SARS‐CoV‐2 and omicron variant detection with a high selectivity, sensitivity, and low‐cost silicon bio‐nanosensor

Abstract

The recent SARS-CoV-2 pandemic has highlighted the urgent need for novel point-of-care devices to be promptly used for a rapid and reliable large screening analysis of several biomarkers like genetic sequences and antibodies. Currently, one of the main limitations of rapid tests is the high percentage of false negatives in the presence of variants and, in particular for the Omicron one. We demonstrate in this work the detection of SARS-CoV-2 and the Omicron variant with a cost-effective silicon nanosensor enabling high sensitivity, selectivity, and fast response. We have shown that a silicon (Si) nanowires (NW) platform detects both Sars-CoV-2 and its Omicron variant with a limit of detection (LoD) of four effective copies (cps), without any amplification of the genome, and with high selectivity. This ultrasensitive detection of 4 cps allows to obtain an extremely early diagnosis paving the way for efficient and widespread tracking. The sensor is made with industrially compatible techniques, which in perspective may allow easy and cost-effective industrialization.

PCR‐Free Innovative Strategies for SARS‐CoV‐2 Detection

“…Based on these variabilities, the corresponding sensing performances are wide and they range between some thousands of cps to few cps per reaction (10 5 -2 cps/reaction). Respect to the real clinical samples, there are two examples [65,87] that prove the possibility for real use in qualitative test (yes/no answers), while only one study [83] demonstrated a quantitative detection using extracted real SARS-Cov-2 samples with a LoD of 4 cps/reaction, overcoming the PCR LoD that corresponds to ≈10 cps/reaction. Based on the above considerations, it is evident that, although these technology are very promising, however further extensive clinical validations are necessary to be used in commercial assays.…”

“…Reproduced with permission under the terms of the CC BY license. [ 83 ] Copyright 2023, the Authors. Published by Wiley‐VCH GmbH.…”

“…in 2023 proposed an optical biosensor based on silicon nanowires for the PCR‐free molecular detection of a synthetic SARS‐CoV‐2 and its real Omicron variant. [ 83 ] The nanostructuring of silicon lead to the emission of light upon the quantum confinement effect. [ 84 ] This signal was gradually quenched by the accumulation of the viral target genomes captured by oligonucleotide probes on top of the silicon nanowires, as described in Figure 6b.…”

“…All sensors, in fact, lacked of an on‐board integration of a specific chemistry and module by which performing the SARS‐CoV‐2 RNA purification that, so far, was always executed outside of the sensor. [ 77–98 ] In this sense, literature reports some solutions based on miniaturized microfluidic and silicon‐based modules [ 96,97 ] or high performances lysis buffers combined to heat inactivation process [ 98 ] that could be suitable for the integrated RNA/DNA extraction in a PoC format. This type of integration would increase the speed and automation of the entire molecular analysis toward a self‐patient screening approach.…”

“…b) Silicon nanowires optical biosensor for the PCR-free detection of Omicron variant of SARS-CoV-2. Reproduced with permission under the terms of the CC BY license [83]. Copyright 2023, the Authors.…”