Abstract
Nanostructured sensors based on localized surface plasmon resonance (LSPR) offer a number of advantages over other optical sensing technologies, making them excellent candidates for miniaturized, label-free chemical and biological detection. Highly sensitive to local refractive index changes, the resonance peaks of the nanosensors shift by different amounts when subject to different biological and chemical environments. Modifications to the nanostructure surface allow for the detection of specific molecules and chemicals with shifts so sensitive that the presence of single molecules can be detected. However, this extreme sensitivity has its drawbacks. Resonance shifts also occur because of temperature shifts, light-intensity fluctuations, and other environmental factors. To distinguish detection from drift, a secondary sensor region is often required. This often doubles the size of the device, requires two light sources and detectors (or complex optics), doubles the sample volume required (which may be expensive, or may not be possible if the sample quantity is limited), and subjects the reference to potential biofouling. Here, we present a new proof-of-concept multilayered LSPR sensor design that incorporates both a sensing layer and an encapsulated reference layer within the same region. By doing so, we are able to monitor and correct for sensor drift without the need for a secondary reference channel. We demonstrate the suitability of this sensor for sucrose concentration measurements and for the detection of biotin-avidin interactions, while also showing that the sensor can self-correct for drift. We believe that this multilayer sensor design holds promise for point-of-care diagnostics.
Highlights
Surface plasmon resonance (SPR) has long been used as a label-free optical biosensing technique.[1]
SPR relies on the propagation of surface plasmon polaritons on a continuous metal film, whereas localized SPR (LSPR) is localized to the structures on the nanoscale
LSPR allows for the use of more compact optics, does not need precise temperature control, and has the potential to be miniaturized beyond the capabilities of SPR sensors.[5]
Summary
Surface plasmon resonance (SPR) has long been used as a label-free optical biosensing technique.[1]. Prior to the real-time measurements, the nanoplasmonic device was functionalized with MUA.[33,34] This treatment provided a self-assembled monolayer (SAM) with carboxylic acid moieties that were further used to covalently attach biotin hydrazide via ethylcarbodiimide cross-linking.[34] The unreacted sites on the nanostructures were blocked with ethanolamine,[33] and Tween[20] was added to the PBS solution used during the biosensing experiment to prevent avidin from binding to the unblocked regions of the glass base of the device. The sensitivity may be improved by investigating different antenna geometries
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