Polymeric thin films represent an emerging industrial area driven by their enormous technological and commercial potential in interdisciplinary sectors such as chemistry, material science, engineering, and physics. The large selection in terms of materials/composites and the wide range of technological solutions that could be used for their fabrication could create confusion for the final user requiring a quantitative characterization of their properties. This analysis could be even more complex in the case of functionalized polymeric films such as the samples reported in this work. Here we present how thin polymer films can be wholly characterized by applying a multiplicity of optical methods. Films were realized by a special liquid one-step process. Moreover, such polymer films were functionalized here for the first time by mesoporous silica nanoparticles. The nanoparticles were added to a polymeric matrix. We show that a full characterization was achieved by employing three different microscope techniques, i.e., scanning electron microscope, digital holography (DH), and space-time DH. Exploiting such a multimodal methodology can be of great benefit for characterizing the functionalized polymeric thin films. In fact, multiple characterization in different conditions was possible. The results reported in terms of morphological information, thickness distribution, three-dimensional (3D) mapping, large field of view, high magnification, and super resolution of the zoomed area offer a good solution for testing materials and obtaining a quantitative characterization and whole inspection in the case of complex polymeric samples.
Nano graphene-based materials offer interesting physicochemical and biological properties for biotechnological applications due to their small size, large surface area and ability to interact with cells/tissues. Among carbon-based nanomaterials, graphene oxide is one of the most used in biological field. There is an increasing interest in shedding light on the interaction mechanisms of nanographene oxide (nGO) with cells. In fact, the effects on human health of GO, and its toxicological profile, are still largely unknown. Here we show that, by minimizing the oxidation degree of GO, its toxicity is significantly reduced in NIH 3T3 cells. Moreover, we show that mild oxidation of graphene nanoplatelets produces nGO particles, which are massively internalized into the cell cytoplasm. MTT(3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was performed to analyze cell viability. Transmission electron microscopy (TEM) analysis was performed to evaluate nGO internalization mechanism into the cytoplasm under different oxidation degree and concentrations. For the first time, we evaluated quantitatively, the cell volume variation after nGO internalization in live fibroblasts through a label-free digital holography (DH) imaging technique and in quasi-real-time modality, thus avoiding the time-consuming and detrimental procedures usually employed by electron-based microscopy. In conclusion, here we have demonstrated that DH can be a viable tool to visualize and display 3D distributions of nano graphene oxide (nGO) uptake by fibroblast cells. DH opens the route for high-throughput investigation at single cell level for understanding how in different conditions nanoparticles aggregates distribute inside the cells.
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