Polylactic Acid (PLA)-Based Persistent Room-Temperature Phosphorescence Polymer Nanoparticles for Bioimaging

Recent advancements have focused on developing nanoscale persistent room-temperature phosphorescence (pRTP) structures to expand their applicability in biomedical fields. Traditional fabrication methods typically produce surface-coated core–shell pRTP nanoparticles composed of nonbiocompatible pRTP emitters at very high concentrations in the core. To overcome this limitation, polymeric pRTP nanosystems have been presented in this study as a promising alternative by embedding RTP molecules within the biocompatible polymer matrix, thereby significantly reducing the required concentration of RTP molecules. These polymer nanoparticles were fabricated using a biocompatible poly(lactic acid) (PLA) matrix by an effective microemulsion-based method. They exhibited similar pRTP properties to the traditional nanoparticles, showing comparable long-lasting phosphorescence with a lifetime of 118 ms even when the phosphorescent molecule content is below 2%. Moreover, the pRTP polymer nanoparticles with excellent biocompatibility and stability demonstrate interesting reversible photoactivated pRTP properties. They have been successfully applied for in vivo imaging with a high signal-to-noise ratio (SBR) of 2061, maintaining strong and long-lived phosphorescent emissions even for 20 min. These results highlight a viable approach to advancing the pRTP technology for biological applications.