Self-assembled nanogels from polysaccharides grafted with short oligonucleotides: control of size and thermoresponsiveness

Pullulan, a water-soluble polysaccharide, was grafted with short (4-mer and 6-mer) oligonucleotides containing bridged nucleic acids (BNAs) to produce self-assembled nanogels through the formation of oligonucleotide double chains. Dynamic light scattering measurements and transmission electron microscopy images revealed that oligonucleotide-grafted pullulans containing oligonucleotides with different chain lengths, sequences, and numbers of BNA substituents in water formed nanogels and that their aggregation behavior changed with temperature. Gel electrophoresis revealed that the complexation of fluorescently labeled oligonucleotides with these nanogels was possible, and flow cytometry measurements indicated that the cellular uptake of oligonucleotides was significantly enhanced when the oligonucleotides were complexed with the nanogels. Therefore, self-assembled nanogels derived from oligonucleotide-grafted polysaccharides can be applied as carriers of nucleic acids and nucleic acid-conjugated molecules for intracellular delivery. The construction of self-assembled nanogels with oligonucleotide double strands as the association points was achieved by grafting short-chain (4-mer and 6-mer) oligonucleotides containing bridged nucleic acids (BNA), an artificial nucleic acid, onto polysaccharides. The oligonucleotide-grafted polysaccharides, composed of oligonucleotides with varying chain lengths, sequences, and BNA substitution numbers, formed nanogels in water, and their aggregation behavior was found to change with temperature.