The global sanitary crisis caused by the emergence of the respiratory virus SARS-CoV-2
and the COVID-19 outbreak has revealed the urgent need for rapid, accurate, and
affordable diagnostic tests to broadly and massively monitor the population in order to
properly manage and control the spread of the pandemic. Current diagnostic techniques
essentially rely on polymerase chain reaction (PCR) tests, which provide the required
sensitivity and specificity. However, its relatively long time-to-result, including
sample transport to a specialized laboratory, delays massive detection. Rapid lateral
flow tests (both antigen and serological tests) are a remarkable alternative for rapid
point-of-care diagnostics, but they exhibit critical limitations as they do not always
achieve the required sensitivity for reliable diagnostics and surveillance.
Next-generation diagnostic tools capable of overcoming all the above limitations are in
demand, and optical biosensors are an excellent option to surpass such critical issues.
Label-free nanophotonic biosensors offer high sensitivity and operational robustness
with an enormous potential for integration in compact autonomous devices to be delivered
out-of-the-lab at the point-of-care (POC). Taking the current COVID-19 pandemic as a
critical case scenario, we provide an overview of the diagnostic techniques for
respiratory viruses and analyze how nanophotonic biosensors can contribute to improving
such diagnostics. We review the ongoing published work using this biosensor technology
for intact virus detection, nucleic acid detection or serological tests, and the key
factors for bringing nanophotonic POC biosensors to accurate and effective COVID-19
diagnosis on the short term.
A method for quantifying biologically relevant long-non-coding RNAs by combining nucleic acid amplification via asymmetric polymerase chain reaction (PCR) with label-free PCR product detection using silicon photonic microring resonator arrays is described. This approach eliminates the need for fluorophores, which presents a limit for spectral multiplexing in conventional qPCR methods, and rather offers potential for much higher levels of plexity by spatially arraying capture probes. Here, we demonstrate the potential of this technique to detect two differentially expressed lncRNA transcripts and an internal control mRNA transcript in different commercial human tissue specimens, as well as in a glioblastoma cell line using only nanogram input amounts of total RNA. The obtained results were validated using single-plex RT-qPCR and found to be in good agreement, demonstrating the potential of this technique for lncRNA quantification applications.
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