A stable physisorbed layer of packed capture antibodies for high-performance sensing applications

Antibody physisorption at a solid interface is a very interesting phenomenon that has important effects on applications such as the development of novel biomaterials and the rational design and fabrication of high-performance biosensors. The strategy selected to immobilize biorecognition elements can determine the performance level of a device and one of the simplest approaches is physical adsorption, which is cost-effective, fast, and compatible with printing techniques as well as with green-chemistry processes. Despite its huge advantages, physisorption is very seldom adopted, as there is an ingrained belief that it does not lead to high performance because of its lack of uniformity and long-term stability, which, however, have never been systematically investigated, particularly for bilayers of capture antibodies. Herein, the homogeneity and stability of an antibody layer against SARS-CoV-2-Spike1 (S1) protein physisorbed onto a gold surface have been investigated by means of multi-parametric surface plasmon resonance (MP-SPR). A surface coverage density of capture antibodies as high as (1.50 ± 0.06) × 1012 molecules per cm−2 is measured, corresponding to a thickness of 12 ± 1 nm. This value is compatible with a single monolayer of homogeneously deposited antibodies. The effect of the ionic strength (is) of the antibody solution in controlling physisorption of the protein was thoroughly investigated, demonstrating an enhancement in surface coverage at lower ionic strength. An atomic force microscopy (AFM) investigation shows a globular structure attributed to is-related aggregations of antibodies. The long-term stability over two weeks of the physisorbed proteins was also assessed. High-performance sensing was proven by evaluating figures of merit, such as the limit of detection (2 nM) and the selectivity ratio between a negative control and the sensing experiment (0.04), which is the best reported performance for an SPR S1 protein assay. These figures of merit outmatch those measured with more sophisticated biofunctionalization procedures involving chemical bonding of the capture antibodies to the gold surface. The present study opens up interesting new pathways toward the achievement of a cost-effective and scalable biofunctionalization protocol, which could guarantee the prolonged stability of the biolayer and easy handling of the biosensing system.

Publication year: 2023
Authors: Lucia Sarcina a,+, Cecilia Scandurra a,+, Cinzia Di Franco b, Mariapia Caputo c, Michele Catacchio c, Paolo Bollella a,d, Gaetano Scamarcio e,d, Eleonora Macchia c,d,f,*, Luisa Torsi d,f,*
a – Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Via E. Orabona 4, 70125 Bari Italy
b – CNR – Institute of Photonics and Nanotechnologies, 70126 Bari Italy
c – Dipartimento di Farmacia-Scienze del Farmaco, Università degli Studi di Bari Aldo Moro, 70126 Bari Italy
d – CSGI (Centre for Colloid and Surface Science), Via E. Orabona 4, 70125 Bari Italy
e – Dipartimento Interateneo di Fisica “M. Merlin”, Università degli Studi di Bari Aldo Moro, 70126 Bari Italy
f – The Faculty of Science and Engineering, Åbo Akademi University, 20500 Turku Finland
* Corresponding author
+ Lucia Sacina and Cecilia Scandurra equally contributed.
Published in: Journal of Materials Chemistry C, 2023, Vol. 11(27), p. 9093–9106
DOI: 10.1039/d3tc01123b


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