Periodic Reporting for period 1 - NELLAFLOW (New generation of low-cost Lateral Flow Assays (LFAs) coupled with paper-based electrical gas sensors: An application study for the rapid determination of Salmonella in food)
Reporting period: 2022-02-01 to 2025-01-31
Over 420,000 people die each year due to contaminated foodstuffs, yet conventional methods for determining pathogens in food require lengthy procedures, lab-based facilities and trained staff. Lateral Flow Assays (LFAs) are a powerful alternative method for pathogen testing because they are rapid, simple to use, and amenable to Point-of-Need. Current LFAs available in the market only provide binary (yes/no) or semiquantitative responses, lacking the rapidness and sensitivity required for food monitoring due to the limitations of the colorimetric transduction. Many efforts are focused on addressing the lack of quantification on this type of devices by combining LFAs and electrical detection, but the integration of metallic electrodes on nitrocellulose membranes remains a bottleneck. The NELLAFLOW project sought to develop a rapid, quantitative test for the determination of pathogens in food by the integration of paper-based electrical gas sensors (PEGS) as detectors into LFAs. PEGS have already proven to be highly sensitive towards water-soluble gases. They exploit the intrinsic hygroscopic characteristics of cellulose paper and the changes in its ionic conductance in the presence of water-soluble gases.
To fulfil the overall objective, the following technological goals were approached: design and optimization of PEGS for integration into LFA systems; design of an immunoassay for pathogen determination using gas detection; application of the gas sensor-based LFA prototype for real sample testing.
Through a multidisciplinary approach (biomolecular engineering, analytical chemistry, printed electronics, microbiology) NELLAFLOW aimed to tackle a key problem in the food industry with an innovative, versatile technology that can be easily transferred to other application fields.
To fulfil the overall objective, the following technological goals were approached: design and optimization of PEGS for integration into LFA systems; design of an immunoassay for pathogen determination using gas detection; application of the gas sensor-based LFA prototype for real sample testing.
Through a multidisciplinary approach (biomolecular engineering, analytical chemistry, printed electronics, microbiology) NELLAFLOW aimed to tackle a key problem in the food industry with an innovative, versatile technology that can be easily transferred to other application fields.
During the first part of the project, the researcher worked towards the integration of the gas sensors into LFA platforms. The sensors were first combined with nitrocellulose membranes to assess their capacity to measure gas from liquid samples added to the strips. To improve the understanding of the detection mechanism, a colorimetric probe-based system was introduced. The gas sensors were able to detect target gas directly from standards solutions, and as the product of enzymatic reactions.
The researcher then focused on the integration of the biological recognition materials (antibodies), the amplification element (enzyme and substrate) and flow-enhancing components (surfactants, protein-blocking agent) into the LFA platform with gas sensor detection. To minimize the risk and accelerate the development of the integrated system, a model immunoassay, including Immunoglobulin G (IgG) and commercial antibodies, was used as a proof-of-concept. The antibodies were modified accordingly to facilitate the detection of the target gas. This represented the first demonstration of the integration of gas sensors as detectors for LFA.
The use of gas sensors presented multiple challenges, though. For those reasons, the potential of integrating LFA and liquid-based sensors rather than gas sensors was also explored. This deviation of the project resulted in an innovative diagnostics platform, which is currently being assessed for further IP protection and commercialization.
At the final stage of the project, the researcher studied the potential of using gas sensors for food monitoring. The safe integration of gas sensors into packaging without compromising sensitivity, response rate, and stability remains a challenge. The researcher led the study of multiple protective membranes that could be used for the encapsulation of gas sensors into food packaging, with a particular focus on bagged spinach. The performance of the sensors to monitor spinach spoilage was evaluated by correlating the outputs with the microbial counts of the samples. Finally, the sensor system integrated with near-field communication (NFC)-enabled technology operated by a smartphone was demonstrated for the wireless, batteryless detection of spoiled samples. The innovation of this part of the project is currently being assessed for further commercialization.
The global objective of the project was achieved, and the integration of gas sensors as detectors for LFA systems was demonstrated. Actions to properly disseminate and exploit the project results were additionally undertaken. The findings of the project were presented at national and international conferences and led to 5 peer-reviewed publications.
The researcher then focused on the integration of the biological recognition materials (antibodies), the amplification element (enzyme and substrate) and flow-enhancing components (surfactants, protein-blocking agent) into the LFA platform with gas sensor detection. To minimize the risk and accelerate the development of the integrated system, a model immunoassay, including Immunoglobulin G (IgG) and commercial antibodies, was used as a proof-of-concept. The antibodies were modified accordingly to facilitate the detection of the target gas. This represented the first demonstration of the integration of gas sensors as detectors for LFA.
The use of gas sensors presented multiple challenges, though. For those reasons, the potential of integrating LFA and liquid-based sensors rather than gas sensors was also explored. This deviation of the project resulted in an innovative diagnostics platform, which is currently being assessed for further IP protection and commercialization.
At the final stage of the project, the researcher studied the potential of using gas sensors for food monitoring. The safe integration of gas sensors into packaging without compromising sensitivity, response rate, and stability remains a challenge. The researcher led the study of multiple protective membranes that could be used for the encapsulation of gas sensors into food packaging, with a particular focus on bagged spinach. The performance of the sensors to monitor spinach spoilage was evaluated by correlating the outputs with the microbial counts of the samples. Finally, the sensor system integrated with near-field communication (NFC)-enabled technology operated by a smartphone was demonstrated for the wireless, batteryless detection of spoiled samples. The innovation of this part of the project is currently being assessed for further commercialization.
The global objective of the project was achieved, and the integration of gas sensors as detectors for LFA systems was demonstrated. Actions to properly disseminate and exploit the project results were additionally undertaken. The findings of the project were presented at national and international conferences and led to 5 peer-reviewed publications.
NELLAFLOW demonstrated the development of a new class of quantitative LFAs based on gas-phase analysis. By combining the innovative technology of paper-based electrical gas sensors with traditional LFA diagnostic tools, NELLAFLOW provided a ground-breaking solution to a long-term issue. Measuring gas will broaden the possibility of on-site, rapid quantitative determination to multiple applications, such as food allergies, health diagnostics and environmental monitoring. The versatility of the detection platform will enable its rapid adaptation to multiple biomarker detection by changing the biomolecular recognition element.
PEGS are easy to fabricate (e.g. screen-printing), work at room temperature and are suitable for integration into a disposable, wireless and batteryless Near-Field communication (NFC) platform. They provide the possibility of reader-less signal detection using a mobile app, as was demonstrated here with the electrodes on nitrocellulose membranes (for LFA) and the monitoring of food spoilage.
The integrated system comprising gas sensors and LFAs is currently being assessed for IP protection and further commercialization. The alternative studies of electrochemical detection of LFA and the package integration of PEGS to monitor food spoilage are also under consideration for commercial applications. The impact of their application might be massive, particularly for the food industry. Food spoilage and waste pose formidable challenges to achieving a sustainable and efficient food supply chain. The possibility of real-time monitoring of food spoilage and detection of food pathogens will be a game-changer.
PEGS are easy to fabricate (e.g. screen-printing), work at room temperature and are suitable for integration into a disposable, wireless and batteryless Near-Field communication (NFC) platform. They provide the possibility of reader-less signal detection using a mobile app, as was demonstrated here with the electrodes on nitrocellulose membranes (for LFA) and the monitoring of food spoilage.
The integrated system comprising gas sensors and LFAs is currently being assessed for IP protection and further commercialization. The alternative studies of electrochemical detection of LFA and the package integration of PEGS to monitor food spoilage are also under consideration for commercial applications. The impact of their application might be massive, particularly for the food industry. Food spoilage and waste pose formidable challenges to achieving a sustainable and efficient food supply chain. The possibility of real-time monitoring of food spoilage and detection of food pathogens will be a game-changer.