Book Description
Chlamydia trachomatis (Chlamydia) is the most common sexually transmitted infection diagnosed in genitourinary medicine (GUM) clinics and affects one in ten sexually active young people. Neisseria gonorrhoeae (gonorrhoea) is the second most common. They are asymptomatic in at least three-quarters of patients. Untreated infection can lead to serious health problems; including pelvic inflammatory disease and infertility in women. In men, it can cause urethritis and Reiter's Syndrome (arthritis). The number of diagnoses of uncomplicated chlamydia in GUM clinics in England increased by 288% between 1995 and 2006. Co-infection with chlamydia and gonorrhoea is not uncommon. Up to half of patients diagnosed may be infected with both pathogens and, therefore it is important to test sexually active individuals for both chlamydia and gonorrhoea using a multiplex system. Electrochemical detection of specific DNA sequences offers advantages over established fluorescence techniques; including cost and ease of miniaturisation. The electrochemical gene sensor described here uniquely utilises enzymatic T7 Exonuclease digestion to generate ferrocenylated oligonucleotide fragments in a matched (gene sequence presence) sensor. These fragments exhibit a characteristically high response upon electrochemical analysis, using Differential Pulse Voltammetry and have been designed based on the ability to "tune" the oxidation potential of ferrocene by using electron-withdrawing and electron-donating substituent groups. Ferrocenylated oligonucleotide labels have been synthesised, each with a characteristic oxidation potential. Results from a study of the adsorption and electron transfer kinetics of T7 exonuclease - digested and undigested oligonucleotide redox probes at screen-printed carbon paste electrode (SCPE) surfaces will be considered as a basis for the assay discrimination. The high selectivity of the T7 Exonuclease digest is demonstrated using the ferrocenylated oligonucleotides and a triplex genomic electrochemical assay for the detection of Chlamydia trachomatis, Neisseria gonorrhoeae and the human 7 beta-actin gene as an internal control for the assay using clinical samples will be presented.
