Temperature and pH dual-stimuli-responsive phase-change microcapsules for multipurpose applications in smart drug delivery.

Temperature/pH dual-stimuli-responsive phase-change microcapsules (Dual-SR-MEPCM) were designed that can form the basis of smart drug delivery systems. They employed n-eicosane as a phase change material (PCM) microencapsulated in an acrylate-functionalized silica shell via emulsion-templated interfacial polycondensation. A poly(N-isopropylacrylamide-co-acrylate acid) functional layer was then fabricated on the surface of the silica shell through surfactant-assisted radical polymerization. The combination of phase-change microcapsules and stimuli-responsive material results in a system that synchronously implements thermal self-regulation by its PCM core together with controllable drug release through its polymeric functional layer. The resultant Dual-SR-MEPCM exhibits regularly spherical morphology, uniform particle-size distribution and well-defined core-shell microstructure, which indicates successful construction according to our design principle. This system has been further evaluated for multipurpose applications in thermal regulation and drug delivery with independent temperature and pH triggering. The Dual-SR-MEPCM not only shows a high thermal energy-storage capacity of over 160 J/g, but also good anti-leakage performance, thermal cycle stability and high-temperature shape stability. Our studies also reveal independent stimuli-responsive behaviors for temperature and pH when using bovine serum albumin and doxorubicin hydrochloride as model drugs. All of these features indicate that the Dual-SR-MEPCM designed in this study can serve as a promising candidate for smart drug delivery systems, with great potential for future multipurpose applications in advanced pharmaceutical areas.