Fabrication and characterization of dissolving microneedles for transdermal delivery of hypocrellin A

Hypocrellin A (HA) is an efficient photosensitizer for photodynamic therapy in recent years. In order to improve the delivery of this photosensitizer, dissolving HA microneedles were established. Firstly, dissolving microneedles were prepared from HA by a two-step solvent casting method. Then, the dissolving HA microneedle were characterized by stereomicroscope, laser confocal microscope, scanning electron microscope, differential scanning calorimeter (DSC), X-ray diffractometer (XRD) and fourier infrared spectrometer (FTIR). Finally, the transdermal cumulative penetration experiments were conducted. The results showed that the dissolving HA microneedle has a conical shape with an average height of 650 μm. The mechanical strength endure a force of 44.78 N, resulting in 0.20 N per needle. The in vitro transdermal experiment showed that the dissolving HA microneedle almost completely dissolved in 5 min after insertion into the mouse skin. The depth of drug penetration through the skin can reach 601.36 μm. Moreover, the dissolving HA microneedle significantly improved the cumulative transdermal penetration efficiency of the photosensitizer through the skin. Therefore, the present study successfully established a dissolving microneedle of HA, which can quickly dissolve and significantly improve the transdermal delivery efficiency of HA.