An innovative POF-based device for real-time monitoring of binding processes at ultra-low concentrations via a plasmonic sensor combined with a microcuvette chip

Surface plasmonic sensors are widely utilized in bioanalytical and diagnostic laboratories to track interactions between analytes and receptors.1 The primary advantage of plasmonic technology over traditional diagnostic methods is the possibility of label-free monitoring of binding events in real time. However, the expensive chip and the laborious surface chemistries required for functionalization are notable drawbacks. In this study, a novel sensing approach is introduced to detect receptor-target interactions at extremely low concentrations without any kind of sensing surface functionalization. The biosensor operates using a sensitive chip based on a microcuvette device fabricated by drilling the core of a multimode polymer optical fibre (POF) with nanoholes. This is connected in series with a surface plasmon resonance (SPR) D-shaped POF probe, and the detection is performed using a broad-spectrum halogen lamp and a spectrometer. The microhole is filled with a solution containing specific receptors that selectively capture the target molecules from samples placed on top of the filled nanohole. Any changes over time due to analyte-receptor binding alter the mode profile of the light propagating through the POF core, affecting the plasmonic interactions and resulting in a time-dependent shift in the resonance wavelength.2 In particular, The interactions of estradiol and cortisol, with their respective receptors (Estrogen Receptor3 and Glucocorticoid Receptor4) were tested as proof of concept.2 The resonance wavelength shift was monitored over time to trace the interactions between the receptor–target pairs at attomolar concentration.2 This advanced sensing approach acts as a new class of laboratory instruments offering distinctive capabilities in ultra-high sensitivity and affordability.