The invention discloses a circular single-stranded
DNA (deoxyribonucleic acid) molecule containing an inverted repeat terminal sequence and application of the circular single-stranded
DNA molecule, and relates to the technical field of
biology. The annular single-stranded
DNA provided by the invention can comprise two
gene expression cassettes, which can be the same
gene or different genes. When two same genes are inserted, the problem of wrong packaging or empty packaging is avoided no matter whether the
capsid packaging is forward packaging or reverse packaging. When two different genes are inserted, the two genes can be packaged in the same
capsid, so that the effect of expressing two proteins by one
dose of
medicine is realized. Therefore, the traditional AAV three-
plasmid system can be simplified, and the wrong packaging rate of the traditional AAV three-
plasmid system is reduced, so that the AAV
drug yield is improved; meanwhile,
pollution of non-target genes can be effectively avoided, and potential viruses of an AAV three-
plasmid system are removed; and two exogenous genes can be carried at the same time for
gene expression, so that wide application of the AAV vector in the field of gene therapy is promoted.