Synthesis of persistent luminescence nanocage as both drug nanocarrier and autofluorescence-free bioimaging agent for the theranostics of bacterial infection

Persistent luminescent nanoparticles (PLNPs) have promising applications in long-term autofluorescence-free bioimaging due to the long and multiple activatable afterglow nature. Coating a mesoporous shell on the surface of PLNPs is a usual way to give PLNPs additional drug loading capability, but often leads to the reduction of afterglow luminescence. Herein, we report the fabrication of hyaluronic acid (HA) grafted near-infrared (NIR) PLNP with hollow nanocage structure (PLNC) without the need for an additional mesoporous coating for enhanced targeted autofluorescence-free afterglow imaging and nanocarrier mediated drug delivery to treat bacterial infection. The PLNC was prepared by calcinating solid Cr-doped MgSn(OH)6 in a reducing atmosphere. The as-synthesized PLNC not only gave better persistence luminescence than solid Cr-doped zinc gallogermanate PLNPs for autofluorescence-free bioimaging, but also possessed mesoporous structure as a nanocarrier for drug delivery. As a proof of concept, antimicrobial drug rifampicin (RIF) loaded amino modified PLNC (PLNC-NH2) was prepared for antimicrobial application. RIF loaded PLNC-NH2 was further modified with hyaluronic acid (HA) to make RIF loaded PLNC-HA selectively target to the site of bacterial infection. The developed RIF loaded PLNC-HA not only exhibited efficient antimicrobial therapeutic effects, but also provided autofluorescence-free targeted afterglow imaging of the infection site for guided therapy. This work provides a new simple way for the synthesis of mesoporous PLNCs with additional drug delivery function for nanotheranostic application.