Nanoparticle Bragg reflectors: A smart analytical tool for biosensing

Abstract

In this work, we present a novel optical biosensor based on periodically alternated layers of SiO2 and TiO2 nanoparticles grown by wet methods and working as a Bragg mirror in a label free format. The sensing principle relies on the change of the optical response generated by variations in the dielectric constant of the voids due to a biorecognition probe-target event. This change is reflected in a modification in the photonic band gap frequencies of the Bragg reflector. As a proof of concept, biotin and streptavidin biorecognition on the biosensor surface is monitored in label free format, achieving a LOD of 3.09 mg L−1 (54 nM) for the determination of streptavidin. Our proposed biosensor also shows selective determination against a variety of targets (horseradish peroxidase and bovine serum albumin antibody) working in physiological conditions (diluted human serum). To get a picture of the potential of our development and its ease of integration, we incorporated the immunosensor in an electronic consumable technology, such as compact disk, using the optical disk as analytical platform and a CD player detector for the determination of streptavidin. Thus, our findings point out the feasibility of nanoparticle based Bragg reflectors in the biosensing field and open new avenues towards the rational design of a new generation of versatile, easy to fabricate in mass scale and cost-competitive biosensors.