Unravelling the Role of Electric and Magnetic Dipoles in Biosensing with Si Nanoresonators

Abstract

High refractive index dielectric nanoresonators are attracting much attention due to their ability to control both electric and magnetic components of light. Combining confined modes with reduced absorption losses, they have recently been proposed as an alternative to nanoplasmonic biosensors. In this context, we study the use of semi-random silicon nanocylinder arrays, fabricated with simple and scalable colloidal lithography for the efficient and reliable detection of biomolecules in biological samples. Interestingly, electric and magnetic dipole resonances are associated to two different transduction mechanisms: extinction decrease and resonance redshift, respectively. By contrasting both observables, we identify clear advantages in tracking changes in the extinction magnitude. Our data demonstrate that, despite its simplicity, the proposed platform is able to detect prostate specific antigen (PSA) in human serum with limits of detection meeting clinical needs.