Improvement in Compatibility and Drug Release Performance of Hot-Melt Pressure-Sensitive Adhesives by Physical Blending Technique

Background: Hot-melt Pressure-sensitive Adhesives (HMPSA) are eco-friendly pressuresensitive adhesives, with the potential of being used as substrates for transdermal patches. However, due to the low hydrophilicity of HMPSA, the application is limited in the field of Traditional Chinese Medicine (TCM) plasters. Methods: Three modified HMPSA were prepared with acrylic resin EPO, acrylic resin RL100, and Polyvinylpyrrolidone (PVP) as the modifying materials. The physical compatibility between HMPSA and the modifying materials was investigated through in vitro release performance, viscosity, softening point, cohesion, and fluidity, so as to determine the most effective modifying material. The impact of the modified HMPSA on the release properties of different TCM ingredients was elucidated by the performance of water absorption and contact angle behavior. Results: With the addition of the modifying materials, both the viscosity and the softening point of HMPSA were improved, with the flowability reduced and the cohesion maintained. The morphological and structural changes reflected the physical compatibility between HMPSA and the three modifying materials. According to the results of in vitro release experiments, PVP effectively improved the release performance of paeoniflorin, ephedrine hydrochloride, and cinnamaldehyde in HMPSA, with no significant impact on the release performance of eugenol. The changes in the drug release performance of HMPSA may be attributed to the improved hydrophilicity of HMPSA after physical modification. Conclusion: The compatibility and the drug release performance of HMPSA were effectively enhanced after the addition of the modifying materials by the physical blending technique. Among the three modifying materials, PVP has been found to be an ideal modifying material for HMPSA in the field of TCM plasters due to its effects on drug release performance.