Toxicity of the Covalent Organic Framework Material TpPa to Zebrafish

Covalent organic frameworks (COFs) show great potential in environmental remediation, yet the aquatic safety of TpPa (Tp = 1,3,5-triformylphloroglucinol, Pa = p-phenylenediamine), a typical COF, remains unclear. This study employed zebrafish (Danio rerio) to evaluate the environmental toxicity of TpPa and elucidate molecular mechanisms. Zebrafish embryos were exposed to 0–50 mg/L TpPa for 120 h, and developmental toxicity, oxidative stress, and physiological and molecular responses were investigated. Results demonstrated that TpPa exposure exerted concentration- and time-dependent effects. Mortality and malformation rates increased significantly from 5 mg/L, accompanied by reduced body length. The hatching rate showed a biphasic pattern, increasing with concentration at 48 h and decreasing with concentration at 120 h. Spontaneous movement was elevated at 50 mg/L, while heart rate increased dose-dependently starting from 5 mg/L at 48 h and from 1 mg/L at 72 h. Mechanistically, TpPa induced oxidative stress via reactive oxygen species accumulation and impaired the activities of both superoxide dismutase and catalase. These effects activated the p53-mediated apoptotic pathway, reduced the Bcl2/Bax ratio, and disrupted the GH/IGF growth axis and neuromotor regulatory pathways, ultimately causing developmental abnormalities. These findings provide critical data for the environmental safety assessment of TpPa, with direct relevance to establishing health monitoring protocols for COF-exposed aquaculture species.