CRP is a biomarker that has been used since long time to monitor systemic inflammation, infection, and more recently several other human pathologies . Normal CRP levels typically fall within the range of 1 -3 μg mL -1 , while high CRP levels (20 -400 μg mL - 1 ) are associated with inflammation, infectious diseases, cardiovascular disease ( CVDs) , malignant tumors, autoimmune disease, and depression . Although anti-CRP IgG antibodies have been traditionally used for CRP detection, their high production costs, heterogeneity after functionalization, and reliance on human or animal sources in the production process represent critical challenges . Consequently, alternative capture elements, including antibody fragments, peptides, aptamers, polymers, and bacteriophages, have been proposed . In the present work, we employed nanobodies previously isolated by phage display technology because they are small recombinant proteins, inexpensive to produce, and simple to engineer adopting basic molecular biology techniques. The small size of nanobodies potentially allows for a higher binding density on the electrode surface, enhancing sensor sensitivity compared to anti-CRP IgG antibodies .