Franz cell studies, utilizing different human skin and an artificial membrane, evaluating the influence of skin model on permeation of zolmitriptan coated on an array of titanium microprojections, were evaluated. Full thickness and dermatomed
The
In the current study, we evaluated Strat-M (synthetic membrane), full thickness, and dermatomed
Adhesive Dermally Applied Microarray (ADAM) zolmitriptan. (a) 5 cm2 adhesive backing with microprojection array (3 cm2) in applicator ring. (b) Applicator ring press fit onto the bottom of the applicator, and applicator. (c) 60× magnification of zolmitriptan coated microprojections (725 microprojections/cm2 and length 340
ADAM zolmitriptan
Applicator ring attached to applicator
60× magnified section of zolmitriptan coated microprojections
Front view of an individual zolmitriptan coated microprojection (250× magnification)
The test system consisted of an ADAM with a 3 cm2 titanium array with a nominal dose of 1.90 ± 0.05 mg (0.05 mg denotes the standard deviation of the coated dose) zolmitriptan attached to a 5 cm2 adhesive backing. The adhesive backing was seated onto an applicator ring, which had co-molded desiccant. The ADAM zolmitriptan was in a nitrogen purged heat sealed pouch.
Dermatomed human skin was obtained from the New York Presbyterian Hospital Skin Bank (NY, NY) and procured from the posterior trunk from 3 donors (2 males, 1 female; 2 Caucasian, 1 African-American; ages of 50 and 51 yrs). This skin was provided to the testing facility as dermatomed, cryopreserved, and sealed in a water impermeable bag with continuous storage at −70°C. All skin was used within its labeled expiration date.
Full thickness human skin was obtained from Science Care (Phoenix, AZ) and procured from the upper outer arm from 1 donor (male, Caucasian, 40 yrs). This skin was provided to the testing facility as excised full thickness and sealed in a water impermeable bag with continuous storage at −20°C.
Synthetic membrane, Strat-M, was purchased from Millipore Sigma (Burlington, MA) as being 47 mm in diameter with a nominal 300
Normal phosphate buffered saline (pH 7.4 ± 0.1) with 0.008% gentamicin sulfate (PBSg) solution was utilized when the diffusion cells were first mounted and for performance of the skin barrier integrity test. Following the barrier integrity test, the reservoir solution was entirely replaced with the 0.1x phosphate buffered saline (pH 7.4 ± 0.1) with 0.008% gentamicin sulfate (0.1x PBSg). The volume of the receptor medium was 25 mL.
Absorption was measured using the
The Strat-M synthetic membrane was mount directly to the diffusion cell without alteration or modification. The cells were then placed within a rack system and attached to a water circulation system, from which the receptor solution was stirred magnetically at approximately 600 RPM, and its temperature was maintained to achieve a skin surface temperature of 32 ± 1°C.
To ensure the barrier integrity of each skin section, its desorption of water was measured for transepidermal water loss (TEWL). A Delfin VapoMeter (Surrey, UK) probe was activated and placed onto the skin surface, and the TEWL value was recorded. Skin mounted in diffusion cells in which TEWL was less than 25 g/m2/h was considered acceptable. Skin sections that were determined to be unacceptable for dosing may have been used as non-dosed negative sample control cells, if needed. After the barrier integrity test was complete, the receptor solution was replaced with the designated stock receptor solution of a 0.1x PBSg.
Prior to administration of the ADAM zolmitriptan to the skin and membrane sections, a predose (0 hour) sample was collected as the entirety of the receptor solution volume was withdrawn with an approximate 5 mL aliquot of the collected sample saved for subsequent analysis. The receptor solution was replaced with the designated stock receptor solution of 0.1x PBSg. The skin was then temporarily removed from the Franz diffusion cell to allow full access to the epidermal surface. Immediately following ADAM zolmitriptan application, the skin-ADAM combination and the donor compartment (chimney) were replaced onto the receptor compartment of the Franz diffusion cell. At the scheduled sampling time points (3, 5, 10, 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, and 300 minutes), the receptor solution was removed in its entirety and refilled with stock receptor solution, and an approximate 5 mL aliquot of the collected sample was saved for subsequent analysis. For sample analysis, a 5 mL aliquot was lyophilized using vacuum centrifugation (Savant™ SpeedVac™) and reconstituted in 0.25 mL of deionized water. After the last receptor sample was collected, the ADAM zolmitriptan was removed for subsequent extraction and analysis. The skin surface wash was performed using two successive refluxing washes of deionized water. Each wash cycle consisted of at least 10 refluxes. The two wash volumes from each donor cell were pooled to generate a single surface wash sample for each diffusion cell. Following the surface wash, the skin was allowed to dry for no less than 10 minutes. Subsequently, the skin was tape-stripped with up to ten sequential tapes (3M Transpore® tape) to remove and collect the stratum corneum. Tape strips were extracted overnight in deionized water on a horizontal mixer (60 rpm) at ambient temperatures. The skin was then dismounted from the cell and separated by manual dissection into epidermis and dermis for subsequent extraction and analysis. Skin sections were extracted overnight in deionized water on a horizontal mixer (~60 rpm) at ambient room temperature.
Strat-M and the ADAM zolmitriptan array were extracted overnight in deionized water on a horizontal mixer (60 rpm) at ambient temperatures.
The ADAM zolmitriptan systems were applied to the substrate (cadaver skin or Strat-M membrane) using a hand held reusable applicator (total energy = 0.26 J). The ADAM zolmitriptan was attached to the applicator, and the applicator was pressed on the substrate, releasing the patch and applying it with a predetermined force using a previously described method [
Quantification of zolmitriptan in the collected samples was accomplished using a fully validated HPLC method. Samples were analyzed on a Shimadzu Series LC System. The HPLC/UV method used a solvent system consisting of a mobile phase gradient consisting of (Solvent A) 0.1% ammonium acetate with 0.1% acetic acid in water and (Solvent B) methanol and was run through a Phenomenex Luna C18(2) column (100 x 4.6 mm, 3
Replicates within skin donors (2 replicates/donor) were averaged and the standard deviation was calculated for each key parameter. Within donor, averages were then collated and the across donor population mean with standard error was calculated. Strat-M was conducted with 6 replicates, which were averaged, and the standard deviation calculated.
Franz cell experiments are characteristically utilized to assess both
To evaluate the effect of the skin model on microprojection facilitated delivery, full thickness skin (0.70 ± 0.09 mm thickness), dermatomed skin (0.46 ± 0.09 mm), and Strat-M (0.30 ± 0.01 mm thickness) were utilized. Figure
Comparison of mean flux (
The absorption of zolmitriptan from the two skin sources is markedly different. The time to maximum flux was much slower with the full thickness skin in comparison to the dermatomed skin. The time to maximum flux and the shape of the curve for the full thickness skin substrate are in stark contrast to what has been reported by Kellerman et al. [
Figure
Though the Strat-M membrane and the dermatomed skin share a similar permeation curve profile, the peak flux for the Strat-M is significantly lower than that for the dermatomed skin. This phenomenon of very low absorption across synthetic membranes has been reported elsewhere and was attributed to the high elasticity of the synthetic membrane causing the microprojection to retract, such that microprojections do not reside within the created conduits [
Table
Mass balance results, as percent of applied dose (%) of zolmitriptan into and through
|
|
|
---|---|---|
Receptor | 85.46 ± 1.36 | 10.55 ± 6.15 |
Dermis | 0.50 ± 0.04 | - - - |
Epidermis | 0.43 ± 0.16 | - - - |
Stratum Corneum | 0.13 ± 0.04 | - - - |
Surface Wash | 2.57 ± 1.09 | - - - |
Strat-M Extraction | - - - - | 39.76 ± 19.75 |
Ti Array | 3.27 ± 0.36 | 52.79 ± 29.28 |
Total Recovery | 92.35 ± 2.48 | 103.1 ± 9.2 |
In stark contrast to the skin data presented in Table
This study confirmed the influence of choice of
The authors declare that they have no conflicts of interest.