Label-Free Sensing of Infliximab in Full Serum Using Localized Surface Plasmon Resonance (LSPR) in Absorbance Mode

Ron Gill , Nanobiophysics Group, University of Twente, Enschede, The Netherlands (r.gill@saxion.nl)
                  Nanobio Lectorate, Saxion University of Applied Sciences, Enschede, the Netherlands
Kristian Goeken, Nanobiophysics Group, University of Twente, Enschede, The Netherlands
Michael Prijs, BIOS Group, University of Twente, Enschede, The Netherlands
                          Clinical pharmacology department, MST Hospital, Enschede, the Netherlands
Loes Segerink, BIOS Group, University of Twente, Enschede, The Netherlands
Thijs Oude Munnink, Clinical Pharmacology Department, MST Hospital, Enschede, the Netherlands

Gold nanoparticles support localized surface plasmons, which are coherent oscillations of the metal conductance electrons. While surface plasmon polaritons of gold films (used in surface plasmon resonance (SPR)-based sensing) require special methods to match the energy and momentum (such as the use of prisms or grating), localized surface plasmon resonance (LSPR) of gold nanoparticles can be directly excited by light propagating in free space.¹

The position of the surface plasmon resonance peak can be interrogated by measuring either transmitted light (absorbance mode) or scattered light (scattering mode).² In both modes, the position of the plasmon peak is known to be sensitive to the refractive index of the medium in the close vicinity of the nanoparticle’s surface. Although the scattering peaks shifts more than the absorbance peak when the refractive index of the medium changes, absorbance measurement are more compatible with instrumentations available at any biochemistry lab, such as UV-VIS absorbance spectrometers. Although off the shelf spectrophotometers do not have very high spectral resolution, we have recently shown that peak shifts can be determined with a noise level below 10pm when using peak fitting algorithms^3.

The detection of antibodies in a complex media (cell culture media or human serum) is an important analytical problem with both biotechnological applications (in the case of recombinant antibodies producing cells, for example) and medical applications (in the case of allergy detection or immunotherapy supervision).

Here we present our results on the label-free detection of antibodies in complex media. We show that sub-nM concentration of antibodies can be detected, both in buffer and in complex media. We then apply this method for the detection of Infliximab (a therapeutic antibody against TNF-alpha used for the treatment of autoimmune disease) in full serum.

References
1. K. A. Willets and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy and sensing.,” Annu. Rev. Phys. Chem., vol. 58, pp. 267–97, Jan. 2007.
2. J. L. Hammond, N. Bhalla, S. D. Rafiee, and P. Estrela, “Localized surface plasmon resonance as a biosensing platform for developing countries,” Biosensors, vol. 4, no. 2, pp. 172–188, 2014.
3. Gill, R., Goeken, K. and Subramaniam, V., "Fast, single-step, and surfactant-free oligonucleotide modification of gold nanoparticles using DNA with a positively charged tail," Chem. Commun. 49(97), 11400-11402 (2013).

(A) Conventional microplate spectrophotometer used for the measurements. (B) Gold-nanoparticle coated substrate. (C) LSPR shift measured on Gold-nanoparticle substrate, when adding anti-TNF antibody or PBS only to two different substrates (plate 1 and plate 2) prepared on two different weeks.