Bilayer Hydrogel Sheet-Type Intraocular Microrobot for Drug Delivery and Magnetic Nanoparticles Retrieval.

By virtue of minimum invasiveness and driving ability using a magnetic field, drug delivery with the aid of a microrobot has an inherent potential for targeted treatment for the eye. The use of microrobots, however, has the limitation of leaving magnetic nanoparticles (MNPs) in the eye that can cause side effects. In this study, a bilayer hydrogel microrobot capable of retrieving MNPs after drug delivery is proposed that overcomes the limitations of existing microrobots. The bilayer hydrogel microrobot is composed of an MNPs layer and a therapeutic layer. Upon applying an alternating magnetic field (AMF) at the target point, the therapeutic layer is dissolved to deliver drug particles, and then the MNPs layer can be retrieved using a magnetic field. The targeting and MNPs retrieval tests validate the drug delivery and MNPs retrieval ability of the microrobot. The ex vivo bovine vitreous and in vitro cell tests demonstrate the potential for the vitreous migration of the microrobot and the therapeutic effect against retinoblastoma Y79 cancer cells. This bilayer hydrogel sheet-type intraocular microrobot provides a new drug delivery paradigm that overcomes the limitations of microrobot by maintaining the advantages of conventional microrobots in delivering drugs to the eye and retrieving MNPs after drug delivery.