Oligonucleotides are composed of nucleotides with specially designed sequences. Oligonucleotides hybridize with the target gene mRNA or pre-mRNA through complementary base pairing, and can theoretically selectively regulate any target gene and protein expression. Currently, common oligonucleotides are antisense oligonucleotides (ASOs), siRNA (small interfering RNA), microRNA and aptamers, etc.