Drug-loaded nanoparticles and supramolecular nanotubes formed from a volatile microemulsion with bile salt derivatives

The main objective of this study was to form nanoparticles of a model hydrophobic drug, celecoxib, from a volatile microemulsion stabilized by a bile salt derivative. Nanoparticles were obtained by conversion of the microemulsion nanodroplets with the dissolved drug into solid nanometric particles. The use of bile salt derivatives as the surfactants for the formation of a microemulsion enabled significantly higher loading of the drug in both the microemulsion and nanoparticles, compared with the native bile salt. In addition, superior stability of the particles was achieved with the bile salt derivatives, and drug crystallization was inhibited. Interestingly, differences in particle stability and crystallization inhibition were observed between two bile salt derivatives differing only by one hydroxyl group on the bile salt backbone, indicating the delicate balance of interactions in the system. For one of the derivatives, upon dispersion of the nanoparticles in water, they spontaneously arranged into well-defined elongated nanometric tubules as detected and attested by cryo-TEM. It was found that the drug present in nanoparticles induces formation of the nanotubes.