For patients with drug-resistant focal epilepsy, excision of the epileptogenic zone is the most effective treatment approach. However, the surgery is less effective in the 15–30% of patients whose lesions are not distinct when visualized by magnetic resonance imaging (MRI). Here, we show that an intravenously administered MRI contrast agent consisting of a paramagnetic polymer coating encapsulating a superparamagnetic cluster of ultrasmall superparamagnetic iron oxide crosses the blood–brain barrier and improves lesion visualization with high sensitivity and target-to-background ratio. In kainic-acid-induced mouse models of drug-resistant focal epilepsy, electric-field changes in the brain associated with seizures trigger breakdown of the contrast agent, restoring the T1-weighted magnetic resonance signal, which otherwise remains quenched due to the distance-dependent magnetic resonance tuning effect between the cluster and the coating. The electric-field-responsive contrast agent may increase the probability of detecting seizure foci in patients and facilitate the study of brain diseases associated with epilepsy.

对于耐药性局灶性癫痫患者，致痫区切除是最有效的治疗方法。然而，对于 15% 至 30% 的通过磁共振成像 (MRI) 显示病变不明显的患者，手术效果较差。在这里，我们展示了一种静脉注射的 MRI 造影剂，由顺磁性聚合物涂层组成，包裹着超顺磁性的超顺磁性氧化铁簇，可以穿过血脑屏障，并以高灵敏度和目标背景比改善病变可视化。在红藻氨酸诱导的抗药性局灶性癫痫小鼠模型中，与癫痫发作相关的大脑中的电场变化触发造影剂分解，恢复 T1 加权磁共振信号，由于团簇和涂层之间的距离相关的磁共振调谐效应，否则它会保持淬火状态。电场响应造影剂可能会增加检测患者癫痫病灶的可能性，并促进与癫痫相关的脑部疾病的研究。