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 5ʹ-terminus, was proposed through hybridization interaction with its complementary probes coupled on the surfaces of carboxylate polystyrene spheres of 10-µm 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 55 min, and follows a second order reaction with the hybridization constant being 103 levels. Samples of complementary DNA in the range of 0.5–4.0 × 10-9 mol/L can be detected with the limit of determination 4.8 × 10-10 mol/L (3s), but more useful linear range is 4.0–16.0 × 10-9 mol/L, which can be expressed with the linear regression equation of ?F = -9.1+ 2.5 × 109 cDNA-Tex (r = 0.9982).