A new polynucleotide-polysaccharide complex and its application to functional oligonucleotide delivery

Schizophyllan (SPG) is a polysaccharide that belongs to the β-(1-3) glucan family and adopts a triple-helixical conformation in water. When SPG dissolves in dimethyl sulfoxide (DMSO), the triple helix is dissociated to three random coils. When water is added to the DMSO solution (renaturation), the single chain of SPG (s-SPG) collapses owing to both hydrophobic interaction and hydrogen bonding formation, and eventually aggregation takes place with increasing the water content. When this renaturation process is carried out in a mixture containing s-SPG and a single-stranded polynucleotide, a macro-molecular complex is formed, consisting of two s-SPG chains and one polynucleotide chain. This novel complexation was examined with circular dichroism, UV spectroscopy, and gel electrophoresis. We applied to this complex to deliver functional oligonucleotides such as antisense DNA and CpG motifs. The biological functions of these oligonucleotides were extremely enhanced owing to the complexation.