We combine nanofluidics and nanoplasmonics for surface-plasmon resonance (SPR) sensing using flow-through nanohole arrays. The role of surface plasmons on resonant transmission motivates the application of nanohole arrays as surface-based biosensors. Research to date, however, has focused on dead-ended holes, and therefore failed to harness the benefits of nanoconfined transport combined with SPR sensing. The flow-through format enables rapid transport of reactants to the active surface inside the nanoholes, with potential for significantly improved time of analysis and biomarker yield through nanohole sieving. We apply the flow-through method to monitor the formation of a monolayer and the immobilization of an ovarian cancer biomarker specific antibody on the sensing surface in real-time. The flow-through method resulted in a 6-fold improvement in response time as compared to the established flow-over method.

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An in-hole nanohole surface plasmon resonance sensing scheme is demonstrated. Arrays of periodic nanoholes milled through thin layers of SiO(x) and gold were used to detect the binding of organic and biological molecules inside the nanoholes, while blocking the gold surfaces outside the holes. This new approach is more efficient than the previous nanohole array method, where the response was related to binding events taking place inside of the holes and on the top gold surface. The improved sensitivity to binding events and lower detection limit are related to resonant surface plasmon enhanced transmission through the arrays of nanoholes. The sensitivity was found to be 650 nm/RIU and the detection of three attomoles of proteins was estimated from this scheme.