Purification of silk nanoparticles: impact of centrifugation and tangential flow filtration on critical quality attributes

Silk has emerged as a promising biomaterial for formulating protein-based nanocarriers for use as drug delivery systems. Silk nanoparticles can be manufactured using several different methods, including nanoprecipitation through organic desolvation using isopropanol as an antisolvent. The translation of silk nanoparticle manufacture from the bench to the industrial scale requires deeper insights into the manufacturing process, especially nanoparticle purification. Here, we compare the impact of tangential flow filtration (TFF) with widely used centrifugation methods for silk nanoparticle purification. Silk nanoparticles were manufactured using a well-studied semi-batch nanoprecipitation process. We demonstrate that silk nanoparticle purification significantly changed the physicochemical properties, particularly the yield. The silk nanoparticles showed major differences in in vitro cytotoxicity, depending on the purification method used. TFF purification revealed that a change in permeate volume during purification was a key parameter, as low cytotoxicity was correlated with an increase in the diavolume. Overall, TFF emerges as a purification method with high potential for scale-up and faster silk nanoparticle purification.