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NaYbF4 upconverting nanoparticles (UCNPs) have enhanced optical properties compared to the NaYF4 UCNPs. However, synthesis of monodisperse NaYbF4 with controllable size and optical properties poses challenges, and the mechanism of phase transformation remains to be understood. Here, they report on the effect of Na+/Yb3+ molar ratio on the morphological and optical properties of upconverting NaYbF4: 2% Er3+ nanoparticles. Controllable transformation of cubic phase nanoparticles produced with [Na+]/[Yb3+] = 1 to hexagonal phase is achieved by increasing Na+ content. The hexagonal UCNPs produced with [Na+]/[Yb3+] = 4 have significantly enhanced intensity of optical emission of ≈600 times compared with the pure cubic phase crystal. The work reveals that the increasing dislocation of sodium and ytterbium distribution cause the accumulation of the lattice strain with increasing Na+ content, and triggers the lattice strain‐mediated phase transformation in cubic cell, as confirmed by the Density Function Theory simulations. These results provide new insights into the growth of UCNPs and pave the way for developing controlled synthesis of UCNPs for applications as bio‐probes and for energy harvesting. [ABSTRACT FROM AUTHOR]

NaYbF4 upconverting nanoparticles (UCNPs) have enhanced optical properties compared to the NaYF4 UCNPs. However, synthesis of monodisperse NaYbF4 with controllable size and optical properties poses challenges, and the mechanism of phase transformation remains to be understood. Here, they report on the effect of Na+/Yb3+ molar ratio on the morphological and optical properties of upconverting NaYbF4: 2% Er3+ nanoparticles. Controllable transformation of cubic phase nanoparticles produced with [Na+]/[Yb3+] = 1 to hexagonal phase is achieved by increasing Na+ content. The hexagonal UCNPs produced with [Na+]/[Yb3+] = 4 have significantly enhanced intensity of optical emission of ≈600 times compared with the pure cubic phase crystal. The work reveals that the increasing dislocation of sodium and ytterbium distribution cause the accumulation of the lattice strain with increasing Na+ content, and triggers the lattice strain‐mediated phase transformation in cubic cell, as confirmed by the Density Function Theory simulations. These results provide new insights into the growth of UCNPs and pave the way for developing controlled synthesis of UCNPs for applications as bio‐probes and for energy harvesting. [ABSTRACT FROM AUTHOR]

Interdisciplinary sciences have paved the way for the creation of new technologies that could potentially alter how things were conventionally done. Biotechnology and nanotechnology have resulted in the creation of various techniques, one of which is upconversion nanoparticles (UCNPs), which can be conjugated with biomaterials for added functionality. UCNPs work based on optical phenomena referred to as anti-Stoke shift, wherein the nanoparticle absorbs light of a high wavelength (lower energy) and emits light having a lower wavelength (higher energy). This ability to provide luminescent signals when irradiated with near-infrared (NIR) light sources is particularly useful as a consequence of its minimal toxicity and high depth of penetration. When coupled with the appropriate biomaterials, the UCNPs can conjugate with the target under study and via quenching/luminescence recovery and quantitative and qualitative tests can be performed relating to the target molecule, in vivo. These UCNP-nanomaterial structures have proven to be very useful in the in vivo image detection, diagnostic, therapeutic as well as combined approaches for disease treatment, drug delivery, disease diagnosis etc. This review aims at providing an in-depth explanation about the origins of UCNPs, how they may be synthesized, their mechanisms of upconversion (UC), their adaptability and flexibility under in vivo conditions, and the future of the field. Overall representation of Upconverting Nanoparticle (UCNP) synthesis followed by the currently researched/applied modes of utilization for the same. The drug delivery aspect involves loading the porous layer over the UCNP with the required drug while the bio-imaging and therapeutic application (via photothermal therapy and/or photodynamic therapy) involves irradiation of the nanoparticles by tissue-penetrating near-infrared radiation (NIR). [ABSTRACT FROM AUTHOR]

An active TNT (2,4,6-trinitrotoluene) catalytic sensor based on Janus upconverting nanoparticle (UCNP)-functionalized micromotor capsules, displaying “on–off” luminescence with a low limit of detection has been developed. The Janus capsule motors were fabricated by layer-by-layer assembly of UCNP-functionalized polyelectrolyte microcapsules, followed by sputtering of a platinum layer onto one half of the capsule. By catalytic decomposition of hydrogen peroxide to oxygen bubbles, the Janus UCNP capsule motors are rapidly propelled with a speed of up to 110 μm s−1. Moreover, the Janus motors display efficient on–off luminescent detection of TNT. Owing to the unique motion of the Janus motor with bubble generation, the likelihood of collision with TNT molecules and the reaction rate between them are increased, resulting in a limit of detection as low as 2.4 ng mL−1 TNT within 1 minute. Such bubble-propelled Janus UCNP capsule motors have great potential for contaminated water analysis.

If the appropriate immobilization method and carrier support are not selected, partial decreases in the activity of enzymes may occur after immobilization. Herein, to overcome this challenge, an excitation mechanism that enables energy transfer was proposed. Modified upconverting nanoparticles (UCNPs) were constructed and the important role of near-infrared (NIR) excitation in enhancing the catalytic activity of the enzyme was demonstrated. For this purpose, UCNPs were first synthesized via the hydrothermal method, functionalized with isocyanate groups, and then, PEG-L-ASNase was immobilized via covalent binding. UCNPs with and without PEG-L-ASNase were extensively characterized by different methods. These supports had immobilization yield and activity efficiency of >96 % and 78 %, respectively. Moreover, immobilized enzymes exhibited improved pH, thermal, and storage stability. In addition, they retained >65 % of their initial activity even after 20 catalytic cycles. Biochemical and histological findings did not indicate a trend of toxicity in rats due to UCNPs. Most importantly, PEG-L-ASNase activity was triggered approximately 5- and 2-fold under in vitro and in vivo conditions, respectively. Overall, it is anticipated that this pioneering work will shed new light on the realistic and promising usage of NIR-excited UCNPs for the immobilization of enzymes in expensive and extensive applications. [Display omitted] • Upconverting nanoparticles (UCNPs) were designed for PEG-L-ASNase immobilization. • UCNPs had rod-shaped particles and particle size from 80.8 ± 27.2 nm. • The immobilized enzyme showed high stability and reusability. • No biochemical or histological toxicity due to UCNPs was observed in rats. • PEG-L-ASNase activity was triggered 2-fold as in vivo under NIR irradiation. [ABSTRACT FROM AUTHOR]

Abstract: Cancer remains a major killer of mankind. Failure of conventional chemotherapy has resulted in recurrence and development of virulent multi drug resistant (MDR) phenotypes adding to the complexity and diversity of this deadly disease. Apart from displaying classical physiological abnormalities and aberrant blood flow behavior, MDR cancers exhibit several distinctive features such as higher apoptotic threshold, aerobic glycolysis, regions of hypoxia, and elevated activity of drug-efflux transporters. MDR transporters play a pivotal role in protecting the cancer stem cells (CSCs) from chemotherapy. It is speculated that CSCs are instrumental in reviving tumors after the chemo and radiotherapy. In this regard, multifunctional nanoparticles that can integrate various key components such as drugs, genes, imaging agents and targeting ligands using unique delivery platforms would be more efficient in treating MDR cancers. This review presents some of the important principles involved in development of MDR and novel methods of treating cancers using multifunctional-targeted nanoparticles. Illustrative examples of nanoparticles engineered for drug/gene combination delivery and stimuli responsive nanoparticle systems for cancer therapy are also discussed. [Copyright &y& Elsevier]