Natural Ingredients of Transdermal Drug Delivery Systems as Permeation Enhancers of Active Substances through the Stratum Corneum.

In recent years, significant progress has been made in transdermal drug delivery systems, but there is still a search for enhancers that can improve the absorption of active substances through the stratum corneum. Although permeation enhancers have been described in the scientific literature, the use of naturally occurring substances in this role is still of particular interest, because they can offer a high level of safety of use, with a low risk of skin irritation, and high efficiency. In addition, these ingredients are biodegradable, easily available, and widely accepted by consumers due to the growing trust in natural compounds. This article provides information on the role of naturally derived compounds in transdermal drug delivery systems that help them penetrate the skin. The work focuses on the components found in the stratum corneum such as sterols, ceramides, oleic acid, and urea. Penetration enhancers found in nature, mainly in plants, such as terpenes, polysaccharides, and fatty acids have also been described. The mechanism of action of permeation enhancers in the stratum corneum is discussed, and information on the methods of assessing their penetration efficiency is provided. Our review mainly covers original papers from 2017 to 2022, supplemented with review papers, and then older publications used to supplement or verify the data. The use of natural penetration enhancers has been shown to increase the transport of active ingredients through the stratum corneum and can compete with synthetic counterparts.

Extracellular vesicles from recombinant cell factories improve the activity and efficacy of enzymes defective in lysosomal storage disorders.

In the present study the use of extracellular vesicles (EVs) as vehicles for therapeutic enzymes in lysosomal storage disorders was explored. EVs were isolated from mammalian cells overexpressing alpha-galactosidase A (GLA) or N-sulfoglucosamine sulfohydrolase (SGSH) enzymes, defective in Fabry and Sanfilippo A diseases, respectively. Direct purification of EVs from cell supernatants was found to be a simple and efficient method to obtain highly active GLA and SGSH proteins, even after EV lyophilization. Likewise, EVs carrying GLA (EV-GLA) were rapidly uptaken and reached the lysosomes in cellular models of Fabry disease, restoring lysosomal functionality much more efficiently than the recombinant enzyme in clinical use. In vivo, EVs were well tolerated and distributed among all main organs, including the brain. DiR-labelled EVs were localized in brain parenchyma 1 h after intra-arterial (internal carotid artery) or intravenous (tail vein) administrations. Moreover, a single intravenous administration of EV-GLA was able to reduce globotriaosylceramide (Gb3) substrate levels in clinically relevant tissues, such kidneys and brain. Overall, our results demonstrate that EVs from cells overexpressing lysosomal enzymes act as natural protein delivery systems, improving the activity and the efficacy of the recombinant proteins and facilitating their access to organs neglected by conventional enzyme replacement therapies.

Evaluation of ozonized calcium hydroxide as an effective intracanal medicament during root canal procedures: an in vitro observational study.

Achieving thorough disinfection is regarded as one of the pillars in endodontics. Although calcium hydroxide (CH) is one of the routinely used intracanal medicament in endodontics; alternative approaches are gaining popularity to mitigate endodontic pathology. However, CH has to be tested for its dissociation which is a rate-limiting attribute essential for its therapeutic action. The dissociation of CH into OH- and Ca2+ depends on the vehicle used to prepare the paste. This in-vitro study evaluated the use of ozonized olive oil in facilitating calcium ion release and change in pH when combined with CH. Fifty single rooted extracted human mandibular premolars were instrumented with NiTi rotary files (40/6). The teeth were divided into two groups (n = 25 per group) on the basis of vehicle: olive oil (CH + olive oil) and ozonized olive oil (CH + ozonized olive oil) groups. Both olive and ozonized olive oil vehicles allowed the diffusion of ions. However, pastes prepared with ozonized oil showed more ion diffusion, with marked calcium ion release after 15 days and alkalinity was maintained for complete period of 15 days, depicting better support for CH action. The change in calcium ion release and alkalinity were statistically significant in ozonized oil vehicle compared to olive oil vehicle. The present in-vitro study supports the use of ozonized olive oil as a vehicle to be used with CH as an intracanal medicament, considering its anti-microbial potential and sustainable release of calcium ions. The study was approved by the Institutional Ethical Committee of Manubhai Patel Dental College (approval No. MPDC_130/CONS-25/17) on June 4, 2018.

Inflammation-Targeted Delivery of Celastrol via Neutrophil Membrane-Coated Nanoparticles in the Management of Acute Pancreatitis.

Celastrol (CLT)-loaded PEG-PLGA nanoparticles (NPs/CLT) coated with neutrophil membranes (NNPs/CLT) were explored for the management of acute pancreatitis (AP). PEG-PLGA nanoparticles sized around 150 nm were proven to selectively accumulate in the pancreas in rats with AP. NNPs were found to overcome the blood-pancreas barrier and specifically distributed to the pancreatic tissues. Moreover, NNPs showed more selective accumulation in the pancreas than nanoparticles without any membrane coating in AP rats. Compared to CLT solution and the NPs/CLT group, NNPs/CLT significantly downregulated the levels of serum amylase and pancreatic myeloperoxidase in AP rats. Also, using NNPs as the delivery vehicle significantly reduced the systemic toxicity of CLT in AP rats. Together, these results suggest that NNPs/CLT represent a highly promising delivery vehicle for the targeted therapy of AP.

Biocompatible Polymers Modified with d-Octaarginine as an Absorption Enhancer for Nasal Peptide Delivery.

Peptide and protein drugs, which are categorized as biologics, exhibit poor membrane permeability. This pharmacokinetic disadvantage has largely restricted the development of noninvasive dosage forms of biologics that deliver into systemic circulation. We have been investigating the potential use of cell-penetrating peptide-linked polymers as a novel absorption enhancer to overcome this challenge. Since our previous study revealed that biocompatible poly( N-vinylacetamide- co-acrylic acid) modified with d-octaarginine, a typical cell-penetrating peptide, enhanced in vitro permeation of biomolecules such as plasmid DNA and bovine serum albumin through cell membranes, the present study evaluated whether the polymers enhanced in vivo absorption of biologics applied on the mucosa. Mouse experiments demonstrated that d-octaarginine-linked polymers drastically enhanced nasal absorption of exendin-4, whose injection is clinically used. The mean bioavailability was 20% relative to subcutaneous administration, even though it fell short of 1% when exendin-4 alone was administered nasally. The absorption-enhancing function of the polymers was superior to that of sodium caprate and sodium N-(8-(2-hydroxybenzoyl)amino) caprylate, which have been used for humans as an absorption enhancer. In vitro experiments using several biologics with different characteristics revealed that biologics interacted with d-octaarginine-linked polymers and were taken up into cells when incubated with the polymers. The interaction and cellular uptake were enhanced as molecular weights of the biologics increased; however, their charge-dependent in vitro performance was not clearly observed. The current data suggested that biologics formulated with our polymers became an alternative to their conventional invasive parenteral formulations.

Water Activity and Its Significance in Topical Dosage Forms.

Unique properties of thermodynamic activity of solvents in topical semisolids and its effects on in vitro product performance have not been fully understood. Mechanistic investigation was undertaken to demonstrate the significance of thermodynamic potential of solvents [water activity (aw) or solvent activity (as)] on in vitro performance of model topical formulations. Drug transport across synthetic membranes was found to decrease with decreasing water activity of formulations. Similarly, in vitro permeation of model permeant (caffeine) across porcine epidermis was found to decrease with decreasing water activity of formulations. Notably, relatively low water activity formulations (aw, 0.78) induced dehydration in porcine skin associated with significant structural changes like detachment of individual stratum corneum layers. Inclusion of hydrating agents (propylene glycol) in low water activity (aw, 0.78) formulations restored hydration levels and structural integrity of porcine skin. Most importantly, incremental inclusion of propylene glycol in low water activity formulations (aw, 0.78) enhanced in vitro permeation of model permeant (fluorescein sodium). Further investigation revealed that variability in processing conditions (high shear mixing during emulsification step) could modulate water activity in semisolid formulations despite their compositional sameness. In retrospect, water activity was found to be a critical quality attribute of topical semisolid products which impacts overall product performance and drug delivery.

Bile Acid as an Effective Absorption Enhancer for Oral Delivery of Epidermal Growth Factor Receptor-Targeted Hybrid Peptide.

The aim of this study was to improve the oral absorption of epidermal growth factor receptor-targeted hybrid peptide using bile acid as an absorption enhancer. The oral formulation of this peptide was formed through electrostatic interactions between the cationic peptide and anionic bile acid. Comparative studies of in vitro cell permeability and in vivo antitumor effects of peptide and peptide/bile acid complex were performed in Caco-2 cells and in a xenograft mouse model of human gastric cancer. The in vitro permeability of peptide/bile acid complex across Caco-2 cell monolayers was significantly enhanced to about 5.0-fold over those of peptide alone. Furthermore, in vivo mouse xenograft model treated with peptide/bile acid complex showed a 1.6-fold reduction in the mean tumor volume as compared with the peptide alone. A preliminary safety evaluation of blood cells counts, liver enzyme levels, and histopathology of gastrointestinal tissues and main organs showed that the peptide/bile acid complex did not induce any acute toxicity. These results suggest that bile acid is an effective absorption enhancer for improving the oral bioavailability and bioactivity of epidermal growth factor receptor-targeted hybrid peptide.

Alkyl-Modified Oligonucleotides as Intercalating Vehicles for Doxorubicin Uptake via Albumin Binding.

DNA-based drug delivery vehicles have displayed promise for the delivery of intercalating drugs. Here, we demonstrate that oligonucleotides modified with an alkyl chain can bind to human serum albumin, mimicking the natural binding of fatty acids. These alkyl-DNA-albumin complexes display excellent serum stability and are capable of strongly binding doxorubicin. Complexes are internalized by cells in vitro, trafficking to the mitochondria, and are capable of delivering doxorubicin with excellent efficiency resulting in cell death. However, the cellular localization of the delivered doxorubicin, and ultimately the complex efficacy, is dependent on the nature of the linker between the alkyl group and the oligonucleotide.

Recent Update on Nanoemulgel as Topical Drug Delivery System.

Being an emerging transdermal delivery tool, nanoemulgel, has proved to show surprising upshots for the lipophilic drugs over other formulations. This lipophilic nature of majority of the newer drugs developed in this modern era resulting in poor oral bioavailability, erratic absorption, and pharmacokinetic variations. Therefore, this novel transdermal delivery system has been proved to be advantageous over other oral and topical drug delivery to avoid such disturbances. These nanoemulgels are basically oil-in-water nanoemulsions gelled with the use of some gelling agent in it. This gel phase in the formulation is nongreasy, which favors user compliance and stabilizes the formulation through reduction in surface as well as interfacial tension. Simultaneously, it can be targeted more specifically to the site of action and can avoid first-pass metabolism and relieve the user from gastric/systemic incompatibilities. This brief review is focused on nanoemulgel as a better topical drug delivery system including its components screening, formulation method, and recent pharmacokinetic and pharmacodynamic advancement in research studies carried out by the scientists all over the world. Therefore, at the end of this survey it could be inferred that nanoemulgel can be a better and effective drug delivery tool for the topical system.

Time dependence of the enhancement effect of chemical enhancers: Molecular mechanisms of enhancing kinetics.

Chemical enhancers are widely used for facilitating drug penetration in transdermal drug delivery system (TDDS). However, there is a lack of knowledge about how the enhancement effect changes over time. In this study, on the basis of kinetic parameters of enhancement effect, molecular details of the dynamic enhancement process was described and a new hypothesis of the recovery mechanism of the skin barrier function was proposed. Using pretreated skin and flurbiprofen patch, the effects of Azone (AZ) and menthyl decanoate (MT-10) were evaluated with in vitro permeation experiment and further confirmed by confocal laser scanning microscopy (CLSM) and TEWL. The results showed that the enhancement ratio (ER) increased firstly, then reached a plateau and finally decreased. The enhancement effect of MT-10 was slower (Tonset, MT-10>Tonset, AZ), weaker (ERmax, MT-10

Oral self-nanoemulsifying peptide drug delivery systems: impact of lipase on drug release.

It was the aim of this study to evaluate the impact of lipases on the release behaviour of a peptide drug from oral self-nanoemulsifying drug delivery systems. Octreotide was ion paired with the anionic surfactants deoxycholate, decanoate, oleate and dodecylsulphate. The lipophilic character of these complexes was characterised by determining the n-octanol/buffer pH 7.4 partition coefficient. In the following the most hydrophilic complex was incorporated in a likely lipase degradable self-nanoemulsifying drug delivery systems (SNEDDS) formulation containing a triglyceride (olive oil; Pharm.Eur.) and in a likely not lipase degradable SNEDDS containing lipids and surfactants without any ester bonds. After 1:100 dilutions in artificial intestinal fluid (AIF), the lipid droplets were characterised regarding size distribution. With these SNEDDS, drug release studies were performed in AIF with and without lipase. Results showed that the most hydrophobic complex can be formed with deoxycholate in an octreotide:anionic surfactant ratio of 1:5. Even 73.1 ± 8.1% of it could be quantified in the n-octanol phase. SNEDDS containing octreotide | olive oil | cremophor EL | propylene glycol (2|57|38|3) and octreotide | liquid paraffin | Brij 35 | propylene glycol | ethanol (2|66.5|25|5|1.5) showed after dilution in AIF, a mean droplet size of 232 ± 53 nm and 235 ± 50 nm, respectively. Drug release studies showed a sustained release of octreotide out of these formulations for at least 24 h, whereas > 80% of the drug was released within 2 h in the presence of lipase in the case of the triglyceride containing SNEEDS. In contrast the release profile from ester-free SNEDDS was not significantly altered (p < 0.05) due to the addition of lipase providing evidence for the stability of this formulation towards lipases. According to these results, SNEDDS could be identified as a useful tool for sustained oral peptide delivery taking an enzymatic degradation by intestinal lipases into considerations.

A spreadsheet-based method for simultaneously estimating the disposition of multiple ingredients applied to skin.

A spreadsheet-based computer program has been developed to address the problem of simultaneous absorption and evaporation from a multicomponent formulation applied to the skin so that the disposition of each ingredient is tracked. The mass and thickness of the formulation layer (or vehicle) change with time as its components disperse. The presence of each component on the surface of the skin generally affects the activity of the other components at the surface. Thermodynamic activities within the vehicle are governed by either a modified ideal solution model or the UNIversal QUAsiChemical approximation (UNIQUAC) functional group activity coefficient method/UNIQUAC model, at the user's discretion. Program-calculated or experimental solubility limits for the component of greatest interest may be invoked. The predictions of the multicomponent vehicle (MCV) model were compared with human in vitro skin permeation data drawn from an earlier report. Absorption of small to moderate doses of vanillylnonamide from a propylene glycol vehicle was predicted significantly better with the MCV model than with simpler models that track only one component.

Azone® decreases the buccal mucosal permeation of diazepam in a concentration-dependent manner via a reservoir effect.

The purpose of this study was to examine concentration-dependent effects of Azone® (AZ) on the buccal absorption of diazepam (DIAZ). Porcine buccal mucosa was placed in modified Ussing chambers and pretreated with 10 µL of 0%, 5%, 20%, and 50% (w/v) AZ in ethanol. DIAZ was administered to the donor chamber either in solution or a chitosan-based gel. The donor chamber disappearance, receptor chamber appearance, and tissue retention of DIAZ were monitored over 2 h by HPLC, with AZ tissue disposition also measured by liquid chromatography-mass spectrometry profiling of tissue cryosections. DIAZ steady-state flux values significantly (p < 0.05) decreased 1.4- and 2.4-fold in 20% and 50% AZ-pretreated tissues, respectively. Only 20% and 50% AZ-pretreated tissues were also accompanied by an increased loss of DIAZ from the donor chamber, suggesting DIAZ was forming a reservoir in the buccal mucosa with higher AZ concentrations. Indeed, the percentage of the initial DIAZ dose remaining in the mucosa following a 2 h experiment was increased 3.0-fold with a 50% AZ pretreatment compared with control. AZ provided a concentration-dependent reservoir for DIAZ in buccal mucosa, resulting in retarded release into the receptor chamber, an approach that may be exploited for controlled release of DIAZ.

Preparation and evaluation of microemulsion formulations of naproxen for dermal delivery.

Naproxen (Np) is an example of a non-steroidal anti-inflammatory drug (NSAID) commonly used for the reduction of pain and inflammation. In order to develop an alternative formulation for the topical administration of Np, microemulsions were evaluated as delivery vehicles. Four formulations were prepared using isopropyl myristate (IPM) as oil phase, Span 80, Labrafil M, Labrasol, Cremophor EL as surfactants, ethanol as co-surfactant and distilled water or 0.5 N NaOH solution as aqueous phase. The final concentration of Np in the microemulsion system was 100 mg/g (w/w). The physicochemical properties such as electrical conductivity, droplet size, viscosity, pH and phase inversion temperature of microemulsions were measured. Stability tests of the formulations were also performed at 5±2, 25±2 and 40±2°C. The abilities of various microemulsions and selected commercial (C) formulation to deliver Np through the skin were evaluated in vitro using diffusion cells fitted with rat skins. The in vitro permeation data showed that microemulsions increased the permeation rate of Np between 4.335-9.040 times over the C formulation. Furthermore Np successfully permeated across the skin from the microemulsion with the highest flux rate (1.347±0.005 mg·cm(-2)·h(-1)) from a formulation (M4Np) consisting of IPM (2.36 g), Labrosol (0.13 g), Span 80 (0.62 g), ethanol (5.23 g), 0.5 N NaOH solution (0.66 g) and Np (1 g). According to the histological investigations, no obvious skin irritation was observed for the studied microemulsions. These results indicate that the microemulsion formulation may be appropriate vehicles for the topical delivery of Np.

In vitro and in vivo evaluation of three metronidazole topical products.

Two 1% and one 0.75% metronidazole cream products were approved as bioequivalent products. These products were evaluated for their in vivo cutaneous penetration characteristics by dermatopharmacokinetic (DPK) and dermal microdialysis (DMD) sampling methodologies. The same three products were also evaluated for their rheological and in vitro drug release (IVR) properties. Structural differences were observed in the resulting flow curves. However, similar IVR profiles were obtained for the two topical semisolid dosage forms containing 1% metronidazole. For the lower strength product, a higher IVR rate was associated with the lower DPK profile. All three products exhibited similar values of area under the curve when investigated by DMD. This in vitro evaluation corroborated the divergent penetration characteristics found using in vivo methodologies.

Influence of oily vehicles on fetal testis and lipid profile of rats exposed to di-butyl phthalate.

It has been hypothesized that oils containing high levels of omega-3 polyunsaturated fatty acids, such as canola and fish oil, could counteract some of the adverse effects induced by phthalates. In the present study, the influence of different oily vehicles on di-butyl phthalate (DBP)-induced testicular toxicity and lipid profile was investigated. Pregnant Wistar rats were treated by oral gavage from gestation days 13 to 20 with DBP (500 mg/kg/day) diluted in three different vehicles: corn, canola or fish oil. Male fetuses were analyzed on gestation day 20. DBP exposure lowered intratesticular testosterone levels and anogenital distance, regardless of the vehicle used. The percentage of seminiferous cords containing multinucleated gonocytes and cord diameter was increased in DBP-exposed groups, compared with vehicle controls, with no difference between the three DBP-exposed groups. Clustering of Leydig cells was seen in all DBP groups. Lipid profile indicated that administration of canola and fish oil can increase the content of omega-3 fatty acids in rat testis. However, content of omega-3 was diminished in DBP-treated groups. Overall, our results indicate that different oily vehicles did not alter fetal rat testicular toxicity induced by a high DBP dose.

In vitro-in vivo correlation in skin permeation.

PURPOSE: In vitro skin permeation studies have been used extensively in the development and optimisation of delivery of actives in vivo. However, there are few reported correlations of such in vitro studies with in vivo data. The aim of this study was to investigate the skin permeation of a model active, niacinamide, both in vitro and in vivo. METHODS: Conventional diffusion cell studies were conducted in human skin to determine niacinamide permeation from a range of vehicles which included dimethyl isosorbide (DMI), propylene glycol (PG), propylene glycol monolaurate (PGML), N-methyl 2-pyrrolidone (NMP), Miglyol 812N® (MG), and mineral oil (MO). Single, binary or ternary systems were examined. The same vehicles were subsequently examined to investigate niacinamide delivery in vivo. For this proof-of-concept study one donor was used for the in vitro studies and one volunteer for the in vivo investigations to minimise biovariability. Analysis of in vitro samples was conducted using HPLC and in vivo uptake of niacinamide was evaluated using Confocal Raman spectroscopy (CRS). RESULTS: The amount of niacinamide permeated through skin in vitro was linearly proportional to the intensity of the niacinamide signal determined in the stratum corneum in vivo. A good correlation was observed between the signal intensities of selected vehicles and niacinamide signal intensity. CONCLUSIONS: The findings provide further support for the use of CRS to monitor drug delivery into and across the skin. In addition, the results highlight the critical role of the vehicle and its disposition in skin for effective dermal delivery.

Impact of different vehicles for laser-assisted drug permeation via skin: full-surface versus fractional ablation.

PURPOSE: This study aimed to assess impact of different vehicles for laser-assisted skin drug delivery. We also tried to uncover the mechanisms by which different vehicles affect laser-aided skin permeation. METHODS: Full-surface ablative (conventional) and fractional lasers were used to irradiate nude mouse skin. Imiquimod and 5-aminolevulinic acid (ALA) were used as lipophilic and hydrophilic permeants. Vehicles employed included water with 40% polyethylene glycol 400 (PEG 400), propylene glycol (PG), and ethanol. Lipid nanoparticles were also utilized as carriers. RESULTS: In vitro permeation profiles showed improvement in imiquimod flux with conventional laser (2.5 J/cm2) producing a 12-, 9-, and 5-fold increase when loading imiquimod in 40% PEG400, PG, and ethanol, respectively, as compared with intact skin. Nanoparticulate delivery by laser produced a 6-fold enhancement in permeation. Fractional laser produced less enhancement of imiquimod delivery than conventional laser. Laser exposure increased follicular imiquimod accumulation from 0.80 to 5.81 µg/cm2. ALA permeation from aqueous buffer, PEG 400, and PG with conventional laser treatment was 641-, 445-, and 104-fold superior to passive control. In vivo skin deposition of topically applied ALA examined by confocal microscopy indicated the same trend as the in vitro experiment, with aqueous buffer showing the greatest proporphyllin IX signaling. Diffusion of cosolvent molecules into ablated skin and drug partitioning from vehicle to skin are two predominant factors controlling laser-assisted delivery. In contrast to conventional laser, lateral drug diffusion was anticipated for fractional laser. CONCLUSIONS: Our results suggest that different drug delivery vehicles substantially influence drug penetration enhanced by lasers.

Comparison of the skin penetration of Garcinia mangostana extract in particulate and non-particulate form.

The aim of the present study was to solve the water insolubility limitation of the medically and cosmetically interesting substance Garcinia mangostana Linn (GML) extract by encapsulation, and to evaluate and investigate the penetration efficacy of free and encapsulated GML in two different vehicles (water and cream) in porcine ear skin. The follicular penetration depth was determined in 50 hair follicles for each of the four formulations by means of fluorescence microscopy. Tape stripping was used to compare the distribution properties of GML with all formulations on the stratum corneum. The results showed that encapsulated and free GML in the cream base penetrated deeper into hair follicles than if applied in an aqueous base. In addition, encapsulated GML could be distributed more homogeneously on the stratum corneum than the free GML. In conclusion, it was found that encapsulated GML in a cream base had the most effective penetration level in porcine ear skin.