DEGRADABLE POLYCATIONS AS TOOLS TO STUDY POLYELECTROLYTE COMPLEXES AND TO RELEASE THE POLYANION

The formation of IPECs can also occur between charged natural species like plasma proteins or cells, and oppositely charged artificial macromolecules currently proposed for controlled drug delivery and gene therapy. In these latter cases, IPEC formation can be the source of dramatic precipitations, cell aggregations or hemolysis. 2 Interactions between oppositely charged polyelectrolytes depend on many factors. Some are thermodynamic. Others are dynamic such as the order and the rate of component mixing. We have previously shown that selectivity in molecular weight occurs during IPEC formation from polydispersed polyanions. 3 The main difficulty to investigate the formation of IPECs from mixtures of different polyelectrolytes as it is the case in a living system is the analysis of the involved macromolecules strongly bound by cooperative interactions, or in the presence of each other when then can be decomplexed. In the present work, we tested the potential of a method based on polymer degradation and aimed at isolating one of the two types of interacting macromolecules to detect selectivity when polydispersed polyanions and polycations systems come in contact like during injection in the human body. The test was based on the use of a degradable polycation that was complexed with a mixture of non degradable oppositely charged polyions of the same family but with different compositions and charged densities, namely poly(Llysine citramide) or PLCA. PLCA polymers are artificial multifunctional polyelectrolytes composed of building blocks based on head-to-head or headto-tail linked alternating L-lysine and citric acid moieties. The latter is engaged according to either aspartic or glutamic enchainment because of intrachain isomery generated at the stage of the hydrolysis of the intrachain imide of an intermediate compound. 4