Polyrotaxane-containing hydrogels for label-free detection of C-reactive protein (CRP) via diffraction gratings

Abstract

Hydrogels have been investigated as label-free (LF) holographic biosensors thanks to their ability to change the hydrogel structure when interacting with specific analytes. In this work, we report the development of hydrogel-based holographic diffraction gratings incorporating polyrotaxanes as crosslinkers and phosphorylcholine for the selective and label-free detection of C-reactive protein (CRP), which is a key biomarker for cardiovascular disease, sepsis, and inflammatory disorders. Phosphorylcholine-functionalized monomers were added to the hydrogel composition for specific CRP recognition, while methylated polyrotaxanes (PR-Met) were incorporated to enhance mechanical stability and elasticity. The materials were characterized via scanning electron microscopy (SEM), swelling studies, and mechanical compression tests, demonstrating improved robustness compared to conventional hydrogels. Fluorescence-based assays confirmed the specificity of CRP binding, and diffraction efficiency measurements enabled direct quantification with a limit of detection (LOD) of 0.3 mg L⁻¹. The system was successfully tested using certified human serum samples, achieving recovery rates within the clinically accepted range. This study highlights the potential of polyrotaxane-mediated mechanically enhanced hydrogels as a promising platform for biomolecular sensing, offering improved sensitivity, selectivity, and mechanical resilience for future clinical applications.