DNA electrochemical biosensor for the detection of short DNA sequences related to the human immunodeficiency virus

An electrochemical biosensor for the detection of short DNA sequences related to the human immunodeficiency virus type 1 (HIV-1) is described. The sensor relies on the immobilization and hybridization of the 21- or 42-mer single-stranded oligonucleotide from the HIV-1 U5 long terminal repeat (LTR) sequence at carbon paste or strip electrodes. The extent of hybridization between the complementary sequences is determined by the enhancement of the chronopotentiometric peak of the Co(phen)3(3+) indicator. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions are optimized to maximize the sensitivity and speed the assay time. A detection limit of 4 x 10(-9) M HIV-1 U5 LTR segment is reported following a 30 min hybridization. The hybridization biosensor format obviates the use of radioisotopes common in radioactive methods for the detection of HIV-1 DNA. We also report on the direct adsorptive chronopotentiometric stripping measurements of trace levels of various HIV-1 DNAs.