Abstract
Several robust titania (TiO2) coated core/multishell trivalent lanthanide (Ln) upconversion nanoparticles (UCNPs) hybrid architecture designs have been reported for use in photodynamic therapy (PDT) against cancer, utilizing the near-infrared (NIR) excited energy down-shifting and up-conversion chain of Nd3+ (λ793-808 nm) → Yb3+ (λ980 nm) → Tm3+(λ475 nm) → TiO2 to produce reactive oxygen species (ROS) for deep tissue-penetrating oxidative cytotoxicity, e.g., NaLnF4:Yb,Tm (Ln = Y, Gd). Herein, we demonstrate that by doping the Tm3+ emitter ions in the outer shell and the Nd3+ sensitizer ions in the core, the newly designed NaYF4:Nd,Yb@Yb@Yb,Tm@TiO2 hybrid UCNPs exert more ROS production than the reference NaYF4:Yb,Tm@Yb@Nd,Yb@ TiO2 with the Tm3+ ions in the core and the Nd3+ ions in the outer shell, upon 793 nm laser irradiation, primarily due to the shortening of the Tm3+-TiO2 distance of the former with greater Förster resonance energy transfer (FRET) efficiency. After coating with polyallylamine hydrochloride (PAH)/polyethylene glycol folate (PEG-FA), the resulting NaYF4:Nd,Yb@Yb@Yb,Tm@TiO2-PAH-PEG-FA hybrid nanocomposites could be internalized in MDA-MB-231 cancer cells, which also show low dark cytotoxicity and effective photocytotoxicity upon 793 nm excitation. These nanocomposites could be further optimized and are potentially good candidates as nanotheranostics, as well as for other light-conversion applications.
Highlights
In the precision medicine era, in addition to the current types of cancer treatment, i.e., surgery, radiotherapy, chemotherapy and targeted therapy, several other methods including immunotherapy, [1] phototherapy [2,3] and stem cell transplants [4] are either in clinical trials or under research development
The photostability of upconversion nanoparticles (UCNPs)@TiO2-polyallylamine hydrochloride (PAH)-polyethylene glycol folate (PEG-FA) in solution was tested by the reactive oxygen species (ROS) produced after standing for 1 day and 7 days in a similar procedure
After incubation in Dulbecco’s Modified Eagle Medium (DMEM) for 24 h at 37 ◦C under 5% CO2, 100 μL solutions of the UCNPs@TiO2-PAH-PEG-FA in the concentration range of 50–800 μg/mL were added into each well and incubated for 24 h and washed by PBS buffer
Summary
In the precision medicine era, in addition to the current types of cancer treatment, i.e., surgery, radiotherapy, chemotherapy and targeted therapy, several other methods including immunotherapy, [1] phototherapy (i.e., photodynamic and photothermal therapies) [2,3] and stem cell transplants [4] are either in clinical trials or under research development. Several other TiO2 coated UCNPs have been reported, including: (i) with dual-TiO2/hypocrellin A photosensitizers and hyaluronic acid targeted molecules with 808 nm excitation, [25] (ii) with doxorubicin-loaded NaYF4:Yb,Tm-TiO2 for chemo- and PDT combination therapy with 980 nm excitation, [26] (iii) with a NaGdF4:Yb shell between the core NaGdF4:Yb,Tm and the sensitizer NaNdF4:Yb and an outer NaGdF4 shell (i.e., NaGdF4:Yb,Tm@NaGdF4:Yb@NaNdF4:Yb @NaGdF4@mSiO2@TiO2) to reduce the respective energy back transfer from Tm3+ to Nd3+ ions and surface quenching [27]. SeeSffifccfhhicceeiimemenneeccyy11..ttooTTphhpererooccddoouurrceece/e/ssRhhReOeOllllSS//ssthhthheeaallnllnhhthtyyhebberrriierddefefUUererCCennNNccePPeTssTmNNm-ddY--Y-bYYb-bbN-N--TTddmm-T-T--iTOTiOii2OO2(22(rri((igllgeehhfftttt)))),,wwdduooueuuelltddotosaahscchhhooirieetrevvteneeneggeddrreeTaaTmttmee3rr+3+F-F-TTRRiiOEEOTT22 distance upon 793 nm NIR laser excitation. distance upon 793 nm NIR laser excitation
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