Optical Detection of CoV-SARS-2 Viral Proteins to Sub-Picomolar Concentrations

Abstract

The emergence of a new strain of coronavirus in late 2019, SARS-CoV-2, led to a global pandemic in 2020. This may have been preventable if large scale, rapid diagnosis of active cases had been possible, and this has highlighted the need for more effective and efficient ways of detecting and managing viral infections. In this work, we investigate three different optical techniques for quantifying the binding of recombinant SARS-CoV-2 spike protein to surface-immobilized oligonucleotide aptamers. Biolayer interferometry is a relatively cheap, robust, and rapid method that only requires very small sample volumes. However, its detection limit of 250 nM means that it is not sensitive enough to detect antigen proteins at physiologically relevant levels (sub-pM). Surface plasmon resonance is a more sensitive technique but requires larger sample volumes, takes longer, requires more expensive instrumentation, and only reduces the detection limit to 5 nM. Surface-enhanced Raman spectroscopy is far more sensitive, enabling detection of spike protein to sub-picomolar concentrations. Control experiments performed using scrambled aptamers and using bovine serum albumin as an analyte show that this apta-sensing approach is both sensitive and selective, with no appreciable response observed for any controls. Overall, these proof-of-principle results demonstrate that SERS-based aptasensors hold great promise for development into rapid, point-of-use antigen detection systems, enabling mass testing without any need for reagents or laboratory expertise and equipment.

SARS-CoV-2 spike protein detection through a plasmonic D-shaped plastic optical fiber aptasensor

“…The specific biosensor has then been built on an SPR in POFs device and optical measurements confirmed the specific protein binding in a nanomolar range. The obtained ability to detect the SARS-CoV-2 Spike protein in the nanomolar range is similar to that recently achieved exploiting a similar bio-receptor on an SPR conventional probe [ 48 ] and a similar SPR platform in POFs combined with a specific MIP receptor layer [ 49 ].…”

“…Our limit of detection is not so far from that published by Stanborough and coworkers, who using our same aptamer sequence on a standard SPR instrument, observed that 5 nM spike protein can be clearly distinguished from the baseline [ 48 ]; however, they used a conventional SPR instrument where instrument setup and microfluidic are well optimized and also a different chemistry based on thiols.…”

Aptamer Applications in Emerging Viral Diseases

“…RT-PCR tests can detect the smallest amounts of virus RNA in the acute phases, but fail to distinguish between infectious or non-infectious virus. In addition, sample preparation is not trivial and requires advanced infrastructure and resources [ 110 , 111 ]. Serological tests on the other hand, such as ELISAs, can only detect antibodies that are present in the later stages of the infection.…”

Nanobiotechnology enabled approaches for wastewater based epidemiology

“…are present, paper sensors can be functionalized with specific recognition elements (e.g., proteins, antibodies, aptamers) for specific binding and detection [ 4 ]. Recently, SARS-CoV-2 spike proteins were detected at the ∼ 250 nM level by applying 10 μL of sample to oligonucleotide aptamers and Ag colloids immobilized onto polytetrafluoroethylene (PTFE) membrane filters [ 43 ]. In addition, Au coated polyethylene naphthalate (PEN) polymer substrate have been modified with aptamer DNA for detection of influenza A H1N1 virus at a 97 PFU/mL detection limit [ 44 ].…”