Patent ID: 7816337

Claim:
A composition for delivering a polynucleotide to a mammalian cell in vivo comprising: a reversibly-modified membrane active polyamine-polynucleotide conjugate wherein: a) the reversibly-modified membrane active polyamine is linked to the polynucleotide via a labile covalent bond; and, b) the reversibly-modified membrane active polyamine consists of a negatively charged polymer that is not membrane active wherein the negative charge comes from a plurality of carboxyl groups linked to the polymer via pH-labile covalent linkages wherein cleavage of the pH-labile covalent bonds in response to a decrease in pH results in cleavage of the carboxyl groups from the polymer and formation of amine groups thereby forming a membrane active polyamine, and wherein c) the membrane active polyamine has a molecular weight greater than 10,000 daltons.