Development of a novel localized surface plasmon resonance (LSPR) biosensor for relevant protein biomarker detection at point-of-care (POC)

LSPR (localized surface plasmon resonance) platforms offer label-free, sensitive, rapid, robust and versatile detection of biomolecules, being a desirable technology for Point of Care (POC) diagnostics.¹ Gold nanoparticles are often used in these platforms for its biocompatibility and simple antibody immobilization.² Nevertheless, this technology still presents challenges that need to be overcome, for POC integration, such as: improve the limit of detection (LOD) and the selectivity in complex media, develop multiplexing platforms for multiple detection of biomarkers as well as automated forms of fluid control.¹

We present a novel LSPR technology constituted by thin films of TiO₂ and CuO with embedded gold nanoparticles. The nanocomposite films were deposited by reactive DC magnetron sputtering and subjected to post-deposition thermal annealing up to 600 ºC. The thickness of the thin films is lower than 100 nm, and the atomic concentrations of Au was close to 13 % in both matrices. The manufacturing of these films is cost-effective and simple to up-scale, since the production process is straightforward and reproducible. It also allows the tuning of several parameters in order to optimize the LSPR signal and, therefore, improve detection mode sensitivity.³

The surface characterization of these nanocomposite films was performed by SEM and revealed Au nanoparticles with 50 nm diameter average covering about 18% of thin film surface, for the Au/CuO thin films, and between 15 to 20 nm covering 8% of thin film surface, for Au/TiO₂ thin films. AFM analysis revealed a roughness of 2.64 nm for Au/TiO₂ and 3.45 nm for Au/CuO. The size and surface exposure of Au nanoparticles is appropriated for effective antibody immobilization, which gives to these nanoplasmonic thin films a great potential for protein biomarker detection at POC settings.