Water soluble and water stable non-covalent adducts of sodium poly(α,L-glutamate)/poly(ethylene glycol).: Method of preparation and characterization of structure

Water soluble and water stable non-covalent adducts of sodium poly(alpha,L-glutamate) (PGNA, Mol.Wt. 17, 32 and 38 K) and poly(ethylene glycol) (PEG, Mol.Wt. 10 K) were prepared by solution blending. The adducts were purified by a phase separation technique. Two-dimensional (2D)-NOESY H-1-NMR spectroscopy studies show that PEG was non-covalently bound to PGNA by hydrophobic interactions between CH2 groups of PEG and methylene (both ss and gamma CH2 ) groups of PGNA in an aqueous solution. Because of the nature and strength of hydrophobic interactions between PEG and PGNA, adducts with a different degree of water stability may be prepared. Studies indicate that the PGNA 17K/PEG 10 K adducts were significantly more water stable than the PGNA 32K/PEG 10 K adduct. Prolonged water stability (> 2 weeks at 25 degrees C) was observed for the ss binding (i.e., PEG bound to inner layer of PGNA molecule) compared to gamma binding (i.e. PEG in the outer layer of PGNA).