Development of a nanoparticle microfluidic colour device for point-of-care diagnostics

Abstract

Through a novel immunoassay nanoparticles (NPs) are captured via immune-reactive proteins and positioned as a sub-monolayer just a few nanometres above a light reflective surface. Here the particles and the mirror form a nanometric interference system with a tuneable colour throughout the full spectrum of light. This concept, which was inspired by nature (‘wings of a butterfly’), creates an intensive colour clearly visible to the eye. By adaptation of this technique point-of-care (POC) tests become more sensitive, specific and time efficient. The novel format employs a combination of microfluidics and ‘resonance-enhanced absorption’ (REA) of gold and palladium nanoparticles quantifying interleukin-6 as an important parameter of acute sepsis. The colour intensity of the rapid test is boosted by using a subsequent silver enhancement. This performed in situ in just two to three minutes and a sensitivity of < 500 pg/ml was obtained.