Microscopic and Spectroscopic Imaging and Thermal Analysis of Acrylates, Silicones and Active Pharmaceutical Ingredients in Adhesive Transdermal Patches

Abstract

Dermal or transdermal patches are increasingly becoming a noteworthy alternative as carriers for active pharmaceutical ingredients (APIs), which makes their detailed physicochemical evaluation essential for pharmaceutical development. This paper demonstrates mid-infrared (FTIR) and Raman spectroscopy with complementary microscopic methods (SEM, optical and confocal Raman microscopy) and differential scanning calorimetry (DSC) as tools for the identification of the state of model API (testosterone TST, cytisine CYT or indomethacin IND) in selected adhesive matrices. Among the employed spectroscopic techniques, FTIR and Raman may be used not only as standard methods for API identification in the matrix, but also as a means of distinguishing commercially available polymeric materials of a similar chemical structures. A novel approach for the preparation of adhesive polymers for the FTIR analysis was introduced. In silicone matrices, all three APIs were suspended, whereas in the case of the acrylic PSA, Raman microscopy confirmed that only IND was dissolved in all three acrylic matrices, and the dissolved fraction of the CYT differed depending on the matrix type. Moreover, the recrystallization of TST was observed in one of the acrylates. Interestingly, a DSC analysis of the acrylic patches did not confirm the presence of the API even if the microscopic images showed suspended particles.

Design, Development, and Evaluation of Treprostinil Embedded Adhesive Transdermal Patch

“…The patches did not show any signs of treprostinil crystals; probably, the drug is in molecular form and embedded in the adhesive. However, a few white spots on the surface could be due to the backscattered light effect, as generally noticed in the SEM images of transdermal patches [47]. Overall, the optimized patch morphology seems suitable for transdermal application.…”

“…from the image that the surface of the patch was free from drug crystals, while the drug, adhesive matrix and enhancer are homogeneously distributed. The microstructure of the patch surface of the prepared transdermal patch could be thoroughly visualized using SEM [47]. Hence, SEM was utilized to examine the topography of the optimized patch.…”

Ionic Liquid-Based Immunization Patch for the Transdermal Delivery of Antigens

“…An ideal transdermal patch should have a smooth surface [37]. However, some transdermal patches may have rough surfaces depending on the type of PSA [38]. The surface morphology of SP-4098 and SP-4287 were investigated by scanning electron microscopy (SEM) and found to be smooth (Figure 2).…”

“…PSAs with a functional group interact with drug molecules and surfactants present in a patch and play a crucial role in the thermophysical properties of patches [40]. Low values for both moisture absorption and moisture content are desirable for an ideal transdermal patch [38,41].…”

“…the thermophysical properties of patches [40]. Low values for both moisture absorption and moisture content are desirable for an ideal transdermal patch [38,41].…”