Retrieval of material from vessel lumens can be improved by electrically enhancing attachment of the material to the thrombectomy system. The system can an interventional element configured to be delivered to a treatment site and to be electrically coupled to an extracorporeal power supply. The interventional element can be surface treated (e.g., via electrochemical anodization) to achieve a desired electrical conductivity gradient over the surface of the interventional element. The electrical conductivity gradient can result in a more desirable surface charge distribution upon delivery of electrical current to the interventional element.