ELECTRIC-FIELD DIRECTED NUCLEIC-ACID HYBRIDIZATION ON MICROCHIPS

Selection and adjustment of proper physical parameters enables rapid D NA transport, site selective concentration, and accelerated hybridizat ion reactions to be carried out on active microelectronic arrays. Thes e physical parameters include DC current, voltage, solution conductivi ty and buffer species. Generally, at any given current and voltage lev el, the transport or mobility of DNA is inversely proportional to elec trolyte or buffer conductivity. However, only a subset of buffer speci es produce both rapid transport, site specific concentration and accel erated hybridization. These buffers include zwitterionic and low condu ctivity species such as: D-and L-histidine; 1- and 3-methylhistidines; carnosine; imidazole; pyridine; and collidine, In contrast, buffers s uch as glycine, beta-alanine and gamma-amino-butyric acid (GABA) produ ce rapid transport and site selective concentration but do not facilit ate hybridization. Our results suggest that the ability of these buffe rs (histidine, etc.) to facilitate hybridization appears linked to the ir ability to provide electric field concentration of DNA; to buffer a cidic conditions present at the anode; and in this process acquire a n et positive charge which then shields or diminishes repulsion between the DNA strands, thus promoting hybridization.