Integration Of Electrochemiluminescence And Nanotechnology For The Sensitive Detection Of Haptoglobin: One Biomarker For Multiple Diseases

Haptoglobin (Hp) plays an important part in the binding and transporting of hemoglobin. The plasma concentration of Hp increases several-fold in carcinoma, tissue necrosis, coronary artery, schizophrenia, and in the event of an inflammatory stimulus such as infection, injury, or malignancy, whether local (vascular) or systemic (extravascular).

Hp has been reported to be involved in modulating the immune response, autoimmune diseases, and major inflammatory disorders. Elevated Hp levels are sometimes found in diabetes mellitus, renal disease, and endocrine imbalance. Diseases such as intravascular hemolysis, anemia, malaria, liver disease, jaundice, cirrhosis, mononucleosis, and transfusion of incompatible blood can significantly lower the amount of Hp in plasma. Clearly, Hp has a great clinical importance as a biomarker in diagnostics and monitoring the response of multiple diseases.

Currently, electrochemiluminescence (ECL), an electrochemical phenomenon in which light is emitted without producing heat when high voltage is applied to a suitable electrochemical system, has become an important and powerful analytical technology. As a result, ECL-based biosensors have gained immense popularity. However, ECL behavior greatly depends on electrode materials, dimensions, surface area, electronic conductivity, and size.

However, nanotechnology is the branch of modern inter-and multidisciplinary science which deals with materials, substance, compounds, and biomolecules having all or at least one dimension in 100 nm. Such materials are collectively known as nanomaterials (NMs). Physicochemical properties of NMs include a large surface-to-volume ratio, high aspect-ratio, and high electronic conductivity, and examples include gold nanoparticles (AuNPs) and single-walled carbon nanotubes (SWCNTs).

Further, two or more NMs could be mixed in definite proportions to form composite materials using biopolymers such as chitosan (CS). Such developed composite materials synergistically interact to produce desirable properties such as high effective surface area, electronic conductivity, high ECL intensity, and biocompatibility as demonstrated by a nanocomposite of cadmium telluride quantum dots (CdTe-QDs), AuNPs, SWCNTs, and CS (CdTe-QDs/AuNPs/SWCNTs/CS).

Therefore, in this work, ECL and nanotechnology were integrated to fabricate an ECL biosensor on a carbon nanofiber, screen-printed electrode (CNFs-SPE) modified with the nanocomposite of CdTe-QDs/AuNPs/SWCNTs/CS. The aim was to produce highly sensitive, highly specific, resistant to non-target proteins, rapid, and reliable, with the ability to detect a wide range of Hp concentration in a serum, label-free, the potential to mass-production, economical, and eco-friendly biosensor for Hp detection that could be stored for a long period of time.

Using increased ECL intensity, increased electron conductivity, and increased effective surface area of CdTe-QDs/AuNPs/SWCNTs/CS-nanocomposite modified electrode, a label-free ECL biosensor was fabricated for the detection of Hp. This fabricated biosensor demonstrated a dynamic linear range of detection of Hp from 0.1 pg mL^-1 to 10 ng mL^-1 with an LOD 100 fg mL^-1. In addition to high specificity, interference-resistant excellent reproducibility, and longer storage time, the proposed biosensor to detect Hp also demonstrated high potential to detect the Hp in biological samples. Therefore, the developed platform using nanotechnology could also be used to design economical and eco-friendly, highly selective and sensitive ECL biosensors to detect other clinically important biomarkers such as cardiac troponin I and ciprofloxacin.