RESUMEN
In this research, we conducted a systematic evaluation of the synthesis parameters of a multi-responsive core-shell nanocomposite (Fe3O4 nanoparticles coated by poly(N-isopropylacrylamide) (PNIPAM) in the presence of chitosan (CS) (Fe3O4@PNIPAM-CS). Scanning electron microscopy (SEM) was used to follow the size and morphology of the nanocomposite. The functionalization and the coating of Fe3O4 nanoparticles (Nps) were evaluated by the ζ-potential evolution and Fourier Transform infrared spectroscopy (FTIR). The nanocomposite exhibited a collapsed structure when the temperature was driven above the lower critical solution temperature (LCST), determined by dynamic light scattering (DLS). The LCST was successfully shifted from 33 to 39 °C, which opens the possibility of using it in physiological systems. A magnetometry test was performed to confirm the superparamagnetic behavior at room temperature. The obtained systems allow the possibility to control specific properties, such as particle size and morphology. Finally, we performed vincristine sulfate loading and release tests. Mathematical analysis reveals a two-stage structural-relaxation release model beyond the LCST. In contrast, a temperature of 25 °C promotes the diffusional release model. As a result, a more in-depth comprehension of the release kinetics was achieved. The synthesis and study of a magnetic core-shell nanoplatform offer a smart material as an alternative targeted release therapy due to its thermomagnetic properties.
RESUMEN
In this work, a capacitive sensor made of recycled material is proposed to monitor oil quality in automotive workshops in order to reduce the waste of useful lubricant oil caused by shorter periods of use than those established by the manufacturers. The sensor was fabricated from a recycled aluminum heat sink and used to measure the permittivity of oil samples. The proposed method was compared with Fourier-transform infrared spectroscopy analysis to evaluate degradation parameters, as described in standard practice ASTM E-2412. The obtained results showed good agreement between both techniques, validating the use of the proposed sensor to evaluate oil condition. The use of permittivity measurements could be used to evaluate oil quality in an easier, faster, and economical way compared with other laboratory tests.