Bozena Michniak

Electrospun nanofibrous polymeric scaffold with targeted drug release profiles for potential application as wound dressing.

We have successfully fabricated a dual drug release electrospun scaffold containing an anesthetic, lidocaine, and an antibiotic, mupirocin. Two drugs with different lipophilicities were electrospun from a poly-l-lactic acid (PLLA) solution with a dual spinneret electrospinning apparatus into a single scaffold. The release of the drugs from the scaffold showed different profiles for the two drugs. Lidocaine hydrochloride exhibited an initial burst release (80% release within an hour) followed by a plateau after the first few hours. Mupirocin exhibited only a 5% release in the first hour before experiencing a more sustained release to provide antibacterial action for over 72 h. For comparative purposes, both drugs were spun from a single spinneret and evaluated to determine their release profiles. The scaffold maintained its antibiotic activity throughout the processes of electrospinning and gas sterilization and supported cell viability. It has been reported in the literature that interactions between polymer and drug are known to govern the pattern of drug release from electrospun scaffolds. Here, it was found that the presence of the two drugs in the same polymer matrix altered the release kinetics of at least one drug. Based on the release profiles obtained, the dual spinneret technique was the preferred method of scaffold fabrication over the single spinneret technique to obtain a prototype wound healing device.

The effects of terpene enhancers on the percutaneous permeation of drugs with different lipophilicities

Four model drugs were selected based on their lipophilicity denoted as log P (nicardipine hydrochloride log P -0.99 +/- 0.1, hydrocortisone log P 1.43 +/- 0.47, carbamazepine log P 2.67 +/- 0.38, and tamoxifen log P 7.87 +/- 0.75). The enhancing activities of four terpene enhancers (fenchone log P 2.13 +/- 0.30, thymol log P 3.28 +/- 0.20, D-limonene log P 4.58 +/- 0.23, and nerolidol log P 5.36 +/- 0.38) were tested in vitro across full thickness hairless mouse skin with each of the evaluated drugs formulated in hydroxypropyl cellulose gel formulations. The relationships between lipophilicity (log P) of the terpene enhancers and model drugs and efficacy (represented by the enhancement ratio of flux ER(flux)) of the drugs when coadministered with the enhancers were examined using linear regression. Terpene enhancers had significant effect on the percutaneous permeation of the model drugs. Nerolidol (highest lipophilicity) provided the highest increase in the flux of the evaluated model drugs. The flux of nicardipine hydrochloride increased by approximately 135-fold, hydrocortisone by 33-fold, carbamazepine 8-fold, and tamoxifen 2-fold. The lowest increase in the flux was observed with fenchone. Linear relationships were generated between the ER(flux) of nicardipine hydrochloride, hydrocortisone, carbamazepine, and tamoxifen and the log P of the terpene enhancers [r = 0.951, (P = 0.049), r = 0.977, (P = 0.023), r = 0.942, (P = 0.057), and r = 0.874, (P = 0.126), respectively]. Furthermore, the four terpene enhancers produced linear relationships, indicating that they were more effective at enhancing the penetration of hydrophilic drugs rather than lipophilic drugs r=-0.824 (P=0.176) for fenchone, r = -0.891 (P = 0.109) for thymol, r = -0.846 (P = 0.154) for limonene, and r = -0.769 (P = 0.232) for nerolidol.

The effect of terpene enhancer lipophilicity on the percutaneous permeation of hydrocortisone formulated in HPMC gel systems

The percutaneous permeation of hydrocortisone (HC) was investigated in hairless mouse skin after application of an alcoholic hydrogel using a diffusion cell technique. The formulations contained one of 12 terpenes, the selection of which was based on an increase in their lipophilicity (log P 1.06-5.36). Flux, cumulative receptor concentrations, skin content, and lag time of HC were measured over 24 h and compared with control gels (containing no terpene). Furthermore, HC skin content and the solubility of HC in the alcoholic hydrogel solvent mixture in the presence of terpene were determined, and correlated to the enhancing activity of terpenes. The in vitro permeation experiments with hairless mouse skin revealed that the terpene enhancers varied in their ability to enhance the flux of HC. Nerolidol which possessed the highest lipophilicity (log P = 5.36+/-0.38) provided the greatest enhancement for HC flux (35.3-fold over control). Fenchone (log P = 2.13+/-0.30) exhibited the lowest enhancement of HC flux (10.1-fold over control). In addition, a linear relationship was established between the log P of terpenes and the cumulative amount of HC in the receptor after 24 h (Q(24)). Nerolidol, provided the highest Q(24) (1733+/-93 microg/cm(2)), whereas verbenone produced the lowest Q(24) (653+/-105 microg/cm(2)). Thymol provided the lowest HC skin content (1151+/-293 microg/g), while cineole produced the highest HC skin content (18999+/-5666 microg/g). No correlation was established between the log P of enhancers and HC skin content. A correlation however, existed between the log P of terpenes and the lag time. As log P increased, a linear decrease in lag time was observed. Cymene yielded the shortest HC lag time, while fenchone produced the longest lag time. Also, the increase in the log P of terpenes resulted in a proportional increase in HC solubility in the formulation solvent mixture.

Influence of Drug Lipophilicity on Terpenes as Transdermal Penetration Enhancers

Percutaneous absorption-enhancing effects on the skin of hairless mice of 11 monoterpenes [1, (+)-limonene; 2, (-)-menthone; 3, (+)-terpinen-4-ol; 4, alpha-terpineol; 5, 1,8-cineole; 6, (+)-carvone; 7, (-)-verbenone; 8, (-)-fenchone; 9, p-cymene; 10, (+)-neomenthol; and 11, geraniol] were investigated using three different model drugs (caffeine, hydrocortisone, triamcinolone acetonide [TA]) with varying lipophilicities. Terpenes were applied at 0.4 M in propylene glycol (PG) to mouse skin. The model drugs were applied as suspensions in PG 1 hr following enhancer pretreatment. The combination of terpenes in PG provided significant enhancement of the permeation of caffeine through mouse skin. The most active compounds 10 and 11 increased permeation by between 13-fold and 16-fold. The terpenes also enhanced the delivery of hydrocortisone, but not to as great an extent. The most active compounds 3 and 4 increased permeation between 3.9-fold and 5-fold. The compounds examined did not significantly increase the delivery of TA. The most active compound 4 only increased delivery 2.5-fold, while the next most active compound 6 only increased delivery 1.7-fold. Overall, these results indicate that the combination of terpenes with PG can significantly increase the transdermal penetration of the hydrophilic drug caffeine and the polar steroid hydrocortisone.

Percutaneous penetration enhancers : local versus transdermal activity

The stratum corneum, poses a formidable challenge to formulators of drug delivery systems. Several approaches have been utilized to facilitate entry of drugs into the lower skin layers. Traditionally, permeation enhancers were designed to deliver high drug concentrations across the skin into the systemic circulation. The use of many of these agents resulted in unpleasant or toxic side effects. However, in recent years there has been a search for compounds that exhibit low toxicity, and maintain their enhancing activity. More recently, there has been interest in agents that may be used in topical formulations to prevent the passage of active ingredients or excipients into the lower skin layers. These so-called skin retardants have potential uses in many over-the-counter (OTC) skin formulations, such as sunscreens and pesticides, where the site of action is restricted to the skin surface or upper skin layers. Research in the area of permeation enhancement or retardation is yielding valuable insights into the structure-activity relationships of enhancers as well as retardants.

A photo-crosslinked poly(vinyl alcohol) hydrogel growth factor release vehicle for wound healing applications

The objective of this study was to develop and evaluate a hydrogel vehicle for sustained release of growth factors for wound healing applications. Hydrogels were fabricated using ultraviolet photo-crosslinking of acrylamide-functionalized nondegradable poly(vinyl alcohol) (PVA). Protein permeability was initially assessed using trypsin inhibitor (TI), a 21 000 MW model protein drug. TI permeability was altered by changing the solids content of the gel and by adding hydrophilic PVA fillers. As the PVA content increased from 10% to 20%, protein flux decreased, with no TI permeating through 20% PVA hydrogels. Further increase in model drug release was achieved by incorporating hydrophilic PVA fillers into the hydrogel. As filler molecular weight increased, TI flux increased. The mechanism for this is most likely an alteration in protein/gel interactions and transient variations in water content. The percent protein released was also altered by varying protein loading concentration. Release studies conducted using growth factor in vehicles with hydrophilic filler showed sustained release of platelet-derived growth factor (PDGF-β,β) for up to 3 days compared with less than 24 hours in the controls. In vitro bioactivity was demonstrated by doubling of normal human dermal fibroblas numbers when exposed to growth factor-loaded vehicle compared to control. The release vehicle developed in this study uses a rapid and simple fabrication method, and protein release can be tailored by modifying solid content, incorporating biocompatible hydrophilic fillers, and varying protein loading concentration.

Evaluation of a human bio-engineered skin equivalent for drug permeation studies

AbstractPurpose. To test the barrier function of a bio-engineered human skin (BHS) using three model drugs (caffeine, hydrocortisone, and tamoxifen) in vitro. To investigate the lipid composition and microscopic structure of the BHS. Methods. The human skin substitute was composed of both epidermal and dermal layers, the latter having a bovine collagen matrix. The permeability of the BHS to three model drugs was compared to that obtained in other percutaneous testing models (human cadaver skin, hairless mouse skin, and EpiDerm™). Lipid analysis of the BHS was performed by high performance thin layered chromatrography. Histological evalulation of the BHS was performed using routine H&E staining. Results. The BHS mimicked human skin in terms of lipid composition, gross ultrastructure, and the formation of a stratum corneum. However, the permeability of the BHS to caffeine, hydrocortisone, and tamoxifen was 3-4 fold higher than that of human cadaver skin. Conclusions. In summary, the results indicate that the BHS may be an acceptable in vitro model for drug permeability testing.

In vitro evaluation of a series of Azone analogs as dermal penetration enhancers. II. (Thio) amides

Abstract The sorption promoting ability of nine Azone ( N -dodecylazacycloheptan-2-one) analogs was tested against the model drug, hydrocortisone 21-acetate using a hairless mouse skin model in vitro. The synthesis of these compounds is presented. The enhancers were applied in propylene glycol, 1 h prior to the application of the steroid which was applied as a saturated suspension in the same vehicle. All but enhancers 3–5, 8 , and 9 were applied at 0.4 M. The remaining enhancers (all solids) were applied at their respective saturation solubilities. Flux, receptor concentrations, and skin accumulation of hydrocortisone acetate were measured over 24 h and compared with controls (no enhancer) and three model enhancers: Azone ( N -dodecylazacycloheptan-2-one), 2-pyrrolidinone, and N -methyl-2-pyrrolidinone. Pre-treatment of skin with the Azone analogs markedly increased penetration and skin retention of the steroid. The greatest enhancement of flux was observed for 2 , where flux increased 53.8-fold over control and 2.76-fold over Azone; receptor concentrations were 35.37-fold and skin retentions 1.6-fold higher than control. Compound 1 gave the greatest skin retention enhancement ratio (ER) (2.2 over control) of the series, while 2-pyrrolidinone produced an ER of 3.2, and Azone 1.5 compared with controls at an ER of 1.0.

Amphiphilic star-like macromolecules as novel carriers for topical delivery of nonsteroidal anti-inflammatory drugs.

The objective of this study was to evaluate amphiphilic star-like macromolecules (ASMs) as a topical drug delivery system. Indomethacin, piroxicam, and ketoprofen were individually encapsulated into the ASMs using coprecipitation. The effects of the ASMs on percutaneous permeation of nonsteroidal anti-inflammatory drugs (NSAIDs) across full thickness, hairless mouse skin were evaluated in vitro using modified Franz diffusion cells. In addition, solubility and in vitro release experiments were performed to characterize ASMs behavior in aqueous media. Poly(ethylene glycol) (PEG) and Pluronic P-85 were used as polymer controls to compare the role of PEG and amphiphilic behavior in the ASMs. In vitro release experiments indicated that ASMs can delay drug release (P⋖05), whereas solubility measurements showed that ASMs can increase NSAIDs aqueous solubility (P⋖05). Percutaneous permeation studies revealed that ASMs decreased both flux and Q24 of drugs compared with the control (P⋖10). Skin pretreatment studies with ASM-containing solution before drug application demonstrated that pretreatment similarly influenced NSAID percutaneous permeation. In conclusion, ASMs likely slow drug permeation through 2 mechanisms, delayed drug diffusion from its core and skin dehydration by its shell. Thus, ASMs may be useful for delayed dermal delivery or prevention of compound permeation through the skin (eg, sunscreens, N,N-diethyl-m-toluamide [DEET]) from aqueous formulations.

Enhanced iontophoretic delivery of buspirone hydrochloride across human skin using chemical enhancers

Buspirone hydrochloride (BH) is a structurally and pharmacologically unique anxiolytic that is used to treat a variety of different anxiety conditions. The marketed product is named BuSpar. The in vitro iontophoretic delivery of BH through human skin was investigated in order to evaluate the feasibility of delivering a therapeutic dose of BH by this route. We also examined the influence of co-formulations of chemical enhancers (Azone, oleic acid, menthone, cineole, and terpineol) on BH permeation, both without iontophoresis and with iontophoresis-to look for possible synergistic effects. By applying iontophoresis at 0.5 mA/cm(2), it was possible to achieve a BH steady state flux of approximately 350 microg/cm(2)h, which would be therapeutically effective if clinically duplicated. Importantly, 24 h of iontophoresis at 0.5 mA/cm(2) did not affect skin morphology and after the current was switched off, the skins permeability to BH rapidly reverted to its pre-iontophoretic level. Without iontophoreis, BH transdermal flux was significantly enhanced by the application of 2.5% (v/v) concentrations of Azone, oleic acid, or menthone but not cineole or terpineol. Furthermore, this paper identified a synergistic transport enhancement effect developing when very low current (0.025 mA/cm(2)) iontophoresis was applied in conjunction with Azone treatment.