Disclosed is a product that includes an optical sensor; a target-responsive hydrogel matrix on a surface of the optical sensor (where the hydrogel matrix comprises one or more target-specific receptors and one or more target analogs), and one or more high refractive index nanoparticles within the hydrogel matrix, where a detectable change occurs in a refractive index of the hydrogel matrix when contacted with one or more target molecules. Sterile packages and detection devices containing the product, and methods of detecting a target molecule using the product, are also disclosed.