Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing

Nanostructured materials premise to revolutionize the label-free biosensing of analytes for clinical applications, leveraging the deeper interaction between materials and analytes with comparable size. However, when the characteristic dimension of the materials reduces to the nanoscale, the surface functionalization for the binding of bioreceptors becomes a complex issue that can affect the performance of label-free biosensors. Here we report on an effective and robust route for surface biofunctionalization of nanostructured materials based on the layer-by-layer (LbL) electrostatic nano-assembly of oppositely-charged polyelectrolytes, which are engineered with bioreceptors to enable label-free detection of target analytes. LbL biofunctionalization is demonstrated using nanostructured porous silicon (PSi) interferometers for affinity detection of streptavidin in saliva, through LbL nano-assembly of a bi-layer of positively-charged poly(allylamine hydrochloride) (PAH) and negatively-charged biotinylated poly(methacrylic acid) (b-PMAA). High sensitivity in streptavidin detection is achieved, with high selectivity and stability, down to a detection limit of 600 fM

The Electrochemical Society, find out more Layer-By-Layer Nanoassembly Of Polyelectrolites Engineered With Bioreceptors For High-Sensitivity Optical Label-Free Biosensing With Nanostructured Porous Silicon

Here we report the layer-by-layer (LbL) nanoassembly of charged polyelectrolytes engineered with bioreceptors as an effective and robust alternative to covalent biofunctionalization (e.g., organosilanization and hydrosilylation) for affinity biosensing with porous silicon (PSi) interferometers [1]. As a proof of concept demonstration, a bi-layer of positively-charged poly(allylamine hydrochloride) (PAH) and negatively-charged biotinylated poly(methacrylic acid) (b-PMAA) is assembled onto the surface of oxidized PSi interferometers for the affinity detection of streptavidin in buffer and raw saliva. The LbL nanoassembly allows a homogenous coating of the inner PSi surface, ensuring a robust anchoring of the bioreceptors and, in turn, high sensitive and selective detection of streptavidin, also in raw saliva, down to a theoretical detection limit of 600 fM. This pushes PSi based biosensors at detection limit comparable to that of state-of-the-art nanostructured photonic and plasmonic platforms for biosensing. Further, the development and employment of polymers engineered with several bioreceptors or with stronger dissociation properties (e.g. PSS) could broaden the applications LbL nano-assembly in biosensing and in biomedical applications