Determination of single-stranded DNA through its hybridization with complementary probes coupled on the surfaces of carboxylate polystyrene spheres

A sensitive assay of single-stranded DNA in samples, labeled with a Texas Red (Tex) on its 5'-terminus, was proposed through hybridization interaction with its complementary probes coupled on the surfaces of carboxylate polystyrene spheres of 10-mum in diameter. In a phosphorus buffer solution (pH 6.8) of ionic strength higher than 0.15 mol/L, the hybridization interaction of the complementary DNA samples with the 20-mer DNA probes connected on the surfaces of polystyrene spheres can reach equilibrium about 55min, and follows a second order reaction with the hybridization constant being 10(3) levels. Samples of complementary DNA in the range of 0.5-4.0 x 10(-9) mol/L can be detected with the limit of determination 4.8 x 10(-10) mol/L (3 sigma), but more useful linear range is 4.0-16.0 x 10(-9) mol/L, which can be expressed with the linear regression equation of DeltaF=-9.1+2.5 x 10(9) c(DNA-Tex) (r = 0.9982).