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  • br Materials and methods br Results and discussion

    2018-10-26


    Materials and methods
    Results and discussion
    Conclusions
    Acknowledgements The authors would like to thank the Engineering and Physical Sciences Research Council (EPSRC) UK, for the financial support of this work through the projects with grant numbers EP/I004653/1 and EP/L002132/1.
    Introduction Celiac disease (CD) is a chronic inflammatory disease of the small intestine that affects genetically susceptible individuals. This disease is unique in that the critical etiologic factor has been identified as the ingestion of gluten found in grains of wheat, barley, rye and triticale. Upon ingestions of those proteins, the symptoms showed by patients affected by CD can be severe, thus the diagnosis and treatment must be fast [1]. The diagnostic procedure is performed through serological tests and histological examination of at least one biopsy [23]. In the recent years, the area of serological testing for CD has developed greatly, since it is less invasive than biopsy [26]. Among all serological tests, recently, a lot of attention has been given to the analysis of nicergoline against the deamidated gliadin peptides (GPs) due to their promising performance as compared to the most commonly used antigliadin antibodies (AGA), endomysial antibodies (EMA) and tissue transglutaminase antibodies (tTG). Recent studies have demonstrated that the detection of antibodies for GPs can be applied for the diagnosis of celiac disease and for monitoring the adherence of CD patients to gluten free diet (GFD). The determination of antibodies is generally based on enzyme linked immunosorbent assay (ELISA) based screening tests [28]. The ELISA process includes a series of washing, mixing, and incubation steps, which are labor intensive and time consuming, which often takes several hours, sometimes even up to 2days to perform one single assay. Most of the time required in a long immunoassay is mostly because of the long incubation time attributed to inefficient mass transport for the immunoagents to move from a solution to the surface, where the conjugation occurs because the immunoreaction itself is relatively rapid [17]. Moreover, the immunoagents used in immunoassays are relatively expensive. To improve the throughput of these processes, robotic systems can be used for fluid handling, but this solution is only available to wealthy laboratories and requires significant maintenance efforts and a large laboratory footprint. Therefore, there is a demand to develop an automated and miniaturized platform for immunoassay. Miniaturized analytical equipment based on lab-on-chip device (LoC) [18], has been growing due the possible advantages which can be gained by the used of these devices compared to standard analytical equipment, [13] such as (i) consumption of low sample volume, (ii) rapidity of analysis, (iii) easy handling and (iv) multiple target analysis. These advantages can potentially improve the performance and reduce the operating cost of conventional immunoassays. In particular, LoC have been extensively studied to develop point-of care (POC) devices in the field of health-care and diagnostic. In these devices, biological components are usually immobilized on a solid-state surface, which interacts with the analyte. The interactions are detected by using electrochemical or, more often, optical methods [14,21]. In this context, surface chemistry treatments of microchip play a critical role because assortment deeply influence the biomolecular recognition in terms of selectivity and sensitivity [13]. These chemical treatments may negatively affect the functionality of detection elements such as photodiodes, when these are integrated on the microsystem. As a consequence, microfluidic chips for POC are often based on off-chip detection (e.g. using CCD or CMOS sensors) with difficulty in producing low-cost and portable systems. Recently, we reported the development of an ELISA-on-chip device for the detection of GPs [10]. Nevertheless, in this ELISA-on-chip device, the serum to be analyzed was handled manually, by spotting a few microliter of sample on the array. As a consequence, the analysis is time consuming and more exposed to inaccuracies of the personnel.