Luminescence Resonance Energy Transfer System Research Articles

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 luminescence-based aptasensor for the detection of thyroid-stimulating hormone in serum.

Thyroid-stimulating hormone (TSH) plays a crucial physiological and pathological role in humans, and a timely and sensitive detection of TSH is critical for early diagnosis and prevention of thyroid-related diseases. Herein, we developed a simple wash-free biological aptasensor based on luminescence resonance energy transfer (LRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and tetramethylrhodamine (TAMRA) for the detection of TSH with high sensitivity. In this LRET system, UCNPs as donors and TAMRA as receptors were modified with nucleic acid aptamers Apt-1 and Apt-2, respectively. When TSH was present, the two aptamer strands both specifically recognized TSH to form a hairpin-like structure, thereby shortening the space between UCNPs and TAMRA. The LRET occurred under radiation of 980-nm light. By detecting the change of upconversion luminescence (UCL) intensity (I545nm), the activity of TSH was quantified. The resulting detection dynamic range and the limit of detection were 0.1-5.0 mIU·L-1 and 0.065 mIU·L-1, respectively. The aptasensor using UCNPs as LRET donors was capable of effectively eliminating the background interference of a complicated biological environment, and showed good specificity because of the excellent recognition function of aptamers. Due to high sensitivity, easiness of fabrication, operational convenience, and selectivity, the UCL-based aptasensor is a promising candidate for clinical TSH determination. Based on nucleic acid aptamer and the mechanism of luminescence resonance energy transfer (LRET) between upconversion nanoparticles (UCNPs) donor and tetramethylrhodamine (TAMRA) receptor, an aptasensor was constructed for the quantitative analysis of TSH activity in serum by testing the change of I545nm.

An NIR dual-emitting/absorbing inorganic compact pair: A self-calibrating LRET system for homogeneous virus detection

Many conventional optical biosensing systems use a single responsive signal in the visible light region. This limits their practical applications, as the signal can be readily perturbed by various external environmental factors. Herein, a near-infrared (NIR)-based self-calibrating luminescence resonance energy transfer (LRET) system was developed for background-free detection of analytes in homogeneous sandwich-immunoassays. The inorganic LRET pair was comprised of NIR dual-emitting lanthanide-doped nanoparticles (LnNPs) as donors and NIR-absorbing LnNPs as acceptors, which showed a narrow absorption peak (800 nm) and long-term stability, enabling stable LRET with a built-in self-calibrating signal. Screened single-chain variable fragments (scFvs) were used as target avian influenza virus (AIV)-binding antibodies to increase the LRET efficiency in sandwich-immunoassays. The compact sensor platform successfully detected AIV nucleoproteins with a 0.38 pM limit of detection in buffer solution and 64 clinical samples. Hence, inorganic LnNP pairs may be effective for self-calibrating LRET systems in the background-free NIR region.

Turn-on detection of glutathione S-transferase based on luminescence resonance energy transfer between near-infrared to near-infrared core-shell upconversion nanoparticles and organic dye.

Glutathione S-transferase (GST) is a detoxification enzyme of the liver and kidney. Based on the toxicological effect of GST, it is of great significance to develop a rapid and sensitive detection method for GST. In this work, a new luminescence resonance energy transfer (LRET) system has been designed to detect glutathione S-transferase in the near-infrared (NIR) region by utilizing NaGdF4:Yb3+,Tm3+@NaYF4 upconversion nanoparticles (UCNPs) as the donor and NIR dye-806@Glutathione (IR806@GSH) as the acceptor. NaGdF4:Yb3+,Tm3+@NaYF4 UCNPs were synthesized by a coprecipitation method and surface modification of NOBF4. The donor (positively charged) interacted with the acceptor (negatively charged) via electrostatic interactions to bring them into close proximity; then, LRET occurred and the luminescence was quenched. In the presence of GST, GST can specifically interact with the GSH of IR806@GSH molecule, making IR806@GSH far away from the donor surface, inhibiting the LRET, and restoring the luminescence of the UCNPs. There was a good linear relationship between the luminescence recovery intensity of UCNPs and GST concentration, ranging from 0.11 to 14.19nM, and the detection of limit was 0.06nM. The method has been used in the detection of GST in human serum samples and is expected to have potential applications in the biological field. Graphical abstract A luminescence resonance energy transfer system was developed for determination of glutathione S-transferase in the near-infrared region by utilizing NaGdF4:Yb3+,Tm3+@NaYF4 upconversion nanoparticles as the donor and NIR dye-806@Glutathione as the acceptor.

An efficient NIR-to-NIR signal-based LRET system for homogeneous competitive immunoassay

Upconversion nanoparticles (UCNPs) are promising materials for biological applications based on luminescence resonance energy transfer (LRET). In contrast to classical RET donors such as quantum dots, gold nanoparticles, UCNPs can emit near-infrared (NIR) upon the NIR irradiation, which provides enhanced signal-to-noise due to strong penetration and low autofluorescence in the NIR region known as the diagnostic window. Here we report the first efficient NIR-to-NIR signal-based LRET system for the detection of progesterone, chosen as a proof-of-concept target, via homogeneous competitive immunoassay. To enhance the efficiency of LRET, we constructed inert-core/active-shell/inert-ultrathin shell UCNPs (NaYF4@NaYF4:Yb,Tm@NaYF4) as an LRET donor and a compact progesterone/horseradish peroxidase/IRdyeQC-1 (P-HRP-dyes) complex as an LRET acceptor. The designed donor and acceptor showed significantly improved LRET efficiencies (95% and 85% for donor and acceptor, respectively) compared with conventional donor and acceptor (70% and 50%, respectively). Using the developed NIR-to-NIR LRET system, progesterone was successfully detected with a background-free signal and low limit of detection (1.36 pg/ml in ten-fold diluted human serum). We believe that the efficient NIR-to-NIR signal-based LRET system developed here has potential as a simple probe for homogeneous competitive immunoassay, with the ability to rapidly detect biomarkers.

A paper-based multiplexed resonance energy transfer nucleic acid hybridization assay using a single form of upconversion nanoparticle as donor and three quantum dots as acceptors

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reductive amination to evaluate the multiplexing capacity of luminescence resonance energy transfer (LRET) between UCNPs and quantum dots (QDs). This is the first account of a multiplexed bioassay strategy that demonstrates the principle of use of a single form of UCNP as donor and three different color emitting QDs as acceptors to concurrently determine three analytes. Broad absorbance profiles of green, orange and red QDs that spanned from the first exciton absorption peak to the UV region were in overlap with a blue emission band from UCNPs composed of NaYF4 that was doped with 30% Yb3+, 0.5% Tm3+, allowing for LRET that was stimulated using 980 nm near-infrared radiation. The characteristic narrow and well-defined emission peaks of UCNPs and QDs allowed for the collection of luminescence from each nanoparticle using a band-pass optical filter and an epi-fluorescence microscope. The LRET system was used for the concurrent detection of uidA, Stx1A and tetA gene fragments with selectivity even in serum samples, and reached limits of detection of 26 fmol, 56 fmol and 76 fmol, respectively.

A Single Excitation‐Duplexed Imaging Strategy for Profiling Cell Surface Protein‐Specific Glycoforms

AbstractThis work develops a site‐specific duplexed luminescence resonance energy transfer system on cell surface for simultaneous imaging of two kinds of monosaccharides on a specific protein by single near‐infrared excitation. The single excitation‐duplexed imaging system utilizes aptamer modified upconversion luminescent nanoparticles as an energy donor to target the protein, and two fluorescent dye acceptors to tag two kinds of cell surface monosaccharides by a dual metabolic labeling technique. Upon excitation at 980 nm, only the dyes linked to protein‐specific glycans can be lit up by the donor by two parallel energy transfer processes, for in situ duplexed imaging of glycoforms on specific protein. Using MUC1 as the model, this strategy can visualize distinct glycoforms of MUC1 on various cell types and quantitatively track terminal monosaccharide pattern. This approach provides a versatile platform for profiling protein‐specific glycoforms, thus contributing to the study of the regulation mechanisms of protein functions by glycosylation.

A Single Excitation-Duplexed Imaging Strategy for Profiling Cell Surface Protein-Specific Glycoforms.

This work develops a site-specific duplexed luminescence resonance energy transfer system on cell surface for simultaneous imaging of two kinds of monosaccharides on a specific protein by single near-infrared excitation. The single excitation-duplexed imaging system utilizes aptamer modified upconversion luminescent nanoparticles as an energy donor to target the protein, and two fluorescent dye acceptors to tag two kinds of cell surface monosaccharides by a dual metabolic labeling technique. Upon excitation at 980 nm, only the dyes linked to protein-specific glycans can be lit up by the donor by two parallel energy transfer processes, for in situ duplexed imaging of glycoforms on specific protein. Using MUC1 as the model, this strategy can visualize distinct glycoforms of MUC1 on various cell types and quantitatively track terminal monosaccharide pattern. This approach provides a versatile platform for profiling protein-specific glycoforms, thus contributing to the study of the regulation mechanisms of protein functions by glycosylation.

<sup></sup>Determination of Doxorubicin Based on Luminescence Resonance Energy Transfer of NaYF<sub>4</sub>:Yb,Tm Nanoparticles

NaYF4:Yb,Tm nanoparticles possessing blue upconversion emission were prepared by microwave-assisted solvothermal method, and used as the donor to set up a luminescence resonance energy transfer system with doxorubicin for rapid detection of doxorubicin. There was a linear relationship of I = 4.98×102 - 9.92C (R = 0.9995) between luminescent intensity and concentration of doxorubicin in the range of 0-66.23 mmol·L-1. A detection limit of 0.69 mmol·L-1 (3s) was obtained by the LRET system with a RSD of 1.6% (60 mmol·L-1 , n=11). This approach is expected to be used for the clinical detection of doxorubicin in medicine.

Upconversion nanoparticle based LRET system for sensitive detection of MRSA DNA sequence

In this short communication we report an efficient and versatile method for the detection of methicillin-resistant staphylococcus aureus (MRSA) DNA sequence with high sensitivity and specificity. This method is based on upconversion nanoparticles (UCNs) and luminescence resonance energy transfer (LRET) between NaYF4:Yb, Er UCNs, the energy donor, and carboxytetramethylrhodamine (TAMRA), the energy acceptor. The NaYF4:Yb, Er UCNs were prepared with citrate capping thus dispersible in aqueous solutions. MRSA capture oligonucleotides were covalently immobilized onto the surface of the UCNs. TAMRA labeled MRSA DNA report oligonucleotides were brought close to the UCNs upon sandwich hybridization between the capture and report oligonucleotides and a long MRSA target DNA, resulting in an efficient LRET. Specific detection of MRSA DNA sequences with a detection limit as low as 0.18nM was achieved using this method. To the best of our knowledge, this is the first report to detect MRSA DNA sequence by using UCNs as energy donor through an efficient LRET process.

Synthesis of surface amino-functionalized NaGdF 4:Ce,Tb nanoparticles and their luminescence resonance energy transfer (LRET) with Au nanoparticles

Luminescent/magnetic dual-functional NaGdF 4:Ce,Tb nanoparticles were first synthesized via a solvothermal method with rare earth stearate as the precursor, and the luminescence resonance energy transfer of NaGdF 4:Ce,Tb to Au nanoparticles was studied. The synthesized NaGdF 4:Ce,Tb were ellipsoidal nanoparticles, with pure hexagonal structure and an average size of 15 nm. The nanoparticles emit strong emission at 544 nm under the 246 nm excitation, and show good paramagnetic at room temperature. After surface amination by the typical Stöber method, the as-prepared NaGdF 4:Ce,Tb nanoparticles were served as the donor for the LRET with Au nanoparticles. Good linear relationships between the luminescence intensities of NaGdF 4:Ce,Tb (at 490 nm and 544 nm) and the concentration of Au nanoparticles were obtained, indicating a great potential application prospect of the LRET system in bioassays.

Synthesis of NaYF4:Yb/Er/Gd up-conversion luminescent nanoparticles and luminescence resonance energy transfer-based protein detection

High-quality NaYF4:Yb/Er/Gd up-conversion nanoparticles (UCNPs) were first synthesized by a solvothermal method using rare earth stearate, sodium fluoride, ethanol, water, and oleic acid as precursors. Doped Gd3+ ions can promote the transition of NaYF4 from cubic to hexagonal phase, shorten the reaction time, and reduce the reaction temperature without reducing the luminescence intensity of NaYF4:Yb/Er UCNPs. X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and luminescence spectroscopy were applied to characterize the UCNPs. The nanoparticles exhibited small size and excellent green up-conversion photoluminescence, making them suitable for biological applications. After the surfaces of NaYF4:Yb/Er/Gd UCNPs were modified with amino groups through the Stöber method, they could be brought close enough to the analytically important protein called R-phycoerythrin (R-PE) bearing multiple carboxyl groups so that energy transfer could occur. A luminescence resonance energy transfer (LRET) system was developed using NaYF4:Yb/Er/Gd UCNPs as an energy donor and R-PE as an energy acceptor. As a result, a detection limit of R-PE of 0.5μg/ml was achieved by the LRET system with a relative standard deviation of 2.0%. Although this approach was first used successfully to detect R-PE, it can also be extended to the detection of other biological molecules.

Immunoassay of Goat Antihuman Immunoglobulin G Antibody Based on Luminescence Resonance Energy Transfer between Near-Infrared Responsive NaYF4:Yb, Er Upconversion Fluorescent Nanoparticles and Gold Nanoparticles

Near-infrared (NIR) light can penetrate biological samples and even tissues without causing sample damage and avoid autofluorescence from biological samples in fluorescence detection. Thus, a luminescence resonance energy transfer (LRET)-based immunoassay that can be excited by NIR irradiation is a promising approach to the analysis of biological samples. Here we demonstrate the use of NIR-to-visible upconversion nanoparticles (UCNPs) as an energy donor, which can emit a visible light upon the NIR irradiation, and gold nanoparticles (Au NPs) as an energy acceptor, which can absorb the visible light emitted from the donor, to develop a sandwich-type LRET-based immunoassay for the detection of goat antihuman immunoglobulin G (IgG). Amino-functionalized NaYF(4):Yb, Er UCNPs and Au NPs were first prepared and then conjugated with the human IgG and rabbit antigoat IgG, respectively. The NIR-excited fluorescence emission band of human IgG-conjugated NaYF(4):Yb, Er UCNPs (lambda(max) = 542 nm) partially overlaps with the visible absorption band of the rabbit antigoat IgG-conjugated colloidal Au NPs (lambda(max) = 530 nm), satisfying the requirement of spectral overlap between donors and acceptors for LRET. A LRET system was then formed when goat antihuman IgG was added to a mixture of human IgG-modified NaYF(4):Yb, Er UCNPs (donor) and rabbit antigoat IgG-modified Au NPs (acceptor). The sandwich-type immunoreactions between the added goat antihuman IgG (primary antibody) and the two different proteins (antigen and secondary antibody on the surface of the donors and acceptors, respectively) cross-bridge the donors and acceptors and thus shorten their spacing, leading to the occurrence of LRET from UCNPs to Au NPs upon NIR irradiation. As a result, the quenching of the NIR-excited fluorescence of the UCNPs is linearly correlated to the concentration of the goat antihuman IgG (in the range of 3-67 microg x mL(-1)) present in the system, enabling the detection and quantification of the antibody. Such sandwich-type LRET-based approach can reach a very low detection limit of goat antihuman IgG (0.88 microg x mL(-1)), indicating that this method is applicable for the trace protein detection. This approach is expected to be extended to the detection of other biological molecules once the donor and acceptor nanoparticles are modified by proper molecules that can recognize the target biomolecules.

Luminescence resonance energy transfer based on β-NaYF4:Yb,Er nanoparticles and TRITC dye

β-NaYF4:Yb,Er nanoparticles (NPs) are one of the most efficient upconversion materials, which can convert near-infrared light to higher-energy light through multiple photon absorptions or energy transfer. In addition, they may be attractive alternative donors for luminescence resonance energy transfer (LRET) studies, because of their sharp absorption and emission profiles, high quantum yields, large anti-stokes shifts, long lifetime, low toxicity, and superior photo-stability. In principle, many problems of fluorescence resonance energy transfer (FRET), such as excitation of acceptors, emission overlaps between donors and acceptors, high background noise, potential toxicity, and instability, can be overcome using β-NaYF4:Yb,Er NPs as energy donors. Because the organic coating induced separation can significantly reduce the energy transfer efficiency and aqueous FRET system is difficult to be applied in devices, we demonstrate a novel NP-dye LRET system in solid state. The emission of the β-NaYF4:Yb,Er NPs at 539 nm overlaps with the absorption of the tetrametrylrhodarnine isothiocyante (TRITC), satisfying the requirement of LRET process. Since TRITC molecules are adsorbed on the β-NaYF4:Yb,Er NPs by an electrostatic interaction, the interaction distance is suitable for LRET without any further modulation. The resultant solid LRET system is ready for the further applications for devices.