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Bioprinted superparamagnetic nanoparticles for tissue engineering applications: synthesis, cytotoxicity assessment, novel hybrid printing system

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ABSTRACT Novel technologies are required in tissue engineering to manufacture three-dimensional organs with complex architecture. While superparamagnetic nanoparticles have been widely used in medicine for magnetic resonance imaging and targeted drug delivery, they have not been extensively applied in tissue engineering. These nanoparticles would allow active patterning and non-destructive imaging during tissue growth and development. However, no inexpensive method exists for synthesis of commercial amounts of these nanoparticles with controlled morphology, chemistry and size. Furthermore, superparamagnetic nanoparticle cytotoxicity mechanisms are not well understood, which makes it difficult to control or block adverse nanoparticle effects on human health. In this dissertation, superparamagnetic iron oxide nanoparticles were produced by flame synthesis using a coflow diffusion flame. Nanoparticle flame synthesis has significant advantages, including improved nanoparticle property control and commercial production rate capability with minimal post-processing. Final iron oxide nanoparticle morphology, elemental composition, and particle size was controlled by changing flame configuration, flame temperature, and additive loading, and morphology, elemental composition, and particle size of the synthesized nanoparticles were analyzed by electron microscopy (TEM, ESEM, EDS), and Raman Spectroscopy. Then flame synthesized iron oxide nanoparticle interaction with endothelial cells was compared to commercially available iron oxide nanoparticles. Flame synthesized particles showed no statistically significant toxicity difference from commercially available nanoparticles, as measured by Live/Dead assay, Alamar blue, and lactase dehydrogenase release. Both synthesized and purchased nanoparticles localized inside the cell cytoplasm as shown by TEM images. Iron oxide nanoparticles resulted in an increase in reactive oxygen species (ROS) formation in cells within the first three hours after nanoparticle uptake, and this ROS formation contributed to actin cytoskeleton disruption. Finally, a new hybrid nano-bioprinting technique that facilitates manipulation and tracking of cells and bioactive factors within a three-dimensional tissue construct was developed. This technique combined the initial patterning capabilities of syringe-based cell deposition with the active patterning capabilities of superparamagnetic nanoparticles. Superparamagnetic iron oxide nanoparticles, either in the alginate biopolymer or loaded inside endothelial cells, were bioprinted using the hybrid solid freeform fabrication direct cell writing system and they were manipulated using an external magnet and imaged by MicroCT.

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