Complexes of polyglutamic acid and long-chain alkanoylcholines: nanoparticle formation and drug release

Ionic complexes of microbial poly(γ-glutamic acid) and alkanoylcholines are fully bio-based comb-like systems able to self-organize in an ordered amphiphilic structure made of hydrophobic and hydrophilic alternating layers. Incubation of complex films under physiological conditions for one month promoted dissociation of the complex and hydrolysis of the choline ester without almost degradation of polyglutamic acid. Complex decomposition rates were depending on alkanoyl chain length and on complex stoichiometry as well. Nanoparticles with 50-100 nm diameter were successfully prepared from the stearoylcholine complex with a surfactant to polymer ratio of 0.75 and loaded with theophylline, carbamazepine or doxorubicin drugs. The releasing of the drugs from nanoparticles took place upon incubation at very different rates depending on the drug. Theophylline and carbamazepine were discharged in hours whereas doxorubicin was very slowly delivered along months. The observed differences were related to the different interaction mechanism operating between the drug and the complex.