posted on 2024-03-14, 06:29authored byAnnu Balhara, Santosh K. Gupta, Kathi Sudarshan, Sourav Patra, Avik Chakraborty, Sudipta Chakraborty
This work reports an “all-in-one”
theranostic
upconversion
luminescence (UCL) system having potential for both diagnostic and
therapeutic applications. Despite considerable efforts in designing
upconversion nanoparticles (UCNPs) for multimodal imaging and tumor
therapy, there are few reports investigating dual modality SPECT/optical
imaging for theranostics. Especially, research focusing on in vivo
biodistribution studies of intrinsically radiolabeled UCNPs after
intravenous injection is of utmost importance for the potential clinical
translation of such formulations. Here, we utilized the gamma emission
from 169Er and 171Er radionuclides for the demonstration
of radiolabeled ZnAl2O4:171/169Er3+ as a potent agent for dual-modality SPECT/optical imaging.
No uptake of radio nanoformulation was detected in the skeleton after
4 h of administration, which evidenced the robust integrity of ZnAl2O4:169/171Er3+. Combining
the therapeutics using the emission of β– particulates
from 169Er and 171Er will be promising for the
radio-theranostic application of the synthesized ZnAl2O4:169/171Er3+ nanoformulation. Cell toxicity
studies of ZnAl2O4:1%Er3+ nanoparticles
were examined by an MTT assay in B16F10 mouse melanoma cell lines,
which demonstrated good biocompatibility. In addition, we explored
the mechanism of UCL modulation via defect engineering by Bi3+ codoping in the ZnAl2O4:Er3+ upconversion
nanophosphor. The UCL color tuning was successfully achieved from
the red to the green region as a function of Bi3+ codoping
concentrations. Further, we tried to establish a correlation of UCL
tuning with the intrinsic oxygen and cation vacancy defects as a function
of Bi3+ codoping concentrations with the help of electron
paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy
(PALS) studies. This study contributes to building a bridge between
nature of defects and UC luminescence that is crucial for the design
of advanced UCNPs for theranostics.