(96c) Functionalized Membranes: Layer-by-Layer Assembly for Bioseparation Applications

The adsorption of biomolecules by membranes containing charged layers was studied. Poly-L-glutamic acid (PLGA) covalently bonded to the functional groups of either nylon membranes containing acyl-anhydride or gold-plated polycarbonate track-etched membranes functionalized with an aldehyde. An aqueous solution of Poly(allylamine hydrochloride) (PAH) was then permeated through the membrane (pH~6). At this pH, the PLGA is negatively charged while the PAH has positively charged amine groups. Thus, electrostatic interactions caused PAH to be immobilized as the second layer. The third layer consisted of either Poly(acryllic acid) or Poly(styrene-sulfonate), which are negatively charged at pH~6. Quantitative analysis of the layers was used to determine the net charge of the membrane. The charge interactions of these membranes was then further characterized by passing low molecular weight charged molecules through the membranes. The protein avidin was sometimes added to the layered membranes. Because the avidin was held in place by electrostatic interactions and was not covalently bonded directly to the membrane, it was believed that more of its active sites would be available for interaction with a biotinylated compound. The relative adsorption of biotin by these membranes was compared to that of membranes with direct covalent attachment of avidin. Project supported by NIEHS.