Flow-Through vs Flow-Over: Analysis of Transport and Binding in Nanohole Array Plasmonic Biosensors

摘要

We quantify the efficacy of flow-through nanohole sensing,nas compared to the established flow-over format, throughnscaling analysis and numerical simulation. Nanoholenarrays represent a growing niche within surface plasmonnresonance-based sensing methods, and employing thennanoholes as nanochannels can enhance transport andnanalytical response. The additional benefit offered by flowthroughnoperation is, however, a complex function ofnoperating parameters and application-specific bindingnchemistry. Compared here are flow-over sensors and flowthroughnnanohole array sensors with equivalent sensingnarea, where the nanohole array sensing area is taken asnthe inner-walls of the nanoholes. The footprints of thensensors are similar (e.g., a square 20 μm wide flow-overnsensor has an equivalent sensing area as a square 30 μmnwide array of 300 nm diameter nanoholes with 450 nmnperiodicity in a 100 nm thick gold film). Consideringntransport alone, an analysis here shows that given equivalentnsensing area and flow rate the flow-through nanoholenformat enables greatly increased flux of analytes to thensensing surface (e.g., 40-fold for the case of Q ) 10 nLmin). Including both transport and binding kinetics, ancomputational model, validated by experimental data,nprovides guidelines for performance as a function ofnbinding time constant, analyte diffusivity, and runningnparameters. For common binding kinetics and analytes,nflow-through nanohole arrays offer ∼10-fold improvementnin response time, with a maximum of 20-fold improvementnfor small biomolecules with rapid kinetics.