Emerging strategies of engineering retinal organoids and organoid-on-a-chip in modeling intraocular drug delivery: Current progress and future perspectives.

[Display omitted] • Advance in engineering retinal organoids (ROs) and organoid-on-a-chip (ROoC) and their recent challenges are summarized. • Recreating microphysiological environments of retina in vitro with microvascular and multi-tissue interactions is detailed. • The integration of biosensors in chip platform for in situ and real-time monitoring of ROs and ROoC platforms is emphasized. • Modeling of intraocular drug delivery and development of innovative strategies based on ROs and ROoC platforms is anticipated. Retinal diseases are a rising concern as major causes of blindness in an aging society; therapeutic options are limited, and the precise pathogenesis of these diseases remains largely unknown. Intraocular drug delivery and nanomedicines offering targeted, sustained, and controllable delivery are the most challenging and popular topics in ocular drug development and toxicological evaluation. Retinal organoids (ROs) and organoid-on-a-chip (ROoC) are both emerging as promising in-vitro models to faithfully recapitulate human eyes for retinal research in the replacement of experimental animals and primary cells. In this study, we review the generation and application of ROs resembling the human retina in cell subtypes and laminated structures and introduce the emerging engineered ROoC as a technological opportunity to address critical issues. On-chip vascularization, perfusion, and close inter-tissue interactions recreate physiological environments in vitro, whilst integrating with biosensors facilitates real-time analysis and monitoring during organogenesis of the retina representing engineering efforts in ROoC models. We also emphasize that ROs and ROoCs hold the potential for applications in modeling intraocular drug delivery in vitro and developing next-generation retinal drug delivery strategies. [ABSTRACT FROM AUTHOR]