Multiwell cartridge with integrated array of amorphous silicon photosensors for chemiluminescence detection: development, characterization and comparison with cooled-CCD luminograph

We propose a disposable multiwell microcartridge with integrated amorphous silicon photosensors array for bio- and chemiluminescence-based bioassays, where the enzymatic reactions and the detection unit are coupled on the same glass substrate. Each well, made in a polydimethylsiloxane (PDMS) unit, hosts an enzymatic reaction that is monitored by one photosensor of the array. Photosensors were characterized in terms of their dark current background noise and response to different wavelengths of visible light in order to determine their suitability as detection devices for chemical luminescent phenomena. Calibration curves of the photosensors' response to different luminescent systems were then evaluated by using the chemiluminescent reactions catalyzed by alkaline phosphatase and horseradish peroxidase and the bioluminescent reaction catalyzed by firefly luciferase. Limits of detection in the order of attomoles for chemiluminescence enzymes and femtomoles for luciferase and sensitivities in the range between 0.007 and 0.1 pA pmol(-1) L were reached. We found that, without the need of cooling systems, the analytical performances of the proposed cartridge are comparable with those achievable with state-of-the-art thermoelectrically cooled charge-coupled device-based laboratory instrumentation. In addition, thanks to the small amount of generated output data, the proposed device allows the monitoring of long-lasting reactions with significant advantages in terms of data-storage needs, transmission bandwidth, ease of real-time signal processing and limited power consumption. Based on these results, the operation in model bioanalytical assays exploiting luminescent reactions was tested demonstrating that a-Si:H photosensors arrays, when integrated with PDMS microfluidic units, provide compact, sensitive and potentially low-cost microdevices for chemiluminescence and bioluminescence-based bioassays with a wide range of possible applications for in-field and point-of-care bio-analyses.