Towards label-free mid-infrared protein assays: in-situ formation of bare gold nanoparticles for surface enhanced infrared absorption spectroscopy of bovine serum albumin

Abstract

Surface enhanced infrared absorption spectroscopy (SEIRAS) with attenuated total reflection (ATR) configuration has been used to determine bovine serum albumin (BSA) protein adsorbed onto bare gold nanoparticles (AuNPs). The AuNPs forming the SEIRA-active substrate were directly synthesized inside the ATR liquid cell taking advantage of stainless steel assisted synthesis via the walls composing the ATR compartment. The formation of the AuNPs can be directly monitored via the enhancement of the corresponding water absorption features. The absorbance of BSA at the AuNPs deposited onto the Si ATR waveguide is significantly enhanced when compared to bare Si, thereby improving the sensitivity of detection. Apparently, the presence of the AuNPs layer at the ATR waveguide surface at the measured conditions does not affect the secondary structure of the protein. Measurements were performed in water and confirmed in deuterium oxide, which significantly reduces the strongly absorbing mid-infrared background of water in the spectral regime of interest. The limits of detection achieved for BSA protein analysis in water and deuterium oxide media are 1.93 and 4.15 mg•L −1 , respectively, and the precisions at a 250 mg•L −1 concentration are 11.9% and 8.1%, respectively.

Surface enhanced infrared absorption spectroscopy based on gold nanostars and spherical nanoparticles

“…However, the saturation process can be fitted with a Langmuir isotherm (Fig. S-6) which represent an adsorption process of the protein within the first monolayer, as also shown in literature [44].…”

A mid-infrared lab-on-a-chip for dynamic reaction monitoring

“…Other approaches for protein sensing reported in literature, especially those based on SEIRAS (Surface Enhanced IR Absorption Spectroscopy) combined with traditional ATR-techniques, result in even better LODs than our QCLD (factor of ~2.1 to ~18.1). But they rely on more complex schemes, by e.g., adding different types of Au nanoparticles 71 , 72 . This is in contrast to the not yet funtionalized surface of our QCLD-sensor, which is part of future work 73 , 74 .…”

Octave-spanning low-loss mid-IR waveguides based on semiconductor-loaded plasmonics

“…This allows monitoring wide concentration ranges characterized by sensor linearity and high saturation thresholds [20]. But even those new and other comparable improved devices still require rather bulky experimental setups relying on external components including flow cells [18], [20], [21] and M. David, I. C. Doganlar, D. Nazzari, E. Arigliani, M. Sistani, H. Detz, W. M. Weber, G. Strasser, and B. Hinkov are with the Institute of Solid State Electronics & Center for Micro-and Nanostructures, TU Wien, Vienna, Austria (e-mail: mauro.david@tuwien.ac.at ; borislav.hinkov@tuwien.ac.at). D. Wacht, G. Ramer, and B. Lendl are with the Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.…”