Norfloxacin-poly(L-lysine citramide imide) conjugates and structure-dependence of the drug release

Norfloxacin (Nflx), an antibiotic which is active against some intracellular bacteria, was coupled to a polymeric carrier, namely poly(L-lysine citramide) via a lysine or an ethylcarbamate spacer to obtain a macromolecular prodrug. The carrier, which derived from the two metabolites citric acid and L-lysine, is known to be biocompatible and slowly degradable under slight acidic conditions. Conjugates were characterised by UV, 1H and 13C NMR and SEC. The presence of Norfloxacin and the lysine type spacer caused chain aggregation, due to a probable physical cure. The release of Norfloxacin from these prodrugs and from a prodrug where Norfloxacin is bound to the carrier backbone without spacer arm was investigated comparatively in vitro. Conjugation via a carbamate-type linkage appeared as a method to achieve the release of Norfloxacin from a PLCA-type conjugate at neutral.