Structural characterization of emulsion-type cataplasms with cross-linked networks and systematic establishment of structural parameters

Compared with conventional cataplasms, those incorporating a cross-linked network structure significantly enhance their mechanical strength and cohesion, endowing them with good formability and adhesion properties, solving problems such as cold flow and slippage, thereby greatly increasing the convenience of use. However, systematic studies investigating the structural profiling of cross-linked networks in cataplasms remain scarce, limiting a comprehensive understanding of their functional significance. Therefore, we developed a systematic methodology to characterize emulsion-type cataplasms (as a model formulation) with cross-linked network structures, classifying their key structural parameters into four levels. The primary structures defined formability and adhesion, ensuring intact and durable skin adhesion. The secondary structure was intermediates formed by the drug and oily components. The tertiary structure was a dynamic structure, evaluating the quality changes of cataplasms during processes such as crosslinking and storage. The quaternary structure was a molecular structure, representing the mechanism by which the cross-linked network structure was formed. The factors influencing structural parameters and the laws between the intrinsic structures were investigated. Furthermore, we established threshold values for the primary structures, indicating when cataplasms possess optimal formability. This study offers new insights for cataplasm design and provides valuable references for industrial development. This work first proposes and systematically establishes structural parameters for emulsion-type cataplasms with cross-linked networks at four levels, offering new insights into the design of formulations.