Amphiphilic cholesteryl grafted sodium alginate derivative: Synthesis and self-assembly in aqueous solution

A novel water soluble amphiphilic sodium alginate derivative grafted with 3 cholesteryl groups per 100 hexuronic acid residues (CSAD-3) has been first synthesized with N,N′-dicyclohexylcarbodiimide as a coupling agent and 4-(N,N′-dimethylamino)pyridine as a catalyst at room temperature. The result of fluorescence analysis shows that CSAD-3 forms self-aggregates in 0.15 mol/L aqueous NaCl solution and its critical aggregation concentration (CAC) is 0.33 g/L. The value of CAC decreases with increase of the concentration of aqueous NaCl solution. The CSAD-3 self-aggregates are able to encapsulate hydrophobic compounds like pyrene. The hydrodynamic diameter of CSAD-3 self-aggregates in aqueous NaCl solution is 136 nm determined by dynamic light scattering measurement. The oblate particles with the size about 100–200 nm are observed in the negatively dyed TEM image of CSAD-3 self-aggregates.