Microneedle-assisted delivery of verapamil hydrochloride and amlodipine besylate

The aim of this project was to study the effect of stainless steel solid microneedles and microneedle rollers on percutaneous penetration of verapamil hydrochloride and amlodipine besylate.Verapamil, 2-(3,4-dimethooxyphenyl)-5-[2-(3,4 dimethoxyphenyl)ethyl-methyl-amino]-2-propan-2-yl-pentanenitrile is a calcium channel blocker agent that regulates high blood pressure by decreasing myocardial contractilty, heart rate and impulse conduction. Amlodipine, (R, S)-2-[(2-aminoethoxy) methyl]-4-(2-chlorophenyl)-3-ethoxycarbonyl-5-methoxycarbonyl-6-methyl-1, 4-dihydropyridine, is a calcium channel blocker that is used for the management of hypertension and ischemic heart disease. Passive penetration of verapamil and amlodipine across the skin is low. In vitro studies were performed with microneedle-treated porcine ear skin using vertical static Franz diffusion cells (PermeGear, Hellertown, PA, USA). The receiver chamber contained 5 ml of PBS (pH7.4) and was constantly maintained at 37 °C temperature with a water circulation jacket. The diffusion area of the skin was 1.77 cm². The donor compartment was loaded with 1 ml of the solution containing 2.5 mg/ml of amlodipine besylate. The donor chamber was covered with parafilm to avoid evaporation. Passive diffusion across untreated porcine skin served as control. Aliquots were taken every 2 h for 12 h and analyzed by liquid chromatography–mass spectrometry. Transcutaneous flux of verapamil increased significantly from 8.75 μg/cm²/h to 49.96 μg/cm²/h across microneedle-roller treated porcine skin. Percutaneous flux of amlodipine besylate following the use of stainless steel microneedles was 22.39 μg/cm²/h. Passive flux for the drug was 1.57 μg/cm²/h. This enhancement of amlodipine flux was statistically significant. Transdermal flux of amlodipine with microneedle roller was 1.05 μg/cm²/h in comparison with passive diffusion flux of 0.19 μg/cm²/h. The difference in flux values was also statistically significant. Stainless steel solid microneedles and microneedle rollers increased percutaneous penetration of verapamil hydrochloride and amlodipine besylate. It may be feasible to develop transdermal microneedle patches for these drugs.     

Fabrication of Dissolving Polymer Microneedles for Controlled Drug Encapsulation and Delivery: Bubble and Pedestal Microneedle Designs

Dissolving microneedle patches offer promise as a simple, minimally invasive method of drug and vaccine delivery to the skin that avoids the need for hypodermic needles. However, it can be difficult to control the amount and localization of drug within microneedles. In this study, we developed novel microneedle designs to improve control of drug encapsulation and delivery using dissolving microneedles by (i) localizing drug in the microneedle tip, (ii) increasing the amount of drug loaded in microneedles while minimizing wastage, and (iii) inserting microneedles more fully into the skin. Localization of our model drug, sulforhodamine B in the microneedle tip by either casting a highly concentrated polymer solution as the needle matrix or incorporating an air bubble at the base of the microneedle achieved approximately 80% delivery within 10 min compared to 20% delivery achieved by the microneedles encapsulating nonlocalized drug. As another approach, a pedestal was introduced to elevate each microneedle for more complete insertion into the skin and to increase its drug loading capacity by threefold from 0.018 to 0.053 μL per needle. Altogether, these novel microneedle designs provide a new set of tools to fabricate dissolving polymer microneedles with improved control over drug encapsulation, loading, and delivery.     

Influence of Array Interspacing on the Force Required for Successful Microneedle Skin Penetration: Theoretical and Practical Approaches

Insertion behaviour of microneedle (MN) arrays depends upon the mechanical properties of the skin and, MN geometry and distribution in an array. In addressing this issue, this paper studies MN array insertion mechanism into skin and provides a simple quantitative basis to relate the insertion force with distance between two MNs. The presented framework is based on drawing an analogy between a beam on an elastic foundation and mechanism of needle insertion, where insertion force is separated into different components.A theoretical analysis indicates that insertion force decreases as interspacing increases. For a specified skin type, insertion force decreased from 0.029 to 0.028 N/MN when interspacing at MN tip was increased from 50 μm (350 μm at MN base) to 150 μm (450 μm at MN base).However, dependence of insertion force seems to decrease as the interspacing is increased beyond 150 μm. To assess the validity of the proposed model, a series of experiments was carried out to determine the force required for skin insertion of MN. Experiments performed at insertion speed of 0.5 and 1.0 mm/s yielded insertion force values of 0.030 and 0.0216 N, respectively, for 30 μm interspacing at MN base (330 μm interspacing at tip) and 0.028 and 0.0214 N, respectively, for 600 μm interspacing at MN base (900 μm interspacing at tip). Results from theoretical analysis and finite element modelling agree well with experimental results, which show MN interspacing only begins to affect insertion force at low interspacing (< 150 μm interspacing at MN base). This model provides a framework for optimising MN devices, and should aid development of suitable application method and determination of force for reliable insertion into skin.     

Antidermatitic Perspective of Hydrocortisone as Chitosan Nanocarriers: An Ex Vivo and In Vivo Assessment Using an NC/Nga Mouse Model

The aim of this study to administer hydrocortisone (HC) percutaneously in the form of polymeric nanoparticles (NPs) to alleviate its transcutaneous absorption, and to derive additional wound-healing benefits of chitosan. HC-loaded NPs had varied particle sizes, zeta potentials, and entrapment efficiencies, when drug-to-polymer mass ratios increased from 1:1 to 1:8. Ex vivo permeation analysis showed that the nanoparticulate formulation of HC significantly reduced corresponding flux [~24 μg/(cm² h)] and permeation coefficient (~4.8 × 10^? 3 cm/h) of HC across the full thickness NC/Nga mouse skin. The nanoparticulate formulation also exhibited a higher epidermal (1610 ± 42 μg/g of skin) and dermal (910 ± 46 μg/g of skin) accumulation of HC than those associated with control groups. An in vivo assessment using an NC/Nga mouse model further revealed that mice treated with the nanoparticulate system efficiently controlled transepidermal water loss [15 ± 2 g/(m² h)], erythema intensity (232 ± 12), dermatitis index (mild), and thickness of skin (456 ± 27 μm). Taken together, histopathological examination predicted that the nanoparticulate system showed a proficient anti-inflammatory and antifibrotic activity against atopic dermatitic (AD) lesions. Our results strongly suggest that HC-loaded NPs have promising potential for topical/transdermal delivery of glucocorticoids in the treatment of AD. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1063–1075, 2013     

Absorption of Polyethylene Glycol (PEG) Polymers: The Effect of PEG Size on Permeability

Polyethylene glycol (PEG) polymers are large amphiphilic molecules that are highly hydrated in solution. To explore the permeability properties of different sized PEG polymers across epithelial membranes in vivo, we examined the absorption of fluorescently labeled PEG conjugates sized 0.55-20 kDa from the lung, since this system provides a reservoir that limits rapid diffusion of molecules away from the site of delivery and enables permeability over longer times to be examined. Following intratracheal delivery in rats, the PEG polymers underwent absorption with first-order kinetics described by single exponential decay curves. PEG size produced a marked influence on the rate of uptake from the lung, with half-lives ranging from 2.4 to 13 h, although above a size of 5 kDa, no further change in rate was observed. PEG size likewise affected retention in alveolar macrophages and in lung tissue; whereas smaller PEG sizes (< 2 kDa) were effectively cleared within 48 h, larger PEG sizes (> 5 kDa) remained in lung cells and tissue for up to 7 days. These data demonstrate that PEG polymers can be absorbed across epithelial membranes and that PEG size plays a dominant role in controlling the rate and mechanism of absorption.     

Efficient Ibuprofen Delivery from Anhydrous Semisolid Formulation Based on a Novel Cross-linked Silicone Polymer Network: An In Vitro and In Vivo Study

The use of silicone as a primary polymer in topical semisolid pharmaceutical formulations is infrequent. Recent development of novel silicone materials provides an opportunity to investigate their drug delivery efficiencies. In this study, an anhydrous semisolid formulation was prepared using a novel cross-linked silicone polymer network swollen in isododecane. Similar formulations were prepared using petrolatum, an acrylic, or a cellulose polymer. All formulations contained 5% ibuprofen (IBP). In vitro permeability was evaluated for all formulations and a commercial product using human cadaver epidermis. The silicone formulation delivered IBP more efficiently than all other formulations in terms of flux, cumulative amount, and percent drug release. The silicone formulation showed the maximum flux of 85.9 μg.cm⁻².h⁻¹ and a cumulative IBP release of 261.6 μg in 8 h, whereas the benchmark showed 20.1 μg.cm⁻².h⁻¹ and 30.9 μg, respectively. An in vivo study conducted on rats showed calculated blood AUCs of 59.2 and 17.6 μg.h/g (p < 0.003) for the silicone formulation and the benchmark, respectively. The IBP in excised rat skin was 264 ± 59 μg/g for the silicone formulation and 102 ± 5 μg/g for the benchmark. The results obtained from the in vitro and in vivo studies demonstrate efficient topical IBP delivery by the silicone formulation.     

Coating Solid Dispersions on Microneedles via a Molten Dip‐Coating Method: Development and In Vitro Evaluation for Transdermal Delivery of a Water‐Insoluble Drug

This study demonstrates for the first time the ability to coat solid dispersions on microneedles as a means to deliver water‐insoluble drugs through the skin. Polyethylene glycol (PEG) was selected as the hydrophilic matrix, and lidocaine base was selected as the model hydrophobic drug to create the solid dispersion. First, thermal characterization and viscosity measurements of the PEG–lidocaine mixture at different mass fractions were performed. The results show that lidocaine can remain stable at temperatures up to ∼130°C and that viscosity of the PEG–lidocaine molten solution increases as the mass fraction of lidocaine decreases. Differential scanning calorimetry demonstrated that at lidocaine mass fraction less than or equal to 50%, lidocaine is well dispersed in the PEG–lidocaine mixture. Uniform coatings were obtained on microneedle surfaces. In vitro dissolution studies in porcine skin showed that microneedles coated with PEG–lidocaine dispersions resulted in significantly higher delivery of lidocaine in just 3 min compared with 1 h topical application of 0.15 g EMLA®, a commercial lidocaine–prilocaine cream. In conclusion, the molten coating process we introduce here offers a practical approach to coat water‐insoluble drugs on microneedles for transdermal delivery. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3621–3630, 2014     

Studies on percutaneous penetration of chemicals – Impact of storage conditions for excised human skin

According to international guidelines skin penetration experiments can be carried out using freshly excised or frozen stored skin. However, this recommendation refers to data obtained in experiments with human cadaver skin. In our study, the percutaneous penetration of the occupationally relevant chemicals anisole, cyclohexanone and 1,4-dioxane was investigated for freshly excised as well as for 4 and 30 days at ?20 °C stored human skin using the diffusion cell technique. As indicator for the impairment of skin barrier by freezing cholesterol dissolution was determined in the solvents in exposure chambers of diffusion cells. Considering the percutaneously penetrated amounts, the following ranking was determined: 1,4-dioxane > anisole > cyclohexanone (decline to a factor of 5.9). The differences of fluxes between freshly excised and frozen stored skin (4 and 30 days) were not significant (p > 0.05). Cholesterol dissolved from the skin indicates no significant differences between freshly excised and frozen stored skin. This study shows that freezing of human skin for up to 30 days does not alter the skin barrier function and the permeability of chemicals.     

Plasma protein binding of tetrodotoxin in the marine puffer fish Takifugu rubripes

To elucidate the involvement of plasma protein binding in the disposition of tetrodotoxin (TTX) in puffer fish, we used equilibrium dialysis to measure protein binding of TTX in the plasma of the marine puffer fish Takifugu rubripes and the non-toxic greenling Hexagrammos otakii, and in solutions of bovine serum albumin (BSA) and bovine alpha-1-acid glycoprotein (AGP). TTX (100–1000 μg/mL) bound to protein in T. rubripes plasma with low affinity in a non-saturable manner. The amount of bound TTX increased linearly with the TTX concentration, reaching 3.92 ± 0.42 μg TTX/mg protein at 1000 μg TTX/mL. Approximately 80% of the TTX in the plasma of T. rubripes was unbound in the concentration range of TTX examined, indicating that TTX exists predominantly in the unbound form in the circulating blood of T. rubripes at a wide range of TTX concentrations. TTX also bound non-specifically to H. otakii plasma proteins, BSA, and bovine AGP. The amount of the bound TTX in the plasma of H. otakii and BSA, respectively, was 1.86 ± 0.36 and 4.65 ± 0.70 μg TTX/mg protein at 1000 μg TTX/mL, and that in the bovine AGP was 8.78 ± 0.25 μg TTX/mg protein at 200 μg TTX/mL.     

Effects of microneedle length,density, insertion time and multiple applications on human skin barrier function: Assessments by transepidermal water loss

Microneedle (MN) arrays have attracted considerable attention in recent years due to their ability to facilitate effective transdermal drug delivery. Despite appreciable research, there is still debate about how different MN dimensions or application modes influence permeabilization. This study aimed to investigate this issue by taking transepidermal water-loss measurements of dermatomed human skin samples following the insertion of solid polymeric MNs. Insertions caused an initial sharp drop in barrier function followed by a slower incomplete recovery – a paradigm consistent with MN-generation of microchannels that subsequently contract due to skin elasticity. While 600 μm-long MNs were more skin-perturbing than 400 μm MNs, insertion of 1000 μm-long MNs caused a smaller initial drop in integrity followed by a degree of long term permeabilization. This is explainable by the longest needles compacting the tissue, which then decompresses over subsequent hours. Multiple insertions had a similar effect as increasing MN length. There was some evidence that increasing MN density suppressed the partial barrier recovery caused by tissue contraction. Leaving MNs embedded in skin seemed to reduce the initial post-insertion drop in barrier function. Our results suggest that this in vitro TEWL approach can be used to rapidly screen MN-effects on skin.     

PHARMACEUTICAL TECHNOLOGY: Micro-CT Analysis of Matrix-Type Drug Delivery Devices and Correlation With Protein Release Behaviour

A series of matrix-type drug delivery devices comprising a continuous phase of microporous poly(ε-caprolactone) (PCL) and a dispersed phase of protein particles (gelatin) with defined size ranges (45–90, 90–125 and 125–250 μm) were produced by rapidly cooling suspensions in dry ice followed by solvent extraction from the hardened material. High protein loadings (38–44%, w/w) were achieved and highly efficient protein release (90% of the initial load) was obtained over time periods of 3–11 days depending on particle loading and size range. The duration of protein release was extended from 3 to 11 days reducing the protein load. Quantitative analysis of Micro-CT images identified a three to four times increase in the population of sub-40 mm pores in those matrices which gave rise to accelerated protein release in 24 h (40% rising to 80%) and reduced duration of protein release (11-3 days). Formation of a high density of channels and fissures (connects) between the particles is indicated, which facilitate fluid ingress and diffusion of solubilised protein molecules. Micro-CT analysis also confirmed the uniformity of particle distribution in the matrices and provided measurements of macroporosity within 530% of the theoretical value for materials displaying irregular shaped macropores larger than 90 mm. These findings demonstrate the utility of Micro-CT for optimising the formulation and performance of matrix-type delivery devices for macromolecular entities.     

Pig and guinea pig skin as surrogates for human in vitro penetration studies: A quantitative review

Both human and animal skin in vitro models are used to predict percutaneous penetration in humans. The objective of this review is a quantitative comparison of permeability and lag time measurements between human and animal skin, including an evaluation of the intra and inter species variability. We limit our focus to domestic pig and rodent guinea pig skin as surrogates for human skin, and consider only studies in which both animal and human penetration of a given chemical were measured jointly in the same lab. When the in vitro permeability of pig and human skin were compared, the Pearson product moment correlation coefficient (r) was 0.88 (P < 0.0001), with an intra species average coefficient of variation of skin permeability of 21% for pig and 35% for human, and an inter species average coefficient of variation of 37% for the set of studied compounds (n = 41). The lag times of pig skin and human skin did not correlate (r = 0.35, P = 0.26). When the in vitro permeability of guinea pig and human skin were compared, r = 0.96 (P < 0.0001), with an average intra species coefficient of variation of 19% for guinea pig and 24% for human, and an inter species coefficient of variation of permeability of 41% for the set of studied compounds (n = 15). Lag times of guinea pig and human skin correlated (r = 0.90, P < 0.0001, n = 12). When permeability data was not reported a factor of difference (FOD) of animal to human skin was calculated for pig skin (n = 50) and guinea pig skin (n = 25). For pig skin, 80% of measurements fell within the range 0.3 < FOD < 3. For guinea pig skin, 65% fell within that range. Both pig and guinea pig are good models for human skin permeability and have less variability than the human skin model. The skin model of choice will depend on the final purpose of the study and the compound under investigation.     

Exploiting the Buccal Mucosa as an Alternative Route for the Delivery of Donepezil Hydrochloride

The potential of the buccal mucosa as an alternative route for the systemic delivery of donepezil (DPZ) hydrochloride, and the impact of various skin penetration enhancers on DPZ buccal permeability, was assessed using an in vitro model. DPZ was applied to porcine buccal mucosa in modified Ussing chambers either alone (20 μg/mL) or with different treatment protocols of various enhancers including Azone^® (AZ), deoxycholic acid (DA), polyethylene glycol (PEG) 400, and oleic acid (OA)-PEG 400. DPZ permeated the buccal mucosa very rapidly with a permeability coefficient of 35.6 ± 4.9 × 10^- 6 cm/s, which was not significantly affected by AZ pretreatment. Coapplication of DA 0.6% (w/w), but not DA 0.01% (w/w), reduced the buccal permeation of DPZ (3.5-fold), and PEG 400 reduced the absorption of DPZ in a concentration-dependent manner (1.6- and 18.0-fold reduction at 5% and 50%, w/w, PEG 400, respectively). Coapplication of a combination of OA 1% (v/w) and PEG 400 5% (w/w) further reduced DPZ permeability (5.5-fold), which was demonstrated to result from excipient-induced DPZ precipitation as assessed by light microscopy analysis. These results confirm the feasibility of a novel buccal delivery system for Alzheimer's disease, and suggest various approaches that may be exploited for controlled buccal delivery of DPZ. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1643-1651, 2014     

Albumin/Gentamicin Microspheres Produced by Supercritical Assisted Atomization: Optimization of Size,Drug Loading and Release

In this work, the supercritical assisted atomization (SAA) is proposed, for the first time, not only as a micronization technology but also as a thermal coagulation process for the production of bovine serum albumin (BSA) microspheres charged with Gentamicin sulfate (GS). Particularly, different water solutions of BSA/GS were processed by SAA to produce protein microspheres with different size and antibiotic content. SAA precipitation temperature was selected in the range 100-130°C to generate protein coagulation and to recover micronized BSA in form of hydrophobic aggregates; GS loading was varied between 10% and 50% (w/w) with an encapsulation efficiency which often reached 100%. In all cases, spherical and noncoalescing particles were successfully produced with a mean particle size of 2 μm and with a standard deviation of about ± 1 μm. The microspheres also showed a good stability and constant water content after 60 days of storage. The release profiles of the entrapped drug were monitored using Franz cells to evaluate the possible application of the produced microspheres in wound dressing formulations. Particularly, the microspheres with a BSA/GS ratio of 4:1 after the first burst effect (of 40% of GS loaded) were able to release the GS continuously over 10 days.     

Levosimendan and its metabolite OR-1896 elicit KATP channel-dependent dilation in resistance arteries in vivo

BackgroundLevosimendan and its long-lived metabolite OR-1896 produce vasodilation in different types of vessels by activating ATP-sensitive (K_ATP) and other potassium channels.MethodsIn the present study we applied intravital videomicroscopy to investigate the in situ effects of levosimendan and OR-1896 on the diameters of real resistance arterioles (rat cremaster muscle arterioles with diameters of ~ 20 μm).ResultsLevosimendan and OR-1896 induced concentration-dependent (1 nM – 100 μM) dilations to similar extents in these arterioles (maximal dilation from 23 ± 2 to 33 ± 2 μm and from 22 ± 1 to 32 ± 1 μm, respectively). The arteriolar dilations induced by the selective K_ATP channel opener pinacidil (1 nM – 10 μM) (maximal dilation from 22 ± 4 μm to 35 ± 3 μm) were diminished in the presence of the selective K_ATP channel blocker – glibenclamide (5 μM) (maximal diameter attained: 22 ± 1 μm). Glibenclamide also counteracted the maximal dilations in response to levosimendan or OR-1896 (to 23 ± 3 μm or 22 ± 5 μm, respectively).ConclusionsIn conclusion, this is the first demonstration that levosimendan and OR-1896 elicit arteriolar dilation in vivo, via activation of K_ATP channels in real resistance vessels in the rat.     

The Impact of Polyelectrolyte Structure on the Shape of Nanoassemblies with Cationic Peptides

We investigated how the structure of nanofibers, resulting from interactions between anionic polyelectrolytes and cationic peptides, relies on the properties of the polyelectrolyte component. By using hyaluronate (H), carboxymethylcellulose (CMC), xanthan (X), and ozarelix (O), a cationic decapeptide, we determined the influence of characteristic polyelectrolyte parameters such as size and charge density on the formation of polyelectrolyte-peptide complexes. Transmission electron microscopy of unstained, frozen hydrated, or negatively stained samples revealed that the interaction between different anionic polyelectrolytes and ozarelix led to the formation of distinctly shaped nanofibers. CMC formed rather flexible structures with alternating thin and thick segments within the nanofibers with diameters ranging from 10 to 16 nm and a length of up to 1 μm. Hyaluronate, a high-molecular-mass molecule, formed extra-long aggregates of more than 5 μm. Individual fibers with a diameter of 8 nm aggregated to bigger strands. The nonlinear polysaccharide xanthan gum led to highly coiled structures. The diameter of the respective nanofibers varied between 15 and 25 nm. Isothermal titration calorimetry was used to determine the binding constants and the thermodynamic parameters of the different polyelectrolyte-peptide complexes. The binding constant, which was of the order of 10⁶ M^? 1, indicated a strong binding affinity, but also showed differences among the polyelectrolytes. These differences might be useful for prospective applications as drug delivery systems. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2599–2607, 2013     

Human skin penetration of cobalt nanoparticles through intact and damaged skin

Cobalt nanoparticles (CoNPs) are produced for several industrial and biomedical applications but there is a lack of data on human cutaneous absorption. Cobalt is also a skin sensitizer that can cause allergic contact dermatitis. Co applied as NPs, due to their small size and high surface, can penetrate into the skin in higher amount that bulk material. The aim of this study was to evaluate the absorption of Co applied as NPs in both intact and damaged skin. Experiments were performed using Franz cells and 1.0 mg cm^?2 of CoNPs was applied as donor phase for 24 h. Mean Co content of 8.5 ± 1.2 ng cm^?2 and 1.87 ± 0.86 μg cm^?2 were found in the receiving solutions of Franz cells when the CoNPs suspension was applied on intact skin and on damaged skin, respectively. Twenty-four hours Co flux permeation was 76 ± 49 ng cm^?2 h^?1 in damaged skin with a lag time of 2.8 ± 2.1 h. This study suggests that Co applied as NPs is able to penetrate the human skin in an in vitro diffusion cell system.     

Iontophoretic transport kinetics of ketorolac in vitro and in vivo: Demonstrating local enhanced topical drug delivery to muscle

The objective of the study was to investigate the iontophoretic delivery kinetics of ketorolac (KT), a highly potent NSAID and peripherally-acting analgesic that is currently indicated to treat moderate to severe acute pain. It was envisaged that, depending on the amounts delivered, transdermal iontophoretic administration might have two distinct therapeutic applications: (i) more effective and faster local therapy with shorter onset times (e.g. to treat trauma-related pain/inflammation in muscle) or (ii) a non-parenteral, gastrointestinal tract sparing approach for systemic pain relief. The first part of the study investigated the effect of experimental conditions on KT iontophoresis using porcine and human skin in vitro. These results demonstrated that KT electrotransport was linearly dependent on current density – from 0.1875 to 0.5 mA/cm² – (r² > 0.99) and drug concentration – from 5 to 20 mg/ml (r² > 0.99). Iontophoretic permeation of KT from a 2% hydroxymethyl cellulose gel was comparable to that from an aqueous solution with equivalent drug loading (584.59 ± 114.67 and 462.05 ± 66.56 μg/cm², respectively). Cumulative permeation (462.05 ± 66.56 and 416.28 ± 95.71 μg/cm²) and steady state flux (106.72 ± 11.70 and 94.28 ± 15.47 μg/cm² h), across porcine and human skin, were statistically equivalent confirming the validity of the model. Based on the results in vitro, it was decided to focus on topical rather than systemic applications of KT iontophoresis in vivo. Subsequent experiments, in male Wistar rats, investigated the local enhancement of KT delivery to muscle by iontophoresis. Drug biodistribution was assessed in skin, in the biceps femoris muscle beneath the site of iontophoresis (‘treated muscle’; TM), in the contralateral muscle (‘non-treated muscle’; NTM) and in plasma (P). Passive topical delivery and oral administration served as negative and positive controls, respectively. Iontophoretic administration for 30 min was superior to passive topical delivery for 1 h and resulted in statistically significant increases in KT levels in the skin (91.04 ± 15.48 vs. 20.16 ± 8.58 μg/cm²), in the biceps femoris at the treatment site (TM; 6.74 ± 3.80 vs. <LOQ), in the contralateral site (NTM; 1.26 ± 0.54 vs. <LOQ) and in plasma (P; 8.58 ± 2.37 μg/ml vs. <LOD). In addition to increasing bioavailability, iontophoretic administration of KT showed clear selectivity for local delivery to the biceps femoris at the treatment site – the TM:NTM ratio was 5.26 ± 1.45, and the TM:P and NTM:P ratios were 0.75 ± 0.32 and 0.14 ± 0.04, respectively. Furthermore, the post-iontophoretic concentration of KT in the ‘treated’ biceps femoris muscle and the muscle:plasma ratio were also superior to those following oral administration of a 4 mg/kg dose (6.74 ± 3.80 vs. 0.62 ± 0.14 μg/g and 0.75 ± 0.32 vs. 0.14 ± 0.03, respectively). In conclusion, the results demonstrate that iontophoresis of ketorolac enables local enhanced topical delivery to subjacent muscle; this may have clinical application in the treatment of localised inflammation and pain.     

31P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin

The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R₈, R₁₁, and YKA) through skin intercellular lipids using ³¹P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0–60, 61–120, and 121–180 μm) were collected and analyzed for ³¹P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200 mg/ml of TAT on skin layers, diffusion of TAT, R₈, R₁₁, and YKA in the skin and time dependent permeation of R₁₁ was measured on various skin sections using ³¹P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in ³¹P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100 mg/ml CPP concentration. R₁₁ and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R₁₁ penetration up to 180 μm within 30 min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, ³¹P solid-state NMR can be used to track CPP penetration into different skin layers.     

The application of co-melt-extruded poly(ε-caprolactone) as a controlled release drug delivery device when combined with novel bioactive drug candidates: Membrane permeation and Hanson dissolution studies

Eight bioactive drug compounds (abamectin, amoxicillin, dexamethasone, dexamethasone valerate, ketoprofen, melatonin, oestradiol 17β, and oestradiol benzoate) were combined via melt extrusion and disc pressing processes with a polycaprolactone (PCL) matrix and were then evaluated and compared via membrane diffusion and Hanson dissolution studies. This investigation was to determine the potential of this matrix to act as a controlled release drug delivery vehicle for a number of drugs not previously combined with PCL in a melt extrusion mix. The inclusion of the progesterone/PCL system, for which the drug release behaviour has been well studied before was intended for comparison with the PCL systems incorporating drugs that have received little research attention in the past. Initial studies centred on an evaluation of the permeation ability of the bioactive drugs dissolved in aqueous cyclodextrin solutions through a poly(ε-caprolactone) (PCL) membrane using Valia-Chien side-by-side cells. Permeation rates were mostly low and found to range from 0 to 122 μg h^?1 with only ketoprofen, melatonin, and progesterone displaying rates exceeding 20 μg h^?1. Hanson dissolution release profiles in aqueous alcohol were subsequently measured for the 9 melt extruded PCL/drug combinations and led to Hanson release rates of 0–556 μg cm^?2 h^?0.5 with dexamethasone, dexamethasone valerate, ketoprofen, melatonin, and progesterone giving values exceeding 100 μg cm^?2 h^?0.5. A number of drugs such as the dexamethasones probably performed better than they did in the permeability rate measurements because of the less polar aqueous alcoholic solvent used. In searching for useful correlations between the drug physicochemical properties and release rate, only a moderate correlation (R²=0.5675) between Hanson dissolution release rate and permeation rate was found. This suggests that the release rate and the permeation are both controlled by the rate of drug diffusion through the PCL with release rate involving an additional dissolution process (of the drug) before permeation occurs accounting for the moderate correlation. In general, of the eight drugs considered, it was clear that the oestradiol-based drugs, abamectin, and amoxicillin were generally not suited to drug delivery via PCL under the conditions used. However, ketoprofen was found to be very suitable as a drug candidate for melt extrusion with PCL with dexamethasone valerate, dexamethasone, and melatonin also showing potential as candidates though to a much lesser extent.