Inorganic persistent luminescence materials: Emerging optical theranostic agents

The development of optical theranostics has brought new requirements for the diagnostic and therapeutic properties of optical theranostics agents (OTAs) in recent years. Inorganic persistent luminescence materials (IPLMs) have garnered considerable attention owing to their unique persistent luminescence (PersL). IPLMs offer unique advantages in diagnosis and treatment because of this PersL property, making them ideal candidates for optical theranostic applications. For example, using PersL for bioimaging and biosensing can avoid autofluorescence interference and provide extremely high detection sensitivity. PersL can be used as in vivo nanolights to continuously activate the photosensitizer for prolonged treatment. In addition, the theranostic applications of IPLMs have been substantially expanded by combining advanced features such as specific targeting, multimodal imaging, and drug delivery. In this review, we first introduce the current development in OTAs, basic concept of IPLMs, and IPLMs' characteristics as OTAs. Subsequently, we summarize the recent research progress in the design, synthesis, and surface engineering of IPLMs from the perspective of theranostic applications. Next, we describe the research on the application of IPLMs in bioimaging, therapy, and biosensing, and discuss the current status of toxicological studies on IPLMs. Finally, we provide our perspective on the prospects and challenges in this rapidly developing field.