In vitro assays and nanothermometry studies of infrared-to-visible upconversion of nanocrystalline Er3+,Yb3+ co-doped Y2O3 nanoparticles for theranostic applications


Luminescent spherical, redispersable, and monodisperse Er3+,Yb3+ co-doped Y2O3 nanoparticles were synthesized by homogenous precipitation followed by thermal annealing. Cubic Y2O3 nanoparticles exhibited high colloidal stability in water and biological medium and 90% cell viability toward glioblastoma multiforme cell lines. Confocal microscopy revealed cellular internalization of Y2O3 nanoparticles. Upon excitation at 980 nm, efficient near-infrared to visible upconversion luminescence from Y2O3:Er3+,Yb3+ nanoparticles occurred. The upconversion dynamics was determined by the number of photons, which evidenced that energy transfer by the upconversion mechanism is predominated. On the basis of luminescence nanothermometry studies, the nano particles exhibited features of a primary thermometer with high thermal sensitivity (1.27 +/- 0.05% K-1 (303 K) and large repeatability (>97%), attesting that it can be used as a contactless optical thermal sensor. This primary thermometer is also successfully applied in a cell culture medium showing that the nanoparticles can operate on biological media. This opens the possibility of the use of Y2O3:Er3+,Yb3+ nanoparticles in the design of a theranostic platform, able to simultaneously monitor temperature and, coupled to photosensitizers, produce reactive oxygen species for cancer therapy.



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Dos Santos, LF; Martins, JC; Lima, KO; Gomes, LFT; De Melo, MT; Tedesco, AC; Carlos, LD; Ferreira, RAS; Goncalves, RR

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The authors acknowledge the Brazilian funding agencies FAPESP, CNPq, and CAPES for financial support. This work was developed within the scope of the FAPESP project 2020/05319-9. RRG acknowledges CNPq for financial support (grant number: 303110/2019-8) . LFS ac-knowledges Fapesp (2017/10440-9 and 2018/04588-6) and CNPq (grant number: 142199/2020-6) for the scholarships; and KOL ac-knowledges FAPESP (grant number: 2018/18213-4) . The authors also acknowledge National Photonics Institute - INFo and PRONON-SIPAR Project #25000.077093/2015-86. This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. J.C.M. thanks FCT for the grant SFRH/BD/139710/2018.

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