A paper-based microfluidic platform for the on-site detection of pathogens in wastewater can detect viruses like SARS-CoV-2 and influenza from wastewater samples, providing results in less than 1.5 hours.
The device integrates a paper microfluidic platform with loop-mediated isothermal amplification (LAMP), a highly sensitive technique for amplifying viral RNA without the need for complex thermal cycling equipment. The platform is capable of detecting viral genetic material at concentrations as low as 10 copies per milliliter, a sensitivity comparable to polymerase chain reaction (PCR) tests. Unlike PCR, however, the LAMP-based approach eliminates the need for centralized laboratories and skilled technicians, making it accessible for on-site testing in community settings.
Credit: Science Museum Group
Copyright: Board of Trustees of the Science Museum
The “origami” microfluidic device is designed for ease of use. Wastewater samples are filtered using a simple syringe-based system, which removes impurities while concentrating the viral RNA. The samples are then subjected to the LAMP reaction on the paper device, where fluorescence indicates the presence of viral RNA. The results can be read using a mobile phone camera or a handheld UV light, enabling rapid, semi-quantitative analysis in the field.
The research team tested the device in real-world conditions by sampling wastewater from four quarantine hotels near London Heathrow Airport during the COVID-19 pandemic. Results from the paper device were compared with those from standard laboratory-based RT-qPCR assays. The paper device demonstrated high sensitivity and specificity for detecting the ORF1ab, S, and N genes of SARS-CoV-2, as well as genes associated with influenza A and B.
The field testing showed that the paper device could detect SARS-CoV-2 in community wastewater with similar accuracy to conventional RT-qPCR methods – without the logistical challenges of transporting samples to distant laboratories.
The researchers highlighted the potential of the paper device for future pandemic preparedness, emphasizing its scalability and adaptability. Indeed, the platform can be easily modified to detect other pathogens by changing the LAMP primers used in the assay, making it a versatile tool for monitoring a wide range of infectious diseases in both high- and low-resource settings.
“The sensor provides the advantages of low-cost materials and manufacturing processes, is easy to operate, and has low maintenance requirements – which is important when considering the situation in resource-poor regions (for example, lack of professionals and unstable power supply),” says Zhugen Yang, Professor of Biosensing and Environmental Health at Cranfield University, who led the development of the sentinel sensors. “The sensor is suitable for different user groups, such as health institutions, community organizations, as well as individuals.”
Commenting on the steps to widespread adoption for future pandemic preparedness, Yang says: “The technology must undergo rigorous testing and evaluation to ensure its accuracy, stability, and reliability under different conditions, providing a reliable basis for epidemic monitoring and prevention and control.” Yang also believes the technology needs to be automated and standardized – “so that functions can be expanded and upgraded according to actual needs.”
The Big Technical Challenges
With Zhugen Yang
What were the biggest technical challenges you faced in developing a sensor that is both cost-effective and sensitive enough to detect low viral loads in wastewater?
First, the sensor must have high sensitivity for the detection of ultra-low concentrations of viruses in wastewater. However, this often comes with specificity challenges also due to the impurities. Highly specific primers are essential to bind to the target sequence, enabling the distinction of the target virus from other similar pathogens and thereby enhancing sensitivity and specificity.
Second, the composition of wastewater is complex, with interfering factors such as organic matter, inorganic matter, and microorganisms that can severely impact the accuracy and stability of the sensor. Thus, optimizing the pretreatment of wastewater samples is essential to reduce non-specific adsorption and interference from other substances.
Third, environmental conditions (such as pH and salinity) in different wastewater collection areas can vary significantly. The sensor needs to maintain stable performance under diverse conditions to ensure accuracy and reliability.
Four, it is crucial to adopt low-cost materials and manufacturing processes and enable scale-up for mass production and consistency to achieve cost-effectiveness, enabling widespread deployment in resource-constrained regions.
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