Synthesis of SIS-based hot-melt pressure sensitive adhesives for transdermal delivery of hydrophilic drugs

Abstract A series of epoxidized styrene–isoprene–styrene (SIS) copolymer was obtained with in situ epoxidation. Their epoxidation degrees were analyzed by 1 H nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. SIS, Epoxidized SIS (ESIS), C5 resin, mineral oil and antioxidants were melt-blended to prepare SIS/ESIS-based hot-melt pressure sensitive adhesives (HMPSAs). Their compatibility was studied with differential scanning calorimetry (DSC). The adhesive performances of the HMPSAs were measured, including holding power and 180° peel strength. Geniposide was chosen as a representative hydrophilic drug and it’s in vitro release behavior in the HMPSAs was investigated using a modified Franz type horizontal diffusion cells. It was shown that SIS was successfully epoxidized without side reactions. Although the epoxidation impaired the compatibility between ESIS and other additives, the 180° peel strength increased with the epoxidation degrees of ESIS. Furthermore, the in vitro release behavior of hydrophilic drugs was obviously enhanced with the increment of epoxidation degrees.