Effect of a Localized Oxygen-Releasing Hydrogel Sheet on Early-Stage Infarct Evolution in a Rat Photothrombotic Stroke Model: A Preliminary Study

Ischemic stroke triggers hypoxia, inflammation, and oxidative stress. Local oxygen delivery may prevent secondary injuries. Herein, we implanted a catalase-incorporated thiolated gelatin-based oxygen-releasing hydrogel sheet in a rat model of photothrombosis to evaluate early infarct attenuation and feasibility. Male Sprague-Dawley rats were allocated to four groups (n = 6/group): control at 24 h (G1), with hydrogel sheet at 24 h (G2), control at 72 h (G3), and with hydrogel sheet at 72 h (G4). Focal ischemia was induced with Rose Bengal and targeted illumination through a 6.0-mm cranial defect. A hydrogel sheet was applied to the cortex after surgery. The infarct burden was assessed by 2,3,5-triphenyltetrazolium chloride (TTC) staining and magnetic resonance imaging (MRI), while mRNA expression levels of tumor necrosis factor-α (TNF-α), brain-derived neurotrophic factor (BDNF), and superoxide dismutase (SOD) were measured by quantitative reverse transcription PCR. Body weight was monitored as a safety measure. At 24 h, TTC showed a significant infarct reduction in G2 compared with G1. At 72 h, infarct measures did not differ significantly between G4 and G3. MRI and gene expression analyses did not show statistically significant between-group differences and are presented as exploratory outcomes. Weight and perioperative status were similar across groups, indicating short-term tolerability. The hydrogel sheet was associated with reduced TTC-defined infarct burden at 24 h in this model; confirmatory studies will require larger, powered cohorts, longer follow-up with functional testing, and in vivo oxygen release profiling to optimize dose, placement, and exposure time.