AVS 51st International Symposium
    Biomaterial Interfaces Thursday Sessions
       Session BI+AS+SE-ThM

Paper BI+AS+SE-ThM8
Stability of Polypeptide Multilayers as Studied by in situ Ellipsometry: Effects of Drying and Post-Buildup Changes in Temperature and pH

Thursday, November 18, 2004, 10:40 am, Room 210D

Session: Surface Modification of Biomaterials
Presenter: U. Elofsson, YKI AB, Institute for Surface Chemistry, Sweden
Authors: T.J. Halthur, YKI AB, Institute for Surface Chemistry, Sweden
P. Claesson, KTH, Royal Institute of Technology, Sweden
U. Elofsson, YKI AB, Institute for Surface Chemistry, Sweden
Correspondent: Click to Email
Polyelectrolyte Multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with a initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the Layer-by-Layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles and pH shifts was studied in situ by means of ellipsometry. The filmthickness was found to decrease significantly (approximately 70%) upon drying, but the original film-thickness was regained upon rewetting and the buildup could be continued. The dry thickness was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH was also found to influence the multilayer thickness, leading to swelling and de-swelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.