Fluorescence Resonance Energy Transfer Effect Research Articles

Construction of CDs@β-CD@CCM ratiometric fluorescence probe for FRET-based ClO–-sensing

β-Cyclodextrin (β-CD)-functionalized carbon quantum dots (CDs) loaded with curcumin (CCM) were used for ClO-sensing with high sensitivity and selectivity. This fluorescence resonance energy transfer (FRET)-based sensor was created through attaching CCM to the CDs via β-CD linker. CCM could get into the interior of β-CD triggering the FRET from CDs to CCM, providing an 'off' state of the CDs. However, the effect of FRET was weakened by the ClO-, because the o-methoxyphenol structure from CCM was oxidized to be benzoquinone. The fluorescence intensity of CDs@β-CD@CCM at 440 nm can be heightened and 520 nm from CCM can decrease along with the increased ClO-. Therefore, a ratiometric fluorescence probe for ClO-sensing is successfully constructed. It conforms to a polynomial curve equation which is I440/I520= -0.0268 + 0.0315 CClO-+ 0.0055[CClO-]2(R2= 0.9958) between 0 and 18.4μM ClO-. Furthermore, we also obtain excellent results using this spectrophotometric method for ClO--sensing in pure water and commercial disinfectants, which afford potential in the environment monitoring area. We expect this sensing platform could be helpful in other analogous probes in relevant fields.

Pd(II)-Porphyrin-sensitized smart star polymer photocatalysts: A light-harvesting strategy using fluorescence resonance energy transfer effects

Photochemistry has become a popular topic in the field of sustainability. In particular, photocatalysts are a promising method to deal with environmental pollution, but only a few light sources with limited wavelengths are utilized to activate photosensitizers. Herein, we broaden the range of activation wavelengths of porphyrin-core amphiphilic star polymer photocatalysts by light harvesting. The coumarin moiety was polymerized from the porphyrin core while maintaining the amphiphilic microenvironment of the star polymer. The fluorescence resonance energy transfer (FRET) between porphyrin and coumarin leads to the activation of photocatalysts under both UV-A and UV-B light. Moreover, the copolymer sequence and polymer swelling effects on the FRET efficiency are discussed. The amphiphilic star block copolymer exhibited superior energy transfer efficiency in polar solvents, and its photocatalytic activity was evaluated via 2,5-dimethylfuran (2,5-DMF) photooxidation.

Less interference fluorescence analytical strategy: Bridging substance-triggered ratiometric sensor with convenient preparation and application

High interference and narrow application range are key of bottleneck of recent fluorescence analysis methods, which limit their wide application in the sensing field. Therefore, to overcome these disadvantages, a ratiometric fluorescence sensing system utilizing berberine (BER) and silver nanoclusters protected by dihydrolipoic acid (DHLA-AgNCs) was constructed for the first time in this work, to achieve determination of BER and daunorubicin (Dau). BER aqueous solution (non-planar conformation) has no fluorescence emission. When it was mixed with DHLA-AgNCs, the conformation of BER became planar, producing fluorescence emission at 515 nm besides the fluorescence emission peak of DHLA-AgNCs at 653 nm. With the increase of BER concentration added in system, the fluorescence intensity of BER (planar conformation) at 515 nm increased obviously and the fluorescence intensity of DHLA-AgNCs decreased slightly. Therefore, the dual emission fluorescence sensing system was constructed based on a fluorescence substance and non fluorescence substance, to achieve determination of BER. Meanwhile, based on the bridging effect of BER and fluorescence resonance energy transfer effect from Dau, the altering of two peaks intensity was utilized to achieve determination of Dau. Thus, this dual emission sensing system can not only be used for fluorescence analysis of BER and its analogues, but also based on the bridging effect of BER, allowing the determination of Dau and its analogues that could not be directly measured with silver nanoclusters, expanding the application range of traditional dual emission detection systems. Meanwhile, this system has strong anti-interference ability and low toxicity to the human body and less pollution to the sample and environment. This provides a new direction and universal research strategy for the construction of new fluorescence sensing systems in the future for the analysis of target substances that cannot be directly detected with conventional fluorescence analysis methods.

Design and Construction of a Mixed-Ligand Coordinated Fluorescent Complex and Its Application for Sensing Ions, Antibiotics, and Pesticides in Aqueous Solution

In this work, a fluorescent complex [Zn(NTD)2(DTP)2(H2O)2]·(H2O)0.8 (Complex Zn), (H2NTD = 1,4-naphthalenedicarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) was synthesized. The fluorescent complex was characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and thermogravimetric, elemental, infrared spectroscopy, and fluorescence analyses. In the fluorescence sensing tests, Complex Zn exhibited excellent fluorescence quenching efficiency towards Fe3+, MnO4−, Cr2O72−, nitrofurantoin, and imidacloprid in aqueous media. A mechanism investigation suggested that the fluorescence quenching caused by the quenchers toward the sensor was due to the inner filter effect and the fluorescence resonance energy transfer effect in the fluorescent sensing process.

A novel fluorescent aptasensor based on H-shaped DNA nanostructure and hollow carbon-doped nitrogen nanospheres for sensitive detection of AFB1

The existence of aflatoxin B1 (AFB1) in food has a high carcinogenic effect on humans and animals. In this study, a fluorescent aptasensor for AFB1 detection was studied by designing a unique H-shaped DNA nanostructure and using novel hollow carbon-doped nitrogen nanospheres (HCNS) as the quenching material. The two DNA strands were hybridized to form the skeleton of the H-shaped DNA nanostructure, and the signal probe (S1-FAM) was paired with complementary bases to form the complete H-shaped DNA nanostructure. When AFB1 was absent, the S1-FAM was replaced by AFB1-Apt and was adsorbed by HCNS to generate a fluorescence resonance energy transfer effect (FRET), causing the signal to turn off. In the presence of AFB1, AFB1 specifically bound to AFB1-Apt to form a complex, which led to the stable formation of the S1-FAM into the H-shaped DNA nanostructure, resulting in the signal turn-on. Under the optimal conditions, an excellent linear relationship (R2 = 0.992) was observed between LgCAFB1 and fluorescent intensity ratio in the range of 0.05–500 ng/mL, and the detection limit was 0.023 ng/mL. The designed aptasensor platform was applied to analyze the spiked AFB1 in peanut, corn flour, wheat flour, wine, and black tea with recoveries ranging from 93.6% to 107.2%.

A programmable quantum dot nanosensor guided by three-way junction skeleton-mediated cascade signal amplification for sensitive detection of circRNAs in breast cancer

Circular RNAs (circRNAs) are endogenous covalent circular molecules that can regulate various biological processes in eukaryotes, and their dysregulation is associated with tumorigenesis. Herein, we demonstrate the construction of a programmable quantum dot (QD) nanosensor guided by three-way junction (TWJ) skeleton-mediated cascade signal amplification for sensitive detection of circRNA in clinical breast tissues. The TWJ probe contains a TWJ primer and a TWJ template. The presence of circRNA can specifically hybridize with TWJ probe to form a stable TWJ skeleton, initiating cascade signal amplification to produce abundant linker probes. The resultant linker probes can bind with Cy5-modified signal probes and biotinylated capture probes to yield the sandwich duplexes. Eventually, the immobilization of sandwich duplexes on the 605QD surface yields the 605QD-dsDNA-Cy5 nanoassembly, resulting in effective fluorescence resonance energy transfer (FRET). This nanosensor is free from exogenous reverse transcription primers and complicated probes design, and it exhibits high amplification efficiency, single-base mismatch specificity, and near-zero background signal. It can detect circRNA with attomolar sensitivity, measure endogenous circRNA at the single-cell level, and discriminate circRNA level in breast cancer tissues from adjacent normal tissues. Moreover, this nanosensor can be expanded to detect other circRNAs (e.g., circHIPK3) by easily changing the corresponding target recognition sequences of TWJ probes, with potential applications in biomedical research and molecular diagnosis.

Fluorescence-Recovered Wearable Hydrogel Patch for In Vitro Detection of Glucose Based on Rare-Earth Nanoparticles.

The physiological state of the human body can be indicated by analyzing the composition of sweat. In this research, a fluorescence-recovered wearable hydrogel patch has been designed and realized which can noninvasively monitor the glucose concentration in human sweat. Rare-earth nanoparticles (RENPs) of NaGdF4 doped with different elements (Yb, Er, and Ce) are synthesized and optimized for better luminescence in the near-infrared second (NIR-II) and visible region. In addition, RENPs are coated with CoOOH of which the absorbance has an extensive peak in the visible and NIR regions. The concentration of H2O2 in the environment can be detected by the fluorescence recovery degree of CoOOH-modified RENPs based on the fluorescence resonance energy transfer effect. For in vivo detection, the physiological state of oxidative stress at tumor sites can be visualized through its fluorescence in NIR-II with low background noise and high penetration depth. For the in vitro detection, CoOOH-modified RENP and glucose oxidase (GOx) were doped into a polyacrylamide hydrogel, and a patch that can emit green upconversion fluorescence under a 980 nm laser was prepared. Compared with the conventional electrochemical detection method, the fluorescence we presented has higher sensitivity and linear detection region to detect the glucose. This improved anti-interference sweat patch that can work in the dark environment was obtained, and the physiological state of the human body is conveniently monitored, which provides a new facile and convenient method to monitor the sweat status.

Construction of a three-mode sensor based on gold nanoparticles and carbon quantum dots as probes for the detection of thiosemicarbazone.

In this study, ginkgo leaves were used as a carbon source to synthesize carbon quantum dots (CQDs) with uniform particle size, high fluorescence (FL) intensity and strong stability, using a hydrothermal method. FL could be quenched by the FL resonance energy transfer effect between CQDs and gold nanoparticles (AuNPs), an important FL quenching agent. The electrostatic attraction between thiosemicarbazone (TSC) and citrate on the surface of AuNPs and the formation of a stable Au-S bond between TSC and AuNPs led to the aggregation of AuNPs and thus weakened the quenching effect on CQDs and partly recovered the FL. A sensor in FL mode for the detection of TSC was constructed based on the above-mentioned FL "off" and "on" phenomena. The results showed a good linear correlation in the concentration range 0-1.75 μM, and the limit of detection was as low as 0.05 μM. In addition, the aggregation of AuNPs caused by TSC also led to a change in the absorbance curve and color of the solution; colorimetric and chrominance detection modes were also constructed using these two types of changes, with sensitive responses ranging 0-2.25 μM and 0-1.60 μM and the limits of detection of 0.03 μM and 0.08 μM, respectively. More importantly, these three detection modes obtained satisfactory recovery rates in the detection of the TSC content in river water, liquor and wheat samples, and the detection results were mutually verified (95.18% to 104.96%).

Synthesis of phenol formaldehyde resin (PFR) based fluorescence resonance energy transfer (FRET) composites for double channel detection of latent fingerprints.

A reversible two-channel fluorescent nanocomposite with fluorescence resonance energy transfer (FRET) effect was designed for the development, analysis, and characterization of latent fingerprints (LFPs). For the construction of the FRET probe, a core of mesoporous silicas (MSNs) were used to encapsulate the organic dye rhodamine 6G (RhD-6) as an acceptor, while green-emitting monodisperse phenolic resin nanoparticles (PFR NPs) were selected as a donor. The up-conversion material (UC) of NaYF4:Yb,Er was synthesized using a simple hydrothermal method, and the MSNs-RhD-6/PFR (PRM) was electrostatically adsorbed onto the UC nanoparticles using a layer-by-layer method to obtain MSNs-RhD-6/PFR-UC (PMU). Compared to ordinary single-channel materials, PMU can be excited by different light sources (365 nm UV/980 nm laser) and its fluorescence can be reversibly switched between yellow and green, demonstrating excellent light reversibility. The PMU composites were successfully used to visualize and detect LFPs on various substrate surfaces using a simple powder coating method. Due to the existing FRET effect and dual-channel characteristics, this composite material displays excellent contrast, outperforming commercially available products for wider applicability. Even on complex backgrounds and after aging or washing treatments, it still clearly recognizes fingerprints in first-, second-, and third-level details, showing its great potential in latent fingerprint detection.

Magnetic lanthanide sensor with self-ratiometric time-resolved luminescence for accurate detection of epithelial cancerous exosomes.

Fluorescence-based LB (liquid biopsy) offers a rapid means of detecting cancer non-invasively. However, the widespread issue of sample loss during purification steps will diminish the accuracy of detection results. Therefore, in this study, we introduce a magnetic lanthanide sensor (MLS) designed for sensitive detection of the characteristic protein, epithelial cell adhesion molecule (EpCAM), on epithelial tumor exosomes. By leveraging the inherent multi-peak emission and time-resolved properties of the sole-component lanthanide element, combined with the self-ratiometric strategy, MLS can overcome limitations imposed by manual operation and/or sample complexity, thereby providing more stable and reliable output results. Specifically, terbium-doped NaYF4 nanoparticles (NaYF4:Tb) and deformable aptamers terminated with BHQ1 were sequentially introduced onto superparamagnetic silica-decorated Fe3O4 nanoparticles. Prior to target binding, emission from NaYF4:Tb at 543 nm was partially quenched due to the fluorescence resonance energy transfer (FRET) from NaYF4:Tb to BHQ1. Upon target binding, changes in the secondary structure of aptamers led to the fluorescence intensity increasing since the deconfinement of distance-dependent FRET effect. The characteristic emission of NaYF4:Tb at 543 nm was then utilized as the detection signal (I1), while the less changed emission at 583 nm served as the reference signal (I2), further reporting the self-ratiometric values of I1 and I2 (I1/I2) to illustrate the epithelial cancerous features of exosomes while ignoring possible sample loss. Consequently, over a wide range of exosome concentrations (2.28 × 102-2.28 × 108 particles per mL), the I1/I2 ratio exhibited a linear increase with exosome concentration [Y(I1/I2) = 0.166 lg (Nexosomes) + 3.0269, R2 = 0.9915], achieving a theoretical detection limit as low as 24 particles per mL. Additionally, MLS effectively distinguished epithelial cancer samples from healthy samples, showcasing significant potential for clinical diagnosis.

A bubble-enhanced lanthanide-doped up/down-conversion platform with tumor microenvironment response for dual-modal photoacoustic and near-infrared-II fluorescence imaging

As an important tumor diagnosis strategy in precision medicine, multimodal imaging has been widely studied. However, the weak imaging signal with low spatial resolution and the constant signal of lack of specific activation severely limit its disease diagnosis. Herein, a bubble-enhanced lanthanide-based up/down-conversion platform with tumor microenvironment response for dual-mode imaging, LDNP@DMSN-Au@CaCO3 nanoparticles (named as LDAC NPs) were successfully developed. Combining the advantages of photoacoustic imaging (PAI) and the second near-infrared window (NIR-II) fluorescence imaging (FI), significantly improved the accuracy of diseases diagnosis. LDAC NPs with flower-like structure were synthesized through the encapsulation of uniform lanthanide-doped nanoparticles (NaYbF4:Ce,Er@NaYF4 named LDNPs) with dendritic mesoporous silica (DMSN). The gold nanoparticles (Au NPs) were then in situ grown on the surface of DMSN and the surface were finally coated with a layer of calcium carbonate (CaCO3). Under the excitation of the 980 nm laser, LDNPs showed strong emission of NIR-II at 1550 nm due to the doping of Ce and Er ions, showcasing excellent spatial resolution and deep tissue penetration characteristics, while the resulting visible light emission (540 nm) enables Au NPs to generate PAI signals with the aid of LDNPs via the fluorescence resonance energy transfer effect. In acidic tumoral environment, CaCO3 layer could produce CO2 microbubbles, and the PAI signals of LDAC NPs could be further enhanced with the generation of CO2 bubbles due to the bubble cavitation effect. Simultaneously, the NIR-II FI of LDAC NPs was self-enhanced with the degradation of the CaCO3. This intelligent nanoparticle with stimulus-activated dual-mode imaging capability holds great promise in future precision diagnostics.

Ratiometric fluorometric and colorimetric dual-signal sensing platform for rapid analyzing Cr(VI), Ag(I) and HCHO in food and environmental samples based on N-doped carbon nanodots and o-phenylenediamine

Nitrogen-doped carbon nanodots (N-CNDs) were synthesized simply and efficiently using glutathione. The fluorescence emission of N-CNDs at 430 nm was effectively quenched by the fluorophore 2,3-diaminophenazine (DAP), produced through the oxidation of o-phenylenediamine (OPD) under the catalysis of Cr(VI)/Ag(I). This quenching was attributed to the fluorescence resonance energy transfer effect, while a new fluorescence emission at 560 nm was observed. Furthermore, the redox and chromogenic reaction of Cr(VI) and OPD at pH 5.4 could be effectively inhibited by formaldehyde (HCHO), resulting in the activation of N-CNDs fluorescence and the quenching of DAP fluorescence. Consequently, dual-signal sensing platforms for the rapid analysis of Cr(VI) and Ag(I) using N-CNDs/OPD and HCHO using N-CNDs/OPD/Cr(VI) were successfully constructed. By incorporating a masking reagent such as H2O2 for Cr(VI) and Cl− for Ag(I), the established sensing platform exhibited excellent selectivity and practical applicability for detecting Cr(VI), Ag(I), and HCHO in food and environmental samples.

Attomolar-level detection of respiratory virus long-chain oligonucleotides based on FRET biosensor with upconversion nanoparticles and Au–Au dimer

Upconversion nanoparticles (UCNPs) are promising nanoprobes in DNA/RNA detection, such as respiratory viral RNAs, and siRNA in cancer. However, recent studies have indicated that the sensitivity of UCNP-based biosensors is restricted, ranging from picomolar to femtomolar level. Moreover, most of existing UCNP-based probes are only able to detect short-chain oligonucleotides, which are not suitable for detection of long-chain oligonucleotides in many real applications. In this work, we introduced a new UCNP-based fluorescence resonance energy transfer (FRET) nanoprobe design composed of NaGdF4:Yb3+, Er3+@NaGdF4 core-shell UCNPs (csUCNPs) linking with Au–Au dimer to detect long-chain oligonucleotides of SARS-CoV-2 N-gene. Compared with typical single gold nanoparticles (AuNPs) in FRET biosensors, our theoretical investigation shows that a stronger electromagnetic field is generated in the Au–Au dimer where the plasmon resonance can enhance FRET efficiency and increase the working distance. Thus, the synergetic effect of plasmonic resonance and FRET enables a greater quenching efficiency (QE) of Au–Au dimer to UCNPs, which leads to more remarkable upconversion luminescence (UCL) recovery for each target gene recognition. Importantly, our design significantly improved the limit of detection (LOD) to attomolar level, with a linear response ranging from 2 aM to 2 fM. Moreover, the clinical detection with inactivated SARS-CoV-2 samples was successfully performed with excellent specificity within 30 min using the developed UCNPs biosensors incorporated with Au–Au dimer. This UCNP biosensor based on Au–Au dimer strategy with ultra-sensitivity and good selectivity opens a new path for clinical diagnosis without target amplification and plays an instructive role in other virus diagnosis.

Fluorescence “turn-on” sensing for five PDE5 inhibitors in functional food based on bimetallic nanoclusters

Some phosphodiesterase type-5 (PDE5) inhibitors are active ingredients of prescription drugs that are widely used in the treatment of erectile dysfunction (ED). Recently, a large number of substances with this activity have been developed. Illegal addition of PDE5 inhibitors to foods could lead to cardiovascular diseases and even death, which poses a serious threat to food safety, therefore an on-site rapid screening method is urgently needed. Herein, a host functionalized bimetallic nanoclusters, CD/Au Ag NCs, were synthesized through self-assembly of 6-Aza-2-thiothymine gold nanoclusters (ATT-Au NCs), Arginine silver nanoclusters (Arg-Ag NCs) and carboxymethyl β-cyclodextrin (β-CMCD). The introduction of Rhodamine 6G (R6G) could quench the fluorescence of CD/Au Ag NCs based on the inner filter effect (IFE) and fluorescence resonance energy transfer effect (FRET). Importantly, it was discovered that several PDE5 inhibitors exhibited a higher binding affinity to β-CMCD and could displace R6G binding with CD cavity, which disrupted the fluorescence quenching effects and resulted in the fluorescence recovery of CD/Au Ag NCs. This fluorescence turn-on signal could be utilized for the detection of PDE5 inhibitors. At present, emerging PDE5 inhibitor analogues pose a great challenge to food safety due to their unknown efficacy and safety. The proposed method holds the advantages of high sensitivity, simple probe synthesis, easy operation, and simultaneous detection of multiple PDE5 inhibitors. Meanwhile, the successful application in functional food sample demonstrated its high application potential in multiple PDE5 inhibitors screening.

An ultra-sensitive fluorescent Aptamer sensor based on 2D MOF for detection of HER2 in serum

Reducing background signal and improving detection sensitivity is one of the main research directions of optical biosensors. Based on the structure and functional characteristics of MOFs, the optical sensing system is constructed, which does not require the pre-treatment of complex biological samples or the catalysis of biological enzymes, and can be directly used for the detection of HER2 in serum. In this paper, the fluorescence resonance energy transfer effect between Co/Fe-MOFs and HER2 Aptamer modified fluorescent group FAM was used to make FAM-Apt undergo fluorescence quenching. When the target is present, FAM-Apt specifically binds to HER2 and simultaneously disconnects from Co/Fe-MOFs surface. FAM was recovered, and a reproducible fluorescence sensing system was successfully constructed for the detection of HER2 in serum. The two-dimensional nanosheets and bimetallic structures of Co/Fe-MOFs have greater specific surface area and fluorescence quenching ability. The results showed that the sensor system had good reproducibility (RSD=2.4%), and the detection range of HER2 was 0.01–10 ng/mL under the best conditions, and the estimated detection limit was 6.67 pg/mL.

FRET causing misleading signal from fluorescein excited by the violet laser in flow cytometry.

Multiple immunolabeling introduces high risks of interferences between fluorescences. As an example, in analyzing T cell clonality, we recently reported a fluorescence resonance energy transfer (FRET) effect providing an unexpected signal on B770 (PE-Cy7) detector, on the Vβ-PE positive CD3 APC-Alexa750+ T cell subsets. Here, we report another FRET effect produced by the violet laser in Vβ-FITC positive CD3-Pacific Blue (PB) T cells providing signal on V550 (Krome Orange; KrO) detector. The study was performed on fresh whole blood, labeled with anti-CD3-PB, CD8-KrO, Vbeta FITC, Vbeta PE, CD4 AA750 then fixed, treated for erythrolysis, and washed before analysis on DxFlex cytometer from Beckman Coulter. Data were analyzed using Kaluza software. Using this panel, we repeatedly observed an added CD8dim-KrO (V550) cell population on all Vβ FITC positive T cells. The unexpected green signal excited by the violet laser was still observed after removing anti-CD8-KrO (FMO) but disappeared where either anti-CD3-PB or anti-Vβ-FITC was removed. The effect was also observed with an anti-TCR gamma delta-FITC labeling, but not with another FITC labeled antibody targeting a protein out of the CD3-TCR complex. The analysis of fluorochrome spectra confirms that PB emission and FITC excitation spectra partly overlap. This observation clearly reminds users that FRET can give misleading results in case of labeling of very close markers with complementary fluorochromes. This risk has to be considered in panel design. These observations clearly highlight the potential for FRET to give misleading results in cases where very close markers are labeled with complementary fluorochromes. This risk must be considered when designing panels. To our knowledge, this is the first description of a FRET between PB and FITC as acceptor thus excited by the violet laser.

An upconversion nanosensor with phenolic-like functionality for accurate identification of chlorpyrifos in grapes

The inappropriate use of the organophosphorus pesticide chlorpyrifos (CPF) in agricultural production could be harmful to the environment and non-target organisms. Here, we prepared a nano-fluorescent probe with phenolic function based on covalently coupled rhodamine derivatives (RDP) of upconverted nano-particles (UCNPs) for trace detection of chlorpyrifos. Due to the fluorescence resonance energy transfer (FRET) effect in the system, the fluorescence of UCNPs is quenched by RDP. The phenolic-functional RDP is converted to the spironolactone form when it captures chlorpyrifos. This structural shift prevents the FRET effect in the system and allows the fluorescence of UCNPs to be restored. In addition, the 980nm excitement conditions of UCNPs will also avoid interference from non-target fluorescent backgrounds. This work has obvious advantages in terms of selectivity and sensitivity, which can be widely applied to the rapid analysis of chlorpyrifos residues in food samples.

Multi-functionalized Metallo-Supramolecular Spoked Wheels: Their Emission-Tunable Hierarchically Assembled System with Dye Molecules.

Supramolecular architectures with multiple emissive units are especially appealing due to their desired properties, such as artificial light harvesting and white-light emission. But fully achieving multi-wavelength photoluminescence in a single supramolecular architecture remains a challenge. In this paper, functionalized supramolecular architectures containing twelve metal centers and six pyrene moieties were nearly quantitatively synthesized by multi-component self-assembly and fully characterized by 1D and 2D nuclear magnetic resonance, dynamic light scattering, electrospray ionization mass spectrometry, traveling-wave ion mobility mass spectrometry, and transmission electron microscopy. Moreover, the hierarchical nano-assemblies were prepared by introducing anionic dyes to the positively charged self-assembled framework, which contained three luminescence centers, namely, pyrene, tpy-Cd coordination parts, and Sulforhodamine B anions. Such a hierarchically assembled system displayed tunable emission by taking full advantage of aggregation-induced emission enhancement, aggregation-caused quenching, and fluorescence resonance energy transfer effects and showed the diverse emission colors. This research provides a new insight for constructing multiple emissive metallo-supramolecular assemblies.

Background-Quenched Aggregation-Induced Emission through Electrostatic Interactions for the Detection of Poly(ADP-ribose) Polymerase-1 Activity.

Poly(ADP-ribose) polymerase-1 (PARP1) is a potential biomarker and therapeutic target for cancers that can catalyze the poly-ADP-ribosylation of nicotinamide adenine dinucleotide (NAD+) onto the acceptor proteins to form long poly(ADP-ribose) (PAR) polymers. Through integration with aggregation-induced emission (AIE), a background-quenched strategy for the detection of PARP1 activity was designed. In the absence of PARP1, the background signal caused by the electrostatic interactions between quencher-labeled PARP1-specitic DNA and tetraphenylethene-substituted pyridinium salt (TPE-Py, a positively charged AIE fluorogen) was low due to the fluorescence resonance energy transfer effect. After poly-ADP-ribosylation, the TPE-Py fluorogens were recruited by the negatively charged PAR polymers to form larger aggregates through electrostatic interactions, thus enhancing the emission. The detection limit of this method for PARP1 detection was found to be 0.006 U with a linear range of 0.01~2 U. The strategy was used to evaluate the inhibition efficiency of inhibitors and the activity of PARP1 in breast cancer cells with satisfactory results, thus showing great potential for clinical diagnostic and therapeutic monitoring.

Photochromic Polyurethane Coatings with Cross-Linked Structure and Self-Healing Behavior Based on the FRET Effect.

Intelligent fluorescent coatings have received widespread attention in the encryption technique field such as anti-counterfeit, while the traditional fluorescent coatings are easy to be damaged by external force. In this study, the fluorescent and self-healing anti-counterfeit coatings are prepared after rational molecular design. Two polymers containing fluorescent groups, including polyurethane containing the anthracene (AN) side group and polyimide containing the naphthalenediimide (NDI) structure are synthesized to realize multiple color changes with fluorescence through simply blending. Due to the overlapping fluorescence spectra of the groups, enabling the fluorescence resonance energy transfer effect (FRET), the coating with different group ratios exhibits tunable fluorescence under the same excitation light, providing diverse patterns. Moreover, due to the reversible photo-crosslinking and thermal de-dimerization properties of anthracene, the recording, erasure, and rewriting of the surface pattern can be realized, and the fluorescent anti-counterfeit coatings exhibit excellent self-healing properties after cross-linking due to the FRET effect, which solves the problem of poor healing and ensures the stability and integrity. The fluorescent coating with cross-linked structure and self-healing behavior based on the FRET effect greatly expands the functional applications of traditional polyurethane materials.