Quantitative Comparison of Protein Adsorption and Conformational Changes on Dielectric-Coated Nanoplasmonic Sensing Arrays

Abstract

Nanoplasmonic sensors are a popular, surface-sensitive measurement tool to investigate biomacromolecular interactions at solid-liquid interfaces, opening the door to a wide range of applications. In addition to high surface sensitivity, nanoplasmonic sensors have versatile surface chemistry options as plasmonic metal nanoparticles can be coated with thin dielectric layers. Within this scope, nanoplasmonic sensors have demonstrated promise for tracking protein adsorption and substrate-induced conformational changes on oxide film-coated arrays, although existing studies have been limited to single substrates. Herein, we investigated human serum albumin (HSA) adsorption onto silica- and titania-coated arrays of plasmonic gold nanodisks by localized surface plasmon resonance (LSPR) measurements and established an analytical framework to compare responses across multiple substrates with different sensitivities. While similar responses were recorded on the two substrates for HSA adsorption under physiologically-relevant ionic strength conditions, distinct substrate-specific behavior was observed at lower ionic strength conditions. With decreasing ionic strength, larger measurement responses occurred for HSA adsorption onto silica surfaces, whereas HSA adsorption onto titania surfaces occurred independently of ionic strength condition. Complementary quartz crystal microbalance-dissipation (QCM-D) measurements were also performed, and the trend in adsorption behavior was similar. Of note, the magnitudes of the ionic strength-dependent LSPR and QCM-D measurement responses varied, and are discussed with respect to the measurement principle and surface sensitivity of each technique. Taken together, our findings demonstrate how the high surface sensitivity of nanoplasmonic sensors can be applied to quantitatively characterize protein adsorption across multiple surfaces, and outline broadly-applicable measurement strategies for biointerfacial science applications.

Conformational stability as a quality attribute for the cell therapy raw material human serum albumin

“…Therefore, the LSPR technique is not only sensitive to protein adsorption uptake but is also sensitive to the extent of adsorption-related deformation of the protein molecules on the sensor surface. [55][56][57] pBSA shows a slightly higher optical extinction peak shi (Dl) than pHSA, i.e. the reverse of the DF shis observed in QCM-D (Fig.…”

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

“…The properties of the protein are related to its primary structure, specifically the sequence of amino acids and functional groups available for bonding. The variety of chemical residues cause the protein to interact differently with the groups on the surface [66,67,68] (Figure 4).…”

Scalable Fabrication of Quasi-One-Dimensional Gold Nanoribbons for Plasmonic Sensing

“…The final wavelength shift of the dip 1 position is in good agreement with absolute values observed in our previous work, whereby the adsorption of bovine or human serum albumin onto Si or TiO 2 surfaces led to LSPR peak shifts in the range 0.50-1.5 nm. 44,59 However, similar to DOPC lipid vesicle adsorption, the shift in the position of dip 1 resulting from BSA adsorption was relatively low when normalized to the bulk RI sensitivity. To determine whether this smaller shift was due to lower amounts of BSA adsorbed on indium oxide Au nanoribbon arrays or to differences in surface sensitivity, we extracted the time-resolved wavelength shifts for peak 2 during BSA adsorption ( Figure S6b).…”

“…To investigate this mismatch further, we characterized adsorption of a protein biomolecule, BSA, which is widely employed in a variety of applications, often as a blocking agent to prevent nonspecific adsorption on sensor surfaces. [60][61][62][63] Recent efforts have relied on nanoplasmonic sensing strategies to quantify the adsorption of serum albumin on various surfaces for understanding adsorptive processes, 40,44,59 as well as for investigating protein corona formation. [64][65][66][67] After obtaining baseline signals in Tris buffer, 100 μM BSA in Tris buffer was introduced at a flow rate of 100 μL/min and adsorption was monitored as a function of time on three different substrates.…”