoiding systemic side effects of statins. Bioinspired hydrogels were prepared with monomers that resemble hydrophobic (ethylene glycol phenyl ether methacrylate) and amino (2-aminoethyl methacrylamide hydrochloride) functionalities of the active site of HMG-CoA. Best performing CLs loaded >6 mg/g, in vitro fulfilled the release demands for daily wearing, and showed anti-inflammatory activity (lowering TNF-α). High hydrostatic pressure sterilization preserved the stability of both the drug and the hydrogel network. Ex vivo tests revealed the ability of pravastatin to accumulate in cornea and sclera and to penetrate through transscleral route. In vivo tests (rabbits) confirmed that, compared to eye drops and for the same dose, CLs provided significantly higher pravastatin levels in tear fluid within 1 to 7 h of wearing. Moreover, after 8 h wearing pravastatin was present in cornea, sclera, aqueous humour and vitreous humour. Strong correlations between percentages of drug released in vitro and in vivo were found. Effects of volume and proteins on release rate and Levy plots were identified.

Fabrication of Ethosomes Containing Tocopherol Acetate to Enhance Transdermal Permeation: In Vitro and Ex Vivo Characterizations.

Background: Tocopherol acetate (TA) is known as a skin moisturizing and photoprotective agent. One major drawback with tocopherol and its derivatives remains its limited stability. Aim: To develop highly stable TA-containing ethosomal gel (TAEG) as an advanced dosage form. Methods: A cold method technique was used to produce the ethosomes. An in vitro evaluation of viscosity, conductivity, and pH stability was carried out for three months. An in vitro physical characterization of the nanoparticles (NPs) that included particle size (PS), zeta potential (ZP), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy analysis was then performed. Organoleptic evaluation, thermostability at 8 °C, 25 °C, 40 °C and 40 °C ± 75% RH, pH, conductivity, viscosity, and spreadability measurements were also performed in vitro for three months. An ex vivo permeation study was performed in phosphate-buffered solution (1× PBS; pH 5.5 or pH 7.4) at 37 ± 0.2 °C by using rat abdominal skin and the Franz diffusion cell method. The data of three independent experiments were expressed as mean ± SD. A two-way ANOVA was applied to compare data on TAEG versus TA control gel (TACG). Results: PS of the ethosomes was in the range of 144−289 nm. A total of nine formulations were developed. Optimized TAEG formulation (TA-5) was selected based on the highest entrapment efficiency (EE) of 99.71%, while the stability, the PS, and the uniformity-based polydispersity index (PDI) were also among the best. TA-5 exhibited smooth spherical ethosomal NPs with PS of 200.6 nm, ZP value of −18.6 V, and PDI of 0.465. Stability data obtained for TA-5 in terms of rheology, conductivity, and pH presented no significant change (p > 0.05) during the entire study duration. Rheological studies indicated that TA-5 followed a non-Newtonian behavior of shear thinning system. The ex vivo drug permeation was 44.55 ± 0.01% in TA-5 and the drug retention in skin was 51.20%, which was significantly higher than TACG as observed after 24 h permeation study (p < 0.05). Conclusions: The newly developed TAEG formulation appears promising to enhance the effectivity of TA and its topical application.

Formulation of liposomes loading lentisk oil to ameliorate topical delivery, attenuate oxidative stress damage and improve cell migration in scratch assay.

Pistacia lentiscus L. is a sclerophyllous shrub capable of growing under harsh climatic conditions especially in the Mediterranean Basin. Different products can be obtained from this plant, such as essential oil, mastic gum or even fixed oil. The last is well known for its flavor which is mainly exploited in the food industry. Additionally, it has been traditionally used in the treatment of skin diseases, but, at the moment, any suitable formulation for skin delivery has been formulated and its biological effects was not deeply confirmed. Given that, in the present study, the lentisk oil has been formulated in liposomes at different concentrations (10, 20, 30 mg/ml) and their physicochemical, technological and main biological properties have been evaluated. Vesicles were prepared by using natural soy lecithin and a green and organic solvent free method, thus obtaining spherical, small (~ 118 nm), homogeneously dispersed (0.27) and highly negatively charged (~ -62 mV) vesicles. The used amount of oil loaded in liposomes (10, 20, 30 mg/ml) modulated the penetration ability of vesicles in the skin, favoring the deposition of the payload in the deeper strata. The loading in the vesicles potentiated the ability of oil to counteract the damaging effects caused by hydrogen peroxide in keratinocytes and fibroblasts and facilitate their migration in a cell monolayer lesion. Overall findings suggested that the incorporation of lentisk oil in liposomes made from soy lecithin can be an alternative and natural approach to exploit it in pharmaceutical ad cosmetical applications and manufacturing natural products suitable for the treatment of skin lesions.

Topical gel based nanoparticles for the controlled release of oleanolic acid: design and in vivo characterization of a cubic liquid crystalline anti-inflammatory drug.

BACKGROUND: Oleanolic acid (OA) has multiple pharmaceutical applications including anti-inflammatory activity, but low permeability of the molecule limits its widespread use. METHODS: A cubic liquid crystalline nanoparticle (LCNP)-based gel was prepared as a potential topical delivery system for OA. The LCNP-based gel was optimized using rheological, drug release kinetic, and ex vivo permeation studies. RESULTS: The studies showed that the OA was trapped in the interior of the LCNP with a crystal form of Pn3m space. The optimized LCNP formulation performed well using in vitro release studies for up to 12 h (85.49 ± 0.21%). Ex vivo permeation studies showed that the LCNP-based gel formulation was superior to a standard gel formulation. The r2 value from the Peppas equation indicated good linearity, but showed irregular (non-Fickian) diffusion, suggesting that drug release was controlled by multiple processes. CONCLUSIONS: In this study, OA-loaded LCNPs were prepared by the precursor method, resulting in a well-characterized OA-LCNP gel preparation. The gel was shown to be effective in a rodent carrageenan-induced hind paw inflammation model with sustained efficacy after a single application.

How to define the experimental conditions of skin permeation assays for drugs presenting biopharmaceutical limitations? The experience with testosterone.

Cutaneous permeation assays are crucial to attest the performance or bioequivalence of topical or transdermal products. Although the official guidelines (e.g., FDA/EMA) play a key role in harmonizing the experimental design, alternative methods are often proposed by the scientific community, which makes it difficult to compare results from different studies. In this review, permeation assays with testosterone (TST) were selected to show this high variability in drug transport rate. The main sources of variation discussed were tissue thickness, animal model, donor and receptor fluid constitution, type of solubilizing agent used in aqueous fluids, drug concentration, degree of supersaturation, skin lipid content, number of experimental times and the physical-chemical stability of the molecule in test fluids. This variation becomes even more critical for molecules that present biopharmaceutical limitations such as TST. In addition, the skin presents specific receptors for this hormone due to its physiological action in this region of the body, which makes the evaluation of the TST transport rate in this tissue even more challenging. The impact of each experimental parameter mentioned above on the flux or permeation coefficient of TST is discussed in detail in the review. Assays used to evaluate tissue integrity are also presented.

Preparation and Evaluation of Imatinib Loaded Transfersomal gel for the Treatment of Rheumatoid Arthritis.

In the present study, imatinib-loaded transfersomal gel (imatinib-TFS-Gel) was developed to minimize the oral dosing frequency and side effects during rheumatoid arthritis (RA) therapy. Imatinib-loaded transfersomes (imatinib-TFS) were prepared by the film-hydration method. The effects of lecithin content, lecithin/ EA ratio, and the type of EA on the characteristics of the imatinib-TFS were studied using a D-optimal design. Morphology of imatinib-TFS was investigated using scanning electron microscopy. The optimized imatinib-TFS formulation was used to prepare imatinib-TFS-Gel with the aid of Carbopol 940 as the gelling agent. The Optimized imatinib-TFS had a spherical shape with the particle size of 140.53 ± 0.87 nm, polydispersity index of 0.44 ± 0.01, the zeta potential of -17.63 ± 0.65 mV, encapsulation efficiency of 98.70 ± 0.38%, and release efficiency of 81.26 ± 0.70 %. Ex-vivo skin permeation studies through the rat skin showed that the cumulative amount of imatinib permeated from imatinib-TFS-Gel was significantly higher than that from imatinib-Gel. The RA rat model indicated a substantial reduction in paw edema during the 14 days study following the application of imatinib-TFS-Gel as compared with imatinib-Gel. Therefore, imatinib-TFS-Gel can be considered as a promising drug delivery system for the treatment of RA.

Versatility of hydrogel-forming microneedles in in vitro transdermal delivery of tuberculosis drugs.

Current therapy of tuberculosis (TB) has several limitations, such as risk of liver injury and intestinal dysbiosis due to frequent oral administration of antibiotics. Transdermal administration could be used to improve antibiotic delivery for treatment of Mycobacterium tuberculosis infection. Therefore, we developed a novel approach, using hydrogel-forming microneedle (MN) arrays to transdermally deliver TB drugs, namely rifampicin, isoniazid, pyrazinamide and ethambutol, which have different physicochemical properties. These drugs were individually prepared into three types of drug reservoirs, including lyophilised tablets, directly compressed tablets and poly(ethylene glycol) tablets. Formulations of each drug reservoir type were optimised to achieve a rapidly dissolving tablet, and further integrated with hydrogel-forming MN arrays for in vitro permeation studies. Three types of hydrogel formulation were manufactured using different type of polymers and crosslinking processes. These MN arrays were then evaluated in terms of swelling ability, morphology and physical properties. Results of solute diffusion studies showed that drug permeation across the swollen hydrogel membrane was affected mostly by physiochemical properties and functional groups of each drug. In the in vitro studies, the amount of permeated drug through the hydrogel-forming MN arrays across the dermatomed neonatal porcine skin was affected by the drug solubility and reservoir design. The highest permeation of rifampicin (3.64 mg) and ethambutol (46.99 mg) were achieved using MN arrays combined with the poly(ethylene glycol) tablets and directly compressed tablet, respectively. For isoniazid and pyrazinamide, the highest drug permeation was attained using lyophilised reservoir with the amount of drug delivered approximately 58.45 mg and 20.08 mg, respectively. These equate to transdermal delivery of approximately 75% (rifampicin), 79% (isoniazid), 20% (pyrazinamide) and 47% (ethambutol) of the drugs loaded into the reservoirs on average. Importantly, the results of this work have demonstrated the versatility of hydrogel formulations to deliver a TB drug regime using MN arrays. Accordingly, this is a promising approach to deliver high dose of TB drugs.

Preformulation-Assisted Design and Characterization of Modified Release Gastroretentive Floating Extrudates Towards Improved Bioavailability and Minimized Side Effects of Baclofen.

Baclofen immediate release mode of administration exhibit sharp plasma peaking that results in the emergence of side effects like hypotension. This research employs preformulation studies to design an optimum dosage form for baclofen to enhance therapeutic outcomes. These studies include partition coefficient and ex-vivo permeation studies. Partition coefficient was found to be 1.27 at pH 7.4. Permeation studies confirmed the presence of specialized transport mechanism through the GIT. It was concluded that an ideal formulation of baclofen should provide slow-release of the drug to avoid sharp peaking. Modified-release floating extrudates of baclofen were prepared using Carbopol 934 and HPMC with different gas-forming agents. Different release-retarding materials (Eudragit L100, Eudragit RS100 and Cetyl alcohol) were used as ingredients in the binder solutions. The prepared extrudates were assessed for their drug content, floating ability, friability properties and in vitro release properties. The prepared extrudates recorded buoyance characteristics for 24 h with a floating lag time varying from 0 to 73.34 s. The optimized extrudates manifested extended baclofen release for up to 8 h compared to 0.2 h for marketed baclofen tablets. This approach was found efficient to provide greater bioavailability and minimize hypotension associated with commercial baclofen tablets.

A stability-indicating ultra-fast liquid chromatography method for the assay of the main flavonoids of Achyrocline satureioides (Marcela) in porcine skin layers and nanoemulsions.

INTRODUCTION: Achyrocline satureioides (marcela or macela) is a plant widely used in folk medicine in South America. Recently, there has been increasing interest for the development of skin care products containing A. satureoides extracts, due to its well-documented antioxidant, antiherpetic, and wound healing properties. OBJECTIVES: The present study aimed to develop and validate a yet unexplored stability-indicating and robust ultra-fast liquid chromatography (UFLC) method for the simultaneous quantification of the main flavonoids of A. satureioides in extracts, nanoemulsions, and porcine skin layers. MATERIAL AND METHODS: The chromatographic separation of flavonoids quercetin, luteolin, and 3-O-methylquercetin was performed on a Luna C18 analytical column (100 mm × 2.0 mm i.d.; particle size 2.5 µm) using isocratic elution with methanol/phosphoric acid 1% (48:52 v/v) with a flow rate of 0.3 mL/min at 40°C. RESULTS: The method was found to be specific, linear (R > 0.998), precise, accurate, and robust for all flavonoids assayed in A. satureioides extract, nanoemulsions, and porcine ear skin. A low matrix effect was noted for all complex matrices. The stability-indicating UFLC method was evaluated by submitting isolated flavonoids, a mixture of standards, and A. satureioides extract to acidic, alkaline, oxidative, UV-A/UV-C light, and thermal stress conditions. No peaks were found co-eluting with the flavonoids of interest in all matrices. The robustness of the method was confirmed using Plackett-Burman experimental design. CONCLUSION: The short run time (8 min) and reliability of the method could be useful for the determination of A. satureioides flavonoids in topical product development since extracts of this medicinal plant have been used to treat various skin disorders.

In Vitro and Ex Vivo Evaluation of Nepafenac-Based Cyclodextrin Microparticles for Treatment of Eye Inflammation.

The aim of this study was to design and evaluate novel cyclodextrin (CD)-based aggregate formulations to efficiently deliver nepafenac topically to the eye structure, to treat inflammation and increase nepafenac levels in the posterior segment, thus attenuating the response of inflammatory mediators. The physicochemical properties of nine aggregate formulations containing nepafenac/γ-CD/hydroxypropyl-ß (HPß)-CD complexes as well as their rheological properties, mucoadhesion, ocular irritancy, corneal and scleral permeability, and anti-inflammatory activity were investigated in detail. The results were compared with a commercially marketed nepafenac suspension, Nevanac® 3 mg/mL. All formulations showed microparticles, neutral pH, and negative zeta potential (-6 to -27 mV). They were non-irritating and nontoxic and showed high permeation through bovine sclera. Formulations containing carboxymethyl cellulose (CMC) showed greater anti-inflammatory activity, even higher than the commercial formulation, Nevanac® 0.3%. The optimized formulations represent an opportunity for topical instillation of drugs to the posterior segment of the eye.

3D-Printed Franz cells - update on optimization of manufacture and evaluation.

OBJECTIVES: Laboratory in vitro permeation processes require the use of modified Franz type diffusion cells which are conventionally fabricated from glass. Fragility and high cost are frequently associated with this type of laboratory apparatus. The purpose of our present research was to develop a simple, economical and versatile approach to manufacture Franz type cells using additive manufacturing (AM). METHODS: Graphical Franz diffusion cell designs were reproduced with a stereolithography (SLA) 3D printer and assessed over a minimum period of 24 h. The surface morphology of AM printouts was analysed before and after compatibility studies using scanning electron microscopy (SEM). Comparative permeation studies in both glass and AM Franz type diffusion cells were conducted using a caffeine solution (1.5 mg mL-1 ), applied to a model silicone membrane. RESULTS: Testing of the 3D printed scaffolds confirmed similar recovery of the permeant when compared to glass cells: 1.49 ± 0.01 and 1.50 ± 0.01 mg mL-1 , respectively, after 72 h. No significant differences were visible from the SEM micrographs demonstrating consistent, smooth and non-porous surfaces of the AM Franz cells' core structure. Permeation studies using transparent 3D printed constructs resulted in 12.85 ± 0.53 µg cm-2 caffeine recovery in the receptor solution after 180 min with comparable permeant recovery, 11.49 ± 1.04 µg cm-2 , for the glass homologues. CONCLUSION: AM constructs can be considered as viable alternatives to the use of conventional glass apparatus offering a simple, reproducible and cost-effective method of replicating specialised laboratory glassware. A wider range of permeants will be investigated in future studies with these novel 3D printed Franz diffusion cells.

OBJECTIF: les processus de perméation in vitro en laboratoire nécessitent l'utilisation de cellules de diffusion de type Franz modifiées, fabriquées traditionnellement en verre. La fragilité et un coût élevé sont fréquemment associés à ce type d'appareil de laboratoire. L'objectif de nos travaux de recherche actuels était de développer une approche simple, économique et polyvalente pour fabriquer des cellules de type Franz à l'aide de la fabrication additive (FA). MÉTHODES: les conceptions des cellules de diffusion Franz graphiques ont été reproduites avec une imprimante 3D stéréolithographie (SLA) et évaluées sur une période minimum de 24 h. La morphologie de surface des impressions FA a été analysée avant et après des études de compatibilité à l'aide de la microscopie électronique à balayage (MEB). Des études comparatives de perméation des cellules de diffusion de type Franz en verre et FA ont été réalisées à l'aide d'une solution de caféine (1,5 mg ml-1 ) appliquée à un modèle de membrane en silicone. RÉSULTATS: les tests des supports imprimés 3D ont confirmé une récupération similaire du perméant par rapport aux cellules de verre : 1,49 ± 0,01 et 1,50 ± 0,01 mg ml-1 , respectivement, après 72 h. Aucune différence significative n'a été observée sur les micrographiques MEB, montrant des surfaces cohérentes, lisses et non poreuses de la structure centrale des cellules Franz FA. Les études de perméation utilisant des constructions transparentes imprimées en 3D ont conduit à une récupération de la caféine de 12,85 ± 0,53 µg cm-2 dans la solution de récepteur après 180 min avec une récupération de perméant comparable, 11,49 ± 1,04 µg cm-2 , pour les homologues de verre. CONCLUSION: les constructions FA peuvent être considérées comme des alternatives viables à l'utilisation d'appareils de verre conventionnels offrant une méthode simple, reproductible et rentable de réplication de la verrerie de laboratoire spécialisée. Une gamme plus large de perméants sera étudiée dans de futures études avec ces nouvelles cellules de diffusion Franz imprimées en 3D.

Influence of skin furrows on tape stripping in characterizing the depth of skin penetration.

The stratum corneum (SC), the outermost layer of the skin and its major barrier for penetration, contains furrows of different depths on its surface. The presence of these furrows might lead to erroneous interpretation of the results in skin permeation studies using tape stripping, in which the material trapped in the furrows removed by the tapes representing different layers of the SC might be interpreted as material penetrating within these layers. The present objective was to investigate the effect of skin furrows on tape stripping results. Non-penetrating fluorescent materials were topically applied to split-thickness human and full-thickness porcine skin samples. Tape stripping was applied, and the tapes were assessed by fluorescence microscopy and quantitative analyses. The microscopy images were assessed visually to determine the presence of the applied material in the furrows. The penetration depth of the material was examined and the fluorescence content and pattern in each tape were analyzed. The results suggested that skin furrows could be important in the first 10 tapes, affecting the quantification of materials in the SC, particularly in permeation studies of materials with low penetration into the SC. Depending on the properties of the materials, skin rinsing could reduce the impact of furrows.