(Bio)Sensing Using Nanoparticle Arrays: On the Effect of Analyte Transport on Sensitivity

Abstract

There has recently been an extensive amount of work regarding the development of optical, electrical, and mechanical (bio)sensors employing planar arrays of surface-bound nanoparticles. The sensor output for these systems is dependent on the rate at which analyte is transported to, and interacts with, each nanoparticle in the array. There has so far been little discussion on the relationship between the design parameters of an array and the interplay of convection, diffusion, and reaction. Moreover, current methods providing such information require extensive computational simulation. Here we demonstrate that the rate of analyte transport to a nanoparticle array can be quantified analytically. We show that such rates are bound by both the rate to a single NP and that to a planar surface (having equivalent size as the array), with the specific rate determined by the fill fraction: the ratio between the total surface area used for biomolecular capture with respect to the entire sensing area. We characterize analyte transport to arrays with respect to changes in numerous parameters relevant to experiment, including variation of the nanoparticle shape and size, packing density, flow conditions, and analyte diffusivity. We also explore how analyte capture is dependent on the kinetic parameters related to an affinity-based biosensor, and furthermore, we classify the conditions under which the array might be diffusion- or reaction-limited. The results obtained herein are applicable toward the design and optimization of all (bio)sensors based on nanoparticle arrays.

Microfluidic Analyte Transport to Nanorods for Photonic and Electrochemical Sensing Applications

“…It can be seen that plottedi nt his manner,a ll of the data taken from FE simulations have ac lose match to the analytical solutionsf or transport to an anodisk. For nanocyliders under conditions such that Pe np < 1, numerical data were within 5% of those calculated via Equation (5). For nanorods the differen- .…”

“…We show that our approximation provides accurate prediction of transport to these shapes over a wide range of convective/diffusive conditions. Results from this study can be readily combined with the theory previously reported by Lynn and Homola to predict steady‐state rates of transport to arrays nanorods.…”

“…Figure 6p lots the data from these simulations, in the dimensionless form of 4 _ N c o Dl o ,a safunction of Pe np .W e comparet he FE simulation data with analytical solutions for transport to an anodisk ( Figure 6, red line). Specifically,w ep lot the solution given by both Phillips [17] as well as am odified [5] solution of that given by Stone [18] for low and high PØclet number flow,r espectively.T hese solutions are rewritten here as Equation (5):…”

“…[4] We recently demonstrated that analyte transport to an array of NPs is dependento nt he size and shapeo ft he individual NPs composing the array. [5] This dependency becomes especially relevant for nanorod-based sensors, as the aspect ratio of individual nanorods (and thus rates of analyte interaction) can have orders of magnitude variations across different applications. Accurate prediction of rates of transport can greatlya id in both sensor design and optimization, as well as the analysis of experimental data.…”

Plasmonic biosensors fabricated by galvanic displacement reactions for monitoring biomolecular interactions in real time

“…nanoparticles is well-established today and encompasses chemical [7], photochemical [8], and biological routes [9]. The research on LSPR sensors is a very active area and nowadays encompass the optimal arrangement of gold nanostructures on sensor surfaces for providing optimal analyte transport [10,11], the combination plasmonic structures with other materials (e.g., fluorescent quantum dots for surface-enhanced fluorescence) [12], miniaturization [13], and surface-enhanced Raman spectroscopy leading to the detection of single molecules [14]. However, simple and cost-and timeefficient fabrication strategies for highly sensitive LSPR sensors utilizing shifts in the spectral position of the LSPR for signal transduction were most often fabricated by deposition of wetchemically prepared gold nanoparticles on substrate surfaces.…”