Single-atom Pt doped nanoceria for enhanced cell phagocytosis and nanozyme activities in keratitis immune regulation

During keratitis treatment, oxidative stress and inflammation often result in corneal neovascularisation, scarring, and reduced light transmittance. In this study, single-atom Pt/CeO₂ is synthesized, exhibiting significantly enhanced catalase-like and superoxide dismutase-like activities for the elimination of superoxide anions (•O₂^-), hydrogen peroxide (H₂O₂), and hydroxyl radicals (•OH). Doping single-atom Pt onto CeO₂ increases the Ce³⁺ concentration in the Ce³⁺/Ce⁴⁺ ratio from 39.12% to 58.66%, as confirmed by electron spin resonance, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. In vitro studies demonstrate that single-atom Pt/CeO₂ effectively reduces intracellular ROS levels in H₂O₂-activated human corneal epithelial cells. Additionally, it exerts an anti-inflammatory effect on LPS-stimulated RAW264.7 macrophages, significantly decreasing the expression of interleukin-1β, interleukin-6, and tumour necrosis factor-α. In vivo, in an LPS-induced keratitis animal model, single-atom Pt/CeO₂ accelerates corneal ulcer healing and preserves corneal light transmittance, attributed to its anti-inflammatory properties, enzyme-like activities, and ability to promote cell migration. This study offers a novel approach for treating various inflammatory and autoimmune diseases.