Passive and iontophoretic transport enhancement of insulin through porcine epidermis by depilatories: permeability and fourier transform infrared spectroscopy studies

Ternary Deep Eutectic Solvents System of Colchicine, 4-Hydroxyacetophenone, and Protocatechuic Acid and Characterization of Transdermal Enhancement Mechanism

This study aimed to prepare colchicine (CO), 4-hydroxyacetophenone (HA), and protocatechuic acid (CA) contained in transdermal rubber plasters into a more releasable and acrylate pressure-sensitive adhesive (PSA) to optimize traditional Touguling rubber plasters (TOU) with enhanced transdermal permeability by using deep eutectic solvents (DES) technology. We compared the difference in the release behavior of CO between rubber plaster and PSA, determined the composition of the patch through pharmacodynamic experiments, explored the transdermal behavior of the three components, optimized the patch formula factors, and improved the penetration of CO through the skin. We also focused on elucidating the interactions among the three components of DES and the intricate relationship between DES and the skin. The melting point of DES was determined using DSC, while FTIR, 13C NMR, and ATR-FTIR were used to explore the intricate molecular mechanisms underlying the formation of DES, as well as its enhancement of skin permeability. The results of this investigation confirmed the successful formation of DES, marked by a discernible melting point at 27.33°C. The optimized patch, formulated with a molar ratio of 1:1:1 for CO, HA, and CA, significantly enhanced skin permeability, with the measured skin permeation quantities being 32.26 ± 2.98 µg/cm2, 117.67 ± 7.73 µg/cm2, and 56.79 ± 1.30 µg/cm2 respectively. Remarkably, the optimized patch also demonstrated similar analgesic and anti-inflammatory effects compared to commercial diclofenac diethylamide patches in different pharmacodynamics studies. The formation of DES altered drug compatibility with skin lipids and increased retention, driven by the interaction among the three component molecules through hydrogen bonding, effectively shielding the skin-binding sites and enhancing component permeation. In summary, the study demonstrated that optimized DES patches can concurrently enhance the penetration of CO, HA, and CA, thereby providing a promising approach for the development of DES in transdermal drug delivery systems. The findings also shed light on the molecular mechanisms underlying the transdermal behavior of DES and offer insights for developing more effective traditional Chinese medicine transdermal drug delivery systems.

An investigation on percutaneous permeation of flurbiprofen enantiomers: The role of molecular interaction between drug and skin components

This work aimed to investigate skin permeation profiles of chiral flurbiprofen and clarify the molecular mechanism of transdermal permeation difference of enantiomers. The in vitro transdermal permeation of enantiomers through rat skin was studied by diffusion cells. Physicochemical parameters of model chiral drugs were determined. Molecular interaction between chiral flurbiprofen and ceramides of skin was investigated by FTIR, ¹³C NMR and molecular docking. The skin permeation mechanism of chiral drugs was characterized by ATR-FTIR, Raman spectra, DSC and molecular dynamic simulation. The results showed that the amount of the permeation and retention amount of (S)-flurbiprofen was 1.5 times over that of (R)-flurbiprofen. And it was proven that the difference was not induced by physicochemical properties but the molecular interaction between drug-skin components. (S)-flurbiprofen was easy to form stronger hydrogen bonding with -CONH group of skin lipids due to its steric configuration, which disturbed lipids arrangement more easily according to the results of ATR-FTIR (Δν_asCH₂ = 1.00 cm^-1), Raman spectra (ΔI₂₈₈₂/I₂₈₅₃ = 0.32) and the DSC (ΔT_{m stratum corneum} = 11.75 °C). It was demonstrated more obvious effect on the second structure of keratin by ATR-FTIR study (Δ Amide I = 3.60 cm^-1 and Δ Amide II = 3.38 cm^-1). Better compatibility between (S)-flurbiprofen and lipids was confirmed quantificationally by thermodynamic analysis. In conclusion, the higher interaction between (S)-flurbiprofen and skin components, the higher skin permeation, which contributes to decrease the administration dose and increase the therapeutic effect.

Probing the Role of Ion-Pair Strategy in Controlling Dexmedetomidine Penetrate Through Drug-in-Adhesive Patch: Mechanistic Insights Based on Release and Percutaneous Absorption Process

The purpose of present study was to develop a controlled release drug-in-adhesive patch for transdermal delivery of dexmedetomidine (Dex) using ion-pair technique. Based on the in vitro transdermal experiment, the role of ion-pair on the Dex release behavior and percutaneous absorption process was also investigated. Fourier transform infrared spectroscopy (FTIR), molecular modeling, differential scanning calorimetry (DSC), and rheological test were conducted to probe the effect of ion-pair on the Dex release from patch. Besides, the tape stripping test, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and molecular simulation were carried out to elaborate the action of ion-pair on the Dex percutaneous permeation process. Results showed that the optimized patch prepared with Dex-salicylic acid (SA) showed zero-order skin permeation profile within 24 h; Dex-SA had greater hydrogen bonding formation potential with pressure sensitive adhesive (PSA) than Dex, which resulted in the decrease in the formation ability of free volume of PSA and the increase with the improvement of mechanical strength and chain stiffness of PSA and thus controlled the release rate of Dex from transdermal patch. Besides, the physicochemical properties of Dex such as molecular weight and octanol/water partition coefficient were changed after forming ion-pair with SA, which decreased the permeation ability of Dex. In conclusion, a controlled release drug-adhesive patch for Dex was developed and the mechanism study of ion-pair on the Dex release and percutaneous permeation process was proposed at molecular level.

Study of the Mucoadhesive Potential of Carbopol Polymer in the Preparation of Microbeads Containing the Antidiabetic Drug Glipizide

The present investigation was aimed at exploitation of the mucoadhesive potential of carbopol 934P polymer in developing microbeads of glipizide (GLP) for its effectivity in controlling blood sugar in diabetic patients. Various batches of GLP beads were prepared by an emulsion-solvent evaporation technique using the release-retarding polymer carbopol and subjected to a systematic evaluation such as physical characterization, ex vivo mucoadhesion, hydration and erosion test, and in vitro drug release; and instrumental and in vivo studies were performed with the best formulation. The highest yield and loading efficiency were observed as 94 and ∼90%, respectively. The mean particle size of the microbeads ranged from 832 to 742 μm. The oval shape of the microbeads with slight roughness was apparent in the SEM micrograph. The release period was extended till 18 h. In vitro release of the drug from the beads followed the diffusion and erosion mechanism. In the oral glucose tolerance test (OGTT), there is a significant (p < 0.01) reduction in fasting blood glucose levels in Wistar rat and guinea pig in comparison with that using the marketed product. Results indicated that process parameters-drug-polymer ratio, concentration of the surfactant, and stirring speed-controlled the various characteristics of the microparticles. The mucoadhesivity test ensured strong adherence of the beads to the mucosal membrane in pH 1.2 for a prolonged period. Owing to the mucoadhesivity of carbopol 934P, prolonged release of GLP and reduction of fasting sugar in the animal model were observed to a satisfactory level, and thus, management of diabetes in a better manner is expected with this new formulation.

Effect of different enhancers on the transdermal permeation of insulin analog

Using chemical penetration enhancers (CPEs), transdermal drug delivery (TDD) offers an alternative route for insulin administration, wherein the CPEs reversibly reduce the barrier resistance of the skin. However, there is a lack of sufficient information concerning the effect of CPE chemical structure on insulin permeation. To address this limitation, we examined the effect of CPE functional groups on the permeation of insulin. A virtual design algorithm that incorporates quantitative structure-property relationship (QSPR) models for predicting the CPE properties was used to identify 43 potential CPEs. This set of CPEs was pre-screened using a resistance technique, and the 22 best CPEs were selected. Next, standard permeation experiments in Franz cells were performed to quantify insulin permeation. Our results indicate that specific functional groups are not directly responsible for enhanced insulin permeation. Rather, permeation enhancement is produced by molecules that exhibit positive logK(ow) values and possess at least one hydrogen donor or acceptor. Toluene was the only exception among the 22 potential CPEs considered. In addition, toxicity analyses of the 22 CPEs were performed. A total of eight CPEs were both highly enhancing (permeability coefficient at least four times the control value) and non-toxic, five of which are new discoveries.

A skin permeability model of insulin in the presence of chemical penetration enhancer

Enhancing transdermal delivery of insulin using chemical penetration enhancers (CPEs) has several advantages over other non-traditional methods; however, lack of suitable predictive models, make experimentation the only alternative for discovering new CPEs. To address this limitation, a quantitative structure-property relationship (QSPR) model was developed, for predicting insulin permeation in the presence of CPEs. A virtual design algorithm that incorporates QSPR models for predicting CPE properties was used to identify 48 potential CPEs. Permeation experiments using Franz diffusion cells and resistance experiments were performed to quantify the effect of CPEs on insulin permeability and skin structure, respectively. Of the 48 CPEs, 35 were used for training and 13 were used for validation. In addition, 12 CPEs reported in literature were also included in the validation set. Differential evolution (DE) was coupled with artificial neural networks (ANNs) to develop the non-linear QSPR models. The six-descriptor model had a 16% absolute average deviation (%AAD) in the training set and 4 misclassifications in the validation set. Five of the six descriptors were found to be statistically significant after sensitivity analyses. The results suggest, molecules with low dipoles that are capable of forming intermolecular bonds with skin lipid bi-layers show promise as effective insulin-specific CPEs.

Transdermal delivery of a readthrough-inducing drug: a new approach of gentamicin administration for the treatment of nonsense mutation-mediated disorders

To induce the readthrough of premature termination codons, aminoglycoside antibiotics such as gentamicin have attracted interest as potential therapeutic agents for diseases caused by nonsense mutations. The transdermal delivery of gentamicin is considered unfeasible because of its low permeability through the dermis. However, if the skin permeability of gentamicin could be improved, it would allow topical application without the need for systemic delivery. In this report, we demonstrated that the skin permeability of gentamicin increased with the use of a thioglycolate-based depilatory agent. After transdermal administration, the readthrough activity in skeletal muscle, as determined using a lacZ/luc reporter system, was found to be equivalent to systemic administration when measured in transgenic mice. Transdermally applied gentamicin was detected by liquid chromatography-tandem mass spectrometry in the muscles and sera of mice only after depilatory agent-treatment. In addition, expansion of the intercellular gaps in the basal and prickle-cell layers was observed by electron microscopy only in the depilatory agent-treated mice. Depilatory agent-treatment may be useful for the topical delivery of readthough-inducing drugs for the rescue of nonsense mutation-mediated genetic disorders. This finding may also be applicable for the transdermal delivery of other pharmacologically active molecules.

Pharmacokinetics of a Lidocaine Patch 5% in Dogs

Lidocaine is increasingly used in transdermal drug delivery systems for different pain conditions in human medicine whereby several pharmacokinetic studies have demonstrated minimal systemic absorption in men. In the present study, the pharmacokinetics of a lidocaine patch 5% was studied in six dogs. In the first experiment, one single lidocaine patch was applied for 12 h to the lateral side of the thorax after removing the hair either by clipping or by the application of a depilatory agent, according to a two-way crossover design. No potential adverse effects induced by the patches were observed in either group. In dogs with clipped hair, a mean peak plasma lidocaine concentration of 62.94 ng/ml was obtained after 10.67 h. In the depilatory group, a mean peak plasma concentration of 103.55 ng/ml was reached after 9.27 h. Significant differences in the AUC(0 --> infinity), C(max), k(a) and T(1/2a) were noticed between the two groups. No significant differences were found for the elimination parameters and for T(max). In the second experiment, the patches were applied for 60 h to the clipped skin in order to study the absorption kinetics after a prolonged application period. There, the mean peak lidocaine plasma concentration was 45.18 ng/ml achieved after 24 h and a final concentration of 29.37 ng/ml was obtained at 60 h. In conclusion, all dogs tolerated the transdermal lidocaine patch well. The results of this study suggest that there is an overall minimal absorption from the lidocaine patch. However, the application of a depilatory agent leads to a more rapid and increased absorption of lidocaine.

Transdermal delivery of zidovudine (AZT): the effects of vehicles, enhancers, and polymer membranes on permeation across cadaver pig skin

The purpose of this study was to investigate the effects of vehicles, enhancers, and polymer membranes on 3'-azido-3'-deoxythymidine (AZT) permeation across cadaver pig skin. Four binary vehicles (ethanol/water, isopropyl alcohol/water, polyethylene glycol 400/water, and ethanol/isopropyl myristate [IPM]) were tested for AZT solubility and permeability across pig skin; ethanol/IPM (50/50, vol/vol) demonstrated the highest AZT flux (185.23 microg/cm2/h). Next, the addition of various concentrations of different enhancers (N-methyl-2-pyrrolidone [NMP], oleic acid, and lauric acid) to different volume ratios of ethanol/IPM was investigated for their effect on AZT solubility and permeability across pig skin. The use of 2 combinations (ethanol/IPM [20/80] plus 10% NMP and ethanol/IPM [30/70] plus 10% NMP) resulted in increased AZT solubility (42.6 and 56.27 mg/mL, respectively) and also high AZT flux values (284.92 and 460.34 microg/cm2/h, respectively) without appreciable changes in lag times (6.25 and 7.49 hours, respectively) when compared with formulations using only ethanol/IPM at 20/80 and 30/70 volume ratios without addition of the enhancer NMP. Finally, AZT permeation across pig skin covered with a microporous polyethylene (PE) membrane was investigated. The addition of the PE membrane to the pig skin reduced AZT flux values to 50% of that seen with pig skin alone. However, the AZT flux value attained with ethanol/IPM (30/70) plus 10% NMP was 215.31 microg/cm2/h, which was greater than the target flux (208 mug/cm2/h) needed to maintain the steady-state plasma concentration in humans. The results obtained from this study will be helpful in the development of an AZT transdermal drug delivery system.

Iontophoretic Enhancement of Leuprolide Acetate by Fatty Acids, Limonene, and Depilatory Lotions Through Porcine Epidermis

The effect of chemical enhancers (e.g., fatty acids, limonene, depilatory lotions) and iontophoresis was investigated on the in vitro permeability of leuprolide acetate through porcine epidermis. Franz diffusion cells and Scepter iontophoretic power source were used for the percutaneous absorption studies. Anodal iontophoresis was performed at 0.2 mA/cm2 current density. Fatty acids used were palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and linolenic (C18:3) acids. The passive and iontophoretic flux were significantly (p < 0.05) greater through fatty acids-treated porcine epidermis in comparison to the control (untreated epidermis) for leuprolide acetate. The passive and iontophoretic permeability of leuprolide acetate increased with increasing number of cis double bonds. Among the fatty acids tested, linolenic acid (C18:3) exhibited the maximum permeability of leuprolide acetate during passive (51.42 x 10(-4) cm/hr) and iontophoretic (318.98 x 10(-4) cm/hr) transport. The passive and iontophoretic flux of leuprolide acetate were significantly (p < 0.05) greater through the limonene and depilatory lotion treated epidermis in comparison to their respective control. In conclusion, iontophoresis in combination with chemical enhancers synergistically increased (p < 0.05) the in vitro permeability of leuprolide acetate through porcine epidermis.