Coronavirus (COVID-19) Testing: Smartphone-based rapid, inexpensive and portable method
Image: https://www.abc.net.au/news/2020-04-16/coronavirus-testing-expands-who-can-get-tested-and-where/12153004
Since the epidemic of COVID-19 in December
2019, the scientific community began to search and discover the rapid, robust,
portable and inexpensive ways to detect the pathogen from COVID-19 patients. As
of now, the scientific and diagnostic community is completely relying on highly
reliable but expensive, resources and time-consuming method of pathogen
detection; that is a real-time polymerase chain reaction (RT-PCR). Keeping in
mind the need of rapid, smart and inexpensive way of pathogen detection; a
multi-institutional team of scientists from the United States of America has
developed a portable device that made this puzzle so simple to solve.
Two
scientist from the University of Illinois at Urbana-Champaign, USA, professor Brian
Cunningham from department of electrical and computer engineering and professor
Rashid Bashir from department of bioengineering, lead the study and has
published their study in the journal Lab
on Chip. In this study, scientists developed the smartphone-based
rapid deoxyribonucleic acid (DNA) testing cartridge; which can efficiently
perform the same test as PCR machines does, within 30 minutes and presents the results
in a smartphone application for could sharing. The whole process is really
robust and rapid which may take less than an hour.
Before
we jump into detail of this smart cartridge, let’s have a really quick glance
over RT-PCR working principle.
Principle
of RT-PCR working
Real
time-PCR is a variant of conventional PCR and runs multiple processes
step-by-step. Real time PCR can be performed from DNA or RNA. RT-PCR through
RNA has two main steps. In the first step, prior to conversion of ribonucleic
acid (RNA) to complementary DNA (cDNA), RNA extraction is done and then cDNA
synthesis is carried out. In the second step, cDNA is used to amplify the DNA
fragments by repeated heating/cooling cycles at different temperature. RT-PCR
system detects the amplified DNA with specific DNA binding dye (SYBER Green or
any other) (Biosystems,
2014).
Principle
of Smartphone-based cartridge
Smartphone-based
cartridge uses a little different procedure to amplify the DNA fragments from the
collected samples. The cartridge contains essential chemicals for the lysis of
samples and amplification of DNA fragments from lysed clinical samples. In this
cartridge, clinical sample is lysed with lysis buffer and then DNA present in
the lysate is used as template for on-chip amplification of DNA by using
isothermal approach at 60-65°C for approximately 30 minutes. The smartphone
uses an application to detect DNA amplification by green florescence when
illuminated with blue LED light.
The
concept of using isothermal approach is to minimize the heat/cool cycles, save
time and resources for the reaction settings. Each micro-capillary on the
cartridge uses only minute amount of reaction mixture of 1 µl (1000 µl = 1 L). While
the idea of involving smartphone was to detect rapidly, make the device
portable, easy & ready to use and inexpensive as compared to RT-PCR system
(approximate costs $ 18,000- 23,000).
Purpose
of current study
This
study was aimed to detect the genomic DNA from viral and bacterial pathogens of
equine related respiratory disease of horses. These pathogens can only cause
severe respiratory disease in horses but fortunately not harmful to human,
scientists said. This team has successfully amplified and detected the
pathogenic DNA within clinically approved ranges, using nasal swabs of horses. Which
means that this model can also be designed for the detection of COVID-19 viral
DNA with some important amendments, for human as well. As this model can also
use a multiplex (several genes) amplification, so, multiple pathogens can be
detected at the same time which ultimately increases the power of this testing
system.
How
this model could benefit the community?
The
cartridge can be mounted on the camera of smartphones and the nasal swab
extracts or blood samples can be entered into the cartridge to test the sample.
By using this model, it can be easily suggested that who should continue to quarantine
him/herself or ready to join the society with certain precautionary measures.
This model can also be helpful on several occasion, as on airports to test the people
to tell either one should be allowed to take flight e.g., to attend conference
or concert, for business deal or whatever the purpose is, or not. Negative
results could be used to allow the people to join the conference or concert
etc.
As
this model uses the smartphones, the results can easily be monitored by
government bodies for policy making or physicians to guide people what to do
next? This could also be very handful in self-testing for COVID-19 during
quarantine, sharing test results with doctor rather than sending samples to
clinical laboratory for testing. It will also reduce the cost of COVID-19
testing, it there is need of bulk testing.
Closing
note
Overall
this model presents the best solution for the bulk testing of COVID-19 at this
time. This cartridge lacks some of the reagents or settings for testing COVID-19
of human clinical samples. As SARS-CoV-2 is an RNA virus, so the RNA must be
converted to cDNA and then RT-PCR for complete testing. Scientists are working
to ensure that cartridge contains all the reagents for one-step COVID-19
testing; which would contain all the essential reagents to convert RNA to cDNA
and then amplification process.
Author’s
information
Muhammad
Numan has written the
summary of this scientific publication referenced as Sun et al., 2020.
References
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