A Pseudo‐Two‐Dimensional Reaction–Diffusion Model for Rational Design of Antibacterial–Antioxidant Ag– ZnO /Fucoidan Nanocomposites

ABSTRACT Reactive oxygen species (ROS)–generating nanocomposites exhibit strong antibacterial activity; however, uncontrolled ROS release often induces oxidative toxicity and limits their practical applicability. Achieving a rational balance between antimicrobial efficacy and antioxidant protection therefore remains a key challenge in the engineering design of ROS‐active materials. In this study, a pseudo‐two‐dimensional (P2D) reaction–diffusion model is developed to mechanistically describe ROS generation, transport, and scavenging in Ag–ZnO/Fucoidan nanocomposites. The framework embeds spatially segregated source–sink behavior into a computationally one‐dimensional domain by introducing a pseudo‐coordinate that represents Ag–ZnO catalytic sites and fucoidan scavenging regions. Site‐limited ROS generation with product inhibition, super‐linear scavenging kinetics within the fucoidan matrix, and composition‐dependent diffusivity suppression are incorporated to capture nonlinear feedback between reaction and transport processes. Model predictions are validated against independent experimental antibacterial data, including zone of inhibition and minimum inhibitory concentration, as well as antioxidant DPPH radical‐scavenging measurements without post hoc parameter fitting. The results reveal a strong inverse correlation between cumulative near‐surface ROS exposure and antibacterial performance ( R 2 = 0.97) and successfully reproduce the experimentally observed nonmonotonic scavenging behavior ( R 2 = 0.94). A sharp kinetic crossover in fucoidan loading ( ϕ * Fu ≈ 0.27) is identified, separating regimes of net ROS production and net ROS quenching and providing a mechanistic explanation for the coexistence of high antibacterial efficacy and reduced oxidative leakage. Overall, the proposed P2D framework offers a computationally efficient and physically interpretable strategy for the rational design and optimization of multifunctional ROS‐active nanocomposites in biomedical and related engineering applications.