br Acknowledgments This work was supported by SENTAN Japan S

Acknowledgments This work was supported by SENTAN, Japan Science and Technology Agency (JST). Part of the microfluidic channel fabrication was conducted at the AIST Nano-Processing Facility, supported by the “Nanotechnology Platform Program” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Original wafers for the waveguide-mode sensor chips were supplied by the Advanced Functional Materials Research Center of Shin-Etsu Chemical Co., Ltd. We thank Prof. H. Suzuki and Prof. M. Yokokawa of the Institute of Materials Science, Tsukuba University for providing technical advice regarding microfluidics.
Introduction The need for portable and simple analytical devices that can be used at the point-of-care (POC) for real-time analysis of samples and timely accurate diagnosis is a major driving force for the development of integrated lab-on-chip devices that combine several laboratory functions on a single chip [1]. Among optical detection strategies, chemiluminescence (CL) offers the advantages of high detectability in low volumes and simple instrumentation required for its measurement (no lamps, filters, or specific optical arrangements) [2]. Indeed, CL, i.e., the generation of photons by a chemical reaction, and particularly enzyme-catalyzed CL, has been shown to provide superior analytical performance in miniaturized analytical formats [3,4]. Despite several applications described in the literature, one of the main challenges that needs to be faced for achieving commercial success is integration. Differently from colorimetric-based assays, in which visual observation or microspectrophotometers can be exploited, CL assays most often require a separate instrument to measure light emission, thus limiting its market exploitability and dextromethorphan hydrobromide degree [5]. Smartphone CMOS cameras can be exploited as portable luminometers for on-site CL quantitative measurements, although ultrahigh detectability cannot be yet reached with such devices [6]. Recently, on-chip integration of organic [7] and inorganic [8] photosensors has been proposed to enable highly sensitive detection of CL reactions, thus prompting the development of innovative portable analytical devices with enhanced sensitivity and multiplexed capabilities. In particular, starting from the pioneer paper of Kamei et al. [9], different research groups are focused on the development of hydrogenated amorphous silicon (a-Si:H) photosensors to achieve on-chip detection within a lab-on-chip [10]. Taking advantage of the low-temperature deposition process (below 250°C), a-Si:H photosensors can be grown on glass and polymers, ideal supports for lab-on-chip devices. This feature is coupled with two very important optoelectronic characteristics: a very low dark current in reverse bias, which determines a very low detection limit with respect for example to organic-based photosensors [3] and a quite high photosensitivity in the ultraviolet [11] and in the visible [12,13] range, which determine, even in the absence of a sensor cooling system, analytical performances in lab-on-chip application comparable to those achieved with cooled CCD imagers [14,15]. We have recently proposed an integrated cartridge in which an array of 16 a-Si:H photosensors was employed to independently monitor as many CL or bioluminescence reactions, showing its excellent analytical performance and reaching attomole level limits of detection [14]. Herein, we further explored the applicability and performance of such integrated device in diagnostics, i.e., detection and typization of Parvovirus B19 DNA, which was selected as a model analyte. For this purpose, a disposable portable microfluidic cartridge with integrated a-Si:H photosensors has been developed and employed for multiplex detection of Parvovirus B19 genotypes exploiting oligonucleotide array capture and CL detection. The cartridge is composed of a glass slide on which an array of thin film a-Si:H photosensors has been deposited on one side, while the opposite side has been arrayed with three B19 genotype specific probes and coupled with polydimethylsiloxane (PDMS) microfluidic layer. Biotin-labeled targets were captured by genotype-specific immobilized probes and then hybrids were detected by means of an avidin-horseradish peroxidase (HRP) conjugate and CL reaction. To enable POC applicability, all the hybridization assay protocol does not require specific conditions regarding cleanliness, refrigeration or temperature control and fluid delivery is based only on capillary forces. Moreover the analysis could be performed employing a low amount of sample (50μL), within less than 1h. Portable custom electronics was employed for read-out of the CL signals that were detected by the a-Si:H photosensors, each placed in correspondence of one capture oligonucleotide spot. The results are easily readable and there is no need of specialized personnel for their interpretation, since the detection of the target analyte is simply ascribable to the presence of a photon emission.