The best of both worlds – protection and detection
Nonwovens as filters for face-masks, as well as other critical items of PPE, have proved essential in the global fight against Covid-19.
What is less recognised is that nonwoven materials also serve as the cellulosic carriers and absorbent reservoirs in diagnostic kits such as the latest lateral flow tests (LFTs), which are now being viewed as essential in opening up countries again, as vaccination programmes gather pace. They will also serve as early-warning systems against new strains and future outbreaks.
The simple-to-manufacture LFTs employ a nano-colloidal gold testing method already used in diagnostics prior to the pandemic and results have shown a huge increase in the effectiveness and accuracy of testing with this technology. The kits can rapidly produce a positive result even when a lower level of antigens of the virus is present in the sample which is vital for finding asymptomatic individuals and potential ‘super-spreaders’.
INDEX™ exhibitor Ahlstrom-Munksjö has been developing a range of components for rapid test kits for decades. Since the beginning of the pandemic, the company has been supporting diagnostics companies in their efforts to develop efficient Covid-19 screening devices.
Specifically designed for use in flow-through and lateral flow assays, its ReliaFlow portfolio includes, sample pads for blood, saliva and other liquid samples, a range of conjugate release pads from which manufacturers can choose the best solution for different applications, as well as absorbent pads to ensure proper flow.
“We’re now seeing rapid mass testing used in many different locations, particularly, for example, in trying to keep aircraft free of infected passengers, or in looking after major events,” said World Health Organisation Special Envoy David Nabarro. “Using LFTs will keep economies open, health systems safe and allow audiences to attend entertainment and sporting events.”
Innova Medical – the world’s largest manufacturer of LFTs, headquartered in Toronto, Canada – produced more than 10 million test kits daily but is now ramping this up to 50 million and its rivals are expected to follow suit with expansion programmes.
Meanwhile, combining both protection with detection, a colour-changing test strip that can be attached to a nonwoven face mask and be used to detect SARS-CoV-2 in a wearer’s breath or saliva has been developed at the University of California San Diego,
The development project, which received $1.3 million from the US National Institutes of Health (NIH), is aimed at providing simple, affordable and reliable surveillance of Covid-19 infections that can be repeated daily and easily implemented in resource-poor settings.
“In many ways, masks are the perfect wearable sensor for our current world,” says Jesse Jokerst, professor of nanoengineering at the UC San Diego Jacobs School of Engineering. “We’re taking what many people are already wearing and repurposing them, so we can quickly and easily identify new infections and protect vulnerable communities.”
The test strips, which can be affixed to any mask, are being designed to detect the presence of protein-cleaving molecules, called proteases, produced from infection with the virus.
The idea is that as the user breathes through the mask, particles – including SARS-CoV-2 proteases if the user is infected – will accumulate in the test strip. At the end of the day or during a mask change, the user will conduct the test. The test strip is equipped with a blister pack that the user squeezes, releasing nanoparticles that change colour in the presence of the relevant proteases. A control line on the test strip will show what a positive result should look like. This process is similar to checking the results of a home pregnancy test.
“Think of this as a surveillance approach, similar to having a smoke detector in the house,” said Jokerst. “It would just sit in the background every day and if it gets triggered, then you know there’s a problem and that’s when you would look into it with more sophisticated testing,”
The test strips can be easily mass-produced via roll-to-roll processing to keep costs down to minimum.
“We want this to be affordable enough for daily testing,” Jokerst says. “This would allow facilities at high risk such as group homes, prisons, dialysis clinics and homeless shelters to monitor for new infections earlier and more frequently, to reduce spread.”