title: A monolithic silicon based integrated signal generation and detection system for monitoring DNA hybridisation.
abstract: The aim of this work was to develop an integrated solution to DNA hybridisation monitoring for diagnostics on a monolithic silicon platform. A fabrication process was developed incorporating a gold initiation electrode patterned directly onto a PIN photodiode detector. Patterned interdigitated type electrodes exhibited the smallest reduction in photodiode sensitivity, therefore these were chosen as the ECL initiator design. A novel DNA hybridisation assay was developed based on the displacement of a partially mismatched complementary strand by a perfectly matched labelled complementary strand. Pre-hybridised thiolated oligonucleotide and unlabelled 25% mismatched oligonucleotide were assembled on the gold initiation electrode. On addition of the labelled perfectly complementary oligonucleotide, the mismatched strands were displaced and a signal was generated. The sensitivity of the photodiode to light emitted at 620 nm, the ruthenium emission wavelength, was determined and subsequently, the diode current response to light generated by flow addition of ruthenium solution was found to be measurable to a concentration of 10 fM. Pre-hybridised duplex DNA, consisting of thiolated oligonucleotide and ruthenium labelled complementary oligonucleotide, was assembled on the gold initiation electrode. The difference between the current measured during flow of buffer and the ECL co-reactant TPA was three orders of magnitude, indicating that DNA assembled on the surface comprised sufficient ruthenium to generate a measurable signal. Finally, the displacement of unlabelled partial mismatch oligonucleotide from the sensor surface was monitored on addition of the ruthenium labelled perfectly complementary oligonucleotide in TPA flow and the measured photodiode current response was up to 50 times greater.
authors.affiliation: Department of Chemistry I.F.M., University of Torino, via P. Giuria n.7, 10125 Torino, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Bertolino
authors.forename: Marion
authors.initials: M
authors.lastname: Macsweeney
authors.forename: Jane
authors.initials: J
authors.lastname: Tobin
authors.forename: Brendan
authors.initials: B
authors.lastname: O'Neill
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Sheehan
authors.forename: Salvatore
authors.initials: S
authors.lastname: Coluccia
authors.forename: Helen
authors.initials: H
authors.lastname: Berney
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004247:DNA / Q000032:analysis* / Q000737:chemistry*; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017403:In Situ Hybridization / Q000295:instrumentation* / Q000379:methods; D008163:Luminescent Measurements / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity; D012825:Silicon / Q000737:chemistry; D018511:Systems Integration
chemical_list: D004247:DNA; D012825:Silicon