Two-Dimensional Dissipative Paper-Based Immunoassay with Oxygen Vacancy-Enriched CeO₂ Nanozymes for Portable Cancer Screening

Rapid, low-cost, and efficient cancer screening in developing regions is urgently needed. In this work, we proposed a peroxidase-like reaction system centered on endogenous Ce coordination differences by exploring the surface oxygen overflow of modulated Ce-O-Ce coordination, thus realizing a two-dimensional nanozyme-linked immunosorbent assay (NLISA) on paper. As a result of facet-selective O rearrangement and spillover, the CeO₂(100) facet exhibited a high O vacancy environment, providing potential catalytic sites for substrate adsorption and intermediate transfer and improving the electronic structure of the surrounding Ce. It was noteworthy that the spontaneous rearrangement of the (100) facets dominated the CeO₂ nanoscale with the highest value of the catalytic constant (5.15 × 10³), which corresponded to more than 5 times that of the catalytic efficiency of the (110) facets. As a proof-of-concept, we employed a two-dimensional-dissipative NLISA on-paper chromogenic system for cancer screening based on the output of biological to chemical signals. This work opens a new avenue for the construction of efficient enzyme-like catalytic reactions and commercial cancer screening platforms by exposing the Ce-O coordination environment.