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Drug Delivery

Drug Delivery - Poster Session A

Poster J8 - Design and Fabrication of a Zero Order Kinetics Transdermal Patch for Addison’s Disease

Thursday, October 24, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Primary adrenal insufficiency or Addison’s disease is an endocrine disorder resulting from the insufficient production of the hormones cortisol and aldosterone by the adrenal glands (Addison’s Disease - Symptoms and Causes - Mayo Clinic, 2024). To treat this disease, medications such as hydrocortisone, prednisone, or methylprednisolone pills are prescribed and taken on a schedule every 4-6 hours during the day (Addison’s Disease - Diagnosis and Treatment - Mayo Clinic, 2024). If patients do not regularly take their scheduled medications, underdose, or overdose their medication there are increased risks of life-threatening complications such as an Addisonian crisis that may cause extreme weakness, fatigue, low blood pressure and major organ failure (Addison’s Disease - Symptoms and Causes - Mayo Clinic, 2024). To improve treatment scheduling concerns, we designed and fabricated a transdermal microneedle patch that would consistently deliver a simulated cortical steroid over an extended duration.

Materials and

Methods:  The design was developed in SolidWorks and composed of a 5x5 microneedle array, reservoir, and adhesive bandage (Figure 1). Needles were spaced 7 mm apart in a 30 mm × 30 mm area centered on the 40 mm×40 mm base made of Formlabs BioMed Clear V4 Resin. Each needle had a 400 µm diameter offset hole 200 µm from the base center and square pyramidal base length and height of 1500 µm. A reservoir made of the same resin with 40 mm × 40 mm base, a centered 30 mm × 30 mm square with 1.50 mm depth, 1000 µm diameter center loading hole, and a 400 µm diameter air displacement hole in each corner. Assembled total volume was 1350 µl and adhesive bandage of 50 mm × 50 mm with 0.10 mm depth was used for air displacement facilitating drug flow.

The array and reservoir were post processed in isopropyl alcohol (IPA) for 15 minutes followed by a 5-minute IPA wash before curing at 50°C for 60 minutes. The device was manually assembled using adhesive and cured for 6 hours minimum. A standard dilution curve of blue McCormick food coloring dye in saline (simulating corticosteroid) was made. Device was loaded with 25 µl of dye in 1325 µl of saline solution on a suspension culture dish loaded with 12.5 ml of saline. Aliquots of 100 µl were placed into a 96-well plate for 11 hours and drug absorbance at 600 nm was measured using a spectrophotometer for all aliquots.

Results, Conclusions, and Discussions: The optical density curve had a linear fit trendline equation of y = 0.3085x – 0.0027 and gave an R2 of 0.999 (Figure 2). The trendline was then used to find the mean and standard deviation of concentrations of the aliquots. Aliquots had a mean concentration of 1.094±0.018 mg/ml at 1 hr, 5.068±0.034 mg/ml at 5 hr, and 10.848±0.103 mg/ml at 11 hr. The drug delivery kinetics had a linear fit trendline equation of y = 1x + 3E-5 yielding an R2 of 0.99 (Figure 3). These results imply a zero kinetic drug release through the transdermal microneedle patch over extended periods of time to improve Addisonian patient outcomes. Future work involves solubilizing a corticosteroid for the analysis of drug delivery through the mechanism, developing a manufacturing process, and ex-vivo puncture testing for evaluation of capillary action in uptake of the solubilized corticosteroid.

Our design of a transdermal microneedle patch successfully displayed a zero-order drug release over time. This work allows for further studies in drug delivery mechanisms that could play a pivotal role in improving the outcomes of Addison’s disease patients as well as potentially initiate new treatment delivery options for other diseases.

Acknowledgements (Optional):  Financial support was provided by NSF grant 2140104 to Hossein Tavana.