Luminescence Resonance Energy Transfer Research Articles

Persistent Luminescence Lifetime-Based Near-Infrared Nanoplatform via Deep Learning for High-Fidelity Biosensing of Hypochlorite.

In light of deep tissue penetration and ultralow background, near-infrared (NIR) persistent luminescence (PersL) bioprobes have become powerful tools for bioapplications. However, the inhomogeneous signal attenuation may significantly limit its application for precise biosensing owing to tissue absorption and scattering. In this work, a PersL lifetime-based nanoplatform via deep learning was proposed for high-fidelity bioimaging and biosensing in vivo. The persistent luminescence imaging network (PLI-Net), which consisted of a 3D-deep convolutional neural network (3D-CNN) and the PersL imaging system, was logically constructed to accurately extract the lifetime feature from the profile of PersL intensity-based decay images. Significantly, the NIR PersL nanomaterials represented by Zn1+xGa2-2xSnxO4: 0.4 % Cr (ZGSO) were precisely adjusted over their lifetime, enabling the PersL lifetime-based imaging with high-contrast signals. Inspired by the adjustable and reliable PersL lifetime imaging of ZGSO NPs, a proof-of-concept PersL nanoplatform was further developed and showed exceptional analytical performance for hypochlorite detection via a luminescence resonance energy transfer process. Remarkably, on the merits of the dependable and anti-interference PersL lifetimes, this PersL lifetime-based nanoprobe provided highly sensitive and accurate imaging of both endogenous and exogenous hypochlorite. This breakthrough opened up a new way for the development of high-fidelity biosensing in complex matrix systems.

Ultrasensitive upconverting nanoprobes for in situ imaging of drug-induced liver injury using miR-122 as the biomarker

Drug-induced liver injury (DILI) is a frequent adverse drug reaction. The current clinical diagnostic methods are inadequate for accurate and early detection of DILI due to the lack of effective diagnostic biomarkers. Hepatocyte-specific miR-122 is released from injured hepatocytes promptly and its efflux is significantly correlated with the progression of DILI. Therefore, achieving precise in situ detection of miR-122 with high sensitivity is vital for early visualization of DILI. Herein, a new nanoprobe, consisting of miR-122 aptamer, upconversion nanoparticles (UCNPs) and Prussian blue nanoparticles (PBNPs) was introduced for the early and sensitive detection of DILI in situ. As the nanoprobes reached in the liver, miR-122 aptamer-based entropy-driven strand displacement (ESDR) signal amplification reaction was triggered and luminescence resonance energy transfer (LRET) between UCNPs and PBNPs was responded to achieve the high-fidelity detection of DILI. A negative correlation was observed between the intensity of upconversion luminescence (UCL) and the concentration of miR-122. UCL imaging conducted both in vivo and ex vivo indicated that a reduction in miR-122 concentration led to an increase in UCL intensity, revealing a precise state of DILI. The detection technique demonstrated a positive correlation between signal intensity and severity, offering a more straightforward and intuitive method of visualizing DILI.

Biporous silica nanostructure-induced nanovortex in microfluidics for nucleic acid enrichment, isolation, and PCR-free detection

Efficient pathogen enrichment and nucleic acid isolation are critical for accurate and sensitive diagnosis of infectious diseases, especially those with low pathogen levels. Our study introduces a biporous silica nanofilms-embedded sample preparation chip for pathogen and nucleic acid enrichment/isolation. This chip features unique biporous nanostructures comprising large and small pore layers. Computational simulations confirm that these nanostructures enhance the surface area and promote the formation of nanovortex, resulting in improved capture efficiency. Notably, the chip demonstrates a 100-fold lower limit of detection compared to conventional methods used for nucleic acid detection. Clinical validations using patient samples corroborate the superior sensitivity of the chip when combined with the luminescence resonance energy transfer assay. The enhanced sample preparation efficiency of the chip, along with the facile and straightforward synthesis of the biporous nanostructures, offers a promising solution for polymer chain reaction-free detection of nucleic acids.

Amyloid detection in neurodegenerative diseases using MOFs.

Neurodegenerative diseases (amyloid diseases such as Alzheimer's and Parkinson's), stemming from protein misfolding and aggregation, encompass a spectrum of disorders with severe systemic implications. Timely detection is pivotal in managing these diseases owing to their significant impact on organ function and high mortality rates. The diverse array of amyloid disorders, spanning localized and systemic manifestations, underscores the complexity of these conditions and highlights the need for advanced detection methods. Traditional approaches have focused on identifying biomarkers using imaging techniques (PET and MRI) or invasive procedures. However, recent efforts have focused on the use of metal-organic frameworks (MOFs), a versatile class of materials known for their unique properties, in revolutionizing amyloid disease detection. The high porosity, customizable structures, and biocompatibility of MOFs enable their integration with biomolecules, laying the groundwork for highly sensitive and specific biosensors. These sensors have been employed using electrochemical and photophysical techniques that target amyloid species under neurodegenerative conditions. The adaptability of MOFs allows for the precise detection and quantification of amyloid proteins, offering potential advancements in early diagnosis and disease management. This review article delves into how MOFs contribute to detecting amyloid diseases by categorizing their uses based on different sensing methods, such as electrochemical (EC), electrochemiluminescence (ECL), fluorescence, Förster resonance energy transfer (FRET), up-conversion luminescence resonance energy transfer (ULRET), and photoelectrochemical (PEC) sensing. The drawbacks of MOF biosensors and the challenges encountered in the field are also briefly explored from our perspective.

Magnetic-responsive upconversion luminescence resonance energy transfer (LRET) biosensor for ultrasensitive detection of SARS-CoV-2 spike protein

Upconversion nanoparticles (UCNPs) are ideal donors for luminescence resonance energy transfer (LRET)-based biosensors due to their excellent upconversion luminescence properties. However, the relatively large size of antibodies and proteins limits the application of UCNPs-based LRET biosensors in protein detection because the large steric hindrance of proteins leads to low energy transfer efficiency between UCNPs and receptors. Herein, we developed a magnetic responsive UCNPs-based LRET biosensor to control the coupling distance between antibody-functionalized UCNPs (Ab-UCNPs) as donors and antibody-PEG linker-magnetic gold nanoparticles (Ab-PEG-MGNs) as acceptors for ultrasensitive and highly selective detection of SARS-CoV-2 spike proteins. Our results showed that this platform reversibly shortened the coupling distance between UCNPs and MGNs and enhanced the LRET signal with a 10-fold increase in the limit of detection (LOD) from 20.6 pg/mL without magnetic modulation to 2.1 pg/mL with magnetic modulation within 1 h. The finite-difference time-domain (FDTD) simulation with cyclic distance change confirmed the distance-dependent LRET efficiency under magnetic modulation, which supported the experimental results. Moreover, the applications of this magnetic-responsive UCNP-based LRET biosensor could be extended to other large-size biomolecule detection.

Dual-responsive persistent luminescence nanoflowers for glutathione detection and imaging

Glutathione (GSH) is one of the important substances to maintain the redox balance in vivo, accurate monitoring of its changes is conducive to the early diagnosis and treatment of related diseases. Herein, we reported a two-in-one nanoflower-structured sensing platform (ZCGO@MnO2) with luminescence resonance energy transfer (LRET) property and oxidase-like activity for dual-mode detection of GSH. The sensor consisted of persistent luminescence nanoparticles (PLNPs) with near-infrared emission and manganese dioxide (MnO2) with luminescence quenching ability and oxidase-like activity. The addition of GSH could reduce MnO2 to Mn2+, resulting in the recovery of persistent luminescence and inhibition of oxidase-like activity, then achieving persistent luminescence and colorimetric dual-mode signal outputs. The sensor utilized the persistent luminescence of PLNPs to eliminate the background interference of the complex biological matrix, improved the signal-to-noise ratio (S/N) of detection and took advantage of dual-mode sensing to improve the accuracy of detection, showing excellent analytical performance. Besides, the sensor was capable of monitoring changes in intracellular GSH levels through bioimaging. This work provides new ideas for the design of sensors in complex samples and broadens the application of PLNPs in the field of biosensing.

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

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

A Highly Sensitive Luminescent Upconversion Nanosensor for Turn-On Detection of As3.

A luminescent nanoprobe (NP), MnO2-modified Er3+/Yb3+-codoped Ag2MoO4 upconversion nanoparticles (UCNPs; cod-AMO-3/MnO2), was constructed for rapid, sensitive, and selective "turn-on" detection of trace As3+. Herein, two kinds of luminescent NPs were developed based on luminescence resonance energy transfer (LRET) between cod-AMO-3 as the energy donor and MnO2 as the energy acceptor. By using MnO2 as the matrix in cod-AMO-3/MnO2 fluorometric assay, the upconversion luminescence (UCL) intensity (IUCL) of the cod-AMO-3 probe was quenched significantly through LRET, illustrating MnO2 as an efficient quencher for UCL. With the addition of As3+, a stable bidentate binuclear (BB) corner-sharing bridged complex (As5+-MnO2) was probably formed, which alters the surface of the upconversion NP, leading to gradual separation between UCNPs and MnO2 and subsequent recovery of IUCL. Interestingly, it possessed superior sensitivity, reaction kinetics, and also high selectivity toward As3+ in aqueous solution. Our optimized cod-AMO-3/MnO2 nanocomposite (NComp) demonstrated a linear range of 0-150 ppb and an ultrasensitive detection limit of 0.028 ppb for As3+, which is extremely below the regulatory level, signifying the promising practical usage of this system. To the best of our knowledge, such a surface-modified Ln3+-codoped Ag-based nanosensor being applied for As3+ detection probably has not been reported yet, and it is rather unexplored. In a nutshell, the ability to monitor the As3+ concentration may enable the rational design of a convenient platform for a diverse range of environmental monitoring applications.

Ratiometric upconversion-luminescence in-situ sampling aptasensing platform integrated with smartphone-based device for visual detection of 17β-estradiol

Rapid initial screening of health markers and food hazards are crucial indicators for ensuring human well-being. Hence, an upconversion-luminescence based aptasensing platform for the in-situ sampling of hazards has been proposed with portable equipment for point-of-care testing (POCT). The aptasensing platform consists of a polymethylmethacrylate needle and a paper-based microfluidic strip patterned with a sacrificial valve, paraffin barriers, and three independent detection zones. The detection zones were assembled with a luminescence resonance energy transfer system constructed by the core/shell/shell structure of upconversion nanoparticles (UCNPs) as the donor, SYBR Green Ⅰ as the acceptor with an aptamer bridge. The biosensing platform has been extended for 17β-estradiol to validate its feasibility in a dual-mode signal readout system based on smartphone imaging and spectrometer. Under the optimal conditions, good linear relationships were achieved based on images (0.05–200 ng/mL) and ratiometric spectra (0.02–200 ng/mL), respectively. Thus, the biosensing platform with portable equipment might provide an economic and viable route for POCT.

Upconversion nanoparticles anchored MnO2 nanosheets for luminescence “turn on” detecting hydrogen peroxide

The sensitively and reliably detecting hydrogen peroxide (H2O2) is of significant for biology and environment protection fields. Herein, we reported a high sensitive H2O2 nanoprobe based on upconversion nanoparticles (UCNPs) anchored MnO2 nanosheets. In which, DNA modified NaYF4@NaYF4:Yb,Tm core–shell nanoparticles were anchored onto the MnO2 nanosheets surface via π-π stacking. Owing to the luminescence resonance energy transfer, the blue luminescence of UCNPs was effectively quenched by MnO2 nanosheets, then the luminescence could be restored by adding H2O2 for reducing MnO2 to Mn2+, and achieving a H2O2 concentration-dependent luminescence change, the detection limit could reach to 0.23 nM (S/N = 3). The proposed method could detect H2O2 in serum, lake water and real samples. Thus, a desired upconversion luminescence sensing strategy for detection H2O2 in life and environmental analysis was successfully constructed. It may be provide a potential tool in disease diagnosis and environmental monitoring fields.

Synergistic effect enhancing the energy transfer efficiency of carbon dots-based molecular beacon probe for ultrasensitive detection of microRNA

An ultrasensitive molecular beacon (MB) probe employing carbon dots (CDs) as energy donor and organic dye and graphene oxide (GO) as synergistic quencher was constructed for microRNA-21 (miRNA-21) determination. The MB probe (CDs-MB-BHQ1) was first fabricated by conjugating CDs on the 5′ end of BHQ1-tagged MB, and the fluorescence of CDs decreased owing to the occurrence of luminescence resonance energy transfer (LRET). GO was introduced as a synergistic quencher, thus effectively enhancing the energy transfer efficiency through the interaction between GO and the loop region of MB. In the presence of miRNA-21, it hybridized with loop of MB, thus bringing CDs-MB-BHQ1 away from the surface of GO and increasing the distance between CDs and BHQ1. Owing to the inhibition of LRET process, the fluorescence of CDs at 513 nm (excitation at 490 nm) was recovered. This probe exhibited excellent specificity and could be applied to miRNA-21 determination (0.5–800 pM). Moreover, this proposed probe could monitor the content of miRNA-21 in real human serums, and accuracy were verified by qRT-PCR method (Er ≤ 15.3%) and recovery experiments (recoveries ranged from 88.0% to 105%).

Surface plasmon field enhanced upconversion luminescence for the screening and detection of phenolic environmental estrogens

The endocrine system's interference caused by environmental estrogens (EEs) residue in food is a topic of public concern. Here, we construct an aptasensor for the sensitive detection of EEs based on luminescence resonance energy transfer (LRET). With MoS2 nanosheets acting as the energy acceptor and upconversion luminescence nanoparticles@gold nanoparticles (UCNPs@Au) as the luminescence donor, autofluorescence from food is prevented from interfering. The in-situ deposition of AuNPs not only induces local field enhancement to significantly increase the luminescence intensity of UCNPs, but also conduces to the modification of aptamer through Au-S bond. This aptasensor can respond to multiple estrogens thanks to the choice of a universal aptamer that recognizes phenolic hydroxyl group, and it offers the probability to screen unidentified phenolic estrogens. This method has a high sensitivity and a low limit of detection (LOD), and the satisfactory recovery rates acquired from water and milk samples confirmed its considerable application value.

NIR-excited imaging and in vivo visualization of β-galactosidase activity using a pyranonitrile-modified upconversion nanoprobe

β-galactosidase (β-gal) is a diagnostic biomarker of primary ovarian cancers. The development of effective fluorescent probes for investigating the activity of β-gal will be beneficial to cancer diagnosis. Herein, a near-infrared (NIR) excited ratiometric nanoprobe (DCM-β-gal-UCNPs) by assembling pyranonitrile dye (DCM-β-gal) on the surface of upconversion nanophosphors (UCNPs) was designed for the evaluation of β-gal activity in vivo. Upon the interaction with β-gal, a marked decrease of upconversion luminescence (UCL) signal in the green channel was observed owing to the luminescence resonance energy transfer from the UCNPs to pyranonitrile chromophore, whereas the NIR UCL emission at 800 nm was almost no influence. Thus, the β-gal activity could be quantitatively detected by the UCL intensity ratio of UCL543 nm/UCL800 nm with the limit of detection of 3.1 × 10−4 U/mL. Moreover, DCM-β-gal-UCNPs was effectively applied for monitoring β-gal fluctuation in living cells and zebrafish by a ratiometric UCL signal excited by 980 nm laser. We envision that nanoprobe DCM-β-gal-UCNPs might be used as a potential bioimaging tool to disclose more biological information of β-gal in β-gal-associated diseases in the future.

An upconverted nanoparticle-porphyrin metal-organic framework platform for near-infrared detection of nitenpyram.

A ratiometric nitenpyram (NIT) upconversion luminescence sensor UCNPs-PMOF was fabricated from a metal-porphyrin organic framework (PMOF) and pretreated UCNPs. The reaction between NIT and the PMOF releases the H2TCPP (5,10,15,20-tetracarboxyl phenyl) porphyrin ligand, which enhances the absorption of the system at 650 nm, and reduces the upconversion emission intensity of the sensor at 654 nm through a luminescence resonance energy transfer (LRET) mechanism, thus achieving the quantitative detection of NIT. The detection limit was 0.21 μM. Meanwhile, the emission peak of UCNPs-PMOF at 801 nm does not change with the concentration of NIT, and the emission intensity ratio (I654 nm/I801 nm) is used to achieve the ratiometric luminescence detection of NIT, and the detection limit is 0.22 μM. UCNPs-PMOF has good selectivity and anti-interference to NIT. In addition, it has a good recovery rate in actual sample detection, which indicates that it has high practicability and reliability in NIT detection.

Rapid point-of-care detection of SARS-CoV-2 RNA with smartphone-based upconversion luminescence diagnostics

Accurate COVID-19 screening via molecular technologies is still hampered by bulky instrumentation, complicated procedure, high cost, lengthy testing time, and the need for specialized personnel. Herein, we develop point-of-care upconversion luminescence diagnostics (PULD), and a streamlined smartphone-based portable platform facilitated by a ready-to-use assay for rapid SARS-CoV-2 nucleocapsid (N) gene testing. With the complementary oligo-modified upconversion nanoprobes and gold nanoprobes specifically hybridized with the target N gene, the luminescence resonance energy transfer effect leads to a quenching of fluorescence intensity that can be detected by the easy-to-use diagnostic system. A remarkable detection limit of 11.46 fM is achieved in this diagnostic platform without the need of target amplification, demonstrating high sensitivity and signal-to-noise ratio of the assay. The capability of the developed PULD is further assessed by probing 9 RT-qPCR-validated SARS-CoV-2 variant clinical samples (B.1.1.529/Omicron) within 20 min, producing reliable diagnostic results consistent with those obtained from a standard fluorescence spectrometer. Importantly, PULD is capable of identifying the positive COVID-19 samples with superior sensitivity and specificity, making it a promising front-line tool for rapid, high-throughput screening and infection control of COVID-19 or other infectious diseases.

Lanthanide-Based Nanoprobes for Time-Resolved Luminescence Imaging on Various Ions and Molecules

Lanthanide-doped upconversion nanoparticles (Ln-UCNPs) have been extensively explored in the biological field. In particular, Ln-UCNPs with near-infrared (NIR) fluorescence have tremendous potential for biological imaging because of their outstanding photo-and chemo-stability, extended photoluminescence lifetimes, low long-term toxicities and narrow photoluminescence bandwidths as well as minimal background interferences. Using predesigned energy transfer routes makes it possible to get upconversion luminescence from lanthanides' 4f-4f optical transitions. This article clarifies the key working principles and superiorities of Ln-UCNPs for bioimaging. A crucial overview of recent advances in biological detection adopting lanthanide-based luminescence resonance energy transfer (LRET) mechanisms is presented while emphasizing the importance of modifying Ln-UCNPs to obtain a more efficient energy transfer mechanism.

Time-Resolved Persistent Luminescence Encoding for Multiplexed Severe Acute Respiratory Syndrome Coronavirus 2 Detection.

Capable of precise simultaneous multitarget identifications within a minimized sample, optical multiplexing is vital for accurate diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) while remaining spectral crowding and background interfering. In merits of an autofluorescence-free background and high-capability throughput, a persistent luminescence (PersL) lifetime/color binary encoding strategy was herein proposed for SARS-CoV-2 diagnosis. Based on luminescence resonance energy transfer processes, the intense lifetimes and representative emissions of PersL nanoplatforms were rationally manipulated to create a temporal coding dimension within a wide seconds-to-minutes range through three individual channels. Particularly, at least four populations of barcoding in a certain channel were successfully decoded by a purpose-built time-resolved PersL technology. As a proof-of-concept, functionalized PersL nanoplatforms were further well developed for the simultaneous quantification of five-plex SARS-CoV-2 biomarkers with limits of detection in the subnanomolar range. Remarkably, PersL nanoplatforms enabled a highly differentiable discrimination of multitargets at various concentrations of ultralow background and high-fidelity resolutions, thereby advancing a powerful tool for optical multiplexing in biomedical applications.

ENGINEERING THE NaYF4:Yb3+/Tm3+ UPCONVERSION NANOPARTICLE LUMINESCENCE ENERGY TRANSFER FOR A RATIOMETRIC pH INDICATOR

Fluorescent dye 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) is used to develop a ratiometric pH indicator based on NaYF4:Yb3+/Tm3+ upconversion nanoparticles (UCNPs). HPTS was functionalized onto the UCNP surfaces via a modified co-condensation silica coating (UCNP@SiO2-HPTS). The as-prepared UCNP@SiO2-HPTS core-shell nanostructure was characterized with transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and photoluminescence spectroscopy. Luminescence resonance energy transfer (LRET) from NaYF4:Yb3+/Tm3+ UCNP to HPTS was found to exhibit pH-sensitivity simultaneously under near-infrared (NIR) irradiation (λ = 980 nm).

A novel dual-flux immunochromatographic test strip based on luminescence resonance energy transfer for simultaneous detection of ochratoxin A and deoxynivalenol.

Mycotoxins are secondary metabolites of fungi, which seriously threaten human health. Among them, ochratoxin A (OTA) and deoxynivalenol (DON) have become the main factors that pollute cereals and by-products. In order to achieve simultaneous detection of OTA and DON quantitatively, a novel dual-flux immunochromatographic assay (dICA) was established. The dual-flux assay is based on upconversion nanoparticles (UCNPs) as fluorescence tags to label antigens and gold nanoparticles (AuNPs) as fluorescence quencher to label monoclonal antibodies (mAbs). The intensity of the green fluorescence (540nm) of UCNPs can be used as an analytical signal, indicating the formation of antigen-antibody immune complexes, thereby indicating the presence or absence of the target analyte. Theintensity of the red fluorescence (660nm) of UCNPs is not affected and can be used as a quality control signal, and the dual-flux bidirectional single-line labeling mode allows for the simultaneous detection of two different mycotoxins on two test lines. This work indicated that the developed dICA provided a sensitive, rapid, and reliable on-site simultaneous detection of multiple mycotoxins.

DNAzymes-conjugated upconversion nanoamplicon for in-situ ultrasensitive detection and imaging of microRNA in vivo

Upconversion nanoparticles (UCNPs) are promising materials for imaging biomolecules and predicting the progression of diseases, especially for tumors. However, conventional luminescence resonance energy transfer (LRET) based nanosensors remain challenging with complicated modification and unsatisfactory sensitivity. Herein, a sensing platform integrating confined emission effect and cycling amplification strategy into one substrate with high LRET efficiency and sensitivity has been developed for the in-vitro and in-vivo detection of microRNA-21. Washing UCNPs with hydrochloric acid was conducted for electrostatic absorption of 8–17 DNAzyme labeled with BHQ1 (8–17 DNAzyme-BHQ1) and complementary capturing template-aDNA3 complex (CPT-aDNA3) to form energy donor–acceptor pair (UCNPs-BHQ1) and capture miR-21. It not only avoids the complex modification procedure but also shortens the distance between the donor (UCNPs) and the acceptor (BHQ1). The quenching efficiency of 60.94 % was obtained. Targeted miR-21 could bind with CPT to release aDNA3 that can unlock 8–17 DNAzyme-BHQ1 to form aDNA3-DNAzyme-BHQ1 duplex. This aDNA3-DNAzyme-BHQ1 duplex owning -rA- group can be cleaved by Zn2+ so that UCNPs restored green UCL emission because of the desorption of BHQ1. aDNA3 becomes dissociative again to trigger the next cycle. This UCNP@DNAzyme-BHQ1/CPT- aDNA3 achieved a wide linear range from 4 × 10-14 M to 1 × 10-8 M with a low limit detection of 31 fM for the sensitive detection of miR-21 in vitro. Furthermore, it was successfully applied to the real-time intracellular detection of miR-21 in HeLa cells and in-vivo monitoring of miR-21 expression in KS-01 treated tumor-bearing mouse. This proposed DNA-conjugated upconversion nanoamplicon provides new sights into monitoring of anti-cancer active ingredients efficacy and the progress evaluation of miRNA-related diseases.