Investigation of Methacryloyl-Modified Gelatin-Based Hydrogels for Inkjet-Printed Biosensors and Their Adherence to Polyethylene Terephthalate and Oriented Polypropylene Substrates

The COVID-19 pandemic has highlighted the need for rapid, simple, and cost-effective point-of-care testing (POCT) methods for pathogen detection. Hydrogel-based biosensing has emerged as an increasingly popular approach, offering advantages such as reagent storage and multiplexing capabilities. In this study, we have functionalized different polymer substrates to ensure an adequate adherence of methacryloyl-modified gelatin-based hydrogel spots that function as biosensors. Different hydrogel formulations were tested for their suitability in a point-of-care testchip. Our findings demonstrate the good adherence properties of amino-functionalized and subsequent methacrylated polymer materials, specifically polyethylene terephthalate (PET) and oriented polypropylene (OPP), when used as substrates for hydrogel biosensors. Moreover, we successfully identified an optimal formulation for the hydrogel ink, consisting of amino-functionalized methacryloyl-modified gelatin with a biopolymer content of 3.5% (w/w) and a photoinitiator content of 0.0875%. This formulation not only enables printing with a piezoelectric 2D printer but also exhibits excellent hydrogel stability and adherence to the functionalized substrates. These results contribute to the development of reliable and efficient POCT methods for pathogen detection, addressing the limitations of current diagnostic capabilities. The study emphasizes inkjet-based functionalization, with comprehensive characterization of printability including viscosity, surface tension, and density, and provides expanded methodological details to ensure reproducibility. Practical application: This study demonstrates the successful functionalization of PET and OPP polymers as substrates for point-of-care test chips, paving the way for advanced diagnostic solutions. By amino-functionalization and methacryloylation of the surfaces, covalent bonding with biosensors was achieved, ensuring stability and adherence. A methacryloyl-modified gelatin-based hydrogel ink, optimized for piezoelectric printing, was identified for biosensor fabrication. The selected ink minimizes fluorophore quenching, preserving biosensor sensitivity. Among the tested materials, OPP showed superior adherence due to its non-polar characteristics. These findings enable the creation of multiplexed test chips capable of detecting multiple pathogens simultaneously, addressing a crucial gap in rapid and reliable diagnostics. Although the hydrogel-based biosensors have not yet been tested with encapsulated LAMP, this integration marks the next step toward fully functional point-of-care testing. Ultimately, this research advances the development of robust diagnostic platforms, with applications in healthcare settings for timely pathogen identification and disease management.