IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Monday Sessions
       Session BI-MoP

Paper BI-MoP1
Silica-Elastin Like Polypeptide Smart Membranes-Switchable Molecular Filters

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Biorecognition Poster Session
Presenter: G.V. Rama Rao, The University of New Mexico
Authors: G.V. Rama Rao, The University of New Mexico
S. Balamurugan, The University of New Mexico
G.P. Lopez, The University of New Mexico
D. Meyer, Duke University
A. Chilkoti, Duke University
Correspondent: Click to Email
Elastin-like polypetides (ELPs) are a class of synthetic polypetides comprising of Val-Pro-Gly-Xaa-Gly where Xaa is any amino acid with the exception of proline and exhibit inverse solubility temperature behavior in aqueous solutions. They undergo a transition from hydrophilic (extended conformation) to hydrophobic (compacted conformation) at the lower critical solution temperature (LCST). We demonstrate in this study that when ELPs are encapsulated in a silica matrix, the ELPs can act as molecular switches that control the selective permeability of the membranes. The pores resulting from the transition can selectively transport different molecular species depending on their size. Two different ELPs of molecular weights of 60 kDa (ELP1-150) and 13 kDa (ELP4-30) were used for the present study. Silica-ELP membranes were prepared by sol-gel processing on microcon centrifugal filter units with 30,000 -100,000 molecular weight cut-off membranes and on 1 inch diameter of ultrafiltration discs. The LCST of the membranes was established by permeation measurements and static contact angle measurements. Differential scanning calorimetric studies were employed to determine the LCST of bulk gels and found to be 34 and 44°C for ELP1-150 and ELP4-30 respectively. Cycling of the membranes between 25 and 40-45°C indicates that the membranes possessed reversible, variable permeability while maintaining good mechanical stability. Permeation experiments with various molecular weights of poly(ethylene glycol) (PEGs) on centrifugal filters and ultrafiltration membranes clearly demonstrated that these membranes are acting as a molecular switches by being impermeable below the LCST and permeating the lower molecular weights of PEGs and filtering out higher molecular weight PEGs above LCST.