Electrochemical Immunosensors for Celiac Disease Detection

Abstract

Unfortunately, a high percentage of people with celiac disease (CD) is not yet diagnosed. The disease could begin at any age and the different produced symptoms may complicate the diagnosis, delay the treatment and worsening the living conditions of the patient. Therefore, early diagnosis of the disease when patients have few or not symptoms is really important and can help to improve the patients’ life quality. In these cases, a small bowel biopsy, which is the most accurate detection method, is completely ruled out, and blood tests should be key to the early diagnosis. Although, biopsy is still the most common method for confirming the CD diagnosis, the detection of diseasespecific autoantibodies strongly support this diagnosis. The most useful biomarkers to make the preliminary diagnosis through blood tests are: IgA anti-tissue transglutaminase (tTG), antiendomysium (EMA), and antideaminated forms of gliadin peptides (DGP) antibodies, since they have the highest accuracy [1,2]. Detection of IgG anti-tTG antibodies, although with less specificity for CD diagnosis, is also used and, is particularly important when the patient has IgA deficiency. Furthermore, these antibodies are also used to monitoring CD patients because its levels tend to decrease after 6 to 24 months on a gluten-free diet [3]. The improvement of blood tests efficacy to detect the CD could allow a comprehensive screening of the population and, thus, properly treat people suffering from this uncomfortable disease by implementing a gluten-free diet as soon as possible. However, the screening programs are not carried out because, currently, routine analyses are too expensive, and the administration cannot afford this cost for a broad spectrum of the population. For this reason, the development of low cost analytical devices that can be used in screening programs is a meaningful goal. In recent years, enzyme linked immunosorbent assays (ELISA) have been the most widely used technique for the detection of biomarkers [4]. ELISA can be used to detect virtually any protein due to the potential manufacture of specific antibodies to the analyte of interest. However, this technique has certain drawbacks such as the need of bulky instrumentation and the possibility to get false signals from the colorimetric detection. Therefore, the electrochemical detection method seems to be a promising alternative in view of the equipment miniaturization, multianalyte detection capability and the requirement of low sample volume. Furthermore, large-scale production of these electronic devices allows a significant reduction in the cost. The adaptation of ELISA to the electrochemical detection is the electrochemical immunosensors (EIs). EIs are self-contained integrated devices capable to provide quantitative analytical information using an immobilized immunological recognition element and an electrochemical based-transducer which converts the biological interaction into a measureable signal [5]. Ideal characteristics of EIs are: low cost and disposable devices, with inexpensive readers and with fast response without sacrificing good analytical characteristics for the resolution of the clinical problem of interest. Furthermore, they should be portable to be used in a decentralized way and by non-technical users at home, an ambulance or health centres. These are called point-of-care (POC) devices [6], defined as medical testing at or near the site of patient care, often accomplished through the use of handheld instruments. The most representative example is the glucose sensor for diabetics introduced in the last decades of the twentieth century.