Polyelectrolyte droplets facilitate versatile layer-by-layer coating for protein loading interface.

Polyelectrolyte multilayers were formed on a quartz crystal microbalance (QCM) substrate by using polyelectrolyte droplets. In this study, poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrene sulfonate) (PSS) were used. The formation of the multilayers was evaluated in terms of changes in the frequency of the QCM. The polymer droplet could be used to fabricate a polyelectrolyte multilayer. Model protein adsorption such as that in bovine serum albumin and its release behavior were compared with the ionic strength in the media. Moreover, the secondary structure of the adsorbed protein was evaluated by analyzing its circular dichroism spectrum. The adsorbed protein maintained its secondary structure on the layer-by-layer (LbL) membrane. This result strongly supports the fact that the multilayers fabricated by the polyelectrolyte droplet were similar in quality to those fabricated via an alternating adsorption process. In summary, the polyelectrolyte droplet method is a good candidate for the preparation of LbL assemblies in the biomedical field.