Chemiluminescence (CL) is a widely used detection technique in biosensing due to its high sensitivity, simplicity of analysis and low cost. These characteristics make it commonly used to quantify hydrogen peroxide (H₂O₂) by carrying out its reaction with luminol in the presence of the horseradish peroxidase enzyme (HRP). Hydrogen peroxide is a clinically relevant biomarker since it appears to be involved in numerous pathologies including diabetes, cancer, Parkinson’s disease, Alzheimer’s disease and cardiovascular and neurodegenerative disorders. In addition, H₂O₂ is a reaction product of various oxidases such as glucose oxidase ¹ and, therefore, can be used to indirectly quantify the substrates of these enzymes. Hydrogels are hydrophilic, highly water-swellable polymer networks that have become of great interest in the development of biosensors, owing to their high biocompatibility and ability to incorporate foreign substances while preserving a benign environment for biosensing. Due to the 3D porous structure of hydrogels, which increases the surface area of these materials, it is possible to load large amounts of recognition bioelements while maintaining the native structure of the biomolecules². A CL guanosine-derived hydrogel was prepared via the simultaneous incorporation of luminol and hemin. The self-assembled hydrogel consisted of K⁺-stabilized hemin/G-quadruplex structures, showing significant peroxidase-like activity to the H₂O₂-mediated oxidation of luminol³. After adding H₂O₂, the generated CL signal lasts for several minutes and is intense enough to be captured via smartphone’s CMOS camera. As a proof of principle, this biomaterial was also used for the indirect detection of glucose in artificial serum samples after the incorporation of glucose oxidase into the hydrogel. The sensor showed a linear response with an estimated limit of detection of 50 µmol L^-1 (equivalent to 5 nmol of glucose)⁴.

References

[1] Calabria et al. Analytical Biochemistry (2020) 600:113760.

[2] Buenger et al. Progress in Polymer Science (2012) 37.12: 1678-1719

[3] Ye et al. Talanta (2021) 230:122351.

[4] Calabria et al. Biosensors (2023) 13.6:650