Upconversion System with Quantum Dots as Sensitizer: Improved Photoluminescence and PDT Efficiency

Abstract

Upconversion nanoparticles (UCNPs) are prospective platforms for bioimaging and phototherapy, but a critical bottleneck is the limited brightness due to the faint absorptivity of lanthanide ions and the low quantum yield. To circumvent this problem, we herein propose our strategy to reconstruct the energy cascade of UCNPs using semiconductor quantum dots (QDs) as light sensitizer of Nd3+/Yb3+ codoped UCNPs. Ag2Se QDs with strong absorption at 808 nm acted as efficient antenna and transferred their energy to Yb3+ via a resonance energy transfer process, significantly enhancing the luminescence of UCNPs. This nanocomposite was then combined with Rose Bengal and applied for photodynamic therapy. Both in vitro and in vivo studies revealed the introduction of QDs improved the therapeutic performance remarkably. Our study suggests Ag2Se QDs with excellent photophysical properties can be promising agents to overcome the shortcomings of UCNPs and further strengthen their applications.

Quo Vadis, Nanoparticle-Enabled In Vivo Fluorescence Imaging?

“…163 Given the poor absorption capabilities of RE 3+ (owing to the forbidden 4f-4f nature of most of the electronic transitions involved in the photoluminescence of these ions 164 ), RENPs are the contrast agents that would more substantially benefit from a boost of their light harvesting prowess. To that end, coupling of semiconductor NPs and RE 3+ has been performed both decorating RENPs with Ag2S 165 or Ag2Se 166 NPs, and doping RE 3+ ions in QDs. 167 These strategies are incredibly advantageous on paper, but they involve the step of energy transfer from the absorbing moiety (semiconductor NP) to the emitting RE 3+ ion: a critical step whose efficiency often limits the efficacy of these approaches.…”

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

“…Moreover, the surface chemistry of the two species can be tuned independently depending on the coupling strategy one wants to pursue. Two particularly relevant examples are represented by the amalgamation of NIR-absorbing SNCs of Ag2S 93 or Ag2Se 94 with LNPs to achieve brighter NIR-II or visible UC emission, respectively. Zhang et al synthesized the final hybrid Ag2S-NaYF4:Yb 3+ ,Er 3+ nanostructure leveraging the electrostatic interaction between the positively charged surface of ligand-free LNPs and the carboxylic group of mercaptopropionic acid (MPA) on the surface of Ag2S SNCs.…”

Optical Waveguides and Integrated Optical Devices for Medical Diagnosis, Health Monitoring and Light Therapies

“…Importantly, biocompatible optical fibers and waveguides with highly effective optical structures, exhibiting high transparence and low optical loss, can deliver light into deep target regions. Moreover, nanoparticles such as upconversion materials and bioluminescent molecules can be activated by NIR light [ 112 ]. Notably, a wireless photonic device used for monitoring the light dose is reported to achieve therapeutic light delivery for cancer PDT [ 113 ].…”