Layer-by-layer assembled protein/polymer hybrid films: nanoconstruction via specific recognition

In the present study it is shown that streptavidin-containing multilayer fi lms with varying numbers of polyelectrolyte spacer layers can be fabricated reproducibly using optimized deposition conditions. Direct alternation of streptavidin and PLB leads to multilayer systems with an average streptavid in thickness of 5.3 nm, which is in good agreement with the dimensions of t he protein. When the streptavidin layers are spacered by more polyelectroly te layers, the distance between the protein sheets is increased up to, e.g. 6.5 nm in the case of (PLB/PSS/PAH/PSS/PLB) as spacer layer. X-ray reflect ivity reveals that streptavidin increases the surface roughness of the film s, probably due to the rigid three-dimensional structure of the protein. Th e control of surface roughness seems to be essential for a successful multi layer build-up. The property of PLB to provide for multilayer construction by two different interactions (electrostatic and specific) allowed to probe the interpenetration depth of adjacent layers. For the [PLB/(PSS/PL)(2)/st reptavidin] system an interpenetration depth of about 4 polymer layers corr esponding to approximately 3.4 nm has been derived. These data are in agree ment with a model for pure polyelectrolyte films obtained from neutron and X-ray reflectivity data. (C) 1998 Published by Elsevier Science Limited. Al l rights reserved.