Comparison of antibody immobilization on renewable nanocrystals for paper-based detection

Introduction Polysaccharide-based nanomaterials offer renewable and tunable platforms for biosensing applications. This study compares the physicochemical properties and biosensing performance of cellulose nanocrystals (CNCs), chitosan nanocrystals (ChNCs), and CNC/chitosan (CNC/ Ch) composites as supports for human CD66e (CEACAM5) antibodies, an established biomarker for epithelial cancers. Methods The materials were comprehensively characterized using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), ζ-potential measurements, hydrodynamic diameter analysis, and surface chemistry profiling to elucidate the role of molecular composition, surface charge, and hydration behavior on antibody immobilization. Antibody‐antigen interactions were quantified using quartz crystal microbalance with dissipation monitoring (QCM-D) and multi-parameter surface plasmon resonance (MP-SPR), enabling real-time evaluation of binding kinetics and saturation behavior across antigen concentrations. Results CNC/ Ch composites demonstrated a less variable antigen-binding response compared to individual CNC and ChNC supports, likely due to the synergistic interplay of cationic chitosan at the interface and the high surface area and structural stability of CNCs. Preliminary paper-based prototype tests validated the composite’s signal response in a low-cost, field-deployable format, demonstrating its translational potential for rapid diagnostic development. Discussion This work establishes structure‐function relationships among biopolymer nanocrystals in biosensing contexts as promising platforms for antibody-based cancer diagnostics and paper-based rapid detection testing applications. Future work should focus on optimizing paper/nanocrystal interface, impact of complex carrier matrices, and specificity and selectivity limits.