Surface-attached peptide nucleic acids (PNA) are shown to retain their unique and efficient hybridization properties, reported in solution studies. PNA recognition layers thus offer significant advantages for sequence-specific DNA biosensors, compared to their DNA counterparts. These advantages include significantly higher sensitivity and specificity (including greater discrimination against single-base mismatches), faster hybridization at room and elevated temperatures, minimal dependence on ionic strength, and use of shorter (10−15-mer) probes. Such unique properties and advantages are illustrated in connection with electrochemical detection of the hybridization event using the Co(phen)3 3+ redox indicator and a carbon paste electrode transducer. The new capabilities and opportunities afforded by the use of PNA surface probes are discussed.

No abstract

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.

No abstract