Rotating rod renewable microcolumns for automated, solid-phase DNA hybridization studies

The development of a new temperature-controlled renewable microcolumn now cell, for solid-phase nucleic acid hybridization in an automated sequential injection system is described. The now cell included a stepper motor-driven rotating rod with the working end cut to a 45 degrees angle. In one position, the end of the rod prevented passage of microbeads while allowing fluid now; rotation of the rod by 180 degrees releases the beads. This system was used to rapidly test many hybridization and elution protocols to examine the temperature and solution conditions required for sequence-specific nucleic acid hybridization. Target nucleic acids labeled with a near-infrared fluorescent dye were detected immediately postcolumn during all column perfusion and elution steps using a now-through fluorescence detector. Temperature control of the column and the presence of Triton X-100 surfactant were critical for specific hybridization. Perfusion of the column with complementary oligonucleotide (200 mu L, 10 nM) resulted in hybridization with 8% of the DNA binding sites on the microbeads with a solution residence time of less than 1 s and a total sample perfusion time of 40 s. The use of the renewable column system for detection of an unlabeled PCR product in a sandwich assay was also demonstrated.