A light-controlled hydrogel for regulating oxidative stress in the treatment of psoriasis

Psoriasis is a common chronic autoinflammatory skin disease characterized by excessive proliferation of keratinocytes and marked thickening of the stratum corneum. The condition is often recurrent and difficult to cure, and its development is closely associated with redox imbalance. Excessive accumulation of reactive oxygen species (ROS) at the lesional sites drives inflammatory responses. Additionally, the impaired epidermal barrier in psoriatic lesions renders the skin susceptible to secondary bacterial infections, which further exacerbates the disease. However, elevated ROS also possesses potential therapeutic effects by inducing keratinocyte apoptosis and inhibiting epidermal hyperplasia. Achieving controllable synergy between ROS generation and elimination remains a challenge. Here, we develop a light-controlled hydrogel for staged psoriasis treatment. The hydrogel integrates Chlorella for ROS scavenging and silver‑zinc oxide heterojunction nanoparticles (Ag@ZnO) for photocatalytic ROS generation, forming a composite system denoted as Chl-Ag@ZnO/C-P (Chlorella and Ag@ZnO‑loaded carboxymethyl chitosan/polyvinyl alcohol hydrogel). In the initial dark phase, Chlorella scavenges pathological ROS to alleviate inflammation. Upon light irradiation, Ag@ZnO generates therapeutic ROS to induce keratinocyte apoptosis, while Chlorella simultaneously produces oxygen to enhance the photodynamic effect. This light-controlled bidirectional ROS regulation enables sequential anti-inflammatory and pro-apoptotic actions. In an IMQ-induced psoriasis mouse model, the hydrogel reduced epidermal thickness, decreased inflammatory cytokines (IL-17A, TNF-α), and restored ROS levels. The results demonstrate that this hydrogel system regulates oxidative stress in a staged manner for psoriasis treatment.