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Silica nanoparticles (SNPs) can be employed as model systems in the design of separation of biologics (vaccines, cells, therapeutic proteins). The use of SNPs addresses the need to safely develop and design advanced separation techniques outside biological labs as part of multidisciplinary collaborative teams. This research tests the hypothesis that the mobility of dispersed SNP (model viruses) in an electric field can be tuned with surface functionalization and used to demonstrate charge-driven separation in a membrane process. To mimic virus functionality, SNPs are surface functionalized. Bare silica nanoparticles have a negative surface functionality. By controlling the extent of functionalization to the SNP, positive surface charge can be added to mimic the virus surface. Another approach to SNP surface functionalization is to add lipids on the outer surface of the particles to give the SNP additional cell-like or virus-like surface properties. Incorporating a dye on the SNPs aids in the quantification of the SNPs.

Nonporous silica particles of around 60-70 nm were synthesized and characterized using a Scanning Electron Microscope (SEM) and Image J software. Dynamic Light Scattering (DLS) was used to confirm the size of suspended particle solution, which was determined to be 60-80 nm. Next, the SNPs were amine-functionalized using 3-aminopropyl)triethoxysilane. To quantify the extent of amine functionalization, acid orange II was bound to the particles at low pH and recovered at high pH. The amount of bound dye was determined from UV-vis spectroscopy. The SNPs were modified by attaching a lipid bilayer containing a dye on the outside surface of the particles for further analysis of charge separations. The surface charge of the SNPs was measured across different batches of the particles by performing zeta potential using DLS. The movement of suspended dye-loaded particles across various membranes in the presence of an applied voltage was tracked. Future work will consist of additional electrodialysis experiments that relate the applied voltage and SNP surface properties to the effectiveness of the charge-based separations.