Abstract
Porous silicon (PSi) thin films have been widely studied for biosensing applications, enabling label-free optical detection of numerous targets. The large surface area of these biosensors has been commonly recognized as one of the main advantages of the PSi nanostructure. However, in practice, without application of signal amplification strategies, PSi-based biosensors suffer from limited sensitivity, compared to planar counterparts. Using a theoretical model, which describes the complex mass transport phenomena and reaction kinetics in these porous nanomaterials, we reveal that the interrelated effect of bulk and hindered diffusion is the main limiting factor of PSi-based biosensors. Thus, without significantly accelerating the mass transport to and within the nanostructure, the target capture performance of these biosensors would be comparable, regardless of the nature of the capture probe–target pair. We use our model to investigate the effect of various structural and biosensor characteristics on the capture performance of such biosensors and suggest rules of thumb for their optimization.
Highlights
Porous silicon (PSi) thin films have been widely studied for biosensing applications, enabling label-free optical detection of numerous targets
Biosensing experiments are performed in a conventional cell setup, illustrated in Figure 1a(i), where the target protein solutions are introduced on the top of the biosensor and incubated
As the target protein diffuses in the bulk solution toward the pore entry [Figure 1a(ii)], it infiltrates into the nanostructure, diffuses, and simultaneously interacts with the immobilized aptamer molecules [Figure 1a(iii,iv), respectively], resulting in an increase in the effective optical thickness (EOT) signal with time
Summary
Porous silicon (PSi) thin films have been widely studied for biosensing applications, enabling label-free optical detection of numerous targets. Biosensors that monitor the binding between a target molecule and a capture probe, by various transducing methods and surface-based detection, in which the capture probes are immobilized on the transducing surface, are among the most widespread bioanalytical tools.[1−5] The performance of planar biosensors based on surface capture is governed by the complex interplay between transport phenomena and reaction kinetics, as modeled by Squires et al.[6] As such, numerous studies have been directed to optimize these systems and elucidate their limiting factors.[7−14]. Anti-protein A aptamer protein A the effect of each of the parameters is a facile way to study
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