Rheo-SAXS study on electrically responsive hydrogels with shear-induced conductive micellar networks for on-demand drug release

This study presents a novel approach to creating electrically responsive hydro-gels utilizing a poly(ethyl-ene oxide)-poly(propyl-ene oxide)-poly(ethyl-ene oxide) (PEO₁₀₀-PPO₆₅-PEO₁₀₀) triblock copolymer, functionalized with benzene-sulfonate end groups to form sF127. This functionalization allows the incorporation of sF127 into F127 micelles, resulting in tailored micelles designated as F₁₈S₂P when combined with poly(3,4-ethyl-ene-dioxy-thio-phene):poly(benzene-sulfonate) (PEDOT:PSS). For comparison, a control system using non-functionalized PEDOT:PSS/F127 micelles, designated F₂₀S₀P, was also developed. Using piroxicam as a model hydro-phobic drug, we evaluated the hydro-gel's drug encapsulation efficiency and electrical responsiveness. The functionalized F₁₈S₂P hydro-gel demonstrated superior performance of electrically stimulated drug release, especially when prepared with a blade-coating process. <i>In situ</i> rheological small-angle X-ray scattering (rheo-SAXS) measurements under large amplitude oscillatory shear revealed that function-alization facilitates crystal plane sliding, leading to the formation of a randomly hexagonal close-packed (rHCP) sliding layer structure. This behavior contrasts with the face-centered cubic to rHCP phase transition observed in the unfunctionalized hydro-gel. <i>In situ</i> SAXS analysis under applied electric fields (E-SAXS) further confirmed the electroresponsive micellar deformation. By integrating the rheo-SAXS and E-SAXS findings with blade-coating processing insights, we identify a clear structure-function relationship that governs the performance of these hydro-gels. The enhanced drug delivery of the function-al-ized F₁₈S₂P hydro-gel is attributed to the electrostatic attraction between the positively charged PEDOT and the negatively charged benzene-sulfonate-functionalized micelles. This interaction creates conductive nanonetworks within the hydro-gel, significantly improving its ability to release drugs in response to electrical stimulation. This work highlights the potential of electrically responsive hydro-gels for precise, localized drug delivery applications.