Luminescence Resonance Energy Transfer Process 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.

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%).

Deep-Depth Imaging of Hepatic Ischemia/Reperfusion Injury Using a Carbon Monoxide-Activated Upconversion Luminescence Nanosystem.

Exploring a chemical imaging tool for visualizing the endogenous CO biosignaling molecule is of great importance in understanding the pathophysiological functions of CO in complex biological systems. Most of the existing CO fluorescent probes show excitation and emission in the region of ultraviolet and visible light, which are not suitable for application in in vivo deep-depth imaging of CO. Herein, a new near-infrared (NIR) to NIR upconversion luminescence (UCL) nanosystem for in vivo visualization of CO was developed, which possesses the merits of high selectivity and sensitivity, a deep tissue penetration depth, and a high signal-to-noise ratio. In this design, upon interaction with CO, the maxima absorption peak of the nanosystem showed a significant blue shift from 795 nm to 621 nm and triggered a remarkable turn-on NIR UCL signal due to the luminescence resonance energy transfer process. Leveraging this nanosystem, we achieved an NIR UCL visualization of the generation of CO biosignals caused by hypoxic, acute inflammation, or ischemic injury in living cells, zebrafish, and mice. Moreover, the protective effect of CO in zebrafish models of oxygen and glucose deprivation/reperfusion (OGD/R) and mice models of lipopolysaccharide-induced oxidative stress (LOS) and hepatic ischemia/reperfusion (HI/R) was also further verified. Therefore, this work discloses that the nanosystem not only serves as a promising nanoplatform to study biological signaling pathways of CO in pathophysiological events, but may also provide a powerful tool for HI/R injury diagnosis.

Engineering of an Upconversion Luminescence Sensing Platform Based on the Competition Effect for Mercury-Ion Monitoring in Green Tea.

Accurately monitoring mercury ions (Hg2+) in food and agriculture-related matrixes (e.g., green tea) is of great significance to safeguard food safety. Here, we employed upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs) to engineer a cysteine (Cys)-assisted anti-Stokes luminescence sensing platform (UCNPs-AuNPs) for precisely detecting residual Hg2+ in green tea through the competition effect. Initially, AuNPs could effectively quench the luminescence of UCNPs through the luminescence resonance energy transfer process, which was then interrupted by Cys-triggered AuNP aggregation via Au-S, thereby restoring UCNP luminescence. Interestingly, owing to the competition effect with AuNPs toward Cys, Hg2+ could weaken the luminescence restoring efficiency, achieving a Hg2+ concentration-dependent luminescence change. On this basis, a facile, reliable, and sensitive upconversion luminescence sensing platform for monitoring residual Hg2+ in green tea was successfully established. This study offers a novel insight into integrating the competition effect and anti-Stokes luminescence for food- and agriculture-related contaminant monitoring.

An aptamer biosensor for CA125 quantification in human serum based on upconversion luminescence resonance energy transfer

CA125 is the most widely used biomarker for the early detection of ovarian cancer. Luminescence resonance energy transfer (LRET)-based probes show pronounced specificity and simplicity for CA125 detection, but they suffer from strong interference from autofluorescence of biosamples. To resolve this problem, near-infrared (NIR)-excitable upconversion nanoparticles (UCNPs) was employed as energy donor to fabricate CA125 biosensor. Carbon dots (CDs) were utilized as energy acceptor for the overlap between the upconversion luminescence (UCL) spectrum of UCNPs and the absorption spectrum of CDs. Aptamer-modified UCNPs were combined with CDs through π-π stacking interaction, which triggered the LRET process and induce UCL quenching with a high quenching efficiency of up to 90%. In presence of CA125, the formation of CA125-aptamer complex blocked the π-π stacking and recovered UCL. The UCL intensity increased linearly with the logarithm of CA125 concentration in the range from 0.01 to 100 U·mL−1. A detection limit of 9.0 × 10−3 U·mL−1 was obtained. This probe is also available for CA125 detection in human serum and may be a useful tool for the early detection of ovarian cancer.

Evaluating spectral overlap with the degree of quenching in UCP luminescence energy transfer systems

The use of organic based fluorophores has been firmly established as a key tool in the biological sciences, with many biological-sensing methods taking advantage of Förster Resonance Energy Transfer (FRET) between different fluorescent organic based dyes following one photon excitation. Nevertheless, the employment of UV-visible absorbing dyes as fluorescent tags and markers typically suffer from several drawbacks including relatively high energy of excitation wavelength, photobleaching and competitive autofluorescence, which often limits their effectiveness and longevity both in vitro and in vivo. As an alternative, lanthanide doped upconverting phosphors (UCP) have emerged as a new class of materials for use in optical imaging and RET sensing; they exhibit high photo- and chemical stability and utilise near infrared excitation. Approaches to sensing a given analyte target employing upconverting phosphors can be achieved by engineering the UCP to operate analogously to fluorescent dyes via Luminescence Resonance Energy Transfer (LRET) and such systems are now becoming central to optically sensing low concentrations of biologically important species and performing distance measurements. Similarly to FRET, the LRET process is distance dependent and requires spectral overlap between the absorption of the acceptor luminophore and the emission of the donor moiety, yet essential measures of the relationship between spectral overlap and the degree of quenching have not yet been established. To address this, we have investigated the Stern-Volmer relationship for a set of six commonly functionalised organic dyes and seven biomolecules that contain key chromophoric co-factors with Gd2SO4:Yb:Er (PTIR545) and Gd2SO4:Yb:Tm (PTIR475) UCPs under low power nIR excitation, and found that for the organic dyes a linear relationship between spectral overlap and degree of quenching is observed. However, this linear relationship is observed to break down for all the biomolecules investigated.

Construction of Time-Resolved Luminescence Nanoprobe and Its Application in As(III) Detection.

As(III) is a toxic heavy metal which causes serious health problems. Therefore, the development of highly sensitive sensors for As(III) detection is of great significance. Herein, a turn-on luminescence resonance energy transfer (LRET) method based on luminous nanorods was designed for As(III) detection. Biotin-labelled As(III) aptamers were tagged to avidin functionalized luminous nanorods as energy donors, while graphene oxide (GO) acted as the energy acceptor. The adsorption of single-stranded DNA on graphene oxide resulted in the efficient quenching of the luminescence of the nanorods through the LRET process. In the presence of As(III), aptamers bonded to As(III) preferentially and resulted in the formation of aptamer-As(III) complexes. The aptamer-As(III) complexes were rubbed off from the GO surface due to their conformational change, which led to the recovery of the luminescence of the nanorods. A good linear relationship between the luminescence intensity and concentration of As(III) was obtained in the range from 1 to 50 ng·mL−1, with a detection limit of 0.5 ng·mL−1. Furthermore, the developed sensors showed good specificity towards As(III) and proved capable of detecting As(III) in the environment and food samples. The proposed time-resolved sensors provide a promising sensing strategy for the rapid and sensitive detection of As(III).

A facile luminescence resonance energy transfer method for detecting cyano-containing pesticides in herbal medicines

It is urgently demanded to establish facile and rapid methods for screening pesticide residues in cultivated herbal medicines to guarantee drug safety. Herein a fluorescent (FL) method was constructed for detecting cyano-containing pesticides by employing the luminescence resonance energy transfer (LRET) behavior between upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs). Negatively-charged citrate-capped AuNPs can be adsorbed onto the surface of positively-charged amino-modified UCNPs by an electrostatic interaction. It resulted in decrease of the FL signal of UCNPs through the LRET process. Cyano-containing pesticides can bind with AuNPs via AuNC metal-ligand coordination and remove citrate from the surface of AuNPs. The replacement process induced aggregation of AuNPs and inhibition of LRET. Thus the pesticides can be detected by a facile procedure within 6 min. Acetamiprid, fenpropathrin and chlorothalonil were adopted as model analytes to study the feasibility of the FL method for the detection of cyano-containing pesticides. With the optimum conditions, acetamiprid, fenpropathrin and chlorothalonil can be detected within the ranges of 0.10–100 ng mL−1, 1.0–100 ng mL−1 and 0.10–50 ng mL−1, with detection limits of 0.015 ng mL−1, 0.24 ng mL−1 and 0.011 ng mL−1, respectively. It has been successfully employed to detect acetamiprid in Lanceolata, Angelica dahurica and Astragalus with acceptable recovery values of 76.0%–120.0%, demonstrating its potential for practical application. The work provides a highly efficient methodologic platform for screening pesticide residues in herbal medicines.

Evaluating spectral overlap with the degree of quenching in UCP luminescence energy transfer systems

The use of organic-based fluorophores has been firmly established as a key tool in the biological sciences, with many biological-sensing methods taking advantage of Förster Resonance Energy Transfer (FRET) between different fluorescent organic-based dyes following one photon excitation. Nevertheless, the employment of UV-visible absorbing dyes as fluorescent tags and markers typically suffer from several drawbacks including relatively high energy of excitation wavelength, photobleaching and competitive autofluorescence, which often limit their effectiveness and longevity both in vitro and in vivo. As an alternative, lanthanide-doped upconverting phosphors (UCP) have emerged as a new class of materials for use in optical imaging and FRET sensing; they exhibit high photo- and chemical stability and utilise near infrared (nIR) excitation. Approaches to sensing a given analyte target employing upconverting phosphors can be achieved by engineering the UCP to operate analogously to fluorescent dyes via Luminescence Resonance Energy Transfer (LRET) and such systems are now becoming central to optically sensing low concentrations of biologically important species and performing distance measurements. Similarly to FRET, the LRET process is distance dependent and requires spectral overlap between the absorption of the acceptor luminophore and the emission of the donor moiety, yet essential measures of the relationship between spectral overlap and the degree of quenching have not yet been established. To address this, we have investigated the Stern-Volmer relationship for a set of six commonly functionalised organic dyes and seven biomolecules that contain key chromophoric co-factors with Gd2SO4:Yb:Er (PTIR545) and Gd2SO4:Yb:Tm (PTIR475) UCPs under low power nIR excitation, and found that for the organic dyes a linear relationship between spectral overlap and degree of quenching is observed. However, this linear relationship is observed to break down for all the biomolecules investigated.

Ratiometric Upconversion Luminescence Nanoprobe with Near-Infrared Ag2S Nanodots as the Energy Acceptor for Sensing and Imaging of pH in Vivo.

A luminescence resonance energy transfer (LRET) system was successfully developed using near-infrared (NIR) Ag2S nanodots (NDs) as the energy acceptors and upconversion nanoparticles (UCNPs) as the energy donors. The system possessing the properties of NIR excitation (980 nm) and NIR emission (795 nm) was used for the ratiometric detection and bioimaging of pH in tumor cells and zebrafish. Glutathione and mercaptopropionic acid (MPA) co-modified Ag2S NDs (GM-Ag2S NDs) were prepared by ligand exchange with an excellent pH-responsive property over a pH range of 4.0 to 9.0. The NIR GM-Ag2S NDs were covalently grafted with silica coated UCNPs, and an efficient LRET platform was developed via modulation of the thickness of the silica coating. Due to the LRET process between UCNPs and GM-Ag2S NDs, a ratiometric luminescence nanoprobe with the properties of NIR excitation-NIR emission was constructed for pH biosensing and bioimaging. On the basis of high contrast bioimaging, the nanoplatform can distinguish between tumor and normal tissue in the zebrafish model.

Lysosome-Assisted Mitochondrial Targeting Nanoprobe Based on Dye-Modified Upconversion Nanophosphors for Ratiometric Imaging of Mitochondrial Hydrogen Sulfide.

Hydrogen sulfide (H2S) is a versatile modulator in mitochondria and involved in numerous diseases caused by mitochondrial dysfunction. Therefore, many efforts have been made to develop fluorescent probes for mitochondrial H2S detection. However, these cationic small molecule probes are inapplicable for in vivo imaging because of the shallow tissue penetration and poor biostability. Herein, a ratiometric upconversion luminescence nanoprobe with an acid-activated targeting strategy is developed for detecting and bioimaging of mitochondrial H2S. The merocyanine triphenylamine-merocyanine (TPAMC)-modified upconversion nanophosphors, acting as the targeting and response component, are encapsulated into a pH-sensitive husk, composed of 1,2-distearoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy-(poly(ethylene glycol))-2000] (DSPE-PEG) and poly(l-histidine)- b-PEG, which improved the nanoprobe's stability during transport in vivo. Under lysosomal pH, the PEG shell is interrupted and the targeting sites are exposed to further attach to mitochondria. Taking advantage of the luminescence resonance energy transfer process between TPAMC and upconversion nanophosphors, the ratiometric detection of mitochondrial H2S can be achieved with high selectivity and sensitivity. Cellular testing reveals the precise targeting to mitochondria via a lysosome delivery process. Importantly, the nanoprobe can be used for monitoring mitochondrial H2S levels in living cells and colon cancer mouse models.

AgInS2-Coated Upconversion Nanoparticle as a Photocatalyst for Near-Infrared Light-Activated Photodynamic Therapy of Cancer Cells.

The development of high-performance near-infrared (NIR) photocatalysts with long-term stability and the elucidation on the working mechanism along with multifunctional activity toward biomedical applications have not been explored sufficiently. Herein, a novel hybrid material of an upconversion nanoparticle (NaYF4/Yb3+,Er3+) (UCN) coated with a ternary semiconductor (AgInS2, AIS) has been synthesized by a simple and robust two-step solvothermal route for NIR light active photocatalysis. Preparation of oleic acid-capped spherical UC nanoparticles (NPs) (∼25 nm) followed by solvothermal decomposition of two precursor complexes Ag(acda) and In(acda)3 resulted in the formation of well-defined NaYF4/Yb3+,Er3+@AgInS2 core-shell nanoparticles (UCN@AIS NPs) (∼90 nm). It has been found that effective energy transfer occurred from NaYF4/Yb3+,Er3+ to AgInS2 by a nonradiative luminescence resonance energy transfer process. Superior photocatalytic decomposition activity was validated in terms of the degradation of methylene blue dye under the exposure of 980 nm NIR laser light with the presence of a UCN@AIS NP catalyst. The degradation process was mediated primarily owing to the formation of a cytotoxic reactive oxygen species (ROS) by the hybrid material under NIR light irradiation, in which UCN performs as a transducer to sensitize AIS and trigger the ROS generation. In vitro cancer cell imaging potentiality of the UCN@AIS NPs was then studied on cervical cancer cells (HeLa cells). The UCN@AIS NPs induced in vitro cervical cancer cell death (photodynamic therapy) with ∼27% efficiency as measured by the MTT assay and thus proved to be a decent candidate for NIR active photocatalysts for biomedical applications.

LRET-based functional persistent luminescence nanoprobe for imaging and detection of cyanide ion

Cyanide anion is an inhibitor of the enzyme cytochrome c oxidase in the fourth complex of the electron transport chain, and usually found in the membrane of the mitochondria of eukaryotic cells, thus exploration of novel analytical methodology for sensitive and accurate detection of cyanide ion in cells is vital and urgent. Herein, we successfully prepared and surface-modified ZnGa2O4:Mn2+ PLNPs with excellent afterglow properties, small size and preferable dispersibility. Furthermore, we report a rational design and fabrication of a functional PL nanoprobe based on luminescence resonance energy transfer (LRET), which for the first time demonstrates detection of cyanide ion without external illumination. The nanoprobe is composed of two main moieties: PLNPs with excellent afterglow properties as energy donor; and DEHSPI, a chromophore with tunable light absorption, as both energy acceptor and CN− recognition element. PL can be effectively quenched by the chromophores assembled on the surface of PLNPs through a LRET process and subsequently recovered upon the addition of CN−. Importantly, the persistent afterglow nature highlights the merits of employing PLNPs as energy donor to eliminate the background noise under in situ excitation. Moreover, the nanoprobe exhibits excellent analytical properties and low cytotoxicity for bio-imaging of CN− in living cells.

BaWO4:Ln3+ Nanocrystals: Controllable Synthesis, Theoretical Investigation on the Substitution Site, and Bright Upconversion Luminescence as a Sensor for Glucose Detection

Simultaneous morphology and upconversion luminescence tuning of BaWO4 nanocrystals excited at 980 nm has been achieved by the successful double doping of different Ln3+ ions. Especially, the substitution sites of Ln3+ into BaWO4 have been investigated by the combination of experimental and density functional theory (DFT) calculations for the first time. The Ba site is the most likely location for BaWO4:Yb3+, BaWO4:Er3+, BaWO4:Tm3+, and BaWO4:Ho3+. However, when codoping Yb3+ with other Ln3+ species into the unit cell of BaWO4, the DFT calculations indicated that it is more likely that Yb3+ engages the W site of BaWO4, while the doped Ln3+ remains at its location at the Ba site, with Yb3+ in the near W layer in the c axis. In addition, a low-cost and sensitive BaWO4:Yb3+/Er3+@Au for glucose detection is designed through a luminescence resonance energy-transfer process and characterized by fluorescence techniques. The limit of detection of BaWO4:Yb3+/Er3+@Au was 3.1 nM. BaWO4:Yb3+/Er3+@Au can be convenientl...

Recent Advances on Functionalized Upconversion Nanoparticles for Detection of Small Molecules and Ions in Biosystems

Significant progress on upconversion‐nanoparticle (UCNP)‐based probes is witnessed in recent years. Compared with traditional fluorescent probes (e.g., organic dyes, metal complexes, or inorganic quantum dots), UCNPs have many advantages such as non‐autofluorescence, high chemical stability, large light‐penetration depth, long lifetime, and less damage to samples. This article focuses on recent achievements in the usage of lanthanide‐doped UCNPs as efficient probes for biodetection since 2014. The mechanisms of upconversion as well as the luminescence resonance energy transfer process is introduced first, followed by a detailed summary on the recent researches of UCNP‐based biodetections including the detection of inorganic ions, gas molecules, reactive oxygen species, and thiols and hydrogen sulfide.

Functionalized Eu(III)-Based Nanoscale Metal-Organic Framework To Achieve Near-IR-Triggered and -Targeted Two-Photon Absorption Photodynamic Therapy.

The postsynthetic-modified nanoscale metal-organic framework (NMOF) probes selected as potential drug delivery platforms and photodynamic therapy agents to fulfill the effective and safe treatment of neoplastic diseases have attracted increasing attention recently. Herein, a Eu(III)-based NMOF probe elaborately postsynthetically modified with a β-diketonate two-photon-absorbing (TPA) ligand is rationally designed and further functionalized by assembling the photosensitizer molecule (methylene blue, MB) in the pores and a cyclic peptide targeting motif on the surface of the NMOF, which could achieve highly efficient near-infrared (NIR)-triggered and -targeted photodynamic therapy (PDT). On the basis of the luminescence resonance energy transfer process between the NMOF donor and the photosensitizer MB acceptor, the probe can achieve a high tissue-penetrable TPA-PDT effect. Thus, the NMOFs in this study play the role of not only the nanocontainer for the photosensitizer but also the energy-transfer donor. Studies in vitro show enhanced cellular uptake and satisfactory PDT effectiveness toward cancer cells compared to the free photosensitizer MB. It is highly expected that this study contributes to the development of smart luminescent diagnostic and therapeutic probes.

Efficient Upconverting Multiferroic Core@Shell Photocatalysts: Visible-to-Near-Infrared Photon Harvesting

We report the two-step synthesis of a core@shell nanohybrid material for visible-to-near-infrared (NIR) photocatalysis. The core is constituted of NaGdF4:Er3+, Yb3+ upconverting nanoparticles (UCNPs). A bismuth ferrite (BFO) shell is assembled around the UCNPs via a hydrothermal process. The photocatalytic degradation assays of methylene orange and 4-chlorophenol reveal that these core@shell nanostructures possess remarkably enhanced reaction activity under visible and NIR irradiation, compared to the BFO powder alone and the BFO-UCNP mixture. Photo-charge scavenger tests and fluorescent assays indicate that hydroxyl radicals play a pivotal role in the photodegradation mechanism. The enhanced photoactivity of the core@shell structure is attributed to the NIR radiation which is converted into visible light by UCNPs, and which is then captured by BFO via a nonradiative luminescence resonance energy transfer process. Therefore, this core@shell architecture optimizes solar energy use by efficiently harvesting visible and NIR photons.

An ultrasensitive aptasensor for Ochratoxin A using hexagonal core/shell upconversion nanoparticles as luminophores

We developed an ultrasensitive luminescence resonance energy transfer (LRET) aptasensor for Ochratoxin A (OTA) detection, using core/shell upconversion nanoparticles (CS-UCNPs) as luminophores. The OTA aptamer was tagged to CS-UCNPs as energy donor and graphene oxide (GO) acted as energy acceptor. The π-π stacking interaction between the aptamer and GO brought CS-UCNPs and GO in close proximity hence initiated the LRET process resulting in quenching of CS-UCNPs luminescence. A linear calibration was obtained between the luminescence intensity and the logarithm of OTA concentration in the range from 0.001ngmL−1 to 250ngmL−1, with a detection limit of 0.001ngmL−1. The aptasensor showed good specificity towards OTA in beer samples. The ultrahigh sensitivity and pronounced robustness in beer sample matrix suggested promising prospect of the aptasensor inpractical applications.

A paper-supported aptasensor for total IgE based on luminescence resonance energy transfer from upconversion nanoparticles to carbon nanoparticles

A paper-supported aptasensor was constructed for total IgE using a luminescence resonance energy transfer (LRET) protocol with upconversion nanoparticles (UCNPs) as energy donors and carbon nanoparticles (CNPs) as energy acceptors. This is the first time that zero-dimensional carbon nanoparticles were used as energy acceptors for paper-based LRET assays. The π-π stacking interaction between the aptamer and CNPs brought the energy donor (UCNPs) and energy acceptor (CNPs) in close proximity, induced the LRET process on the surface of paper and thus led to the luminescence quenching of UCNPs. The introduction of IgE inhibited the energy transfer and hence recovered the luminescence of UCNPs in a concentration-dependent manner, as a result of the recognition between IgE and aptamer. This aptasensor can be used to detect IgE concentration in the range of 0.5–80ng/mL in both buffer solution and human serum samples. The IgE concentrations measured by our method were well correlated to those obtained from chemiluminescence-based clinical assay. Owing to its simplicity and accuracy, the proposed sensor thus showed the potential of clinical applications.

Phenothiazine-cyanine-functionalized upconversion nanoparticles for LRET and colorimetric sensing of cyanide ions in water samples

Abstract Upconversion nanoparticles (UCNPs) could serve as an excellent signaling unit for sensing due to their advantages such as near-infrared excitation, no autofluorescence, low damage to samples and no photobleaching. In this work, a detection platform comprising UCNPs modified with phenothiazine-cyanine (PTZCy) is achieved for efficient cyanide detection based on the luminescent resonance energy transfer (LRET) process. The UCNPs is modified with γ -cyclodextrin ( γ -CD) to increase the solubility in water and meanwhile to generate a hydrophobic cavity for PTZCy and realize detection of CN − in pure water. PTZCy has a significant absorbance with a maximum at 542 nm, which ideally overlaps the emission band of UCNPs at around 540 nm and results in a LRET process to quench the green emission. After addition of CN − , the absorbance intensity of PTZCy at 542 nm decreases dramatically, and the LRET process is terminated and the green emission from UCNPs will be recovered, concurrently, the solution color of PTZC-UCNPs changes from light purple to colorless. This upconverting luminescence recognition of cyanide ions could be finished as soon as the CN − is added, while all the other anions have no influence on the detection process. The detection limit (0.84 μM) is much lower than the reported value obtained from a UCNP-Ir complex based probe (37.6 μM). In addition, the CDs could protect the organic dyes from photobleaching and photodegradation. The results indicate that the cyanide probe in this work is superior when compared with the other UCNPs based cyanide probes. This newly developed sensor allows efficient sensing of CN − in pure water, moreover, it also works well in real water samples taken from underground water or a lake.