Advancing sensitivity in paper-based diagnostics through fiber-attached polymer hydrogels and fluorescence detection

Global climate change, largely caused by human activities, poses significant challenges to various aspects of daily life. As a result, there is a growing awareness and adoption of eco-friendly practices, including the use of sustainable materials. Paper, a ubiquitous product utilized in various applications like packaging, hygiene, and even in advanced technological fields such as rapid test diagnostics, has seen a substantial increase in manufacturing in recent years. During the COVID-19 pandemic, the urgency to monitor population health and detect diseases at early stages has been intensified. Although nitrocellulose is commonly used in lateral flow devices, it has limitations in sensitivity and quantitative accuracy, particularly with low analyte concentrations.
This thesis represents an important initial step toward leveraging cellulose paper-based sheets as material of choice and fluorescence as a detection method, providing a deeper understanding in the field of paper-based diagnostics. Fluorescence offers the advantage of quantitatively determining a target probe, and detecting very low concentrations down to single digit numbers of molecules per µm². This contrasts with colorimetric analysis, which is more suitable for detecting higher analyte concentrations, such as in pregnancy tests, where usually binary results are sufficient. Moreover, the production of fiber-attached polymer hydrogels through the CHic (C, H-Insertion crosslinking) process via dip-coating and photochemical crosslinking has shown great promise in preventing the unspecific adsorption of undesired proteins. This addresses one of the main challenges that has limited research progress in this area in recent years.