Remarkably enhanced upconversion luminescence in Na+ codoped spinel nanoparticles for photothermal cancer therapy and SPECT imaging

Glioblastoma multiforme (GBM) is the most fatal brain tumor and chemo/radiotherapeutic options and other palliative care have not fetched much success in its management due to the highly heterogeneous nature of GBM tissue and the presence of the blood-brain barrier. Impressively, Na+ co-doped ZnAl2O4:Ho3+, Yb3+ upconversion nanoparticles (UCNPs) with remarkably enhanced upconversion luminescence (UCL) have demonstrated good cellular uptake, bio/cyto compatibility and anticancer efficacy in C6 glioma cells. The % cell viability of C6 cells treated with UCNPs decreased to 46% under 980 nm near infrared (NIR) laser exposure exhibiting an excellent potential in photothermal therapy (PTT). Laser power dependence studies explain the UC mechanism and the role of Na+ ions in the UC luminescence enhancement is also investigated using density functional theory (DFT) calculations and positron annihilation lifetime spectroscopy (PALS). The Na+ ion codoping resulted in a significant lowering of zinc vacancies in ZnAl2O4:Ho3+, Yb3+, indicating its effective role in eliminating defect-induced non-radiative channels. Intrinsically (166-Holmium) radiolabeled ZnAl2O4:Yb3+, Ho-166(3+), Na+ has also shown great potential towards in vivo single-photon emission computed tomography (SPECT) imaging. The results presented herein highlight the potential of this highly upconvertible molecule for dual modality SPECT/optical imaging for therapeutic and theranostic applications as well as for photothermal cancer therapy.

Automated summary

Na+ co-doped UCNPs show good cellular uptake, bio/cyto compatibility and anticancer efficacy, suggesting their potential for photothermal therapy and in vivo imaging for glioblastoma.