Impact of Crystalline Structural Differences Between α- and β-Chitosan on Their Nanoparticle Formation Via Ionic Gelation and Superoxide Radical Scavenging Activities

alpha- and beta-Chitosan nanoparticles were obtained from shrimp shell and squid pen chitosan with different set of deacetylation degree (%DD) and molecular weight (MW) combinations. After nanoparticle formation via ionic gelation with sodium tripolyphosphate (TPP), the % crystallinity index (%CI) of the alpha- and beta-chitosan nanoparticles were reduced to approximately 33% and 43% of the initial %CI of the corresponding alpha- and beta-chitosan raw samples, respectively. Both forms of chitosan and chitosan nanoparticles scavenged superoxide radicals in a dose-dependent manner. The %CI of alpha- and beta-chitosan and chitosan nanoparticles was significantly negatively correlated with superoxide radical scavenging abilities over the range of concentration (0.5, 1, 2 and 3 mg/mL) studied. High %DD, and low MW beta-chitosan exhibited the highest superoxide radical scavenging activity (p < 0.05). alpha- and beta-Chitosan nanoparticles prepared from high %DD and low MW chitosan demonstrated the highest abilities to scavenge superoxide radicals at 2.0-3.0 mg/mL (p < 0.05), whereas alpha-chitosan nanoparticles, with the lowest %CI, and smallest particle size (p < 0.05), prepared from medium %DD, and medium MW chitosan showed the highest abilities to scavenge superoxide radicals at 0.5-1.0 mg/mL (p < 0.05). It could be concluded that alpha- and beta-chitosan nanoparticles had superior superoxide radical scavenging abilities than raw chitosan samples.