Descripció del projecte
Despite affecting over 600 million people worldwide, strongyloidiasis is considered one of the most neglected of the neglected tropical diseases (NTDs). Strongyloides stercoralis, the primary parasitic species that causes strongyloidiasis in humans, is responsible for infections that include asymptomatic cases as well as those with symptoms including skin and gastrointestinal conditions and may be life-threatening if left untreated. Whilst other intestinal nematodes, such as the soil-transmitted helminths (STH), have long been considered important human pathogens of public health interest and warranting action by the World Health Organization (WHO), S. stercoralis has not been included in the WHO roadmaps that define global targets and milestones to prevent, control, eliminate, or eradicate NTDs. As a consequence, there have been no formal public health programmes focused on its control. This situation is, however, slowly changing. In 2020, the WHO recognised the importance of strongyloidiasis alongside STH in their 2021-2030 roadmap for NTDs, which included the aim of targeting 96% of countries endemic for S. stercoralis with preventative chemotherapy (PC) using the anthelmintic ivermectin. If this is implemented, it an adequate design and implementation of monitoring and evaluation programs are of utmost importance for the future assessment of the effectiveness of PC against S. stercoralis.
Accurate diagnostics are necessary for an effective control programme for strongyloidiasis. Sensitive diagnostics are first needed to assess the baseline prevalence of parasites in an area, and second, diagnostics with high specificity are needed to monitor the prevalence after the commencement of a control strategy and to assess the effectiveness of one or even several rounds of massive treatment with ivermectin. A range of parasitological, serological, and molecular techniques have been developed and applied, each with strengths and limitations that must be overcome for the implementation of effective diagnostics. Parasitological methods based on microscopy lacks on sensitivity, and molecular methods are far to be applicable in endemic countries due to their high cost and need of specialised material and personnel. By contrast, serological methods that detect antibodies in response to infection are significantly more sensitive than microscopy-based diagnostics, and they may be useful for monitoring active infections, as some studies have identified patients that have become antibody negative within six to twelve months after successful treatment. However, the specificity of serological methods can be limited due to cross-reactivity with other helminths, and the diagnostic accuracy can vary significantly depending on the test format used as well as the source of the targeted antigen material. Therefore, there is an urgent need of a highly accurate diagnostic method for strongyloidiasis, which ideally should be quantitative (in order to discriminate past infections as well as cross-reactivity) and also easily to perfrom in endemic areas as a point-of-car test. In response to this need, in this research project the student will develop an electrochemical biosensor for the identification of strongyloidiasis-specific antibodies.
In particular, the biosensor will rely on the so called E-DNA scaffold architecture. It consists in the use of a DNA molecule to link both a strongyloidiasis antigen and an electrochemical reporter to a graphene-based electrode. In the absence of the target antibody the DNA scaffold has a high-degree of movement, which guarantees an efficient interaction between the electrochemical reporter and the electrode surface. Instead, the presence of the target antibody limits the DNA scaffold movement generating a lower electrochemical signal. The magnitude of the signal decrease is directly related to the concentration of the target antibody. The use of a graphene-based electrode (instead of gold or silver electrodes) ensures high electrochemical sensitivity, low cost and portability; making it an ideal point-of-care diagnostic platform. For the fabrication of the graphene-based electrodes we will use the patented technology of GraphenicaLab (called wax-printed membrane) that allows to quickly and cheaply print thousands of electrodes using pre-functionalized E-DNA graphene scaffold. In this way, thin films with nanometer resolution will be transferred onto a wide variety of substrates using water-based (solvent free) nano-inks and bio-nano-inks with superior performance than well-reported screen-printed electrodes using a green, low cost and versatile technology that can be easily performed with lateral micrometer resolution suitable for rapid building of plastic, paper or textile electronic platforms.
Grau i/o MàsterDuring this three year project the PhD candidate will be responsible for: – Mapping the NIE antigen to identify the most immunogenic epitopes to be included in the E-DNA scaffold sensor; – Develop the E-DNA scaffold sensor using gold standard electrodes; – Identify the most suitable conjugation strategy to modify the graphene-based electrode with the E-DNA scaffold; – Analytically and clinically validate the biosensor response and compare the results with those of gold standard tests; – Potentially validate the sensor in the field.
