The effect of layer thickness and immobilization chemistry on the detection of CRP in LSPR assays

Abstract

The immobilization of a capture molecule represents a crucial step for effective usage of gold nanoparticles in localized surface plasmon resonance (LSPR)-based bioanalytics. Depending on the immobilization method used, the resulting capture layer is of varying thickness. Thus, the target binding event takes place at different distances to the gold surface. Using the example of a C-reactive protein immunoassay, different immobilization methods were tested and investigated with regard to their resulting target signal strength. The dependency of the target signal on the distance to the gold surface was investigated utilizing polyelectrolyte bilayers of different thickness. It could be experimentally demonstrated how much the LSPR-shift triggered by a binding event on the gold nanoparticles decreases with increasing distance to the gold surface. Thus, the sensitivity of an LSPR assay is influenced by the choice of immobilization chemistry.

Cost‐Effective and Robust Multispectral Light‐Emitting Diode Device for the Readout of Plasmonic Microarray Sensors

“…The calculated smallest detectable refractive indices of Δn min, B1 ¼ 3.84 mRIU (1st measurement), Δn min, B2 ¼ 2.26 mRIU (2nd measurement), and Δn min, S ¼ 11.84 mRIU (LbL measurement) show that the sensor together with the measurement setup delivers a good performance despite quite low S B and S S compared to similar sensor chips. [34,35,40] For each spot, all individual steps of an entire glycerol measurement are shown in Figure 5. The average of the mean centroid values of the array from the first and the last water step differs only by less than 0.04 nm.…”

“…AuNP-Array-Chip Preparation: 18 Â 18 mm glass cover slips (160 μm thickness) were modified with APTES as previously described. [34] Further information can also be found in the supporting information. On the respective APTES chips, a microarray was spotted with a noncontact microdispensing system (Nano-Plotter NP 2.1, GeSiM GmbH, Radeberg, Germany).…”

“…Layer by Layer (LbL) Deposition: The surface sensitivity (S S ) measurements were performed as previously described. [34] Further information can also be found in the supporting information. For the calculation of the Δλ and S S (or absorbance for single LED evaluation), at least ten measurement points, from the buffer step at the beginning of the measurement and after the third polyelectrolyte bilayer injection, were taken for the mean values and the standard deviation.…”

“…The achieved sensitivities and S/N ratios are comparable to our previously presented single‐assay LSPR setups. [ 34 ] Thus, the performance and evaluation of arrays with biological samples in relevant concentrations can be conducted using the LED instrument presented in this study. With suitable concentration series and flow rates, even binding kinetic studies in a multiplex approach are possible.…”

Microfluidic‐Generated Seeds for Gold Nanotriangle Synthesis in Three or Two Steps

“…Plasmonic nanoparticles have become well-known materials for rapidly developing optic and photonic technologies thanks to their tunable optical properties. [1][2][3][4][5][6][7][8] Of vast interest are shaped anisotropic nanoparticles that have edges, tips, or corners accumulating surface charges and generating hotspots of electromagnetic field being beneficial for, e.g., surface-enhanced Raman spectroscopy (SERS). [9][10][11] Such structures also have a great potential in catalysis due to a high number of easily accessible -and catalytically very active -surface atoms.…”