Multiscale Sensing of Antibody - Antigen Interactions by Organic Transistors and Single-Molecule Force Spectroscopy

Author(s)

Casalini, Stefano ^[1] ; Dumitru, Andra C. ^[2] ; Leonardi, Francesca ^{[3, 4]} ; Bortolotti, Carlo A. ^[1] ; Herruzo, Elena T. ^[2] ; Campana, Alessandra ^{[3, 5]} ; de Oliveira, Rafael F. ^{[1, 6]} ; Cramer, Tobias ^{[3, 7]} ; Garcia, Ricardo ^[2] ; Biscarini, Fabio ^{[3, 1]}

Affiliation

^[1] Univ Modena & Reggio Emilia, Dipartimento Sci Vita, I-41125 Modena - Italy

^[2] CSIC, Inst Ciencia Mat Madrid, E-28049 Madrid - Spain

^[3] CNR, ISMN, I-40129 Bologna - Italy

^[4] CNR, ISOF, I-40129 Bologna - Italy

^[5] Univ Bologna, Dipartimento Chim G Ciamician, Alma Mater Studiorum, I-40126 Bologna - Italy

^[6] Sao Paulo State Univ, Postgrad Program Mat Sci & Technol, Unesp, BR-17033360 Bauru, SP - Brazil

^[7] Univ Bologna, Dipartimento Fis & Astron, Alma Mater Studiorum, I-40127 Bologna - Italy

• Document type: Journal article
• Source: ACS NANO; v. 9, n. 5, p. 5051-5062, MAY 2015.
• Web of Science Citations: 58

Abstract

Antibody-antigen (Ab-Ag) recognition is the primary event at the basis of many biosensing platforms. In label-free biosensors, these events occurring at solid liquid interfaces are complex and often difficult to control technologically across the smallest length scales down to the molecular scale. Here a molecular-scale technique, such as single-molecule force spectroscopy, is performed across areas of a real electrode functionalized for the immunodetection of an inflammatory cytokine, viz. interleukin-4 (114). The statistical analysis of force distance curves allows us to quantify the probability, the characteristic length scales, the adhesion energy, and the time scales of specific recognition. These results enable us to rationalize the response of an electrolyte-gated organic field-effect transistor (EGOFET) operated as an 114 immuno-sensor. Two different strategies for the immobilization of 114 antibodies on the Au gate electrode have been compared: antibodies are bound to (i) a smooth film of His-tagged protein G (PG)/Au; (ii) a 6-aminohexanethiol (HSC6NH2) self-assembled monolayer on Au through glutaraldehyde. The most sensitive EGOFET (concentration minimum detection level down to 5 nM of 114) is obtained with the first functionalization strategy. This result is correlated to the highest probability (30%) of specific binding events detected by force spectroscopy on Ab/PG/Au electrodes, compared to 10% probability on electrodes with the second functionalization. Specifically, this demonstrates that Ab/PG/Au yields the largest areal density of oriented antibodies available for recognition. More in general, this work shows that specific recognition events in multiscale biosensors can be assessed, quantified, and optimized by means of a nanoscale technique. (AU)

• FAPESP's process: 13/03857-0 - Electrolyte-gated organic field-effect transistors (EGOFETs) for fabrication of new biosensors
• Grantee: Rafael Furlan de Oliveira
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate