The reliability issues of biosensors have been primarily attributed to the stability and degradation problems of biorecognition elements. However, a critical factor that has never been considered is the time-related device integrity with respect to the interfacial behavior of the material under prolonged exposure to buffer solution at a low temperature. In the presence of electrolyte, the interfacial properties of a particular material are expected to depend largely on surface roughness. In this paper, we have fabricated thick and stoichiometric nanoporous silicon oxide with varying surface roughness by controlling the ratio of hydrofluoric acid and dimethyl sulfoxide during anodic etching. The impact of surface roughness on the degradation of impedance characteristics during virus detection in blood has been studied extensively after different preservation time in buffer solution. It has been observed that reliability (i.e., repeatability) is significantly better for surfaces with higher roughness, but response magnitude and sharpness of sensitivity peak improve with lower surface roughness.

Nanopore sensors provide an innovative platform for rapid and label-free biomolecule detection. The analytical information extracted from resistive pulse sensing (RPS) measurement, though powerful has several limitations. To address these challenges, various signal conditioning algorithms have been researched which include efficient clustering and classification of data, applying probabilistic models to reduce information overlap and also leveraging transient analysis of ionic current instead of the steady state RPS measurement. Additionally, as the current is typically in few picoampere regime with high transition rates, its faithful measurement requires precision instrumentation like a patch clamp amplifier with low noise and high bandwidth. However, for practical deployment of such systems, it is necessary to develop portable electronic interface. Significant efforts have been directed globally to develop on-chip customized integrated circuits with low noise, high bandwidth amplifiers. Thus, it is absolutely timely and pertinent to conduct a review on the various signal processing schemes and electronic interfaces for single biomolecule identification using nanopores which will enable to comprehend the current status for its deployment as a commercial platform for genomics and ultrasensitive detection. To the best of our knowledge, the data extraction methodologies and electronic interface schemes for nanopores have not yet been summarized. In this paper, a comprehensive review emphasizing the signal processing algorithms for DNA sequencing and protein identification in complex analyte using functionalized and nonfunctionalized nanopores has been presented along with the onchip low noise electronic interfaces required for field deployable measurement.

Nanopores have been well established as a promising platform for real time stochastic detection of single biomolecules and have made sufficient commercial progress in terms of DNA sequencing. Amongst the various strategies for specific protein estimation in physiological analyte, aptamer functionalized nanopores have been reported to quantify proteins down to few picomolars in control solution. In this paper, we explore the quantification of target protein in serum down to picomolar concentration using aptamer functionalized nanopores. For such cases, the current settles to a new value in multiple steps due to the low dissociation constants of the receptors and the final current blockade sensitivity is the primary indicator of target protein concentration. It has been observed that the current sensitivity histograms not only have a statistical variation (due to the fluctuations in the device fabrication) but also overlap significantly between the different concentration ranges in the picomolar regime, which makes quantification challenging. Here, we introduce probabilistic fuzzy model based on Monte Carlo simulation and demonstrate its ability by quantifying thrombin down to 50-pM concentration in undiluted serum. The method has been verified with 25 test solutions and the results reveal the potential of this computational approach toward lowering the detection limit by three orders of magnitude compared with the existing status, thus enabling the functionalized glass nanopore platform makes great progress toward clinical testing.