LSPR Cuvette for Real-Time Biosensing by Using a Common Spectrophotometer

Although localized surface plasmon resonance (LSPR) transducers can be optically interrogated without the need of light couplers, normally they need tailor-made optical assemblies for signal monitoring. This fact limits the application of LSPR biosensors in laboratories due to lack of specific optical setups. If commercial equipment like common spectrophotometers were suitable for LSPR interrogation, the LSPR technology could be applied more often in detection applications. In this paper, a universal LSPR cuvette has been developed in order to use a commercial spectrophotometer as a real-time biosensor without the need of any extra optical component. By measuring the changes in absorbance at constant wavelength, the equipment provides sensograms where real-time response is monitored. The cuvette, fully compatible with spectrophotometers, is an LSPR flow-cell (volume less than 10 mL) where a gold nanopatterned surface is emplaced as a window. Gold nanopatterns (period 600 nm) based on lines and pillars were simulated, fabricated, measured, and compared. The resolutions of $1.8\cdot 10^{-4}$ and $6.7\cdot 10^{-5}$ refractive index units were found for nanolines and nanopillars, respectively. The label-free detection of an antibody (anti-IgG) was carried out in the LSPR system with a limit of detection of 1.9 nM. The biosensing protocol was rapid and reproducible and allows the reuse of the surface for multiple sample measurements. The achieved analytical features are comparable with other reported LSPR sensors with tailor-made optical setups. These results indicate that the system (LSPR $\text {cuvette} + \text {spectrophotometer}$ ) can be a useful analytical tool to biosensing applications.