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A sensitive platform was constructed for on-site detection of chlorpyrifos by immobilizing a core–shell structured NaYbF 4 @NaYF 4 : Yb3+, Tm3+ UCNPs/MnO 2 composite in calcium alginate hydrogel kit. Specifically, the designed UCNPs fluorescent probe (NaYbF 4 @NaYF 4 : Yb3+, Tm3+) has the blue-violet emission. After mixing with MnO 2 nanoflakes, the blue-violet upconversion (UC) emission is quenched. Thiocholine (TCh), formed through acetylcholinesterase (AChE)-mediated catalysis, reduces MnO 2 nanoflakes to Mn2+ ions, thereby restoring the system's fluorescence. The introduction of chlorpyrifos inhibits AChE activity, accompanied by the quenching of the fluorescence signal. Based on the blue-violet UC emission signal response to chlorpyrifos, fluorescent photos were taken by smartphones. Utilizing a Python-assisted analysis platform, a "one-run" operation simultaneously captures image grayscale values, gray images, and differentiated pseudo-color images related to pesticide concentrations, enabling real-time and rapid quantitative analysis of pesticides. [Display omitted] On-site quantitative analysis of pesticide residues is crucial for monitoring environmental quality and ensuring food safety. Herein, we have developed a reliable hydrogel portable kit using NaYbF 4 @NaYF 4 : Yb, Tm upconversion nanoparticles (UCNPs) combined with MnO 2 nanoflakes. This portable kit is integrated with a smartphone reader and Python-assisted analysis platform to enable sample-to-result analysis for chlorpyrifos. The novel UCNPs maximizes energy donation to MnO 2 acceptor by employing 100 % of activator Yb3+ in the nucleus for NIR excitation energy collection and confining emitter Tm3+ to the surface layer to shorten energy transfer distance. Under NIR excitation, efficient quenching of upconversion blue-violet emission by MnO 2 nanoflakes occurs, and the quenched emission is recovered with acetylcholinesterase-mediated reactions. This process allows for the determination of chlorpyrifos by inhibiting enzymatic activity. The UCNPs/MnO 2 were embedded to fabricate a hydrogel portable kit, the blue-violet emission images captured by smartphone were converted into corresponding gray values by Python-assisted superiority chart algorithm which achieves a real-time rapid quantitative analysis of chlorpyrifos with a detection limit of 0.17 ng mL−1. At the same time, pseudo-color images were also added by Python in "one run" to distinguish images clearly. This sensor detection with Python-assisted analysis platform provides a new perspective on pesticide monitoring and broadens the application prospects in bioanalysis. [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]

Super‐resolution fluorescence microscopy is of great interest in life science studies for visualizing subcellular structures at the nanometer scale. Among various kinds of super‐resolution approaches, image scanning microscopy (ISM) offers a doubled resolution enhancement in a simple and straightforward manner, based on the commonly used confocal microscopes. ISM is also suitable to be integrated with multi‐photon microscopy techniques, such as two‐photon excitation and second‐harmonic generation imaging, for deep tissue imaging, but it remains the twofold limited resolution enhancement and requires expensive femtosecond lasers. Here, the super‐linear ISM (SL‐ISM) pushes the resolution enhancement beyond the factor of two is presented and experimentally demonstrated, with a single low‐power, continuous‐wave, and near‐infrared laser, by harnessing the emission nonlinearity within the multiphoton excitation process of lanthanide‐doped upconversion nanoparticles (UCNPs). Based on a modified confocal microscope, a resolution of ≈120 nm, 1/8th of the excitation wavelength is achieved. Furthermore, a parallel detection strategy of SL‐ISM with the multifocal structured excitation pattern is demonstrated, to speed up the acquisition frame rate. This method suggests a new perspective for super‐resolution imaging or sensing, multi‐photon imaging, and deep‐tissue imaging with simple, low‐cost, and straightforward implementations. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

The rapid photobleaching of near-infrared (NIR) dye-sensitized upconversion nanosystems is one of the crucial problems that has blocked their technological applications. Uncovering the photophysical and photochemical pathways of NIR dyes would help to elucidate the photobleaching mechanism and thereby improve the photostability of the system. Here we investigate the triplet dynamics of NIR dyes and their interaction with triplet oxygen in the typically investigated IR806-sensitized upconversion nanoparticle (UCNP) nanosystem. Low-temperature fluorescence at 77 K provides direct proof of the generation of singlet oxygen (1O2) under 808 nm laser irradiation. Mass spectrometry indicates that all three double bonds in the structure of IR806 can be broken in the photochemical process. Coupling IR806 to the surface of UCNPs can accelerate its triplet dynamics, thus producing more 1O2 to photocleave IR806. Importantly, we find that the addition of β-carotene can scavenge the generated 1O2, thereby providing a simple method to effectively inhibit photobleaching.

Aerogel scaffolds are nanostructured materials with beneficial properties for tissue engineering applications. The tracing of the state of the aerogels after their implantation is challenging due to their variable biodegradation rate and the lack of suitable strategies capable of in vivo monitoring the scaffolds. Upconversion nanoparticles (UCNPs) have emerged as advanced tools for in vitro bioimaging because of their fluorescence properties. In this work, highly fluorescent UCNPs were loaded into aerogels to obtain theranostic implants for tissue engineering and bioimaging applications. 3D-printed alginate-hydroxyapatite aerogels labeled with UCNPs were manufactured by 3D-printing and supercritical CO2 drying to generate personalize-to-patient aerogels. The physicochemical performance of the resulting structures was evaluated by printing fidelity measurements, nitrogen adsorption-desorption analysis, and different microscopies (confocal, transmission and scanning electron microscopies). Stability of the aerogels in terms of physicochemical properties was also tested after 3 years of storage. Biocompatibility was evaluated in vitro by different cell and hemocompatibility assays, in ovo and in vivo by safety and bioimaging studies using different murine models. Cytokines profile, tissue index and histological evaluations of the main organs unveiled an in vivo downregulation of the inflammation after implantation of the scaffolds. UCNPs-decorated aerogels were first-time manufactured and long-term traceable by fluorescence-based bioimaging until 3 weeks post-implantation, thereby endorsing their suitability as tissue engineering and theranostic nanodevices (i.e. bifunctional implants).

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 Förster 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.

Weak luminescence of the small‐sized lanthanide‐doped nanoparticles has limited their applications long. In recent years, there is a growing interest in luminescence thermal enhancement in small‐sized upconversion nanoparticles (UCNPs). The mitigation of surface quenching effects and the improvement of energy transfer (ET) are two convincing explanations for this phenomenon. A systematical investigation on the luminescence dynamics of Yb3+ is implemented. ET rate and then the proportion of ET increases greatly with rising temperatures in Yb3+/Tm3+ codoped system, while an alternative trend can be summarized in Yb3+/Er3+ one. Based on these findings, therefore it can be concluded that the surface quenching mitigation related to the desorption of water molecules on the surface is a common mechanism of the luminescence thermal enhancement. But ET related to the thermally‐activated surface phonons is a special case, it does play a positive role in Yb3+/Tm3+ system. These findings not only explain the upconversion luminescence thermal enhancement in Yb3+/Tm3+ system is more significant but also help to understand thermal enhancement and benefit highly‐sensitive temperature probe design. [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]

AbstractMicroRNAs (miRNAs) are small molecules with significant regulatory functions that have served as biomarkers for the early diagnosis of disease. Accordingly, it is purposeful to develop a rapid, targeted assay for the sensitive, selective, and determination of target miRNAs. Single-band red emission of upconversion nanoparticles (UCNPs) offer high photostability, large anti-Stokes shifts, and low background. Additionally, improving the accuracy via dual-signal fluorescence is also effective for reducing false positive signals induced by background. Herein, taking advantage of the single-band red emission of UCNPs and DNA complementary nanotechnologies, a target-triggered self-assembled dual-signal response biosensor via a strand displacement cascade is reported. The reported approach was used for the determination of miRNA-222 (a model analyte) in serum and the results were similar to those obtained by the polymerase chain reaction (PCR). The spiked recoveries were from 92.5 to 108.4%, indicating that this biosensor has potential for accurate and sensitive determination of miRNAs in biological samples. [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]

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]

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]

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]

Upconversion nanoparticles (UCNPs), particularly those that are highly doped, possess outstanding properties and have demonstrated tremendous application potential. However, novel fine-tuning strategies are urgently required to enhance the upconversion luminescence (UCL) performance of UCNPs. In this study, a series of core–multishell UCNPs highly doped with Ho3+ and Yb3+ ions were synthesized via the oleate route. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and UCL spectra and decay times, and pump power dependency of the synthesized UCNPs were used to examine their morphology, size, and the UCL properties. Ce3+ ions were introduced to enhance Ho3+-based red UCL, and their doping strategy was also optimized based on summarized UCL trends and detailed UCL mechanism analysis. NaHoF 4 :Gd3+@NaGdF 4 :Yb3+,Ce3+@NaGdF 4 :Yb3+ UCNPs that had 10 mol% Ce3+ dopants in their middle shells exhibited better UCL properties than the larger traditional NaGdF 4 :Yb3+,Ce3+,Ho3+ UCNPs, probably because of the combined influence of the energy interactions between the Ce3+ ions and surface groups, sensitizing energy enhancement by active shells, and the positive cooperation between the Ce3+ ions and highly-doped core–shell structures. In this study, the phenomenon of UCL decrease resulting from Ce3+ ion doping was explored. Using unique core–multishell structures with highly-doped activators and sensitizers placed within and outside the structures, respectively, the UCL decrease due to Ce3+ ion doping was attributed to a competition for photons. Doping the UCNPs with Ce3+ ions near the UCNP surfaces favors Ho3+-based red UCL. Our study findings can deepen the understanding of the Ho3+-based UCL mechanisms and increase the potential uses of NaHoF 4 materials in photo-induced therapy. When Ce3+ ions are doped near the nanoparticle surface, they might have energy interactions with surface groups to relieve phonon energy shortage and thus enhance the efficiency of cross-relaxation between Ho3+ and Ce3+ ions. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

Preparation of highly dispersed nanoparticles NaYF4; Yb, Er nanoparticles based on hydrothermal method, and coating of mesoporous silica(MSN) on its outer layer with further modification of polydopamine (PDA) and hyaluronic acid(HA) to prepare composite nanospheres UCNPS© MSN @ PDA-HA・ The structure and morphology were observed by transmission electron microscopy (TEM)・ The composition and luminescence performance were detected by infrared analyzer(FITR) and fluorescence spectrometer・ The results indicate that composite nanospheres have good dispersibility and mesoporous structure, and still exhibit good upconversion luminescence effect after modification with different materials. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT), as one of the most promising cancer therapy methods, is still limited by several drawbacks, such as tissue hypoxia and shallow light penetration of blue-violet light (200–450 nm), and red light (750 nm) is more penetrating to tissues than blue-violet light, but still lower than near-red light (750–1350 nm). Therefore, we proposed a synergistic therapy system by combining the near-infrared light-triggered PDT with nitric oxide (NO)-based gas therapy to enhance the anti-tumor effects. Upconversion nanoparticles (UCNPs) were loaded with the photosensitizers of ZnPc and the NO donors of l-arginine (L-Arg) to obtain the nanocomposites of UCN@mSiO2@ZnPc@L-Arg. Under 980 nm laser irradiation, reactive oxygen species (ROS) could be produced for PDT and react with l-Arg to produce NO, which is previously reported to have a greater killing effect on tumor cells than ROS and also plays an important role in promoting PDT in our study. Both the in vitro and in vivo tests demonstrated that the combined therapy of PDT with NO therapy could enhance the tumor killing effect significantly compared with the unique application of PDT. The UCNPs-based nanocomposites are expected to be widely used in biomedicine for tumor inhibition.

Osteoporosis (OP), the most prevalent bone degenerative disease, has become a significant public health challenge globally. Current therapies primarily target inhibiting osteoclast activity or stimulating osteoblast activation, but their effectiveness remains suboptimal. This paper introduced a “three birds, one stone” therapeutic approach for osteoporosis, employing upconversion nanoparticles (UCNPs) to create a dual-gas storage nanoplatform (UZPA-CP) targeting bone tissues, capable of concurrently generating carbon monoxide (CO) and hydrogen sulfide (H2S). Through the precise modulation of 808 nm near-infrared (NIR) light, the platform could effectively control the release of CO and H2S in the OP microenvironment, and realize the effective combination of promoting osteogenesis, inhibiting osteoclast activity, and improving the immune microenvironment to achieve the therapeutic effect of OP. High-throughput sequencing results further confirmed the remarkable effectiveness of the nanoplatform in inhibiting apoptosis, modulating inflammatory response, inhibiting osteoclast differentiation and regulating multiple immune signaling pathways. The gas storage nanoplatform not only optimized the OP microenvironment with the assistance of NIR, but also restored the balance between osteoblasts and osteoclasts. This comprehensive therapeutic strategy focused on improving the bone microenvironment, promoting osteogenesis and inhibiting osteoclast activity provides an ideal new solution for the treatment of metabolic bone diseases.

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.

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, Förster 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.

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]

Ferroptosis, a unique iron-dependent mode of cell death characterized by lipid peroxide accumulation, holds significant potential for the treatment of glioblastoma (GBM). However, the effectiveness of ferroptosis is hindered by the limited intracellular ferrous ions (Fe2+) and hydrogen peroxide (H 2 O 2). In this study, a novel near-infrared (NIR)-light-responsive nanoplatform (ApoE-UMSNs-GOx/SRF) based on upconversion nanoparticles (UCNPs) was developed. A layer of mesoporous silica and a lipid bilayer were coated on UCNPs sequentially and loaded with glucose oxidase (GOx) and sorafenib, respectively. Further attachment of the ApoE peptide endowed the nanoplatform with BBB penetration and GBM targeting capabilities. Our results revealed that ApoE-UMSNs-GOx/SRF could efficiently accumulated in the orthotopic GBM and induce amplified ferroptosis when combining with NIR irradiation. The UCNPs mediated the photoreduction of Fe3+ to Fe2+ by converting NIR to UV light, and excess H 2 O 2 was produced by the reaction of glucose with the loaded GOx. These processes greatly promoted the production of ROS, which together with inhibition of system Xc− by the loaded sorafenib, leading to enhanced accumulation of lipid peroxides and significantly improved the antiglioma effect both in vitro and in vivo. Our strategy has the potential to enhance the effectiveness of ferroptosis as a therapeutic approach for GBM. A novel nanoplatform (ApoE-UMSNs-GOx/SRF) for the efficient treatment of glioblastoma through NIR-promoted enhanced ferroptosis. [Display omitted] [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]

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]

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]

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]

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]

The development of super-resolution fluorescence microscopy is very essential for understanding the physical and biological fundamentals at nanometer scale. However, to date most super-resolution modalities require either complicated/costly purpose-built systems such as multiple-beam architectures or complex post-processing procedures with intrinsic artifacts. Achieving three-dimensional (3D) or multi-channel sub-diffraction microscopic imaging using a simple method remains a challenging and struggling task. Herein, we proposed 3D highly-nonlinear super-resolution microscopy using a single-beam excitation strategy, and the microscopy principle was modelled and studied based on the ultrahigh nonlinearity enabled by photon avalanches. According to the simulation, the point spread function of highly nonlinear microscopy is switchable among different modes and can shrink three-dimensionally to sub-diffraction scale at the photon avalanche mode. Experimentally, we demonstrated 3D optical nanoscopy assisted with huge optical nonlinearities in a simple laser scanning configuration, achieving a lateral resolution down to 58 nm (λ /14) and an axial resolution down to 185 nm (λ /5) with one single beam of low-power, continuous-wave, near-infrared laser. We further extended the photon avalanche effect to many other emitters to develop multi-color photon avalanching nanoprobes based on migrating photon avalanche mechanism, which enables us to implement single-beam dual-color sub-diffraction super-resolution microscopic imaging. [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]

Abstract 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 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. Graphical Abstract

Lanthanide-doped upconversion nanoparticles (UCNPs) were found promising in photovoltaic devices and nanoscale sensing due to their excellent optical properties. However, the low quantum yields severely limit their practical applications. In this work, we reported the enhanced upconversion emission by near-field modulation on all dielectric interfaces. The flexible polystyrene (PS) sphere array @UCNPs composite was fabricated by self-assembly and the NIR excitation can be highly localized and amplified in the array with proper sphere size, thus promoting the upconversion process. Based on this efficient upconversion composite film, the sensing performance on acetic acid gas were discussed in detail. The good linear relationship between the upconversion luminescence intensity and acetic acid concentration can be achieved with a detection limit of 5.2 ppm at room temperature, which is comparable with the best level reported so far. In addition, such optical signal-based sensors possessed other unique advantages such as easy fabrication, high sensitivity, long-term stability, reusability and flexibility. And the fluorescence signal enhancement factor showed less dependence on the excitation power and can emit effectively at low pump power. This all dielectric fluorescent composite with high efficiency and sensing performance can be helpful in biosensor and flexible security label applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Reprogramming immunosuppressive M2 macrophages into M1 macrophages in tumor site provides a new strategy for the immunotherapy of colorectal cancer. In this study, M1 macrophage-derived exosome nanoprobe (M1UC) with Ce6-loaded upconversion material is designed to enhance the photodynamic performance of Ce6 while reprogramming M2 macrophages at tumor site and producing NO gas for three-mode synergistic therapy. Under the excitation of near-infrared light at 808 nm, the probe can generate 660 nm up-conversion fluorescence, which enables the photosensitizer Ce6 to produce ROS efficiently. In addition, the probe leads the production of NO by nitric oxide synthase on exosomes. Confocal laser and flow cytometry results show that M1UC probe reprograms M2 macrophages into M1 macrophages with an efficiency of 95.12%. The cell experiments show that the apoptosis rate of the three-mode synergistic therapy group is 78.8%, and the therapeutic effect is significantly higher than those of the other single treatment groups. In vivo experiments results show that M1UC probes maximally gather at the tumor site after 12 h of intravenous injection in orthotopic colorectal cancer mice. After 808 nm laser irradiation, the survival rate of mice is 100% and the recurrence rate was 0 within 60 d, and the therapeutic effect is significantly higher than those of other single treatment groups, which is also confirmed by immunohistochemistry. This M1 macrophage-derived exosome nanoplatform which is based on the three modes of immunotherapy, gas therapy and photodynamic therapy, provides a new design idea for the diagnosis and treatment of deep tumors. [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]