Liquid Biopsy beyond Cancer: A miRNA Detection in Serum with Electrochemical Chip for Non-Invasive Coeliac Disease Diagnosis

Coeliac disease is a very common autoimmune disease estimated to affect 1 in100 people worldwide. It occurs in genetically predisposed people where theingestion of gluten leads to damage in the small intestine, and it is accuratelydiagnosticated through duodenal biopsy, an invasive diagnostic method. The liquidbiopsy, generally used for monitoring cancer, is an appealing alternative even forautoimmune pathology such as coeliac disease, allowing for detecting diseaseprogression or resistance to treatment. For this reason, an electrochemical peptidenucleic acid (PNA) device combined with a smartphone-assisted potentiostat fornon-invasive coeliac disease diagnosis is proposed, by measuring the selectedoverexpressed miRNA-486-5p in serum, enlarging the application of liquid biopsyin nontumor pathologies. For highly sensitive detection, the polyester-basedprinted sensor is nanomodified with gold nanoparticles and a synthetic customizedPNA probe. The designed sensor can detect the target analyte in the range of10-100 nMwith a limit of detection of 0.7 nMby measuring the variation of theresponse of the electrochemical mediator hexaammineruthenium in the presenceof PNA-miRNA duplex on the nanostructured working electrode surface. Theanalyses testing serum samples are found in agreement with ones obtained by real-time quantitative polymerase chain reaction (RT-qPCR), demonstrating the reli-ability of this innovative electrochemical chip developed.