A smart hydrogel with pH/magnetic dual sensitivity was synthesized by in-situ synthesis of Fe 3 O 4 inside carboxymethyl chitin hydrogel matrix prepared from Hericium erinaceus residue. The structure, pH/magnetic sensitivity, swelling and drug release behavior of the prepared hydrogels were investigated. The results showed that Fe 3 O 4 nanoparticles were successfully synthesized and uniformly distributed within the hydrogels. The prepared hydrogels could be attracted by the magnet and exhibited sustained shrinkage behavior at low pH, with the desirable pH/magnetic sensitivity. The formed Fe 3 O 4 could be developed inside the hydrogels by increasing the concentrations of precursor Fe 2+ /Fe 3+ ions, and the magnetic sensitivity of hydrogels was enhanced, while the pH sensitivity and swelling degree were weakened. The Fe 3 O 4 content-dependent behavior of the prepared hydrogels suggested the adjustable properties of hydrogels. The release of 5-Fu in simulated gastric and intestinal fluids followed the Fick diffusion mechanism and showed different release rates, indicating the pH-controlled drug release behavior.
Flexible nanofiber membranes are compelling materials for the development of functional multi-mode sensors; however, their essential features such as high cross-sensitivity, reliable stability and signal discrimination capability have rarely been realized simultaneously in one sensor. Here, a novel multi-mode sensor with a nanofiber membrane structure based on multiple interpenetrating networks of bidisperse magnetic particles, sodium alginate (SA), chitosan (CHI) in conjunction with polyethylene oxide hydrogels was prepared in a controllable electrospinning technology. Specifically, the morphology distributions of nanofibers could be regulated by the crosslinking degree of the interpenetrating networks and the spinning process parameters. The incorporation of SA and CHI endowed the sensor with desirable flexibility, ideal biocompatibility and skin-friendly property. Besides, the assembled sensors not only displayed preferable magnetic sensitivity of 0.34 T −1 and reliable stability, but also exhibited favorable cross-sensitivity, quick response time, and long-term durability for over 5000 cycles under various mechanical stimuli. Importantly, the multi-mode stimuli could be discriminated via producing opposite electrical signals. Furthermore, based on the signal distinguishability of the sensor, a wearable Morse code translation system assisted by the machine learning algorithm was demonstrated, enabling a high recognizing accuracy (>99.1 %) for input letters and numbers information. Due to the excellent multifunctional sensing characteristics, we believe that the sensor will have a high potential in wearable soft electronics and human-machine interactions.
In our study, magnetic molecularly imprinted microspheres (MMIMs) were prepared via Pickering emulsion polymerization. The template λ-cyhalothrin (LC), functional monomers and hydrophobic Fe 3 O 4 nanoparticles, served as magnetic carrier, were contained in oil phase. Modified yeast dispersed in water phase was employed as stabilizer to establish stable oil-in-water Pickering emulsion, and the imprinting process was conducted by thermally initiated radical polymerization of functional and cross-linked monomers. Characterization results indicated that the Pickering emulsion and MMIMs were successfully produced. The MMIMs possessed thermal stability (below 200 °C), magnetic sensitivity ( M s = 0.73 emu g −1 ) and magnetic stability (over the pH range of 2.0–8.0). Then, the MMIMs were used as sorbents for the selective recognition of LC. The Langmuir isotherm model gave a better fit to the experimental data, indicating the monolayer molecular adsorption for LC. The adsorption kinetic data was well described by the pseudo-second-order kinetics model, suggesting that the chemical process could be the rate-limiting step in the adsorption of LC. The selectivity study displayed the excellent selective recognition for LC compared to structural analog and non-analog in unitary and binary solutions. Furthermore, the satisfying regeneration capability of the sorbents was proved by at least three repeated adsorption–desorption cycles.
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