Coatings of zein and zein/bioactive glass composites were produced on 316L stainless steel using anodic electrophoretic deposition (EPD). Zein and 45S5 bioactive glass were dispersed in a binary water/ethanol solution. The effects of the zein and bioactive glass concentrations as well as different water/ethanol ratios on the coating characteristics were investigated. Also, the influence of applied voltage and deposition time were analyzed. Prior to EPD, the zeta potential of zein, bioactive glass and zein/bioactive glass suspensions were measured as a function of the pH. The coatings were investigated by optical microscopy, scanning electron microscopy and atomic force microscopy. Coatings with pure zein are homogeneous when using an electrical field strength below or equal to 0.05 V/m. Higher voltages led to a discoloration of the solution which could result from a conformational change of zein. The co-deposition of zein/bioactive glass is very sensitive to the applied voltage and the concentration of zein. High concentrations of zein (10 g/L) increase the viscosity of the solution and reduce the electrophoretic mobility of the bioactive glass. Equal concentration of zein and bioactive glass at a pH of 7.5 with a low electric field strength were found to be the optimum conditions.
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Supporting Information available onlineA flow rate and resistance-based approach for upscaling of microfiltration processes from lab scale to process scale is presented, in correlation with biopharmaceutical processes. Basic element is the modeling of filtration curves using a resistance-in-series model based on the Darcy equation. The influences of the filtration setup and the fouling layer are described as additional resistances that change in course of filtration. The necessary parameters, such as setup resistances and filtration areas, are determined by water flow rate measurements. The model is validated by filtration of a particulate test solution. The presented approach can be used for constant flow and constant pressure driven filtration processes.
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