Upconversion nanoparticles as versatile light nanotransducers for photoactivation applications

Abstract

Remote activation of photoactivable therapeutic compounds by light provides a high spatial and temporal control for activating the therapeutic agent. However, photoactivable compounds are mostly responsive towards ultraviolet (UV) or visible light radiation that has poor tissue penetration depth besides being unsafe to the body in the case of UV light. Nanoparticles with energy upconversion hold potential in overcoming this limit by using safe and deeply penetrating near-infrared (NIR) light. These upconversion nanoparticles (UCNs) act as versatile nanotransducers as they convert NIR light to light of shorter wavelengths that can be tuned to the NIR, visible or UV colors to suit different activation wavelengths. Their highly unusual optical properties to fluoresce with near-zero photobleaching, photoblinking and background autofluorescence are unique and an added benefit when used simultaneously as optional imaging agents. This article reviews recent advancements in the use of UCNs for photoactivation of therapeutic agents. Specifically, we discuss the use of these UCNs for activation of light-sensitive/photocaged molecules or photosensitizers for photocontrolled-delivery and photodynamic therapy.

Smart nanoparticles improve therapy for drug-resistant tumors by overcoming pathophysiological barriers

“…PTT induces ECM degradation and improves NP delivery to solid tumors by converting near-infrared (NIR) light to local heat. Compared to the conventional modalities for cancer therapy, including surgical resection, chemotherapy and radiotherapy, PTT is noninvasive and induces minimal side effects [50,51] . However, the majority of the NPs employed for PTT are inorganic nanomaterials (eg, gold nanorods and carbon nanomaterials).…”

Polyaniline-coated upconversion nanoparticles with upconverting luminescent and photothermal conversion properties for photothermal cancer therapy

“…31 Thus, lanthanidebased upconversion nanoparticles (UCNPs) have special optical characteristics, such as sharp emission lines, large anti-Stokes shifts of several hundred nanometers, and the absence of autofluorescence in biosamples. [32][33][34][35][36][37][38] Therefore, UCNPs have been recently used as building blocks in the construction of multimodal contrast agents for imagingguided therapy. [39][40][41][42][43][44][45] In the current study, upconversion nanoparticles (UCNPs) were first prepared by a typical solvothermal method.…”

Enhancement of up-conversion luminescence of Y₂Ti₂O₇:Yb³⁺/Ho³⁺ nanocrystals by incorporating Li⁺ ions

“…Liu and his collaborators 9) achieved simultaneous control over up-conversion emissions, the crystallographic phase, and particle size of the NaYF 4 + ion doping concentration on the phase evolution, microstructures and up-conversion emissions, was examined in detail, and the possible mechanism for emission enhancement was also proposed.…”

“…During the past decades, research on lanthanide-based up-conversion materials have attracted considerable attention owing to their potential applications in the fields of nanoscale thermometry, 1) spectral converters for solar cells, 2) bio-sensing, bio-imaging, 3) photodynamic therapy of tumour 4) and drug delivery. 5) The low emission efficiency, nevertheless, has become one of the bottlenecks to hinder their practical applications due to the nanoscale particle size.…”