Graphene Amination towards Its Grafting by Antibodies for Biosensing Applications

Abstract

The facile synthesis of biografted 2D derivatives complemented by a nuanced understanding of their properties are keystones for advancements in biosensing technologies. Herein, we thoroughly examine the feasibility of aminated graphene as a platform for the covalent conjugation of monoclonal antibodies towards human IgG immunoglobulins. Applying core-level spectroscopy methods, namely X-ray photoelectron and absorption spectroscopies, we delve into the chemistry and its effect on the electronic structure of the aminated graphene prior to and after the immobilization of monoclonal antibodies. Furthermore, the alterations in the morphology of the graphene layers upon the applied derivatization protocols are assessed by electron microscopy techniques. Chemiresistive biosensors composed of the aerosol-deposited layers of the aminated graphene with the conjugated antibodies are fabricated and tested, demonstrating a selective response towards IgM immunoglobulins with a limit of detection as low as 10 pg/mL. Taken together, these findings advance and outline graphene derivatives' application in biosensing as well as hint at the features of the alterations of graphene morphology and physics upon its functionalization and further covalent grafting by biomolecules.

Keywords: 2D materials; aminated graphene; antibodies; biosensors; grafting; graphene modification; photoelectron spectroscopy.

Figure 1

Examination of the CMGs’ chemistry by means of X-ray photoelectron spectroscopy. (a) The survey; (b) high-resolution N 1s; and (c) C 1s spectra of the initial GO, rGO-Am and Am-ABd layers.

Figure 2

Characterization of the CMGs’ chemistry via X-ray absorption and ATR-FTIR spectroscopies. (a) C K-edge X-ray absorption spectra; (b) N K-edge X-ray absorption spectra; and (c) FTIR-ATR spectra of the studied materials. The absorption bands at 930–1080 cm⁻¹ in the GO spectrum are not denoted. The CO₂ signal at v = 2220–2400 cm⁻¹ is cut out for clarity.

Figure 3

Morphology of the derived CMGs. (a,b) SEM images; (c) TEM images; and (d) corresponding ED patterns of the initial GO (bottom row), rGO-Am (middle row) and Am-ABd (upper row) layers.

Figure 4

(a) SE cut-off spectra, (b) VB photoemission spectra and (c) corresponding second derivatives (-d²I/dE²) of the materials under study.

Figure 5

Sensing performance of the fabricated chip. (a) I–V curves for the rGO-Am and Am-ABd layers taken at both d.c. electric field directions under dry air conditions; the insert shows the photo of the fabricated biosensing chip. (b) The resistance transient recorded under exposure to PBS solution with IgM immunoglobulins of various concentrations in the range of 10–1000 pg/mL. (c) The dependence of chemiresistive response on the concentration of the IgM immunoglobulins.