Protection of polynucleotides against nuclease-mediated hydrolysis by complexation with schizophyllan

Schizophyllan is a beta-(1-->3)-D-glucan existing as a triple helix in water and as a single chain in dimethylsulfoxide (DMSO), respectively. As we already reported, when some homo-polynucleotide (for example, poly(dA) or poly(C)) is added to the schizophyllan/DMSO solution and subsequently DMSO is exchanged for water, the single chain of schizophyllan (s-SPG) forms a complex with the polynucleotide. The present work demonstrates that the polynucleotide bound in the complex is more stable to nuclease-mediated hydrolysis than the polynucleotide itself (i.e., naked polynucleotide), using high-performance liquid chromatography and ultraviolet absorbance technique. A kinetic study for the hydrolysis clarified that the simple Michaelis-Menten relation is held and the maximum velocity for the complex is one-sixth as small as that of the naked polynucleotide. This low hydrolysis rate for the complex suggests that s-SPG is applicable to a carrier for antisense oligonucleotides.