Nanoparticle formation of chitosan induced by 4-sulfonatocalixarenes: utilization for alkaloid encapsulation

Spontaneous formation of positively charged nanoparticles was observed upon mixing more than stoichiometric amount of chitosan with 4-sulfonatocalix[8]arene (SCX8) in acidic solution. The particle size did not change with SCX8 concentration, polymer chain length, and the degree of deacetylation at 0.002 ≤ SCX8/chitosan ≤0.043 molar ratios in 0.01 M HCl. However, larger aggregates were produced when chitosan concentration was increased. The most stable nanoparticles with 160 nm diameter and narrow size distribution were obtained at pH 4 using low molecular weight chitosan. These particles encapsulated coralyne with more than 90 % entrapment efficiency and 15 % loading capacity. A loading ratio of [coralyne]/[SCX8] = 1.7 was achieved without any stability loss. 4-Sulfonatocalix[4]arene induced the formation of slightly smaller nanoparticles than its homologs comprising 6 or 8 phenol units. © 2016, Springer-Verlag Berlin Heidelberg

Reversible Nanoparticle–Micelle Transformation of Ionic Liquid–Sulfonatocalix[6]arene Aggregates

The effect of temperature and NaCl concentration variations on the self-assembly of 1-methyl-3- tetradecylimidazolium (C14mim+) and 4-sulfonatocalix[6]- arene (SCX6) was studied by dynamic light scattering and isothermal calorimetric methods at pH 7. Inclusion complex formation promoted the self-assembly to spherical nanoparticles (NP), which transformed to supramolecular micelles (SM) in the presence of NaCl. Highly reversible, temperature-responsive behavior was observed, and the conditions of the NP−SM transition could be tuned by the alteration of C14mim+:SCX6 mixing ratio and NaCl concentration. The association to SM was always exothermic with enthalpy independent of the amount of NaCl. In contrast, NPs were produced in endothermic process at low temperature, and the enthalpy change became less favorable upon increase in NaCl concentration. The NP formation was accompanied by negative molar heat capacity change, which further diminished when NaCl concentration was raised