DNA sensor. II. Biolayer generation and characterisation

For pt. I see ibid., p. 400-1 (2000). A silicon-based sensor for the direct detection of DNA sequences has been developed. Hybridisation of analyte DNA with complementary sequences immobilised on a silicon transducer induces charge effects that alter the dielectric properties of the surface. This phenomena can be detected by the associated change in the measured capacitance. The biosensor demonstrates sequence specificity and a quantitative response, but is presently hindered by limited sensitivity and poor reproducibility. To address these issues, alternative methods for silicon reconfiguration (see pt. I) and biolayer generation were explored. Biolayer fabrication involved generation of a Si-SiO/sub 2/-Si/sub 3/N/sub 4/ surface rich in hydroxyl groups by plasma etching or chemical treatment. Hydroxyl groups were employed for silanisation with 3-aminopropyltriethoxysilane (3-APTES). Three chemistries were used to covalently attach single stranded probe DNA via the 3-APTES terminal amino group and hybridisation ability was evaluated using a fluorescent technique. Once optimised, this sensor can be elaborated into an array of sensors for sample interrogation with multiple probes. Such an array will be used to determine the antimicrobial susceptibility profile of clinical isolates of Mycobacterium tuberculosis.