Quaternary ammonium palmitoyl glycol chitosan - a new polysoap for drug delivery

A new polysoap, quaternary ammonium palmitoyl glycol chitosan (GCPQ, M-w = 178,000 g mole(-1)) with drug solubilising potential has been synthesised a nd characterised. In solution hydrophobic domains of GCPQ polymeric micelle s were identified by the hypsochromic shift in the lambda (max) of methyl o range and by the increase in the ratio of the fluorescence emission intensi ty of the third and first pyrene vibronic peaks (I-3/I-1). At high aqueous concentrations (>10 mg ml(-1)) GCPQ presents as a gel which solubilises pyr ene (2.5 mM, normal solubility in water similar to 2 muM) on probe sonicati on. Dilution of the gel to a liquid solution of polymeric micelles (less th an or equal to 3.75 mg ml(-1) of GCPQ), results in the observation of fluor escent pyrene excimers (excited dimers) and a high excimer to monomer fluor escence ratio (I-E/I-M). However, attempts to solubilise pyrene at a concen tration of 2.5 mM in a liquid solution of GCPQ (3.75 mg ml(-1)) results in a reduced I-E/I-M value and pyrene precipitation. Viscometry measurements s how a more compact conformation for the polymer solubilising pyrene than th e polymer alone. The polymer is non-haemolytic when present as the liquid s olution and relatively non cytotoxic. In conclusion, a new biocompatible po lysoap, (potential drug solubiliser) is described which forms hydrophobic d omains in solution and shows hysteresis in its solubilisation of pyrene. (C ) 2001 Elsevier Science BN. All rights reserved.