Upconversion Nanostructures Applied in Theranostic Systems

Abstract

Upconversion (UC) nanostructures, which can upconvert near-infrared (NIR) light with low energy to visible or UV light with higher energy, are investigated for theranostic applications. The surface of lanthanide (Ln)-doped UC nanostructures can be modified with different functional groups and bioconjugated with biomolecules for therapeutic systems. On the other hand, organic molecular-based UC nanostructures, by using the triplet-triplet annihilation (TTA) UC mechanism, have high UC quantum yields and do not require high excitation power. In this review, the major UC mechanisms in different nanostructures have been introduced, including the Ln-doped UC mechanism and the TTA UC mechanism. The design and fabrication of Ln-doped UC nanostructures and TTA UC-based UC nanostructures for theranostic applications have been reviewed and discussed. In addition, the current progress in the application of UC nanostructures for diagnosis and therapy has been summarized, including tumor-targeted bioimaging and chemotherapy, image-guided diagnosis and phototherapy, NIR-triggered controlled drug releasing and bioimaging. We also provide insight into the development of emerging UC nanostructures in the field of theranostics.

Nanoparticle-Based Techniques for Bladder Cancer Imaging: A Review

“…However, a recent study reported that autofluorescence affects in vivo imaging even in the NIR II window [ 35 ]. To overcome this problem, upconverting NPs can be used, which are excited by multiple photon interactions to produce a single photon with energy greater than each incoming photon; upconverting NPs are especially convenient since very few organic molecules with upconverting optical properties exist in the living tissues [ 36 , 37 , 38 ].…”

Photo‐Controllable Smart Hydrogels for Biomedical Application: A Review

“…For instance, coumarin has a longer activation wavelength due to its larger area of 𝜋 threshold electrons compared to ONB, so it is proposed that extending the threshold electron area of the photoresponse component is a way to redshift the maximum wavelength of light absorption. [80] At present, there are two technologies for achieving near-infrared photochemical reactions, namely two-photon absorption (TPA) [284,285] and up-conversion (UC) [286,287] based on rare earth materials. TPA technology excites photosensitive components by exposing them to high intensity focused lasers, causing them to instantly absorb a pair of photons with half the energy of a single photon.…”

Graphene oxide nanosheets enhancing the photothermal response of a cellular barrier exposed to near infrared light

“…This is because NIR light (700-1700 nm) shows deeper tissue-penetration than visible light and reduced photodamage to cells and tissues. [10][11][12] The targeted photodynamic therapy and photothermal therapy by NIR were studied to release drugs and overcome the barriers on demand. [12][13][14] Graphene oxide (GO) nanosheets have strong and broad absorption on NIR and could effectively convert NIR light energy to heat, which make it an ideal material to disrupt barriers by thermal effect.…”

“…[10][11][12] The targeted photodynamic therapy and photothermal therapy by NIR were studied to release drugs and overcome the barriers on demand. [12][13][14] Graphene oxide (GO) nanosheets have strong and broad absorption on NIR and could effectively convert NIR light energy to heat, which make it an ideal material to disrupt barriers by thermal effect. [15][16][17][18][19][20] Therefore, the study of the targeted and NIR-irradiative photothermal effect of GO and its effect on the cellular barrier disruption is necessary.…”