Transdermal Delivery of Salmon Calcitonin Using a Dissolving Microneedle Array: Characterization, Stability, and In vivo Pharmacodynamics

Salmon calcitonin (sCT) is a polypeptide drug, possessing the ability to inhibit osteoclast-mediated bone resorption. Just like other bioactive macromolecules, sCT is generally administered to the patients by either injection for poor compliance or through nasal spray for low bioavailability, which limits its use as therapeutic drugs. In the present study, to overcome the limitations of the conventional routes, two new dissolving microneedle arrays (DMNAs) based on transdermal sCT delivery systems were developed, namely sCT-DMNA-1 (sCT/Dex/K90E) and sCT-DMNA-2 (sCT/Dex-Tre/K90E) with the same dimension, meeting the requirements of suitable mechanical properties. An accurate and reliable method was established to determine the needle drug loading proportion in sCT-DMNAs. The stability study exhibited that the addition of trehalose could improve the stability of sCT in DMNA under high temperature and humidity. Further, in vivo pharmacodynamic study revealed that DMNA patch could significantly enhanced relative bioavailability to approximately 70%, and the addition of trehalose was found to be beneficial for sCT transdermal delivery. Therefore, sCT-DMNA is expected to replace traditional dosage form, providing a secure, efficient, and low-pain therapeutic strategy for bone disorders.