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.
Highlights
Nanoplasmonic sensing is a popular surface-sensitive measurement technique for biomolecular detection, and has several compelling features including simple instrumental requirements, label-free format, and high detection sensitivity [1,2,3]
INPSstrategy strategy monitor adsorption and denaturation on dielectricWe employed to to monitor adsorption and denaturation on dielectric-coated coated sensor arrays, which were comprised of randomly-distributed gold nanodisks glass sensor arrays, which were comprised of randomly-distributed gold nanodisks on glass on surfaces surfaces fabricated via hole-mask colloidal lithography and the entire surface was conformally fabricated via hole-mask colloidal lithography and the entire surface was conformally coated coated with a 10-nm thick silica or titania overlayer (Figure 1A)
The adsorption of human serum albumin (HSA) molecules onto the sensor surface leads to a Δλmax shift, molecules onto the sensor surface leads to a ∆λmax shift, and our measurement approach is sensitive and our measurement approach is sensitive to the dry mass of adsorbed HSA molecules
Summary
Nanoplasmonic sensing is a popular surface-sensitive measurement technique for biomolecular detection, and has several compelling features including simple instrumental requirements, label-free format, and high detection sensitivity [1,2,3]. As the decay length of the LSPR-enhanced field is on the length scale of various classes of biomolecules, it is possible to detect biomolecular binding events, and characterize structural transformations that influence the spatial proximity of adsorbed molecules to the sensor surface [7,8,9] These capabilities have proven useful for gaining novel insights into well-studied biomacromolecular interactions involving lipid vesicles [10,11,12,13,14] and supported lipid bilayers [8,15,16,17,18]
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