Effects of various penetration enhancers on penetration of aminophylline through shed snake skin

Mucoadhesive film for oral delivery of vaccines for protection of the respiratory tract

The delivery of vaccines plays a pivotal role in influencing the strength and longevity of the immune response and controlling reactogenicity. Mucosal immunization, as compared to parenteral vaccination, could offer greater protection against respiratory infections while being less invasive. While oral vaccination has been presumed less effective and believed to target mainly the gastrointestinal tract, trans-buccal delivery using mucoadhesive films (MAF) may allow targeted delivery to the mucosa. Here we present an effective strategy for mucosal delivery of several vaccine platforms incorporated in MAF, including DNA plasmids, viral vectors, and lipid nanoparticles incorporating mRNA (mRNA/LNP). The mRNA/LNP vaccine formulation targeting SARS-CoV-2 as a proof of concept remained stable within MAF consisting of slowly releasing water-soluble polymers and an impermeable backing layer, facilitating enhanced penetration into the oral mucosa. This formulation elicited antibody and cellular responses comparable to the intramuscular injection, but also induced the production of mucosal IgAs, highlighting its efficacy, particularly for use as a booster vaccine and the potential advantage for protection against respiratory infections. The MAF vaccine preparation demonstrates significant advantages, such as efficient delivery, stability, and simple noninvasive administration with the potential to alleviate vaccine hesitancy.

Influence of Bile Acids on Clindamycin Hydrochloride Skin Permeability: In Vitro and In Silico Preliminary Study

BACKGROUND AND OBJECTIVE

Topical clindamycin formulations are widely used in clinical practice, but poor bioavailability and restricted skin penetration considerably limit their therapeutic efficacy. Penetration enhancement represents a promising and rational strategy to overcome the drawbacks of conventional topical pharmaceutical formulations. We aim to assess the influence of cholic acid (CA) and deoxycholic acid (DCA) on the permeability of clindamycin hydrochloride by performing the in vitro skin parallel artificial membrane permeability assay (skin-PAMPA) at two relevant pH values (5.5 and 6.5) and the interactions of tested substances with skin ATP-binding cassette (ABC) transporters in silico.

METHODS

After the incubation period, the clindamycin hydrochloride concentrations in both compartments were determined spectrophotometrically, and the apparent permeability coefficients (Papp) were calculated. Vienna LiverTox web service was used to predict the interactions of clindamycin and bile acids with potential drug transporters located in human skin.

RESULTS

Both CA and DCA at the highest studied concentration of 100 μM in the tested solutions increased the skin-PAMPA membrane permeability of clindamycin hydrochloride. This effect was more pronounced for CA and at a higher studied pH value of 6.5, which is characteristic of most dermatological indications treated with topical clindamycin preparations. Clindamycin transport may also be mediated by ABC transporters located in skin and facilitated in the presence of bile acids.

CONCLUSIONS

The results of this study provide a solid foundation for further research directed at the improvement of topical formulations using bile acids as penetration-enhancing excipients, as well as the therapeutic efficacy of clindamycin hydrochloride.

Potentials of human bile acids and their salts in pharmaceutical nano delivery and formulations adjuvants

In the last decade, the attention of the scientific community has been focused on bile acids and their salts as systems for the transportation of drugs; specifically their role as carriers and integration into nanomedicine. Bile acids can play a critical role as drug carriers in the form of chemical conjugates, complexation, mixed micelles formation as well as stabilized bile acid liposomes (bilosomes). The unique molecular structure and interaction of these amphiphilic-steroidal compounds make them an interesting subject of research. This review is based on literature research in order to emphasize the importance of bile acids and their salts as absorption modulators in order to improve therapeutic potentials of low bioavailability drugs.

High efficacy, rapid onset nanobiolosomes of sildenafil as a topical therapy for erectile dysfunction in aged rats

Developing topical sildenafil for local treatment of erectile dysfunction has been of great interest in pharmaceutical research. Sildenafil citrate (SC) exhibited a well-documented success for treatment of several types of erectile dysfunction. However, its oral use is limited by serious adverse effects, poor bioavailability, delayed onset, and drug-drug interactions. This work is the first to design and assess sildenafil-loaded bilosomes for topical local treatment of erectile dysfunction. Different sildenafil-loaded bilosomes were prepared and characterized. Permeability of selected formulations was conducted through full-thickness human skin. Optimized bilosomes integrating sodium tauroglycocholate (STGC) showed spherical shape with good particle size (133 nm), high zeta potential (-53.6 mV) and high entrapment efficiency (87.45%). Ex-vivo permeability study revealed that about 39% of the applied dose permeated within 15 min. Furthermore, in-vivo appraisal of therapeutic efficacy was performed using aged male Sprague-Dawley rats. After single application of 2 mg/kg sildenafil loaded in STGC-bilosomes, behavioral and biochemical evaluation was carried out. Behavioral assessment recorded an increased rats' potency manifested as 2 folds increase in intromission frequency and intromission ratio compared to untreated group. That was accompanied by significant increase in cGMP concentration in corpora cavernosa (P < 0.0001) confirming increased potency. In conclusion, STGC-bilosomes could provide topical treatment of impotence with 20% of the oral dose and fast onset of action (10 min).

Boosting transdermal delivery of atorvastatin calcium via o/w nanoemulsifying system: Two-step optimization, ex vivo and in vivo evaluation

A nanoemulsion system was designed for Atorvastatin calcium (ATOR) transdermal delivery to overcome its poor bioavailability of (30%) resulting from the extensive first-pass effect and dissolution rate-limited in vivo absorption. Pseudo ternary phase diagrams were developed, and various NE formulae were prepared using oleic acid (OA), Tween 80 as surfactant and PEG 400 as cosurfactant, ethanol and limonene as permeation enhancers (PEs). NEs were characterized for morphology, droplet size, zeta potential and in vitro release. The optimized formulae were assessed for ex vivo transdermal permeation and in vivo pharmacodynamic/pharmacokinetic studies. Hypocholesterolemic effect after 7 days skin treatment was detected and compared to oral ATOR dispersion. Finally, blood plasma levels were measured for 24 h for rats received the selected transdermal NE and transdermal drug in OA. The obtained results suggested the low potentiality of NE systems in transdermal delivery of lipophilic drugs, only the addition of PEs is driving factor for increasing drug flux through full thickness rat skin. In the optimized formula, the presence of ethanol and PEG 400 disrupts SC lipids exhibiting rapid ex vivo release profile compared to other NEs and to ATOR in OA. In contrast, the optimized NE achieved a prolonged plasma profile. Transdermal NE was significantly more efficient than oral administration in lowering cholesterol plasma level and in increasing ATOR bioavailability. In conclusion, data revealed no correlation between ex vivo and in vivo studies explained by the collapse of the follicles in ex vivo skin permeation study, leaving only the lipoidal pathway for NE to pass through, thus only NE components, neither nanosizing nor other reported mechanisms, are the main influencing factors. In vivo experiments suggested that o/w NE changed ATOR pathway to follicular delivery leading to accumulation of NE in follicles and consequently a prolonged plasma profile.

Permeability of frog skin to chemicals: effect of penetration enhancers

Rarely do commercial chemical products contain solely the active chemical/ingredient. It is therefore important to consider whether ingredients other than the active may: 1) alter absorption of the active chemical, or 2) be absorbed themselves, resulting in systemic effects. Frogs have highly permeable skin and are routinely exposed to commercial chemical products in the environment or therapeutically. Ethanol and propylene glycol (PG), which have known penetration-enhancing effects, are commonly included in such products. The current study has therefore investigated the in vitro absorption kinetics through Rh. marina skin of three model chemicals – caffeine, benzoic acid, and ibuprofen – formulated individually as solutions containing: 1%, 10% or 30% v/v ethanol, or 20% v/v PG. Differential scanning calorimetry and histology were used to characterise fresh frog skin, investigate the mechanism of these enhancers in frog skin, and to determine whether these enhancers significantly affected skin structure. Results showed that the extent of absorption enhancement was influenced by chemical, enhancer and skin region, and that enhancement was generally not consistent for individual enhancers or skin regions. The exception was 1% v/v ethanol, which did not significantly alter flux across the skin for any of the chemicals evaluated. Caffeine absorption was not enhanced by any of the investigated penetration enhancers, and was in fact significantly reduced by 30% v/v ethanol and PG. Ethanol caused concentration-dependant changes in skin morphology and should be avoided in concentrations ≥10% v/v. PG, however, caused minimal changes to the skin and consistently improved absorption of benzoic acid and ibuprofen through all skin regions. Owing to the significant changes in skin structure following ≥10% v/v ethanol exposure, it is recommended to avoid its use in frogs. For enhancement of penetration of moderately-to-highly lipophilic chemicals, this study has identified 20% v/v PG should to be the enhancer of choice.

Nanoemulsion: A Review on Mechanisms for the Transdermal Delivery of Hydrophobic and Hydrophilic Drugs

Nanoemulsions (NEs) are colloidal dispersions of two immiscible liquids, oil and water, in which one is dispersed in the other with the aid of a surfactant/co-surfactant mixture, either forming oil-in-water (o/w) or water-in-oil (w/o) nanodroplets systems, with droplets 20–200 nm in size. NEs are easy to prepare and upscale, and they show high variability in their components. They have proven to be very viable, non-invasive, and cost-effective nanocarriers for the enhanced transdermal delivery of a wide range of active compounds that tend to metabolize heavily or suffer from undesirable side effects when taken orally. In addition, the anti-microbial and anti-viral properties of NE components, leading to preservative-free formulations, make NE a very attractive approach for transdermal drug delivery. This review focuses on how NEs mechanistically deliver both lipophilic and hydrophilic drugs through skin layers to reach the blood stream, exerting the desired therapeutic effect. It highlights the mechanisms and strategies executed to effectively deliver drugs, both with o/w and w/o NE types, through the transdermal way. However, the mechanisms reported in the literature are highly diverse, to the extent that a definite mechanism is not conclusive.

Absorption-Enhancing Effects of Bile Salts

Bile salts are ionic amphiphilic compounds with a steroid skeleton. Among the most important physiological properties of bile salts are lipid transport by solubilization and transport of some drugs through hydrophobic barriers. Bile salts have been extensively studied to enhance transepithelial permeability for different marker molecules and drugs. They readily agglomerate at concentrations above their critical micelle concentration (CMC). The mechanism of absorption enhancement by bile salts appears to be complex. The aim of the present article was to review bile salt structure and their application as absorption enhancers and the probable mechanism for increasing permeation based on previous studies.