In a widely used format for biosensors, a complex high energyredox process involving Ru(bpy)32+ dye (RuBPY) and co-reactant tripropylamine(TprA) is driven electrochemically to emit ECL light.13,15A charge-coupled device (CCD) camera or photomultiplier tube (PMT)can easily measure this visible light (610 nm). ECL detection has beenadapted in microfluidic immunoarrays to detect proteins utilizingsilica beads with containing Ru(bpy)32+ dye and coated with antibodiesfor detection.4,22 The process used in our laboratory is shown in Fig. 2.We designed an automated reagent and sample delivery modulein an ECL-based microfluidic system for detection of proteins. Thisimmunoarray has six microfluidic channels connected to a 6-channeldetection chamber that houses a 30-well pyrolytic graphite (PG)-SWCNT chip (Fig. 3) with a light-transparent top.25 The well pattern iscomputer generated and laser-jet printed onto glossy paper, then heattransferred onto the PG chip. The computer ink pattern is hydrophobicenough so that it encloses the hydrophilic carbon wells and preventsaqueous solution run-over and cross-contamination during SWCNTgrowth and antibody attachment. Detection is facilitated by the 100 nmRuBPY silica nanoparticles that are coated with antibodies to provideamplification and low fg/mL detection levels using a CCD camera. Theentire device was assembled for ~$500, excluding the CCD camera andpotentiostat. One micropump is connected per channel to a portablesample/reagent cassette preloaded with air-separated samples, buffersand RuBPY-silica nanoparticles. This cassette also has 6 channels, onefor each detection channel. The required solutions are pumped into the6-channel detection chamber with SWCNT wells containing captureantibody according to a preset program. Assay events are controlledby an Arduino microprocessor and open-source software to fullyautomate flow, reagent delivery, and incubation times.

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