Er3+-doped YbPO4 up-conversion porous nanospheres for UCL/CT bimodal imaging in vivo and chemotherapy

The combined use nanotechnology and medical technologies holds great promise for the development and improvement of various theranostic media. Here, based on a facile hydrothermal method, polyethyleneimine (PEI) functionalized YbPO4: Er up-conversion porous nanospheres (UCPSs) were fabricated, which combined the capabilities of up-conversion luminescence (UCL)/X-ray computed tomography (CT) bimodal imaging and drug delivery. The resulting hydrophilic PEI functionalized YbPO4: Er UCPSs (PEI-UCPSs) showed uniform morphology and high crystallinity. Moreover, PEI-UCPSs possessed high drug loading capacity because of their large specific surface area, which was confirmed by the Brunauer-Emmett-Teller (BET) experiment. Cellular experiments indicated that the PEI-UCPSs had low cytotoxicity and confirmed the performance of the pH-mediated cancer targeting of PEI-UCPSs@DOX. Importantly, because of the ideal UCL property and high CT contrast both in vitro and in vivo, YbPO4: Er PEI-UCPSs could be used as an optical probe and a contrast agent for optical and CT imaging, forming a promising platform for simultaneous bioimaging and drug delivery.