Mesoporous magnetic silica particles modified with stimuli-responsive P(NIPAM-DMA) valve for controlled loading and release of biologically active molecules.

Mesoporous magnetic silica particles bearing a stimuli-responsive polymer valve were prepared and their performance as a microcapsule was evaluated. In this study, first, mesoporous magnetic iron oxide (Fe3O4) particles were prepared by a solvothermal method. Then, the magnetic particles were coated with silica and functionalized with vinyl groups using 3-(trimethoxysilyl)-propyl methacrylate (MPS). Subsequently, the Fe3O4/SiO2 composite particles grafted with MPS were used to carry out the seeded precipitation copolymerization of N-isopropylacrylamide (NIPAM) and 2,2-dimethylaminoethyl methacrylate (DMA). Here N,N'-methylenebisacrylamide (MBA) was used as a cross-linker. Brunauer-Emmett-Teller (BET) surface analysis suggested that the mesoporous structure was retained in the final Fe3O4/SiO2/P(NIPAM-DMA-MBA) composite hydrogel particles. The prepared Fe3O4/SiO2/P(NIPAM-DMA-MBA) composite hydrogel microspheres exhibited a pH-dependent volume phase transition. At lower pH values (<7), the inclusion of DMA shifted the volume phase transition to higher temperature because of the protonation of the tertiary amine groups. The composite hydrogel particles possessed a high saturation magnetization (51 emu g-1) and moved under the influence of an external magnetic field. The loading-release behaviour of these biologically active molecules suggested that a portion of the encapsulated guest molecules was released at a temperature below the lower critical solution temperature, LCST (<35 °C).

Mesoporous electromagnetic composite particles: Electric current responsive release of biologically active molecules and antibacterial properties.

Electric current responsive magnetic composite particles are prepared in three steps. In the first step, spherical and mesoporous submicrometer-sized magnetic iron oxide (Fe3O4) core particles are prepared by solvothermal method. Then magnetic Fe3O4 particles are functionalized with amine groups using glycine, where the COO- group of glycine formed a bridging bidentate interaction with the hydroxyl groups on Fe3O4 particle surface. Finally polyaniline (PAni) is grafted onto the functional Fe3O4 surface via in situ seeded chemical oxidative polymerization of aniline. The average size of Fe3O4/PAni composite particles is 418.82 nm with mesoporous surface structure. Electron microscopic images confirmed that PAni pockets are localized on the surface of Fe3O4 core particles. The surface composition is further confirmed by Fourier transform IR (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimety (TG) analyses. Fe3O4/PAni composite particles possessed strong paramagnetic property (47.77 emu g-1). The electrical conductivity of Fe3O4/PAni composite particles (1.46 × 10-4 S cm-1) remained in the same order of magnitude as that of reference PAni particles (3.42 × 10-4 S cm-1). The release behavior of biologically active molecules such as trypsin (TR), albumin (AL) and p-acetamido phenol (pAP) is studied using low intensity electric current as stimuli to prevent degradation. Depending on the nature, up to ˜ 33-88% of adsorbed biomolecules/drug are released from the electromagnetic Fe3O4/PAni composite particles. Compared to Fe3O4 particles, Fe3O4/PAni composite particles exhibited moderate antibacterial property.