Patent ID: 7262006

Claim:
A method for isolating a free circulating, extracellular nucleic acid from a mammalian species sample not previously treated with a cell lysing reagent, wherein said method comprises the steps of: A) admixed in buffer at a pH of less than 7, contacting a sample suspected of containing a nucleic acid with a water-soluble, weakly basic polymer derived by addition polymerization of: 1) from about 15 to 100 weight percent of a water-soluble, weakly basic ethylenically unsaturated polymerizable monomer having at least one group which can be protonated at acidic pH and which is selected from the group consisting of aminoalkyl, imidazolyl, isoxazolyl, pyridyl, piperidyl, piperazinyl, pyrazolyl, triazolyl, tetrazolyl, oxadiazolyl, pryidazinyl, pyrimidyl, pyrazinyl, quinolinyl and quinazolinyl, 2) from 0 to about 35 weight percent of a nonionic, hydrophilic ethylenically unsaturated polymerizable monomer, and 3) from 0 to about 85 weight percent of a nonionic, hydrophobic ethylenically unsaturated polymerizable monomer in an amount sufficient to form a water-insoluble precipitate of said weakly basic polymer with all nucleic acids present in said lysate, B) separating said water-insoluble precipitate from said sample, and C) contacting said precipitate with a base to raise the buffer pH to greater than 7, and thereby releasing said free circulating, extracellular nucleic acids from said weakly basic polymer, said weakly basic polymer derived by addition polymerization of one or more ethylenically unsaturated polymerizable monomers having an amine group which can be protonated at acidic pH.