Positively Charged Particles from Amphiphilic Chitosan

Amphiphilic chitosan derivatives have been well regarded as potential non-viral vectors for gene delivery. Their hydrophobic entities could promote cell permeability whereas their hydrophilic entities especially those carrying positive charges can interact with the negatively charged phosphate groups of DNA. Here in this research, a series of amphiphilic chitosan derivatives having varied amount of hydrophilic positive charges of quaternary ammonium groups were synthesized. Linear hydrocarbon of two different chain length: hexyl and dodecyl were substituted at amino groups of chitosan via reductive alkylation with hexanal and dodecanal and yielded hexyl chitosan (HCS) and dodecyl chitosan (DCS), respectively. HCS and DCS with approximately 30% degree of hydrocarbon substitution were reacted with 1 or 5 equivalents of glycidyltrimethylammonium chloride (GTMAC) under basic condition to incorporate hydrophilic positively charged quaternary ammonium groups and form amphiphilic chitosan derivatives. All derivatives were characterized by 1 H-NMR and ATR-FTIR. As evaluated by dynamic light scattering (DLS) measurements, hydrocarbon chain length and quaternary ammonium entities have a strong impact on the size and zeta potential of the self-assembled particles. Upon preliminary cytotoxicity tests against RAW264.7 macrophage cell, it was found that the higher the zeta potential, the more toxic of the particles.