Non-linear plasmon response to protein binding at a nanostructured gold particle plasmon resonance surface

Reilly, Josephine P. O’; Fisk, Jonathan D.; Rooth, Maxim; Perkins, Elaine A.; Shaw, Andrew M.

doi:10.1039/b611337k

Cited by 4 publications

(9 citation statements)

References 7 publications

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“…Even with all that is currently known about native BSA, detailed information on BSA−AuNP conjugates is relatively sparse. ,,,,− Additionally, a few related studies have examined the adsorption and conformation of BSA onto Au flats. ,, The structure and behavior of BSA in aqueous solution are governed by multiple interactions, including electrostatic, hydrogen bonding, hydrophobic, and van der Waals. In addition, the reaction of the free thiol on the external surface of globular (N form) BSA with the AuNP surface could potentially weaken or alter the tertiary or secondary structure of the BSA molecule, which would likely result in the unfolding of BSA from its compact, globular structure .…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Conformation of Serum Albumin Protein on Gold Nanoparticles Investigated Using Dimensional Measurements and in Situ Spectroscopic Methods

et al. 2011

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ABSTRACT:The adsorption and conformation of bovine serum albumin (BSA) on gold nanoparticles (AuNPs) were interrogated both qualitatively and quantitatively via complementary physicochemical characterization methods. Dynamic light scattering (DLS), asymmetric-flow field flow fractionation (AFFF), fluorescence spectrometry, and attenuated total reflectanceFourier transform infrared (ATR-FTIR) spectroscopy were combined to characterize BSA-AuNP conjugates under fluid conditions, while conjugates in the aerosol state were characterized by electrospray-differential mobility analysis (ES-DMA). The presence of unbound BSA molecules interferes with DLS analysis of the conjugates, particularly as the AuNP size decreases (i.e., below 30 nm in diameter). Under conditions where the γ value is high, where γ is defined as the ratio of scattering intensity by AuNPs to the scattering intensity by unbound BSA, DLS size results are consistent with results obtained after fractionation by AFFF. Additionally, the AuNP hydrodynamic size exhibits a greater proportional increase due to BSA conjugation at pH values below 2.5 compared with less acidic pH values (3.4-7.3), corresponding with the reversibly denatured (E or F form) conformation of BSA below pH 2.5. Over the pH range from 3.4 to 7.3, the hydrodynamic size of the conjugate is nearly constant, suggesting conformational stability over this range. Because of the difference in the measurement environment, a larger increase of AuNP size is observed following BSA conjugation when measured in the wet state (i.e., by DLS and AFFF) compared to the dry state (by ES-DMA). Molecular surface density for BSA is estimated based on ES-DMA and fluorescence measurements. Results from the two techniques are consistent and similar, but slightly higher for ES-DMA, with an average adsorbate density of 0.015 nm -2 . Moreover, from the change of particle size, we determine the extent of adsorption for BSA on AuNPs using DLS and ES-DMA at 21°C, which show that increasing the concentration of BSA increases the measured change in AuNP size. Using ES-DMA, we observe that the BSA surface density reaches 90% of saturation at a solution phase concentration between 10 and 30 μmol/L, which is roughly consistent with fluorescence and ATR-FTIR results. The equilibrium binding constant for BSA on AuNPs is calculated by applying the Langmuir equation, with resulting values ranging from 0.51 Â 10 6 to 1.65 Â 10 6 L/mol, suggesting a strong affinity due to bonding between the single free exterior thiol on N-form BSA (associated with a cysteine residue) and the AuNP surface. Moreover, the adsorption interaction induces a conformational change in BSA secondary structure, resulting in less R-helix content and more open structures (β-sheet, random, or expanded).

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Section: Introductionmentioning

confidence: 99%

Adsorption and Conformation of Serum Albumin Protein on Gold Nanoparticles Investigated Using Dimensional Measurements and in Situ Spectroscopic Methods

et al. 2011

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“…In many cases, especially colloidal gold and silver, the spectrum in the visible region is dominated by a strong localized surface plasmon resonance (LSPR) peak. The maximum of extinction corresponding to the LSPR, λ max , depends on various factors, such as size, shape, the dielectric constant of the material concerned, the distance between adsorbed NPs on the surface, and the dielectric constant of the local environment (e.g., the solvent or the substrate). − Optimization of these physical properties to suit particular applications is the subject of much research. ,, The sensitivity of the LSPR to the local environment, for example, is the basis for the use of gold nanoparticles in biosensors, where the presence of an adsorbed biomolecule significantly perturbs the local refractive index which results in observable spectral shifts in the LSPR. ,− …”

Section: Introductionmentioning

confidence: 99%

In-Situ Measurement of Colloidal Gold Adsorption on Functionalized Silica Surfaces

et al. 2008

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Evanescent wave cavity ring-down spectroscopy (EW-CRDS) has been applied to study, in-situ, the deposition kinetics of commercially available gold colloids on functionalized silica surfaces from quiescent solution. Neither 5 nm nor 20 nm citrate-stabilized nanoparticles were observed to adsorb on clean silica surfaces. Adsorption on a poly-L-lysine functionalized surface, however, occurs readily and irreversibly with the kinetics of adsorption differing markedly for the two particle sizes studied. 5 nm particles adsorb to form a highly disperse submonolayer of individual particles with atomic force microscope images showing no evidence of aggregation. The controlled growth of multilayer nanoparticle / polyelectrolyte films is demonstrated by alternately depositing colloidal particles and poly-L-lysine films. The deposition of multilayer nanoparticle films increases the sensitivity of the functionalized surface to changes in the solvent refractive index. The adsorption kinetics of the 20 nm colloid is more complex than that of the smaller colloid with adsorbed particles acting as nucleation sites for subsequent aggregation with the result that the interfacial absorbance continues to increase indefinitely with time.

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“…[4][5][6][7] An enhancement mechanism involving both an electric field and chemical effect have been invoked. 2,4,8 We recently reported nonlinear protein adsorption kinetics 9 for binding proteins to an 800-nanoparticle cluster showing sensitivity to attogram mL -1 protein concentration, which is a factor of 10 6 more sensitive than observed for a single particle. The electric field between the surface roughness features or aggregated nanoparticles is enhanced, coupling the radiation to the nanoparticle optical scattering 10,11 properties allowing the nanometer-scale structure to act as a local optical aerial.…”

Section: Introductionmentioning

confidence: 97%

“…The aggregation of nanoparticles in salt-destabilized solution was the mechanism used to generate the fractal clusters that demonstrated the nonlinear response to protein binding observed previously. 9 However, controlling the aggregation process in solution is difficult because the kinetic process accelerates when nucleation around the seed particles occurs. Some interesting structures have been trapped during aggregation, including chains and cluster aggregates, but the interface offers a more The optical extinction of the surface has been followed in real time using e-CRDS, and the adsorption and aggregation kinetics have been observed directly.…”

Section: Introductionmentioning

confidence: 99%

Aggregation Kinetics of Gold Nanoparticles at the Silica−Water Interface

et al. 2009

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The aggregation kinetics have been observed for citrate-reduced 15 nm gold nanoparticles at the native silica and modified silica−water interfaces. At the native, negatively charged silica−water interface, two-phase adsorption is observed: a pseudo-Langmuirian adsorption phase and, after an acid wash to remove the citrate ligand from the adsorbed particles, another pseudo-Langmuirian adsorption phase. A kinetic analysis of these phases shows an average adsorption rate constant of (1.5 ± 0.4) × 106 M−1 s−1 with no measurable desorption. Another acid wash induces a nearly linear aggregation phase with a 4-fold faster nanoparticles deposition rate. SEM imaging of the aggregation-phase surface shows the formation of small nanoparticle clusters of <10 particles. Adsorption on a positively charged, aminated silica surface shows a kinetic trace consistent with aggregations at low surface coverages and has a similar adsorption rate to the aggregation phases on the negatively charged surfaces. SEM imaging reveals clusters of many particles of >10. The refractive index sensitivity of the produced surfaces was measured by varying the analyte refractive index at each phase: the aggregated clusters on the positively charged surface are up to 4 times more sensitive.

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Non-linear plasmon response to protein binding at a nanostructured gold particle plasmon resonance surface

Abstract: Rapid adsorption kinetics have been observed for protein binding to a 800 nm aggregated nanoparticle, showing extreme sensitivity resulting from a non-linear particle plasmon response.

Cited by 4 publications

References 7 publications

Adsorption and Conformation of Serum Albumin Protein on Gold Nanoparticles Investigated Using Dimensional Measurements and in Situ Spectroscopic Methods

Adsorption and Conformation of Serum Albumin Protein on Gold Nanoparticles Investigated Using Dimensional Measurements and in Situ Spectroscopic Methods

In-Situ Measurement of Colloidal Gold Adsorption on Functionalized Silica Surfaces

Aggregation Kinetics of Gold Nanoparticles at the Silica−Water Interface

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