How the surrounding environment affects the biosensing performance of resonant nanopillars arrays: Under dry conditions or immersed in fluid

Abstract

In this work we demonstrate the advantage of performing the biosensing process of a refractive index optical biosensor under dry conditions, in comparison with the biosensing structure immersed in fluid. We developed a biosensing experiment over a specific transducer based on resonant nanopillars (R-NPs) arrays. The optical interrogation to monitor the recognition events was firstly performed with the R-NPs in dry, only in contact with the air, and secondly with the R-NPs immersed in water. We observed a significant enhance in the sensitivity of the biosensing curve response for the R-NPs in dry conditions, leading an improvement of the Limit of Detection (LoD) in more than one order of magnitude. These results are also in good correlation with 3D-Finite difference time domain simulations carried out for both fluid conditions. According to this result, any interferometric optical bio-transducer for in-situ diagnosis will improve the sensitivity in case it can operate in dry conditions. Moreover, measuring in simple drops of biological samples, in dry conditions, will be a relevant issue for Point of Care Devices.

Chip-Based Chiral 3D Metamaterial with Functional Core-Shell Architecture for Femtomolar Biodetection

“…The system was then tested for biomolecular recognition (see Methods for details) after antibody immobilization with gluthereldeyde (acting as crosslinker agent between the aminic groups of the polymeric shell and the antibody) and after the incubation of TDP-43 antigen. Analyte measurements at different concentration were then performed in dry medium (see Supplementary S4 for details) [57][58][59] .…”

Optical Vapor Sensors Based on Periodic Resonant Nanopillar Structures

“…We repeated this process for each one of the studied samples and found out that the resonance shift as a function of film thickness is clearly linear in all the cases in this data range, in line with the scientific literature. 24 The slope of this shift can be used to estimate the liquid thickness for an experimental resonance shift. In Table 2 we present this ratio for the different VOC samples of the study.…”

Engineering vertically interrogated interferometric sensors for optical label-free biosensing

“…Full understanding of these four aspects and their interrelation is a key factor to develop finally a commercial point of care device, which should be nowadays the goal to pursue by people working in biosensors field. [69]…”

“…On the other hand, main advantage of nanostructured surface is that the sensing surface is significantly higher and these increase the number of available bioreceptors to recognize the analyte, which results in a better value of sensitivity of the detection. Finally, a not extensively studied aspect of the measurements is the environment of the sensing surface during the measurement [69]. The readout can be performed "on-line" with the sensing area immersed in fluid, typically PBS solution; in this case, the refractive index of the media is close to the value of the refractive index of water (Fig.…”

“…11 a Scheme of pillars immersed in water, b scheme of pillars in dry conditions, and c layout of the measurement system. From [69] In terms of biofunctionalization processes, the use of vertical sensing cells does not represent great differences compared with other types of sensors; although nanostructured materials are more complex to work with, there is an important increase in the sensing surface and thus in the available bioreceptors to detect. Finally, fluidic dry conditions not only simplifies the fluidic setup but also can increase the sensitivity of a sensing cell, for the higher refractive index contrast between air and bioanalyte, compared with water of PBS and bioanalyte.…”