The use of magnetic nanoparticles in nanomedicine keeps expending and, for most applications, the nanoparticles are internalized in cells then left within, bringing the need for accurate, fast, and easy to handle methodologies to assess their behavior in the cellular environment. Herein, a benchtop-size magnetic sensor is introduced to provide real-time precise measurement of nanoparticle magnetism within living cells. The values obtained with the sensor, of cells loaded with different doses of magnetic nanoparticles, are first compared to conventional vibrating sample magnetometry (VSM), and a strong correlation remarkably validates the use of the magnetic sensor as magnetometer to determine the nanoparticle cellular uptake. The sensor is then used to monitor the progressive intracellular degradation of the nanoparticles, over days. Importantly, this real-time in situ measure is performed on a stem cell-spheroid tissue model and can run continuously on a same spheroid, with cells kept alive within. Besides, such continuous magnetic measurement of cell magnetism at the tissue scale does not impact either tissue formation, viability, or stem cell function, including differentiation and extracellular matrix production.

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Nanoreinforced polymers have gained popularity in the last decades since they exhibit enhanced properties (compared to pristine polymers) that are useful in a wide range of applications. Unfortunately, dispersion of nanoparticles (NPs) into polymeric matrices is a major problem since they tend to form agglomerates, limiting the improvement of properties and further applications. In this work, we propose the use of coaxial electrospinning as one-step method to disperse NPs in a polymeric matrix. Particularly, iron oxide (Fe 3 O 4) NP with a monomodal and bimodal size distributions were dispersed in polyvinylidene fluoride (PVDF), a material that is well known for its improved piezoelectric properties when it is processed via electrospinning. The results indicate that the incorporation of NP modified the polymeric fiber depending on their surface-to-volume ratio (smaller NP promoted smaller fiber size). Moreover, transmission electron microscopy revealed a good NP dispersion in the polymer, especially for the smallest NP size (monomodal). Finally, each NP size distributions were well preserved in the electrospun mats compared to the initial NP solutions, demonstrating the suitability of this technique for the fabrication of nanoreinforced PVDF structures with tailored NP size. Overall, this method could represent a facile and practical alternative to fabricate materials with piezoelectric/super-paramagnetic properties.

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