Upconversion nano-particles from synthesis to cancer treatment: A review

Unlabelled LRET biosensor based on double-stranded DNA for the detection of anthraquinone anticancer drugs

Based on upconversion nanoparticles (UCNPs) as energy donor and herring sperm DNA (hsDNA) as molecular recognition element, an unlabelled upconversion luminescence (UCL) affinity biosensor was constructed for the detection of anthraquinone (AQ) anticancer drugs in biological fluids. AQ anticancer drugs can insert into the double helix structure of hsDNA on the surface of UCNPs, thereby shortening the distance from UCNPs. Therefore, the luminescence resonance energy transfer (LRET) phenomenon is effectively triggered between UCNPs and AQ anticancer drugs. Hence, AQ anticancer drugs can be quantitatively detected according to the UCL quenching rate. The biosensor showed good sensitivity and stability for the detection of daunorubicin (DNR) and doxorubicin (ADM). For the detection of DNR, the linear range is 1-100 μg·mL-1 with a limit of detection (LOD) of 0.60 μg·mL-1, and for ADM, the linear range is 0.5-100 μg·mL-1 with a LOD of 0.38 μg·mL-1. The proposed biosensor provides a convenient method for monitoring AQ anticancer drugs in clinical biological fluids in the future.

Cellular temperature probing using optically trapped single upconversion luminescence

BACKGROUND

The thermally coupled energy states that contribute to the upconversion luminescence of rare earth element-doped nanoparticles have been the subject of intense research due to their potential nanoscale temperature probing. However, the inherent low quantum efficiency of these particles often limits their practical applications, and currently, surface passivation and incorporation of plasmonic particles are being explored to improve the inherent quantum efficiency of the particle. However, the role of these surface passivating layers and the attached plasmonic particles in the temperature sensitivity of upconverting nanoparticles while probing the intercellular temperature has not been investigated thus far, particularly at the single nanoparticle level.

RESULTS

The analysis of the study on the thermal sensitivity of oleate-free UCNP, UCNP@SiO₂, and UCNP@SiO₂@Au particles is carried out at a single particle level in a physiologically relevant temperature range (299 K-319 K) by optically trapping the particle. The thermal relative sensitivity of the as-prepared upconversion nanoparticle (UCNP) is found to be greater than that of UCNP@SiO₂ and UCNP@SiO₂@Au particles in an aqueous medium. An optically trapped single luminescence particle inside the cell is used to monitor the temperature inside the cell by measuring the luminescence from the thermally coupled states. The absolute sensitivity of optically trapped particles inside the biological cell increases with temperature, with a greater impact on the bare UCNP, which exhibits higher values for thermal sensitivity than UCNP@SiO₂ and UCNP@SiO₂@Au. The thermal sensitivity of the trapped particle inside the biological cell at 317 K indicates the thermal sensitivity of UCNP > UCNP@SiO₂@Au > UCNP@SiO₂ particles.

SIGNIFICANCE AND NOVELTY

Compared to bulk sample-based temperature probing, the present study demonstrates temperature measurement at the single particle level by optically trapping the particle and further explores the role of the passivating silica shell and the incorporation of plasmonic particles on thermal sensitivity. Furthermore, thermal sensitivity measurements inside a biological cell at the single particle level are investigated and illustrated that thermal sensitivity at a single particle is sensitive to the measuring environment.

Visible-UVC upconversion polymer films for prevention of microbial infection

Bacterial infections caused by the growth and reproduction of pathogenic bacteria on wounds are one of the main reasons that hinder wound healing. Antibacterial wound dressings protect wounds from bacterial infections. Herein, we developed a polymeric antibacterial composite film using polyvinyl alcohol (PVA) and sodium alginate (SA) as the substrate. The film used praseodymium-doped yttrium orthosilicate (Y₂SiO₅: Pr³⁺, YSO-Pr) to convert visible light into short-wavelength ultraviolet light (UVC) to kill bacteria. The YSO-Pr/PVA/SA showed upconversion luminescence in photoluminescence spectrometry tests, and the emitted UVC inhibited Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria in antibacterial tests. In vivo animal tests showed that YSO-Pr/PVA/SA is effective and safe for inhibiting bacteria in real wounds. The in vitro cytotoxicity test further confirmed the good biocompatibility of the antibacterial film. In addition, YSO-Pr/PVA/SA exhibited sufficient tensile strength. Overall, this study demonstrates the potential of upconversion materials for use in medical dressings.

Upconversion nanoparticles@AgBiS2 core-shell nanoparticles with cancer-cell-specific cytotoxicity for combined photothermal and photodynamic therapy of cancers

UCNPs@AgBiS₂ core-shell nanoparticles that AgBiS₂ coated on the surface of upconversion nanoparticles (UCNPs) was successfully prepared through an ion exchange reaction. The photothermal conversion efficiency of AgBiS₂ can be improved from 14.7% to 45% due to the cross relaxation between Nd ions and AgBiS₂. The doping concentration of Nd ions played a critical role in the production of reactive oxygen species (ROS) and enhanced the photothermal conversion efficiency. The NaYF₄:Yb/Er/Nd@NaYF₄:Nd nanoparticles endows strong upconversion emissions when the doped concentration of Nd ions is 1% in the inner core, which excites the AgBiS₂ shell to produce ROS for photodynamic therapy (PDT) of cancer cells. As a result, the as-prepared NaYF₄:Yb/Er/Nd@NaYF₄:Nd@AgBiS₂ core-shell nanoparticles showed combined photothermal/photodynamic therapy (PTT/PDT) against malignant tumors. This work provides an alternative near-infrared light-active multimodal nanostructures for applications such as fighting against cancers.

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UCNPs@AgBiS₂ core-shell nanoparticles firstly prepared via a facile chemical process.

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The photothermal conversion efficiency for UCNPs@AgBiS₂ core-shell nanoparticles reached up to 45%.

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The as-prepared UCNPs@AgBiS₂ core-shell nanoparticles showed superoroir therapeutic efficacy for cancers.

Stability, dissolution, and cytotoxicity of NaYF4-upconversion nanoparticles with different coatings

Upconversion nanoparticles (UCNPs) have attracted considerable attention owing to their unique photophysical properties. Their utilization in biomedical applications depends on the understanding of their transformations under physiological conditions and their potential toxicity. In this study, NaYF4:Yb,Er UCNPs, widely used for luminescence and photophysical studies, were modified with a set of four different coordinatively bound surface ligands, i.e., citrate, alendronate (AA), ethylendiamine tetra(methylene phosphonate) (EDTMP), and poly(maleic anhydride-alt-1-octadecene) (PMAO), as well as silica coatings with two different thicknesses. Subsequently, the aging-induced release of fluoride ions in water and cell culture media and their cytotoxic profile to human keratinocytes were assessed in parallel to the cytotoxic evaluation of the ligands, sodium fluoride and the lanthanide ions. The cytotoxicity studies of UCNPs with different surface modifications demonstrated the good biocompatibility of EDTMP-UCNPs and PMAO-UCNPs, which is in line with the low amount of fluoride ions released from these samples. An efficient prevention of UCNP dissolution and release of cytotoxic ions, as well as low cytotoxicity was also observed for UCNPs with a sufficiently thick silica shell. Overall, our results provide new insights into the understanding of the contribution of surface chemistry to the stability, dissolution behavior, and cytotoxicity of UCNPs. Altogether, the results obtained are highly important for future applications of UCNPs in the life sciences and bioimaging studies.

Subcellular imaging and diagnosis of cancer using engineered nanoparticles

The advances in the synthesis of nanoparticles with engineered properties are reported to have profound applications in oncological disease detection via optical and multimodal imaging and therapy. Among various nanoparticle-assisted imaging techniques, engineered fluorescent nanoparticles show great promise from high contrast images and localized therapeutic applications. Of all the fluorescent nanoparticles available, the gold nanoparticles, carbon dots, and upconversion nanoparticles are emerging recently as the most promising candidates for diagnosis, treatment, and cancer monitoring. This review addresses the recent progress in engineering the properties of these emerging nanoparticles and their application for cancer diagnosis and therapy. In addition, the potential of these particles for subcellular imaging is also reviewed here.

UVA-Triggered Drug Release and Photo-Protection of Skin

Light has attracted special attention as a stimulus for triggered drug delivery systems (DDS) due to its intrinsic features of being spatially and temporally tunable. Ultraviolet A (UVA) radiation has recently been used as a source of external light stimuli to control the release of drugs using a "switch on- switch off" procedure. This review discusses the promising potential of UVA radiation as the light source of choice for photo-controlled drug release from a range of photo-responsive and photolabile nanostructures via photo-isomerization, photo-cleavage, photo-crosslinking, and photo-induced rearrangement. In addition to its clinical use, we will also provide here an overview of the recent UVA-responsive drug release approaches that are developed for phototherapy and skin photoprotection.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.