POLY[(AMINO ACID ESTER)PHOSPHAZENES] AS SUBSTRATES FOR THE CONTROLLED-RELEASE OF SMALL MOLECULES

Three different poly[(amino acid ester)phosphazenes] have been examine d in order to investigate their possible use as drug delivery vehicles . The three polymers are poly[di(ethyl glycinato)phosphazene], poly[di (ethyl alanato)phosphazene] and poly[di(benzyl alanato) phosphazene]. These macromolecules either share the same amino acid residue or the s ame ester group, and this facilitated comparisons of the hydrolytic de composition and the small molecule release profiles of the polymers. T he polymers were synthesized by treatment of poly(dichlorophosphazene) with an excess of the appropriate amino acid ester. Tetrahydrofuran s olutions of each polymer were then thoroughly mixed with ethacrynic ac id, a diuretic, or Biebrich Scarlet, an azo dye. Films cast from these solutions were immersed in aqueous media (pH 7) at 25 degrees C and a t 37 degrees C for approximately 1400 h. During these experiments, the release of the small molecules was monitored by UV/visible spectrosco py. The molecular weight decline and the mass loss of the polyphosphaz ene films were measured.