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In biomedical and optical applications, multifunctional upconverting nanoparticles (UCNPs) play an essential role where non‐invasive temperature sensing and imaging are necessary. UCNPs smaller than 20 nm, which can be excited under 808 nm wavelength, are particularly promising in this area and can be implemented in humans or other mammals. However, new versatile nanoprobes are still needed for biology, especially for challenging studies of small aquatic invertebrates. Such tools allow better monitoring and understanding of their physiology, biochemistry, and ecological responses, which is crucial due to the growing pollution of water reservoirs and climate change. Herein, multifunctional NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ core@shell NPs (15 nm), forming stable aqueous colloids, exhibiting intense emissions under excitation in the first biological window (808 nm), and presenting high thermal sensitivity and resolution related to the thermally coupled energy levels of Er3+ ions, are designed and synthesized. Such properties of UCNPs are further utilized for optical imaging of aquatic invertebrates (Daphnia magna) and temperature detection inside their bodies under 808 nm excitation. This pioneering application of NaYF4:Yb3+, Er3+@NaNdF4:Yb3+ demonstrates the high potential of developed UCNPs for multifunctional applications, especially for bioimaging and temperature sensing within whole organisms. [ABSTRACT FROM AUTHOR]

Targeted drug delivery for primary brain tumors, particularly gliomas, is currently a promising approach to reduce patient relapse rates. The use of substitutable scaffolds, which enable the sustained release of clinically relevant doses of anticancer medications, offers the potential to decrease the toxic burden on the patient's organism while also enhancing their quality of life and overall survival. Upconversion nanoparticles (UCNPs) are being actively explored as promising agents for detection and monitoring of tumor growth, and as therapeutic agents that can provide isolated therapeutic effects and enhance standard chemotherapy. Our study is focused on the feasibility of constructing scaffolds using methacrylated hyaluronic acid with additional impregnation of UCNPs and the chemotherapeutic drug temozolomide (TMZ) for glioma treatment. The designed scaffolds have been demonstrated their efficacy as a drug and UCNPs delivery system for gliomas. Using the aggressive orthotopic glioma model in vivo , it was found that the scaffolds possess the capacity to ameliorate neurological disorders in mice. Moreover, upon intracranial co-implantation of the scaffolds and glioma cells, the constructs disintegrate into distinct segments, augmenting the release of UCNPs into the surrounding tissue and concurrently reducing postoperative damage to brain tissue. The use of TMZ in the scaffold composition contributed to restraining glioma development and the reduction of tumor invasiveness. Our findings unveil promising prospects for the application of photopolymerizable biocompatible scaffolds in the realm of neuro-oncology. [ABSTRACT FROM AUTHOR]

Until now, automation in nanomaterial research has been largely focused on the automated synthesis of engineered nanoparticles (NPs) including the screening of synthesis parameters and the automation of characterization methods such as electron microscopy. Despite the rapidly increasing number of NP samples analyzed due to increasing requirements on NP quality control, increasing safety concerns, and regulatory requirements, automation has not yet been introduced into workflows of analytical methods utilized for screening, monitoring, and quantifying functional groups (FGs) on NPs. To address this gap, we studied the potential of simple automation tools for the quantification of amino surface groups on different types of aminated NPs, varying in size, chemical composition, and optical properties, with the exemplarily chosen sensitive optical fluorescamine (Fluram) assay. This broadly applied, but reportedly error-prone assay, which utilizes a chromogenic reporter, involves multiple pipetting and dilution steps and photometric or fluorometric detection. In this study, we compared the influence of automated and manual pipetting on the results of this assay, which was automatically read out with a microplate reader. Special emphasis was dedicated to parameters like accuracy, consistency, achievable uncertainties, and speed of analysis and to possible interferences from the NPs. Our results highlight the advantages of automated surface FG quantification and the huge potential of automation for nanotechnology. In the future, this will facilitate process and quality control of NP fabrication, surface modification, and stability monitoring and help to produce large data sets for nanomaterial grouping approaches for sustainable and safe-by-design, performance, and risk assessment studies. [ABSTRACT FROM AUTHOR]

The lack of precise spatiotemporal gene modulation and therapy impedes progress in medical applications. Herein, a 980 nm near‐infrared (NIR) light‐controlled nanoplatform, namely URMT, is developed, which can allow spatiotemporally controlled photodynamic therapy and trigger the enzyme‐activated gene expression regulation in tumors. URMT is constructed by engineering an enzyme‐activatable antisense oligonucleotide, which combined with an upconversion nanoparticle (UCNP)‐based photodynamic nanosystem, followed by the surface functionalization of triphenylphosphine (TPP), a mitochondria‐targeting ligand. URMT allows for the 980 nm NIR light‐activated generation of reactive oxygen species, which can induce the translocation of a DNA repair enzyme (namely apurinic/apyrimidinic endonuclease 1, APE1) from the nucleus to mitochondria. APE1 can recognize the basic apurinic/apyrimidinic (AP) sites in DNA double‐strands and perform cleavage, thereby releasing the functional single‐strands for gene regulation. Overall, an augmented antitumor effect is observed due to NIR light‐controlled mitochondrial damage and enzyme‐activated gene regulation. Altogether, the approach reported in this study offers high spatiotemporal precision and shows the potential to achieve precise and specific gene regulation for targeted tumor treatment. [ABSTRACT FROM AUTHOR]

The exceptional optoelectronic properties of lead halide perovskite nanocrystals (PeNCs) in the ultraviolet and visible spectral regions have positioned them as a promising class of semiconductor materials for diverse optoelectronic and photovoltaic applications. However, their limited response to near‐infrared (NIR) light due to the intrinsic bandgap (>1.5 eV) has hindered their applications in many advanced technologies. To circumvent this limitation, it is of fundamental significance to integrate PeNCs with lanthanide‐doped upconversion nanoparticles (UCNPs) that are capable of efficiently converting low‐energy NIR photons into high‐energy ultraviolet and visible photons. By leveraging the energy transfer from UCNPs to PeNCs, this synergistic combination can not only expand the NIR responsivity range of PeNCs but also introduce novel emission profiles to upconversion luminescence with multi‐dimensional tunability (e.g., wavelength, lifetime, and polarization) under low‐to‐medium power NIR irradiation, which breaks through the inherent restrictions of individual PeNCs and UCNPs and thereby opens up new opportunities for materials and device engineering. In this review, we focus on the latest advancements in the development of PeNCs‐UCNPs nanocomposites, with an emphasis on the controlled synthesis and optical properties design for advanced optoelectronic applications such as full‐spectrum solar cells, NIR photodetectors, and multilevel anticounterfeiting. Some future efforts and prospects toward this active research field are also envisioned. [ABSTRACT FROM AUTHOR]

Nanosensitizers having long-lived upconversion emission under near-infrared (NIR) excitation offer unique advantages in terms of reduced background noise and prolonged signal detection for deep tissue therapy of cancer. Herein, we demonstrate a systematic mechanism of energy migration toward achieving long-lived Mn2+ upconversion emission in the multilayered core–shell–shell lattice of NaGdF4:Yb3+,Tm3+,Ca2+/NaGdF4:Yb3+,Ca2+/NaGdF4:Mn2+ upconversion nanoparticles (NPs), following the Yb3+ → Tm3+ → Gd3+ → Mn2+ intermetal ions energy transfer pathway. Furthermore, a rational design of nanosensitizer was achieved by incorporating Er3+ ions into the intermediate shell of multishell NPs, which was subsequently conjugated with the Rose Bengal sensitizer to enable the enhancement in singlet molecular oxygen (1O2) generation under excitation of a 980 nm NIR laser. An intense higher-energy emission in the UV–blue visible region from Tm3+ was achieved by optimizing the amount of Ca2+ in the core–shell NPs, followed by subsequent energy migration to the Mn2+ ion incorporated at the outer shell. The Mn2+ ions were strategically doped in the outer shell of NPs to leverage the catalytic activities of Mn2+ for H2O2 decomposition and decrease the backward energy transfer to the Tm3+ ion. Hence, this approach resulted in a long lifetime of Mn2+ (∼34 ms), attributed to the spin-forbidden 4T1g → 6A1g transition within 3d5 configuration. Additionally, the nanosensitizer demonstrated high 1O2 (∼0.39 μM) generation even at a very low concentration (5 μg/mL) under a laser power of 2 mW cm–2. The hydrogenase-like catalytic activities of Mn2+ exhibited significant oxygen production through decomposition of H2O2. Hence, these findings might contribute to the development of convenient multifunctional nanosensitizers for multimodal bioimaging and therapeutic features, including efficient 1O2 generation and catalytic decomposition of H2O2 (found excessively in a tumor environment) to oxygen for alleviating the hypoxia. [ABSTRACT FROM AUTHOR]

Although conventional therapeutic approaches demonstrate significant success in treating primary tumors, their efficacy diminishes when addressing distant and metastatic tumors, calling for new technologies to transport and activate the therapeutic agents. Here, a core‐shell UCNP@MOF (upconversion nanoparticle — metal organic framework) nanoagents is constructed for Type I and Type II photodynamic therapy under biocompatible near‐infrared light irradiance (at 808 nm) and utilize their pore loading capacity to further realize synergistic immunotherapy in solid tumors. The Cu2+ to Cu+ reduction at the nodes in the MOFs shell is demonstrated to promote the generation of reactive oxygen species via depletion of overexpressed glutathione (GSH) compounds, while tumor microenvironment‐enriched hydrogen peroxide is found to substantially augment the PDT effects. Importantly, the MOFs pore‐loaded indoleamine 2,3‐dioxygenase (IDO) inhibitor, along with s‐nitroso‐n‐acetylpenicillamine (SNAP), upregulated tumor‐infiltrating lymphocytes and induced prominent immunotherapeutic effects in vivo. This core‐shell UCNP@MOF nanoagents have demonstrated effectiveness against both primary and distant tumors in xenografted tumor models, holding promise for treating solid tumors in metastasis. [ABSTRACT FROM AUTHOR]

Chemodynamic therapy (CDT) has emerged as a novel approach to overcome cancer resistance and enhance anticancer efficacy. Despite the considerable effort devoted to current chemodynamic therapeutic agents, developing efficient delivery systems to induce ferroptosis remains demanding due to their limited efficacy and lack of selectivity. Herein, an iron‐based single‐atom upconversion photocatalyst (UmFe‐OA@hPM) mimicking natural horseradish peroxidases has been developed. This nanoformulation not only targets tumors via the existence of a hybrid platelet membrane (hPM) coating but also generates excessive hydroxyl radicals in response to both tumor microenvironment and external laser irradiation. This nanoenzyme overcomes the low tissue penetration of UV light, which sensitizes the iron‐doped graphitic carbon nitride network, attributed to the unique anti‐Stokes shift from infrared to UV displayed by upconversion nanoparticles. Together with an increase in intracellular polyunsaturated fatty acid accumulation induced by oleanolic acid (OA), lipid peroxidation is significantly elevated, leading to the enhancement of CDT. UmFe‐OA@hPM is demonstrated to induce significant ferroptosis in vitro, superior antitumor efficacy in breast cancer mouse models, and suppression of metastasis status when incorporated with an immune checkpoint blockade. These findings provide a potential strategy for developing a precisely controlled CDT to deal with aggressive cancers, especially in combination with immunotherapy. [ABSTRACT FROM AUTHOR]

Photoactivatable carbon monoxide‐releasing molecules (CORMs), typically based on transition‐metal carbonyl complexes, have reliance on activation by UV or visible light that restricts their biomedical applications. To address this limitation, a near‐infrared (NIR)‐responsive nanoplatform is presented based on upconversion nanoparticles (UCNPs) loading with manganese carbonyl complex Mn2(CO)10 that concurrently releases CO and manganese ion (Mn2+). With the UCNPs, the more tissue‐penetrable NIR is used to locally generate UV light for photodecomposition of Mn2(CO)10 into CO and manganese oxide (MnOX), after which MnOX is reduced to Mn2+ by the overexpressed glutathione in cancer cells. Moreover, the released Mn2+ can serve as a magnetic resonance imaging contrast agent to monitor the NIR‐controlled corelease of CO and Mn2+ in real time. Therefore, this nanoplatform can provide a potential strategy for NIR‐enabled spatiotemporally release of CO and Mn2+, enhancing the controlled delivery and biomedical application of CORMs. [ABSTRACT FROM AUTHOR]

An upconversion fluorescence sensing platform was developed with upconversion nanoparticles (UCNPs) as energy donors and gold nanoparticles (AuNPs) as energy acceptors, based on the FRET principle. They were used for quantitative detection of uranyl ions (UO22+) by amplifying the signal of the hybrid chain reaction (HCR). When UO22+ are introduced, the FRET between AuNPs and UCNPs can be modulated through a HCR in the presence of high concentrations of sodium chloride. This platform provides exceptional sensitivity, with a detection limit as low as 68 pM for UO22+ recognition. We have successfully validated the reliability of this method by analyzing authentic water samples, achieving satisfactory recoveries (89.00%–112.50%) that are comparable to those of ICP-MS. These results indicate that the developed sensing platform has the capability to identify trace UO22+ in complex environmental samples. [ABSTRACT FROM AUTHOR]

Owing to their excellent photoelectric and optical properties, lead halide perovskite quantum dots (PeQDs) have attracted great attention and have broad applications in various fields. However, the shortcomings of poor stability and short-wavelength (ultraviolet/visible) excitation restrict their practical applications. Herein, to address the above issues, we report a polyacrylonitrile-based composite film containing CsPbX3 (X = Br and I) PeQDs and β-NaYF4:Yb/Ln (Ln = Tm and Er) upconversion nanoparticles (UCNPs) via an electrospinning strategy. Interestingly, all-inorganic CsPbX3 PeQDs are synthesized through an in situ growth process in polyacrylonitrile nanofibers, which provide a polymer matrix for the protection of PeQDs against decomposition under the effect of an external environment. Upon 980 nm laser irradiation, lanthanide-sensitized UC luminescence of stable CsPbX3 can be realized through radiative energy transfer from Tm3+/Er3+ ions to PeQDs. Consequently, dual-mode luminescence, including downshifting and UC with color-tunable outputs, can be observed from PeQDs under dual-wavelength excitation (UV and NIR). Benefiting from the special luminescent feathers (temperature-sensitive UC and dual-mode luminescence), the as-obtained composite nanofibers exhibit great potential in high-level anticounterfeiting and accurate noncontact thermometry. [ABSTRACT FROM AUTHOR]

Overcoming neural injury and facilitating effective repair pose considerable challenges in the field of neural rehabilitation, characterized by extensive disability and limited recovery rates. A critical aspect of reconstructing a functional nervous system revolves around the successful development of operational axons. In our investigation of rare-earth metal-based upconversion nanoparticles (UCNPs), we have discovered their ability to induce the differentiation of PC-12 cells into neurons. Expanding our inquiry into the implications of UCNPs in neural rehabilitation, we have also applied them in primary mouse neurogenesis, resulting in a significant increase in both neural length and quantity. Furthermore, when used during the induction of primary neural stem cells (NSCs), UCNP treatment has shown a dual effect: it enhances the expression of the neuronal marker TUBB3 while simultaneously inhibiting differentiation into astrocytes. This multifaceted impact was sustained in a prolonged neural sphere differentiation experiment, where UCNPs notably enhance the stability of neuronal axons and facilitate the establishment of intercellular connections. In summary, at the cellular level, introducing UCNPs not only promotes neuronal differentiation in NSCs but also sustains axonal growth, stability, and the formation of intercellular connections. These collective findings highlight the significant potential of UCNPs in advancing the frontiers of neural rehabilitation. [ABSTRACT FROM AUTHOR]

The current works explores the optical contrast property and nanaotheranostic capabilities of the rare earth based Upconversion nanoparticles. Optical coherence tomography (OCT) has been used to explore the particles ability to increase contrast and improve signal intensity. Photo thermal OCT, a function extension of OCT has been used to gauge the photo thermal potential of the nanoparticles. The nanoparticles successfully improved contrast and information from the deeper layers of the sample. The particles also showed excellent capability for use as photo thermal agents. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs) doped with rare earth sensitizers and activators show unique optical properties and promising prospects for emerging applications. Typically, the excitation laser wavelength for UCNPs is selected in accordance with different application demands. However, altering the excitation wavelengths usually influences the upconversion luminescence (UCL) mechanism, necessitating the modification of the lanthanide doping strategy in nanoparticles. By far, a strategy with an excitation wavelength independent of the UCL mechanism is still an urgent need for UCNP applications. Here, we report a wavelength-independent pumping scheme with a flexible excitation wavelength range of 700–900 nm. Specifically, the flexible excitation of Nd3+ was applied to sensitize various activator systems such as Tm3+, Er3+, and Ho3+, all of which can be excited by multiple near-infrared (NIR) wavelengths, displaying consistent and stable spectral characteristics. Through microscopic imaging of dispersed nanoparticles and stained cells, we verified that multiple excitation wavelengths have the possibility of achieving high signal-to-noise ratio imaging. We believe that this approach will provide an in-depth understanding of Nd3+-sensitized upconversion systems and further advance the design for enhancing NIR-stimulated UCL, potentially spanning biomedical imaging, information technology, photocatalysis, and various other emerging fields. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs) and carbon quantum dots (CQDs) have emerged as promising candidates for enhancing both the stability and efficiency of perovskite solar cells (PSCs). Their rising prominence is attributed to their dual capabilities: they effectively passivate the surfaces of perovskite-sensitive materials while simultaneously serving as efficient spectrum converters for sunlight. In this work, we synthesized UCNPs doped with erbium ions as down/upconverting ions for ultraviolet (UV) and near-infrared (NIR) light harvesting. Various percentages of the synthesized UCNPs were integrated into the mesoporous layers of PSCs. The best photovoltaic performance was achieved by a PSC device with 30% UCNPs doped in the mesoporous layer, with PCE = 16.22% and a fill factor (FF) of 74%. In addition, the champion PSCs doped with 30% UCNPs were then passivated with carbon quantum dots at different spin coating speeds to improve their photovoltaic performance. When compared to the pristine PSCs, a fabricated PSC device with 30% UCNPs passivated with CQDs at a spin coating speed of 3000 rpm showed improved power conversion efficiency (PCE), from 16.65% to 18.15%; a higher photocurrent, from 20.44 mA/cm2 to 22.25 mA/cm2; and a superior fill factor (FF) of 76%. Furthermore, the PSCs integrated with UCNPs and CQDs showed better stability than the pristine devices. These findings clear the way for the development of effective PSCs for use in renewable energy applications. [ABSTRACT FROM AUTHOR]

Accurate, rapid and sensitive detection of specific immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies in human samples is crucial for preventing and assessing pandemics, especially in the case of recent COVID-19 outbreaks. However, simultaneous and efficient detection of IgG and IgM in a single system remains challenging. Herein, we developed a multicolor nanosystem capable of quantitatively analyzing anti-SARS-CoV-2 IgG and IgM with high sensitivity within 20 min. The detection system consists of core-shell upconversion nanoparticles (csUCNPs), secondary antibodies labeled with fluorescent dyes (sab), and magnetic nanocrystals (PMF). By leveraging the F€orster resonance energy transfer (FRET) effect, the photoluminescence (PL) intensity of blue and green regions is restored for IgG and IgM detection, respectively. Inspiringly, owing to the introducing of PMF, the limits of detection (LODs) of IgG and IgM tested are improved to 89 fmol L-1 and 19.4 fmol L-1, representing about 416-folds and 487-folds improvement over only-dye dependent system, respectively. Mechanistic investigations reveal that the high collective effect and surface energy transfer efficiency from csUCNPs to PMF contribute to the enhanced detection sensitivity. The assay enables us to quantify clinical vaccinated samples with high specificity and precision, suggesting our multicolor platform can be a promising alternative for clinical point-of-care serological assay. [ABSTRACT FROM AUTHOR]

A long-term prescription of tetracyclines in course dosages is widely applicable for treating bacterial infections such as malaria, cholera, and syphilis. This work aims to optimize the sensing method of tetracyclines using modified upconversion nanoparticles conjugated with tetracycline aptamers in a microtiter plate method. A fluorescence-based spectrophotometer is used to optimize the concentration of tetracyclines relative to their fluorescence quenching readings. The decrease in fluorescence intensity of upconversion nanoparticles when exposed to tetracyclines indicates a possible enhancement in detection sensitivity, with an estimated increase of around ~ 0.1 nM concentration. With the help of tetracycline aptamer conjugated upconversion nanoparticles, we developed a low toxic, susceptible, cost-effective, and simple method for tetracyclines detection. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs) doped with lanthanides are introduced as a significant tool in bioimaging applications. Here in, a comparative study has been performed to understand the cell internalization capacity of folic acid (FA) and arginine-glycine-aspartic acid-lysine (RGDK) ligands. To achieve this goal, polyacrylic acid (PAA) coated UCNPs (NaYF4:Yb3+, Er3+) are conjugated with various surface ligands such as FA and RGDK through a straightforward ligand exchange procedure. Ligand conjugation to UCNPs was characterized with a transmission electron microscope (TEM), Fourier-transform infrared (FT-IR) spectroscopy, zeta potential measurements, nuclear magnetic resonance (NMR) spectroscopy, and NanoDrop measurements. The cellular uptake of the nanoparticles was investigated on the breast cancer MCF-7 cell line. The obtained results demonstrated that folic acid and RGDK functionalized UCNPs showed remarkably higher cellular uptake, which clearly indicates that the specific targeting of UCNPs provides a better quality of sub-cellular imaging at lower energy band region. [ABSTRACT FROM AUTHOR]

Cryotherapy leverages controlled freezing temperature interventions to engender a cascade of tumor‐suppressing effects. However, its bottleneck lies in the standalone ineffectiveness. A promising strategy is using nanoparticle therapeutics to augment the efficacy of cryotherapy. Here, a cold‐responsive nanoplatform composed of upconversion nanoparticles coated with silica – chlorin e6 – hyaluronic acid (UCNPs@SiO2‐Ce6‐HA) is designed. This nanoplatform is employed to integrate cryotherapy with photodynamic therapy (PDT) in order to improve skin cancer treatment efficacy in a synergistic manner. The cryotherapy appeared to enhance the upconversion brightness by suppressing the thermal quenching. The low‐temperature treatment afforded a 2.45‐fold enhancement in the luminescence of UCNPs and a 3.15‐fold increase in the photodynamic efficacy of UCNPs@SiO2‐Ce6‐HA nanoplatforms. Ex vivo tests with porcine skins and the subsequent validation in mouse tumor tissues revealed the effective HA‐mediated transdermal delivery of designed nanoplatforms to deep tumor tissues. After transdermal delivery, in vivo photodynamic therapy using the UCNPs@SiO2‐Ce6‐HA nanoplatforms resulted in the optimized efficacy of 79% in combination with cryotherapy. These findings underscore the Cryo‐PDT as a truly promising integrated treatment paradigm and warrant further exploring the synergistic interplay between cryotherapy and PDT with bright upconversion to unlock their full potential in cancer therapy. [ABSTRACT FROM AUTHOR]

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The possibility of precise movement of YVO4:Yb,Er nanoparticles was studied in this work. Such nanoparticles exhibit upconversion luminescent properties and can serve as an accurate low-invasive probe of changes in the local parameters of the medium (in particular, temperature). Using an atomic force microscope, the substrate region with upconversion nanoparticles deposited from the solution and accompanying residues of the synthesis products was cleaned. The use of mechanical marks on the substrate made it possible to compare the atomic force and optical confocal images of the surface and to register the luminescence from an individual nanoparticle. Elemental analysis and luminescence spectra unambiguously identify the nanoparticle as YVO4:Yb,Er. [ABSTRACT FROM AUTHOR]

Tumor-associated antigen (TAA)–based diagnosis has gained prominence for early tumor screening, treatment monitoring, prognostic assessment, and minimal residual disease detection. However, limitations such as low sensitivity and difficulty in extracting non-specific binding membrane proteins still exist in traditional detection methods. Upconversion luminescence (UCL) exhibits unique physical and chemical properties under wavelength near-infrared light excitation. Rolling circle amplification (RCA) is an efficient DNA amplification technique with amplification factors as high as 105. Therefore, the above two excellent techniques can be employed for highly accurate imaging analysis of tumor cells. Herein, we developed a novel nanoplatform for TAA-specific cell imaging based on UCL and RCA technology. An aptamer–primer complex selectively binds to Mucin 1 (MUC1), one of TAA on cell surface, to trigger RCA reaction, generating a large number of repetitive sequences. These sequences provide lots of binding sites for complementary signal probes, producing UCL from lanthanide-doped upconversion nanoparticles (UCNPs) after releasing quencher group. The experimental results demonstrate the specific attachment of upconversion nanomaterials to cancer cells which express a high level of MUC1, indicating the potential of UCNPs and RCA in tumor imaging. [ABSTRACT FROM AUTHOR]

Ferroptosis, a unique iron-dependent mode of cell death, has been identified as a potential treatment for glioblastoma (GBM). Dihydroartemisinin (DHA) is a ferroptosis inducer with cytotoxicity that is strongly dependent on intracellular Fe2+ levels. However, the effectiveness of DHA is limited by low levels of Fe2+ in tumor cells. To address this issue, a facile strategy was developed by combining near-infrared (NIR)-induced ferrous ion regeneration with DHA in a nanocomposite (ApoE-UPGs-DHA). This nanocomposite synergistically enhanced ferroptosis and offered highly efficient GBM treatment. ApoE-UPGs-DHA were prepared by loading upconversion nanoparticles (UCNPs) and DHA into micelles and subsequently attaching the peptide apolipoprotein E to enable penetration of the blood-brain barrier (BBB) and targeted treatment of GBM. NIR irradiation was applied to induce the regeneration of Fe2+ from Fe3+ mediated by ApoE-UPGs-DHA, thereby promoting ferroptosis in G422 glioma cells. Characterization studies confirmed the successful preparation of ApoE-UPGs-DHA, which had a diameter of 82.3 ± 5.8 nm. The nanocomposite demonstrated good GBM targeting ability in vivo and enhanced uptake by the G422 cells in vitro. ApoE-UPGs-DHA were toxic to G422 glioma cells, and this toxicity was further enhanced by NIR irradiation. Mechanistic studies revealed that ApoE-UPGs-DHA treatment led to a decrease in the intracellular Fe2+ concentration due to the Fenton-like reaction induced by DHA and Fe2+. NIR irradiation was transformed into UV light by ApoE-UPGs-DHA, and then, the Fe3+ generated by the Fenton reaction was photoreduced to Fe2+ by UV light. The replenished Fe2+ significantly promoted the generation of lipid peroxides (LPOs), leading to enhanced ferroptosis and toxicity to ApoE-UPGs-DHA-treated G422 glioma cells. Herein, an NIR-responsive Fe2+-regenerating nanocomposite was successfully prepared to enhance ferroptosis in G422 glioma cells, suggesting a promising alternative GBM treatment strategy. [ABSTRACT FROM AUTHOR]

A biocompatible and versatile silk‐based functional ink with hydrophilic upconversion nanoparticles (UCNPs) that can be printed or painted on arbitrary substrates, including biological surfaces is demonstrated. Hydrophilic UCNPs, ready to be dispersed in aqueous silk fibroin solution, are synthesized in large quantities via facile hydrothermal synthesis using citric acid. Based on a systematic study of dopant control to achieve robust red emission from citrate‐capped UCNPs, three primary colors are obtained, which serve as the basis for the expansion of the color palette. The synthesized UCNPs are homogeneously dispersed in regenerated silk fibroin solutions derived from Bombyx mori cocoons to produce water‐based functional inks. Cyan, magenta, and yellow (CMY) inks are created by combining red, green, and blue (RGB) inks. Demonstrator devices, where a variety of colorful patterns and codes are revealed only under near‐infrared irradiation, are realized through stencil printing or brush painting on flexible polymer films, fruit, leaves, silkworm cocoons, and pig skin. The patterns and codes are highly heat resistant (≈230 °C) and can be easily washed off with water after use. The printable/paintable inks and functions proposed here will provide new opportunities for applications where sustainability, biocompatibility, and intentional luminescence are simultaneously required. [ABSTRACT FROM AUTHOR]

In this work, we present an advancement in the encapsulation of lithium yttrium fluoride-based (YLiF4:Yb,Er) upconversion nanocrystals (UCNPs) with silica (SiO2) shells through a reverse microemulsion technique, achieving UCNPs@SiO2 core/shell structures. Key parameters of this approach were optimized to eliminate the occurrence of core-free silica particles and ensure a controlled silica shell thickness growth on the UCNPs. The optimal conditions for this method were using 6 mg of UCNPs, 1.5 mL of Igepal CO-520, 0.25 mL of ammonia, and 50 μL of tetraethyl orthosilicate (TEOS), resulting in a uniform silica shell around UCNPs with a thickness of 8 nm. The optical characteristics of the silica-encased UCNPs were examined, confirming the retention of their intrinsic upconversion luminescence (UC). Furthermore, we developed a reliable strategy to avoid the coencapsulation of multiple UCNPs within a single silica shell. This approach led to a tenfold increase in the UC luminescence of the annealed particles compared to their nonannealed counterparts, under identical silica shell thickness and excitation conditions. This significant improvement addresses a critical challenge and amplifies the applicability of the resulting UCNPs@SiO2 core/shell structures in various fields. [ABSTRACT FROM AUTHOR]

Luminescence intensity ratio (LIR)-based thermometry has the advantages of high relative sensitivity, fast temperature response, and high spatial resolution. However, the current LIR-based systems are mainly based on thermally coupled energy levels, which have low sensitivity due to the intrinsic limitation of the Boltzmann distribution theory. Here, we report a design of a core–shell–shell nanostructure to improve the thermal sensitivity by using the nonthermally coupled upconversion emissions. Ho3+ and Tm3+ were selected as emitters and spatially separated by an inert interlayer. The upconverted Tm3+ emissions show a dramatical thermal enhancement while the Ho3+ emissions show a decline with increasing temperature, resulting in a huge LIR (695 nm/645 nm) contrast and thereafter a high relative sensitivity (9.78% K–1 at room temperature). In addition, this nanostructure design presents a color change from red to blue at different excitation powers and also from red to green by tuning the excitation laser pulse widths. These results hold great potential in the field of noncontact ultrasensitive temperature sensors and multimodel anticounterfeiting. [ABSTRACT FROM AUTHOR]

Incorporating functionalized TiO2 microarchitectures or upconversion nanoparticles (UCNPs) into photoanodes is deemed to be two effective ways to boost the photovoltaic performance of dye-sensitized solar cells (DSSCs). Nonetheless, studies combining functionalized TiO2 and UCNPs for the development of composite photoanode films in DSSCs still remain scarce. In view of this, we present a facile strategy for the design and preparation of a multifunctional composite photoanode containing P25 nanoparticles, peanut-like (PN) TiO2 microstructures, and NaYF4:Yb,Er@NaYF4:Nd@SiO2 core–shell–shell UCNPs. It is found that the DSSC containing a dual-functional photoanode using PN TiO2 as a light-scattering layer and P25 as a transparent layer can achieve a photovoltaic efficiency of 9.01%, presenting a 26.37% enhancement over the blank device. More importantly, the addition of UCNPs can further enhance the photoelectric performance of the DSSC device, realizing an optimal photovoltaic efficiency of 10.58%, one of the highest reported efficiencies for UCNP-based DSSCs with the common N719 photosensitizer. Such a remarkable improvement is mainly due to a synergetic effect of the UCNPs absorbing the near-infrared light and of the PN TiO2 presenting excellent light-scattering potency. Specifically, steady-state experiments reveal that the best-performing device shows only a small efficiency loss after 120 h of testing, exhibiting good device stability. The present work demonstrates the importance of composite photoanodes in enhancing the photovoltaic performances of solar cells. [ABSTRACT FROM AUTHOR]

Outbreaks of infectious viruses offer a formidable challenge to public healthcare systems and early detection of viruses is essential for preventing virus propagation. In this work, an ultrasensitive plasmon‐enhanced fluorescence resonance energy transfer (FRET) biosensor based on core‐shell upconversion nanoparticle (csUCNP) and gold nanoparticle (AuNP) for accurate detection of SARS‐CoV‐2 viral RNA is presented. In this biodetection assay, the Tm3+/Er3+ co‐doped csUCNP NaGdF4:Yb/Tm@NaYF4:Yb/Er acts as an energy donor and AuNP serves as an energy acceptor. The upconversion emission of Tm3+ and the design of the core‐shell structure led to a simultaneous surface plasmon effect of AuNP. The localized surface plasmon resonance (LSPR) arising from collective oscillations of free electrons significantly enhanced FRET efficiency between Er3+ and AuNP. The as‐prepared biosensor obtained a limit of detection (LOD) as low as 750 am, indicating that the integration of FRET and surface plasmon into one biodetection assay significantly boosted the sensitivity of the biosensor. In addition, samples extracted from clinical samples are also utilized to validate the effectiveness of the biosensor. Therefore, this innovative plasmon‐enhanced FRET biosensor based on Tm3+/Er3+ co‐doped csUCNP may pave the way for rapid and accurate biodetection applications. [ABSTRACT FROM AUTHOR]

Hydrogen‐bonded organic frameworks (HOFs) are crystalline porous materials with permanent voids formed via self‐assembly of organic molecules through hydrogen bonding and intermolecular forces. Further combination of HOFs with functional material would broaden their application horizon but were less explored in existing literature. Herein, a highly porous and photosensitive HOF was successfully coated onto upconversion nanoparticles (UCNPs) to construct a core–shell structure named UNCPs@PFC‐73‐Ni. To enhance spectral overlap and maximize energy conversion efficiency, this study utilized the Er and Tm co‐doped UCNPs, which can effectively convert infrared light into visible light emission thereby exciting the porphyrin shell. Subsequent investigation reveals that the composite exhibits significant photodynamic and photothermal effects under infrared light. Encouraged by its noticeable photoactivity, UCNPs@PFC‐73‐Ni was evaluated as an antibacterial agent against Escherichia coli. Notably, significant antibacterial efficacy was observed, highlighting the potential of UCNPs@PFC‐73‐Ni as an effective antibacterial agent under infrared light irradiation. [ABSTRACT FROM AUTHOR]

In this work, we successfully integrated fluorescent nanodiamonds (FNDs) and lanthanide ion-doped upconversion nanoparticles (UCNPs) in a nanocomposite structure for simultaneous optical temperature sensing. The effective integration of FND and UCNP shells was confirmed by employing high-resolution TEM imaging, X-ray diffraction, and dual-excitation optical spectroscopy. Furthermore, the synthesized ND@UCNP nanocomposites were tested by making simultaneous optical temperature measurements, and the detected temperatures showed excellent agreement within their sensitivity limit. The simultaneous measurement of temperature using two different modalities having different sensing physics but with the same composite nanoparticles inside is expected to greatly improve the confidence of nanoscale temperature measurements. This should resolve some of the controversy surrounding nanoscale temperature measurements in biological applications. [ABSTRACT FROM AUTHOR]

Biomedical assays based on optical nanoprobes play an important role in human health. Optical nanoprobes, the nanomaterials with special optical properties, are widely utilized in biomedical assays. Compared with traditional materials, the well-performed optical nanoprobes have certain properties, such as negligible interferences from the background fluorescence and scattering, simple operations and instruments, high sensitivity, and excellent specificity. This paper reviews the mechanisms, materials, and applications of optical nanoprobes. The mechanisms of optical nanoprobes involve fluorescence, phosphorescence, Forster resonance energy transfer (FRET), upconversion luminescence and chemiluminescence. Time-resolved luminescent nanoprobes are usually prepared from rare earth compounds and quantum dots (QDs). Ultralong inorganic phosphorescent nanoprobes are prepared from transition metal compounds, while ultralong organic phosphorescent nanoprobes are usually prepared from π-conjugated compound nanocrystals that exhibit a rigid confinement to suppress the non-radiative transitions and contain heavy atoms to enhance ISC. Time-resolved luminescent nanoprobes and ultralong phosphorescent nanoprobes minimize background interferences by longer luminescence lifetime. Chemiluminescent nanoprobes are usually prepared from compounds that can react with reactive oxygen species (ROS) to form peroxide bonds. Upconversion luminescent nanoprobes are usually prepared from inorganic rare earth fluoride nanocrystals. Chemiluminescent nanoprobes and upconversion luminescent nanoprobes can avoid background interferences because excitation light of shorter wavelength is not needed. FRET nanoprobes and luminescence quenching nanoprobes are prepared from a donor and an acceptor that can be linked or delinked by the analyte. Optical nanoprobes are applied in both in vitro diagnoses and in vivo imaging. The in vitro applications of optical nanoprobes include the determination of varieties of biomacromolecules and small molecules, while the in vivo imaging involves the diagnoses of inflammation and tumors. [ABSTRACT FROM AUTHOR]

Rapid detection and sensitive analysis of MMZ is of great importance for food safety. Herein, a fluorescent molecularly imprinted sensor based on upconversion nanoparticles (UCNPs) grafted onto covalent organic frameworks (COFs) was designed for the detection of MMZ. COFs with a high specific surface area and excellent affinity serve as substrates for grafting of UCNPs, which can inhibit the aggregation burst of UCNPs and improve the mass transfer rate of the sensor. Through a series of characterizations, it was found that the proposed UCNP-grafted COFs@MIP-based sensor had good optical stability, high adsorption efficiency, strong anti-interference ability, and high sensitivity owing to the integration of the advantages of UCNPs, COFs and MIPs. Under the optimal conditions, a good linear relationship was presented between the fluorescence intensity of UCNP-grafted COFs@MIPs and the methimazole concentration in the range of 0.05–3 mg L−1, and the detection limit was 3 μg L−1. The as-prepared UCNP-grafted COFs@MIPs were successfully applied for the detection of MMZ in actual samples, and the results were relevant with those determined by high-performance liquid chromatography. The sensor has good sensitivity, reusability, and high selectivity, which are highly valuable in the rapid analysis and detection of food safety. [ABSTRACT FROM AUTHOR]

Electrospun nanofibers possess a large surface area and a three-dimensional porous network that makes them a perfect material for embedding functional nanoparticles for diverse applications. Herein, we report the trends in embedding upconversion nanoparticles (UCNPs) in polymeric nanofibers for making an advanced miniaturized (bio)analytical device. UCNPs have the benefits of several optical properties, like near-infrared excitation, anti-Stokes emission over a wide range from UV to NIR, narrow emission bands, an extended lifespan, and photostability. The luminescence of UCNPs can be regulated using different lanthanide elements and can be used for sensing and tracking physical processes in biological systems. We foresee that a UCNP-based nanofiber sensing platform will open opportunities in developing cost-effective, miniaturized, portable and user-friendly point-of-care sensing device for monitoring (bio)analytical processes. Major challenges in developing microfluidic (bio)analytical systems based on UCNPs@nanofibers have been reviewed and presented. [ABSTRACT FROM AUTHOR]

A unique combination of a specific nucleic acid restriction endonuclease (REase) and atom transfer radical polymerization (ATRP) signal amplification strategy was employed for the detection of T790M mutations prevalent in the adjuvant diagnosis of lung cancer. REase selectively recognizes and cleaves T790M mutation sites on double-stranded DNA formed by hybridization of a capture sequence and a target sequence. At the same time, the ATRP strategy resulted in the massive aggregation of upconverted nanoparticles (UCNPs), which significantly improved the sensitivity of the biosensor. In addition, the UCNPs have excellent optical properties and can eliminate the interference of autofluorescence in the samples, thus further improving the detection sensitivity. The proposed upconversion fluorescent biosensor is characterized by high specificity, high sensitivity, mild reaction conditions, fast response time, and a detection limit as low as 0.14 fM. The performance of the proposed biosensor is comparable to that of clinical PCR methods when applied to clinical samples. This work presents a new perspective for assisted diagnosis in the pre-intervention stage of tumor diagnostics in the early stage of precision oncology treatments. [ABSTRACT FROM AUTHOR]

In this work, we report a new concept of upconversion-powered photoelectrochemical (PEC) bioanalysis. The proof-of-concept involves a PEC bionanosystem comprising a NaYF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) reporter, which is confined by DNA hybridization on a CdS quantum dots (QDs)/indium tin oxide (ITO) photoelectrode. The CdS QD-modified ITO electrode was powered by upconversion absorption together with energy transfer effect through UCNPs for a stable photocurrent generation. By measuring the photocurrent change, the target DNA could be detected in a specific and sensitive way with a wide linear range from 10 pM to 1 μM and a low detection limit of 0.1 pM. This work exploited the use of UCNPs as signal reporters and realized upconversion-powered PEC bioanalysis. Given the diversity of UCNPs, we believe it will offer a new perspective for the development of advanced upconversion-powered PEC bioanalysis. [ABSTRACT FROM AUTHOR]

Photoporation techniques based on plasmonic nanoparticles such as gold nanoparticles have been extensively studied for the intracellular delivery of substances via cell membrane disruption. However, the clinical application of AuNP is challenging due to its absorption in the 500 nm region of the light spectrum. To overcome this challenge, upconversion nanoparticles were employed to stimulate AuNP at NIR wavelengths. posAuNP@UCNPs nanocomposites were produced by coating 30 nm UCNPs on 80 nm AuNPs using DOPA-PEI, which were then irradiated with 980 nm NIR light to facilitate their intracellular delivery. TEM and DLS confirmed that posAuNP and UCNP combine to form nanocomposites. Additionally, multiphysics simulation was used to analyze the distribution of the posAuNP electric field based on morphological differences that change as the UCNP ratio increases. Next, effective LED irradiation conditions were established by applying upconverting-photon quenching-mediated perforation influx to C28/I2 cells as suspensions or spheroids. posAuNP@UCNP nanocomposites were confirmed to be effective for the delivery of baricitinib as a treatment for osteoarthritis in a three-dimensional osteoarthritis model. Finally, chondrocyte differentiation was induced through intracellular delivery of baricitinib using posAuNP@UCNPs. The findings suggest that posAuNP@UCNPs have great potential as a tool for non-invasive drug delivery via UCPPin. [ABSTRACT FROM AUTHOR]

The large size of lasers limits their applications in confined spaces, such as in biosensing and in vivo brain tissue imaging. In this regard, micron-sized lasers have been developed. They exhibit great potential for biological detecting, remote sensing, and depth tracking due to their small sizes, sensitive properties of their spectral fingerprints, and flexible positional modulation in the microenvironment. Lanthanide-based luminescent materials that possess long excited-state lifetime, narrow emission bandwidth, and upconversion behaviors are promising as gain mediums for novel microlasers. In addition, lanthanide-based microlasers could be generated under natural ambient conditions with pumped or continuous light sources, which significantly promotes the practical applications of microlasers. Recent progress in the design, synthesis, and biomedical applications of lanthanide-based microlasers has been outlined in this review. Lanthanide ions doped and upconverted lanthanide-based microlasers are highlighted, which exhibit advantageous structures, miniaturized dimensions, and high lasing performance. The applications of lanthanide-based microlasers are further discussed, the upconverted microlasers show great advantages for biological applications owing to their tunable excitation and emission characteristics and excellent environmental stability. Moreover, perspectives and challenges in the field of lanthanide-based microlasers are presented. [ABSTRACT FROM AUTHOR]

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In order to apply near infrared (NIR) light‐activated upconversion nanocrystals (UCNCs) in photochemistry, extremely bright luminescence is needed to excite the ultraviolet (UV)‐visible light absorbing photocatalyst/substrate. In this study, a multilayered UCNC consisting of a β‐NaYF4:Yb0.2, Tm0.005 core, heavily Yb3+‐doped β‐NaYbF4:Y0.09, Tm0.01 intermediate shell, and inert β‐NaYF4 outer shell is prepared. By compartmentalizing the sensitizer (Yb3+)‐activator (Tm3+) pair in the core and intermediate shell with different concentration ratios, a cooperative luminescence effect is discovered. Apart from core emission, energy harvesting followed by sequential energy transfer from a high density of neighboring Yb3+ to Tm3+ in the intermediate shell induces a large population of excited emitter ions. Furthermore, after back energy transfer from the core to intermediate shell, the energy is not quenched by intrinsic trap sites but is instead transferred to Tm3+, further boosting emission in the UV, blue, and NIR regions. The exceptionally bright UCNC is then used to drive NIR‐light‐activated one‐pot multicomponent reactions involving the upconversion energy transfer from UCNC to UV‐visible light absorbing photocatalyst/substrate, Lewis acid catalytic activity of the lanthanide ions (Y3+) on the surface, and photothermal property of the UCNC. The reactions studied include the deacetalization‐Knoevenagel condensation reaction, photooxidation‐cyanation reaction, and hydrodehalogenation‐cyanosilylation reaction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Macrophages are the most abundant cell group in atherosclerosis (AS) lesions and play a vital role in all stages of AS progression. Recent research has shown that reactive oxygen species (ROS) generation from photodynamic therapy (PDT) induces macrophage autophagy to improve abnormal lipid metabolism and inflammatory environment. Especially in macrophage-derived foam cells, which has become a potential strategy for the treatment of AS. In this study, we prepared the conjugate (DB) of dextran (DEX) and bovine serum albumin (BSA). The DB was used as the emulsifier to prepare nanoemulsion loaded with upconversion nanoparticles (UCNPs) and chlorin e6 (Ce6) (UCNPs-Ce6@DB). The DEX modified on the surface of the nanoemulsion can recognise and bind to the scavenger receptor class A (SR-A) highly expressed on macrophages and promote the uptake of macrophage-derived foam cells in AS plates through SR-A-mediated endocytosis. In addition, UCNPs-Ce6@DB-mediated PDT enhanced ROS generation and induced autophagy in macrophage-derived foam cells, enhanced the expression of ABCA 1, a protein closely related to cholesterol efflux, and inhibited the secretion of pro-inflammatory cytokines. Ultimately, UCNPs-Ce6@DB was shown to inhibit plaque formation in mouse models of AS. In conclusion, UCNPs-Ce6@DB offers a promising treatment for AS. [ABSTRACT FROM AUTHOR]

Novel and high-security anti-counterfeiting technology has always been the focus of attention and research. This work proposes a nanocomposite combination of upconversion nanoparticles (UCNPs) and perovskite quantum dots (PeQDs) to achieve color-adjustable dual-mode luminescence anti-counterfeiting. Firstly, a series of NaGdF4: Yb/Tm UCNPs with different sizes were synthesized, and their thermal-enhanced upconversion luminescence performances were investigated. The upconversion luminescence (UCL) intensity of the samples increases with rising temperature, and the UCL thermal enhancement factor rises as the particle size decreases. This intriguing thermal enhancement phenomenon can be attributed to the mitigation of surface luminescence quenching. Furthermore, CsPbBr3 PeQDs were well adhered to the surfaces and surroundings of the UCNPs. Leveraging energy transfer and the contrasting temperature responses of UCNPs and PeQDs, this nanocomposite was utilized as a dual-mode thermochromic anti-counterfeiting system. As the temperature increases, the color of the composite changes from green to pink under 980 nm excitation, while it displays green to non-luminescence under 365 nm excitation. This new anti-counterfeiting material, with its high security and convenience, has great potential in anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is a halophilic and heat-labile gram-negative bacterium and is the most prevalent foodborne bacterium in seafood. In order to develop a rapid and sensitive method for detecting the foodborne pathogenic bacterium Vibrio parahaemolyticus, an aptamer-modified magnetic nanoparticle and an aptamer-modified upconversion nanoparticle were synthesised and used as a capture probe and a signal probe, respectively. The aptamer-modified magnetic nanoparticle, V. parahaemolyticus cell, and aptamer-modified upconversion nanoparticle formed a sandwich-like complex, which was rapidly separated from a complex matrix using a magnetic force, and the bacterial concentration was determined by fluorescence intensity analysis. The results showed that the fluorescence intensity signal correlated positively with the concentration of V. parahaemolyticus in the range of 3.2 × 102 to 3.2 × 105 CFU/mL, with a linear equation of y = 296.40x − 217.67 and a correlation coefficient of R2 = 0.9610. The detection limit of the developed method was 4.4 CFU/mL. There was no cross-reactivity with other tested foodborne pathogens. This method is highly specific and sensitive for the detection of V. parahaemolyticus, and can achieve the qualitative detection of this bacterium in a complex matrix. [ABSTRACT FROM AUTHOR]

Photoclick reactions combine the selectivity of classical click chemistry with the high precision and spatiotemporal control afforded by light, finding diverse utility in surface customization, polymer conjugation, photocross‐linking, protein labeling, and bioimaging. Nonetheless, UV light, pivotal in prevailing photoclick reactions, poses issues, especially in biological contexts, due to its limited tissue penetration and cell‐toxic nature. Herein, a reliable and versatile strategy of activating the photoclick reactions of 9,10‐phenanthrenequinones (PQs) with electron‐rich alkenes (ERAs) with near infrared (NIR) light transduced by spectrally and structurally customized upconversion nanoparticles (UCNPs) is introduced. Under NIR irradiation, the UCNPs become UV/blue nanoemitters uniformly distributed in the reaction system. Enabled by the customized UCNPs, 800 or 980 nm light effectively activates the photocycloaddition reactions via radiative energy transfer in both general and triplet–triplet energy transfer (TTET)‐mediated PQ‐ERA systems. In particular, the novel sandwich structure UCNPs achieve the click reaction with up to 76% production yield in 10 min under NIR light irradiation. Meanwhile, the tricky side effect of photoclick product absorption‐induced quenching is successfully circumvented from the fine‐tuning of the upconversion spectrum. Moreover, through‐tissue irradiation experiments, the authors show that the UCNP‐PQ‐ERA reaction unlocks the full potential of photoclick reactions for in vivo applications. [ABSTRACT FROM AUTHOR]

It remains a fundamental challenge to administer guided regeneration and functional recovery of peripheral nerves after the complete transection. Herein, a new concept to specifically depolarize the membranes of the target acetylcholinergic motor neurons by near infrared (NIR) laser‐triggered optogenetics for promoted functional reconnection of transected peripheral nerves is reported. The approach features the anchoring of acetylcholine‐modified upconversion nanoparticles (UCNP) onto the acetylcholine receptors on the postsynaptic membrane and selective infection of the motor neural cells with adeno‐associated virus loading channelrhodopsin 2 (ChR2). The upconversion fluorescence mediated by UCNP can activate ChR2 protein for membrane depolarization of the acetylcholinergic motor neurons. It induces a cascade of events, including axonal regeneration, Schwann cells remyelination, brain‐derived neurotrophic factor expression enhancement, and the remodeling of neuromuscular junctions (NMJ) from muscle denervation, which leads to promoted functional reconnection of the injured peripheral nerves. The results of behavioral and electrophysiological experiments further verify the functional recovery of transected peripheral nerves by the approach. The UCNP‐mediated optogenetic strategy of minimally invasive, precisely guided, and functional reconnection of injured nerves shall bring great benefits to both fundamental research and translational development in neural regenerative medicine. [ABSTRACT FROM AUTHOR]

Parameters of synthesis are varied to fabricate NaYF4:Yb,Er phosphors with expressed upconversion properties when excited at a wavelength of 980 nm. Data from luminescence spectroscopy shows the particles exhibit temperature sensitivity in the range of 240–350 K, allowing temperature to be measured ratiometrically. [ABSTRACT FROM AUTHOR]

In this work, an upconversion luminescence (UCL) nanosensor for fast detection of ferric ion (Fe3+) and phosphate ion (Pi) is developed based on the inner-filter effect (IFE) between NaYF4:Yb/Er upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex. Fe3+-HB complex has strong absorption band (450–650 nm), which overlaps with the green emission peak of UCNPs at 545 nm. By adding Fe3+ and Pi, the UCNPs-HB system produces the red-shift change of absorption spectrum, which leads to the "on–off-on" process of IFE. So, with the specific recognition ability of HB for Fe3+ and the competitive complexation of Pi for Fe3+, the proposed nanosensor utilizes the UCL change to achieve the detection of the targets. For the detections of Fe3+, the linear range is 10–600 μM with a limit of detection (LOD) of 2.62 μM, and for Pi, the linear range is 5–100 μM with a LOD of 1.25 μM. The results for selectivity, precision, and recovery test are also satisfactory. Furthermore, the real sample detection shows that the proposed nanaosensor has a great potential in environmental and biological systems. An upconversion luminescence (UCL) nanosensor based on the inner-filter effect (IFE) between upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex for the detection of Fe3+ and phosphate ion has been proposed, which is promising to be a convenient and sensitive assay for monitoring Fe3+ and phosphate ion in different environments and biological systems. [ABSTRACT FROM AUTHOR]

Photoinduced reversible deactivation radical polymerization (photo‐RDRP) or photoinduced controlled/living radical polymerization has emerged as a versatile and powerful technique for preparing functional and advanced polymer materials under mild conditions by harnessing light energy. While UV and visible light (λ = 400–700 nm) are extensively employed in photo‐RDRP, the utilization of near‐infrared (NIR) wavelengths (λ = 700–2500 nm) beyond the visible region remains relatively unexplored. NIR light possesses unique properties, including enhanced light penetration, reduced light scattering, and low biomolecule absorption, thereby providing opportunities for applying photo‐RDRP in the fields of manufacturing and medicine. This comprehensive review categorizes all known NIR light‐induced RDRP (NIR‐RDRP) systems into four mechanism‐based types: mediation by upconversion nanoparticles, mediation by photocatalysts, photothermal conversion, and two‐photon absorption. The distinct photoinitiation pathways associated with each mechanism are discussed. Furthermore, this review highlights the diverse applications of NIR‐RDRP reported to date, including 3D printing, polymer brush fabrication, drug delivery, nanoparticle synthesis, and hydrogel formation. By presenting these applications, the review underscores the exceptional capabilities of NIR‐RDRP and offers guidance for developing high‐performance and versatile photopolymerization systems. Exploiting the unique properties of NIR light unlocks new opportunities for synthesizing functional and advanced polymer materials. [ABSTRACT FROM AUTHOR]

The generation and flow of heat in the microscale are involved in a great variety of physical, chemical, and biological processes. Accurate measurement of local temperatures provides essential information for the complete characterization of nano/microdevices and the comprehension of local thermal effects. Using Er3+-doped upconversion nanoparticles (UCNPs) as thermal probes deposited on different thermally active microstructures, we assembled a motorized platform for scanning the upconversion luminescence (UCL) and retrieved temperature readings. We discuss critical aspects of the technique, such as calibration procedures, self-heating of substrate materials, the role of power density of the excitation light, and the uniformity of the coatings. A temperature resolution of 0.24(2) K, a spatial resolution of 0.24(7) μm, and a temporal resolution of 0.034(6) s were achieved. The platform was used for the characterization of two thermally active systems of interest: a microheater device and a photothermal nanoparticle coating immersed in a buffered solution. We emphasize potential applications for this method in the fields of cell biology and explore potential improvements with the use of UCNPs with increased thermal sensitivity, uniform self-assembled monolayer covering, and the integration of specific optical elements in the setup. [ABSTRACT FROM AUTHOR]