Label-free C-reactive protein electronic detection with an electrolyte-gated organic field-effect transistor-based immunosensor

Abstract

In this contribution, we propose a label-free immunosensor, based on a novel type of electrolyte-gated field-effect transistor (EGOFET), for ultrasensitive detection of the C-reactive protein (CRP). The recognition layer of the biosensor is fabricated by physical adsorption of the anti-CRP monoclonal antibody onto a poly-3-hexyl thiophene (P3HT) organic semiconductor surface. A supplementary nonionic hydrophilic polymer is used as a blocking agent preventing nonspecific interactions and allowing a better orientation of the antibodies immobilized onto the P3HT surface. The whole biomolecule immobilization procedure does not require any pretreatment of the organic semiconductor surface, and the whole functionalization process is completed in less than 30 min. Surface plasmon resonance (SPR) measurements were performed to assess the amount of biomolecules physisorbed onto the P3HT and to evaluate the CRP binding proprieties of the deposited anti-CRP layer. A partial surface coverage of about 23 % of adsorbed antibody molecules was found to most efficiently sense the CRP. The electrical performance of the EGOFET immunosensor was comparable to that of a bare P3HT EGOFET device, and the obtained CRP calibration curve was linear over six orders of magnitude (from 4 pM to 2 μM). The relative standard deviation of the individual calibration points, measured on immunosensors fabricated on different chips, ranged between 1 and 14 %, and a detection limit of 2 pM (220 ng/L) was established. The novel electronic immunosensor is compatible with low-cost fabrication procedures and was successfully employed for the detection of the CRP biomarker in the clinically relevant matrix serum. Graphical abstract Schematic of the EGOFET immunosensor for CRP detection. The anti-CRP monoclonal antibody layer is physisorbed on the P3HT organic semiconductor and the CRP is directly measured by a label-free electronic EGOFET transducer.

Integration of Biomaterials into Sensors Based on Organic Thin‐Film Transistors

“…The rapidly developing immunosensors (antibody–antigen sensors) have been actively applied in such fields as food, industry, environmental monitoring, and clinical examinations due to their high specificity, sensitivity, and stability . Lee et al first demonstrated PEDOT:PSS‐based OECTs for prostate specific antigen (PSA) detection .…”

“…These as‐fabricated biosensors showed a high affinity constant of ≈1.1 × 10 7 m −1 at pH 7 with a high degree of charge discrimination, surpassing the available optical detection technique and holding great potential in antibody screening and other biomedical applications. An important protein called C‐reactive protein (CRP), which plays an important protecting role in innate immunity of living organisms, was detected by low‐voltage P3HT‐based electrolyte‐gated OFETs (EGO‐FETs) . Note that a hydrophobic blocking polymer layer was additionally used to limit the nonspecific interactions and enable a better orientation of immobilized anti‐CRP antibodies.…”

Recent Advances and Perspectives in Microfluidics‐Based Single‐Cell Biosensing Techniques

“…FET is very sensitive to changes in local electric properties induced by small variations on the material surface. Hence, various 2D nanomaterials with superior electric properties, such as: silicon nanowires, carbon nanotubes, metal oxides, and organic semiconductors, have been integrated into FET protein sensors . For example, Pui et al demonstrated a silicon‐nanowire FET biosensor for real‐time measurement of tumor necrosis factor‐alpha (TNF‐α) and interleukin‐6 (IL‐6) secreted from macrophages .…”

Recent Trends in Field-Effect Transistors-Based Immunosensors

“…C-reactive protein was ultrasensitively detected by a FET immunosensor based on an organic semiconductor surface composed of poly-3-hexyl thiophene (P3HT) [89]. Monoclonal anti-CRP antibodies were immobilized by physical adsorption onto the gate without any previous surface treatment.…”