Fluorescence Resonance Energy Transfer Nanoprobe Research Articles

Multifunctional Nanoprobe Based on Fluorescence Resonance Energy Transfer for Furin Detection and Drug Delivery.

Triple-negative breast cancer is particularly difficult to treat because of its high degree of malignancy and poor prognosis. A fluorescence resonance energy transfer (FRET) nanoplatform plays a very important role in disease diagnosis and treatment due to its unique detection performance. Combining the properties of agglomeration-induced emission fluorophore and FRET pair, a FRET nanoprobe (HMSN/DOX/RVRR/PAMAM/TPE) induced by specific cleavage was designed. First, hollow mesoporous silica nanoparticles (HMSNs) were used as drug carriers to load doxorubicin (DOX). HMSN nanopores were coated with the RVRR peptide. Then, polyamylamine/phenylethane (PAMAM/TPE) was combined in the outermost layer. When Furin cut off the RVRR peptide, DOX was released and adhered to PAMAM/TPE. Finally, the TPE/DOX FRET pair was constituted. The overexpression of Furin in the triple-negative breast cancer cell line (MDA-MB-468 cell) can be quantitatively detected by FRET signal generation, so as to monitor cell physiology. In conclusion, the HMSN/DOX/RVRR/PAMAM/TPE nanoprobes were designed to provide a new idea for the quantitative detection of Furin and drug delivery, which is conducive to the early diagnosis and treatment of triple-negative breast cancer.

Coordination polymer nanoprobe integrated carbon dot and phenol red for turn-on fluorescence detection of urease activity.

The potential of coordination polymers (CPs) as a host of integrating multiple guest species to construct a fluorescence resonance energy transfer (FRET) nanoprobe was demonstrated. The ZnCPs built from zinc(II) and adenine was employed as a model of CPs to integrate carbon dot (CD) and phenol red (PR) for producing the FRET nanoprobe (CD/PR@ZnCPs). Benefiting from the confinement effect of ZnCPs, the integrated CD and PR can be brought in close proximity to favor the occurrence of FRET process from CD to PR, which leads to the quenching of CD fluorescence. However, the FRET process was disrupted upon the red-shift of PR absorption from 428 to 562nm in alkaline medium, and consequently switches on the fluorescence of CD/PR@ZnCPs. Based on this finding, by utilizing urease to hydrolyze urea and mediate medium pH, a turn-on fluorescent method was established for the detection of urease activity. This fluorescent method has a linear response that covers 5 to 150 U/L urease with a detection limit of 0.74 U/L and exhibits an excellent selectivity over other enzymes. The successful determination of urease in saliva samples demonstrates the applicability of the fluorescent nanoprobe in complex biological matrix.

A metal-organic framework-based fluorescence resonance energy transfer nanoprobe for highly selective detection of Staphylococcus Aureus.

Survival and infection of pathogenic bacteria, such as Staphylococcus aureus (S. aureus), pose a serious threat to human health. Efficient methods for recognizing and quantifying low levels of bacteria are imperiously needed. Herein, we introduce a metal-organic framework (MOF)-based fluorescence resonance energy transfer (FRET) nanoprobe for ratiometric detection of S. aureus. The nanoprobe utilizes blue-emitting 7-hydroxycoumarin-4-acetic acid (HCAA) encapsulated inside zirconium (Zr)-based MOFs as the energy donor and green-emitting fluorescein isothiocyanate (FITC) as the energy acceptor. Especially, vancomycin (VAN) is employed as the recognition moiety to bind to the cell wall of S. aureus, leading to the disassembly of VAN-PEG-FITC from MOF HCAA@UiO-66. As the distance between the donor and acceptor increases, the donor signal correspondingly increases as the FRET signal decreases. By calculating the fluorescence intensity ratio, S. aureus can be quantified with a dynamic range of 1.05 × 103-1.05 × 107 CFU mL-1 and a detection limit of 12 CFU mL-1. Due to the unique high affinity of VAN to S. aureus, the nanoprobe shows high selectivity and sensitivity to S. aureus, even in real samples like lake water, orange juice, and saliva. The FRET-based ratiometric fluorescence bacterial detection method demonstrated in this work has a prospect in portable application and may reduce the potential threat of pathogens to human health.

Albumin-based fluorescence resonance energy transfer nanoprobes for multileveled tumor tissue imaging and dye release imaging

Tumor tissue imaging and drug release imaging are both crucial for tumor imaging and image-guided drug delivery. It is urgent to develop a multileveled tumor imaging platform to realize the multiple imaging applications. In this work, we synthesized an albumin-based fluorescence resonance energy transfer (FRET) probe Cy5/7@HSA NPs containing two near-infrared cyanine dyes (CyBI5 and CyBI7) with high FRET efficiency (97 %). Excellent brightness and efficient FRET inside Cy5/7@HSA NPs enabled high-sensitive cell imaging and tumor imaging. This unique nanoprobe imaged 4T1 tumor-bearing mice with high sensitivity (TBR = 5.2) at 24 h post-injection and the dyes penetrated the tumor interior around 4 h post-injection. The release of dyes from nanoprobes was also tracked. This result shows the strong potential of this albumin-based FRET nanoprobe as multileveled tumor imaging platform for in vivo tumor imaging, drug delivery and image-guided surgery.

Intracellular Pathogen Detection Based on Dual-Recognition Units Constructed Fluorescence Resonance Energy Transfer Nanoprobe.

The intracellular invasion and survival of a pathogen like Staphylococcus aureus (S. aureus) within host cells enable them to resist antibiotic treatment and colonize long-term in the host, which leads to a series of clinical issues. Rapid and specific detection of intracellular bacteria is important in diagnosis of infection and guiding antibiotic administration. Herein, this work reports a simple one-step fluorescence resonance energy transfer (FRET) platform-based strategy to achieve specific and rapid detection of S. aureus in specimens of phagocytic cells. The aptamer modified quantum dots (Aptamer-QDs) and antibiotic molecule of Teicoplanin functionalized-gold nanoparticles (Teico-AuNPs) dual-recognition units to S. aureus are employed as energy donor and acceptor, respectively. Based on the "off" to "on" signal readout mode, when in the presence of target S. aureus, the donor and acceptor are close to each other and bring high FRET efficiency, which is suitable for analysis of intracellular S. aureus. After it was incubated with the sample for 2 h, the as-prepared FRET sensor showed selectivity to the target S. aureus, and the changed fluorescence signal shows an obvious variation with increasing concentration of S. aureus in pure buffer. When the FRET strategy was further applied to assay intracellular S. aureus, there was an obvious fluorescence signal change obtained both by spectrum analysis and visual fluorescence microscope observation when the average number of S. aureus in one host cell (NS.aureus/cell) was as low as 1, which can be attributed to the high fluorescence quenching efficiency of about 41.3%. It could be envisioned that this FRET nanoprobe with high fluorescence quenching efficiency may provide a simple approach for the facile, selective, and rapid diagnosis of an intracellular bacterial infection.

Self-Assembled FRET Nanoprobe with Metal-Organic Framework As a Scaffold for Ratiometric Detection of Hypochlorous Acid.

Metal-organic framework (MOF) has been extensively explored in a number of fields due to its diverse properties. In this work, we demonstrated the potential of MOF in the establishment of a self-assembled fluorescence resonance energy transfer (FRET) system for developing ratiometric fluorescent nanoprobe. For this purpose, zeolitic imidazolate framework-8 (ZIF-8) was selected as a MOF model to entrap carbon dot (CD) and curcumin (CCM) during its self-assembly, which produces CD/CCM@ZIF-8. Benefiting from the confinement effect of ZIF-8, the loaded CD and CCM can be brought in close proximity for energy transfer to occur. Under optimal conditions, a high FRET efficiency of 68.7% can be obtained. Importantly, compared with traditional FRET systems, the fabrication process of CD/CCM@ZIF-8 is much more simple and straightforward, which does not involve the elaborate design and complicated synthesis of molecular linkers. However, in the presence of hypochlorous acid (HClO), the FRET process from CD to CCM will be disrupted, rendering CD/CCM@ZIF-8 to display a ratiometric response to HClO. This finding led to a method for ratiometric fluorescent detection of HClO with a detection limit of 67 nM and excellent selectivity over other reactive oxygen species. We believe that this study can give a new insight into the rational design and application of FRET-based nanoprobes.

Facile construction of AIE-based FRET nanoprobe for ratiometric imaging of hypochlorite in live cells

Fluorescence resonance energy transfer (FRET) nanoprobes based on aggregated induced emission (AIE) molecules are promising for the monitoring of biomolecules in living cells, but this nanoprobe for reactive oxygen species (ROS) has rarely been reported. Here, a novel AIE-based FRET nanoparticles (NPs) is developed for ratiometric detection and imaging of hypochlorite in live cells. Different to common FRET-based nanosensors, the NPs is prepared via facile co-assembly strategy in water using amphiphilic tetraphenylethene (TPE1, energy donor) and thienyl-diketopyrrolopyrrole (NDPP, energy acceptor). This hybrid NPs are uniform spherical, with size of approximately 120 nm. NDPP maintains bright fluorescence inside the hybrid NPs and acts as the reactive unit for hypochlorite in this FRET nanosystem. As a ratiometric fluorescent nanoprobe, the hybrid NPs shows high selectivity to hypochlorite with a detection limit calculated to be 105 nM, thanks to its stable particle size in hypochlorite sensing. Furthermore, the successful ratiometric fluorescent imaging of ClO− in HeLa cells demonstrates that our NPs can effectively pass through the cell membrane and recognize the ClO− in living cells.

Sensitive detection of telomerase activity in cells using a DNA-based fluorescence resonance energy transfer nanoprobe

Telomerase activity is inhibited in normal somatic cells but abnormally high in the majority of cancer cells. Maintenance of active telomerase in cancer cells promotes proliferation and immortalization. With the difference in telomerase activity between cancer and normal cells in mind, we designed a nanoprobe based on quantum dot (QD) and fluorescence resonance energy transfer (FRET). The nanoprobe consisted of a specific sequence of DNA with the two ends labeled with QD as a fluorescent donor and Alexa488 as a fluorescent acceptor, respectively. FRET signal tracking was performed by adjusting the distance between donors and acceptors, and changes in the FRET signal shown to be related to telomerase activity. Incubation of cells with the nanoprobe facilitated sensing of intracellular telomerase activity, and consequent discrimination between normal and cancer cells. Our novel DNA nanoprobe based on QD-FRET achieved sensitive detection of telomerase in cells up to a detection limit of one cell, and quantitative detection of telomerase activity in different numbers of cells. The nanoprobe generated in this study is expected to allow dynamically monitoring of the changes in telomerase activity in cells under treatment with drugs, providing a potential basis for early diagnosis and management of cancer.

Fluorescence and visual detection of fluoride ions using a photoluminescent graphene oxide paper sensor.

The instant and on-site detection of trace aqueous fluoride ions is still a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility of a paper sensor for visual detection of F(-) on the basis of the fluorescence resonance energy transfer (FRET) between photoluminescent graphene oxide (GO) and silver nanoparticles (AgNPs) through the formation of cyclic esters between phenylborinic acid and diol. The fluorescence of GO was quenched by the AgNPs, and trace F(-) can recover the fluorescence of the quenched photoluminescent GO. The increase in fluorescence intensity is proportional to the concentration of F(-) in the range of 0.05-0.55 nM, along with a limit of detection (LOD) as low as 9.07 pM. Following the sensing mechanism, a paper-based sensor for the visual detection of aqueous F(-) has been successfully developed. The paper sensor showed high sensitivity for aqueous F(-), and the LOD could reach as low as 0.1 μM as observed by the naked eye. The very simple and effective strategy reported here could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient FRET nanoprobes.

One-step facile synthesis of hyaluronic acid functionalized fluorescent gold nanoprobes sensitive to hyaluronidase in urine specimen from bladder cancer patients

Gold nanoparticles (AuNPs) have been widely used to develop fluorescence resonance energy transfer (FRET) sensors to detect biological substances, environmental pollutants, and disease markers due to their superior quenching capacity to fluorescence signals. In this study, we report the one-step facile synthesis of fluorescein isothiocyanate-labeled hyaluronic acid (FITC–HA) functionalized fluorescent AuNPs based FRET nanoprobes (FITC–HA–AuNPs) via chemical reduction of HAuCl4 by using FITC–HA as both a reducing and stabilizing agent. Then the FITC–HA–AuNPs FRET nanoprobes were used to detect hyaluronidase (HAase), a new type of disease marker, based on the specific enzymatic degradation of HAase to HA. Compared with similar work, the FITC–HA–AuNPs nanoprobes were much easier to prepare and the detection sensitivity was also high for HAase to reach a detection limit of 0.63UmL−1. More importantly, they also allowed for rapid HAase detection (within 3h) even in complex biological specimens (urine specimens from patients with bladder cancer) with satisfactory accuracy (recovery efficiency in the range of 92.8–106.9% with RSD≤4.85%). Our studies suggested that such a novel design of FITC–HA–AuNPs FRET nanoprobes developed for sensitive, rapid and accurate detection of HAase had exciting potentials for clinical diagnosis of HAase-related diseases, such as bladder cancer.

Synthesis of Fe3O4@Phenol Formaldehyde Resin Core–Shell Nanospheres Loaded with Au Nanoparticles as Magnetic FRET Nanoprobes for Detection of Thiols in Living Cells

A magnetic, sensitive, and selective fluorescence resonance energy transfer (FRET) probe for detection of thiols in living cells was designed and prepared. The FRET probe consists of an Fe(3)O(4) core, a green-luminescent phenol formaldehyde resin (PFR) shell, and Au nanoparticles (NPs) as FRET quenching agent on the surface of the PFR shell. The Fe(3)O(4) NPs were used as the core and coated with green-luminescent PFR nanoshells by a simple hydrothermal approach. Au NPs were then loaded onto the surface of the PFR shell by electric charge absorption between Fe(3)O(4)@PFR and Au NPs after modifying the Fe(3)O(4)@PFR nanocomposites with polymers to alter the charge of the PFR shell. Thus, a FRET probe can be designed on the basis of the quenching effect of Au NPs on the fluorescence of Fe(3)O(4)@PFR nanocomposites. This magnetic and sensitive FRET probe was used to detect three kinds of primary biological thiols (glutathione, homocysteine, and cysteine) in cells. Such a multifunctional fluorescent probe shows advantages of strong magnetism for sample separation, sensitive response for sample detection, and low toxicity without injury to cellular components.

A new FRET nanoprobe for trypsin using a bridged β-cyclodextrin dimer–dye complex and its biological imaging applications

A new self-assembly nanoprobe, mercaptoethylamine-modified-gold nanoparticles-Lysine-bridged-bis(β-cyclodextrins)-fluorescein (MGNPs-Lys-bis(β-CDs)-FL), based on fluorescence resonance energy transfer (FRET) was developed for determination of trypsin firstly in biological systems. With the Lys-bis(β-CDs)-FL complex as an energy donor and mercaptoethylamine (MEA)-modified gold nanoparticles (MGNPs) as an energy acceptor, the two parts assemble an efficient FRET nanoprobe through an amide bond. Trypsin is specific for the hydrolysis of amide linkages of lysine. Therefore, in the presence of trypsin, the nanoprobe is cleaved by trypsin on the binding sites of amide with good specificity and sensitivity, resulting in the fluorescence recovery of the quenched FL. The nanoprobe has good biological applicability and provides a potential assay for further clinical research of trypsin in biosystems.