Development and adhesion evaluation of transdermal rotigotine patches utilizing 3D-printed skin-mimicking substrate,...

Transdermal rotigotine patches, used to treat parkinson's disease, often face challenges in maintaining adequate adhesion, which is crucial for effective drug delivery. Adhesion performance is influenced by environmental conditions such as humidity and temperature, as well as skin characteristics like wrinkles and micro-delaminations that vary with age and sex. Standard adhesion tests using stainless steel (SS) substrates do not accurately mimic human skin, leading to overestimated adhesion strength. This study developed rotigotine matrix transdermal formulations with silicone pressure sensitive adhesive (PSA) and evaluated their adhesion properties at 32 ± 1°C and 75 ± 5 % RH in a stability chamber. Moisture uptake over 24 h was measured using solid-state nuclear magnetic resonance (SSNMR) spectroscopy and attenuated total reflectance-fourier transform infrared- (ATR-FTIR) spectroscopy. Adhesion tests, including probe tack and peel, were performed on SS and 3D-printed acrylonitrile butadiene styrene (ABS) substrates designed with micro-delaminations and wrinkles to simulate skin conditions. In vitro permeation testing (IVPT) studies demonstrated a flux of 10.48 ± 0.61 and 10.03 ± 0.57 μg/h/cm² for formulations with and without mannitol, respectively. SSNMR and ATR-FTIR revealed significant moisture uptake, contributing to adhesion loss. Adhesion forces were significantly lower on ABS compared to SS, with further reductions observed on wrinkled and micro-delaminated surfaces, indicating that SS substrates overestimate adhesion results. This is the first study to combine SSNMR and skin-mimetic substrates for analyzing adhesion loss in transdermal patches, highlighting the potential of moisture-resistant agents like mannitol to enhance patch performance.