Applications of electrochemiluminescence detection on microfabricated devices

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Doctoral thesis (monograph)
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TKK dissertations, 44
The aim of this thesis was to investigate bioanalytical applications of electrochemiluminescence (ECL), which refers to the generation of light at the surface of an electrode. Two types of ECL detection were studied: anodic ECL and cathodic hot electron-induced ECL (HECL). In anodic ECL light is generated at traditional electrode materials, such as noble metal or carbon, while in cathodic HECL thin insulating film-coated electrodes are used, and light generation is initiated by tunnel emission of hot, energetic electrons. Both types of ECL provide high spatial control. ECL applications for hybridization assays were investigated. Short 15-base oligonucleotide probes were immobilized on gold and oxide-coated silicon and aluminum electrodes. Hybridization with complementary targets was detected by ECL. Results showed that the oligonucleotides were successfully immobilized and high surface probe density was achieved. Labeled targets were detected at subnanomolar concentration levels. Two base pair mismatches were successfully discriminated. A homogeneous hybridization assay where hybridization was detected by quenching of anodic ECL of a Ru(bpy)32+ label by another luminophore (Cy5) was performed on thin film carbon electrodes. The quenching efficiency was 78% when the distance between the label moieties was short (≤ 2 nm). Also, an immunoassay on double barrier aluminum/aluminum oxide electrodes with Tb(III) chelate as the HECL label was performed. A microfluidic system was fabricated in poly(dimethylsiloxane) (PDMS) and glass with integrated carbon fiber and platinum electrodes, and tested for direct ECL detection of guanosine. The magnitude of electroosmotic flow (EOF) in PDMS microchannels was determined using the current monitoring method. Results revealed that the origin of the surface charge in PDMS is the same as in silica, but its amount is considerably lower.
electrochemiluminescence, hot electron, DNA hybridization, immunoassay, microfabrication
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