Fluorescence Resonance Energy Transfer Process Research Articles

A novel coumarin-linked tetraphenylethene fluorescent probe for simultaneous sensing of ATP and GSH

Adenosine triphosphate (ATP) as the intracellular energy currency, and glutathione (GSH) as the regulator of redox homeostasis in the cell microenvironment, are all closely associated with numerous important physiological processes in living organisms. However, the fluorescent probes that can simultaneously detect ATP and GSH are rarely reported. Herein, a bifunctional coumarin-linked tetraphenylethene (TPE) probe P1 was successfully developed, which exhibits a red emission at 633 nm owing to the fluorescence resonance energy transfer (FRET) from energy donor coumarin to energy acceptor TPE. P1 can detect ATP with a fluorescence turn-on response at 633 nm in the red channel by complexation-enhanced aggregation mechanism, and showed a ratiometric detection toward GSH through the disruption of the FRET process, accompanied by an increase in the blue channel at 467 nm and a decrease in the red channel at 633 nm. P1 also displays a superior sensitivity and high selectivity to ATP and GSH, with a detection limit of 20.80 nM for ATP and 3.47 µM for GSH. Significantly, P1 can discriminate GSH from ATP and other analytes due to the different response times. Furthermore, P1 can localize mitochondria and has been discovered to be capable of imaging ATP and GSH in living cells and zebrafish.

Dynamic Fluorescence Materials Based on Naphthalimide-Functionalized Silica Aerogels and Applications in Advanced Information Encryption.

With the progress of forgery and decryption, the traditional encryption technology is apparent not enough, which strongly requires the development of advanced multidimensional encryption strategies and technologies. Photo-stimuli responsive fluorescent materials are promising as candidate materials for advanced information encryption. Here, we have reported new photo-stimuli responsive materials by encapsulating photochromic molecules spiropyrans (SPs) into naphthalimide-functionalized silica aerogels. By introducing different modification groups (dimethylamino) into 1,8-naphthalimide, we obtained two kinds of silica aerogels that emit blue and green colors. The naphthalimide-functionalized silica aerogels/dye composite exhibits a blue (dimethylamino-modified naphthalimide-functionalized silica aerogel showing green) emission from naphthalimide of silica aerogels at 450 nm (520 nm) and a red emission around 650 nm of SP. Under exposure to ultraviolet light, SP gradually transformed into the merocyanine (MC) form, and a strong absorption band appeared near 540 nm. At that time, the fluorescence resonance energy-transfer (FRET) process occurred between naphthalimide and the MC isomer. As the irradiation time is extended, the fluorescence color changes continuously from blue (green) to red through the FRET process. Using the time dependence of fluorescence, dynamic encryption patterns and multiple codes were successfully developed based on these functionalized silica aerogels. This work has provided important guidance for designing advanced information encryption materials.

A reliable and selective ratiometric sensing probe for fluorometric determination of P2O74− based on AIE of GSH@CuNCs-assisted by Al-N@CQDs

In this study, a novel composite material was developed for the ratiometric detection of pyrophosphate anion (P2O74−). This composite consisted of Al and nitrogen co-doped carbon dots (Al-N@CQDs) and glutathione-capped copper nanoclusters (GSH@CuNCs). The Al-N@CQDs component, with its high reserved coordination capacity of Al3+, induced the non-luminescent behavior of GSH@CuNCs, resulting in an aggregation-induced emission (AIE) effect. The hybrid material (Al-N@CQDs/GSH@CuNCs) exhibited dual-emission signals at 620 nm and 450 nm after integrating the two independent materials utilizing the AIE effect and the fluorescence resonance energy transfer (FRET) approach. This approach represents the first utilization of this composite for ratiometric detection. Nevertheless, upon the addition of P2O74−, the AIE and FRET processes were hindered due to the higher coordination interaction of Al3+ towards P2O74− compared to the amino/carboxyl groups on Al-N@CQDs. This successful interference of the AIE and FRET processes allowed for the effective estimation of P2O74−. The response ratio (F450/F620) increased with increasing the concentration of P2O74− in the range of 0.035–160 µM, with an impressive detection limit of 0.012 µM. This innovative approach of utilizing hybrid CQDs/thiolate-capped nanoclusters as a ratiometric fluorescent sensor for analytical applications introduces new possibilities in the field. The as-fabricated system was successfully applied to detect P2O74− in different real samples such as water, serum, and urine samples with acceptable results.

Aptamer-based flares hybridized with single-stranded DNA-conjugated MoS2 nanosheets for ratiometric fluorescence sensing and imaging of potassium ions and adenosine triphosphate in human fluids and living cells

Addressing the limitations observed in previous studies, where the quantitative range of nanoprobes for detecting K+ and adenosine triphosphate (ATP) did not cover concentrations found within living cells, the present study aimed to develop ratiometric nanoprobes that can accurately sense changes in K+ and ATP levels in living cells and quantify them in human fluids. The proposed nanoprobes consisted of recognition flares modified with 6-carboxyfluorescein (FAM) and 5-carboxytetramethylrhodamine (TAMRA), along with thiolate single-stranded DNA (ssDNA) and molybdenum disulfide nanosheets (MoS2 NSs). The thiolate ssDNA acts as a linker between the flares and the MoS2 NSs, directly forming a functional nanostructure at room temperature. The direct conjugation of labeled flares to the MoS2 NSs simplifies the fabrication process. In the absence of K+ and ATP, the hybridization of flares and thiolate ssDNA caused FAM to move away from TAMRA, suppressing the fluorescence resonance energy transfer (FRET) process. However, upon the introduction of K+ and ATP, the flares undergo a structural transformation via the formation of G-quadruplex formation and the generation of hairpin-shaped structures, respectively. This structural change leads to the release of the flares from the ssDNA-conjugated nanosheet surface. The release of the flares brings FAM and TAMRA into close proximity, allowing FRET to occur, leading to FRET and static quenching. By monitoring the ratio between the fluorescence intensities of FAM and TAMRA, the concentration of K+ (5–100 mM) and ATP (0.3–5 mM) can be accurately determined by the proposed nanoprobes. The advantages of these nanoprobes lie in their ability to provide ratiometric measurements, which enhance the accuracy and reliability of the quantification process. The proposed nanoprobes offer potential applications as ratiometric imaging probes for monitoring K+ and ATP-related reactions in living cells, providing valuable insights into cellular processes. Additionally, they can be employed for determining the levels of K+ and ATP in human fluids, offering potential diagnostic applications in various clinical settings.

Multiple‐Resonance‐Enhanced Raman Spectroscopy in 2D‐Material‐Capped Tapered‐Fiber Microcavity

AbstractPlasmon‐free surface‐enhanced Raman spectroscopy (SERS) assisted by charge‐transfer (CT) resonance in semiconductors has drawn considerable attention in the past decades due to the extraordinary advantages in chemical stability and homogeneity. Unfortunately, the weak confinement of excitation light in semiconductor nanostructures and 2D materials, due to either their limited refractive indexes or atomic thickness, results in the Raman enhancement by nonmetallic SERS substrates significantly lower than the noble ones. Here a novel plasmon‐free SERS probe is reported by a tapered optical fiber (TOF) coated with monolayer‐MoS2 (ML‐MoS2), where the TOF‐supported whispering‐gallery modes (WGMs) simultaneously regulate multiple‐resonance processes, i.e., excitonic resonance, molecular resonance, charge‐transfer resonance and fluorescence resonance energy transfer processes, in the ML‐MoS2 and analytes. The contribution of the four processes promoted by WGM to enhancement factor of Raman intensity (EFRI) is quantitatively determined by four dye molecules with different energy levels. The Raman enhancement mechanism of WGM‐promoted multiple‐resonances is therefore revealed, for the first time. The maximum EFRI is up to 1.8 × 109 for the limit of detection (LoD) down to 10−14 M. The ML‐MoS2/TOF SERS probes also demonstrated their outstanding feasibility and stability facilitating to trace detection in microdroplets for practical applications in future.

A fast hemostatic and enhanced photodynamic 2-dimensional metal-organic framework loaded aerogel patch for wound management

Achieving rapid hemostasis and highly effective antibacterial holds significant importance in the early-stage treatment of wounds. In this study, a hybrid aerogel patch comprising carbon quantum dots (CQDs) modified 2-dimensional (2D) porphyrinic metal–organic framework (MOF) nanosheets was designed by incorporating gelatin methacrylate (GelMA) and polyacrylamide (PAM) based matrix. On one hand, CQDs were stably doped onto the surface of the 2D MOF nanosheets, thereby enhancing the photodynamic activity through fluorescence resonance energy transfer (FRET) process. After the preparation of hybrid aerogel patch, the patch loaded with CQDs-doped 2D MOF exhibited excellent photodynamic bactericidal activity against Gram-positive Staphylococcus aureus (>99.99 %) and Gram-negative Escherichia coli (>99.99 %). On the other hand, the hybrid patch with highly porous and absorbent structure can rapidly absorb blood to aggregate clotting components and form a hydration barrier covering the wound to enhance hemostasis. Besides, the hemolysis and cytotoxicity assays demonstrated a good biocompatibility of this designed patch. In summary, this 2D MOF-loaded aerogel patch holds a potential to achieve rapid hemostasis and effective anti-infection in the early-stage treatment of traumatic wounds.

Efficient FRET process between CsPbBr3 quantum dots and RhB dye molecules by pressure regulation

Fluorescence resonance energy transfer (FRET) based on quantum dots (QDs) and dye molecules have great application potential in biochemical fields. How to achieve an efficient energy transfer process has become an important research topic. Pressure can be used to regulate the energy transfer process, but its regulation on metal halide perovskite systems is rarely reported. Herein, the efficient FRET process between CsPbBr3 QDs and Rhodamine B (RhB) molecules under high pressure is investigated. Upon compression to 1.3 GPa, the FRET rate of the CsPbBr3–RhB composite reaches 0.21 ns−1 and the FRET efficiency is improved from 12.4% to 62.4%, due to enhanced spectral overlap and shortened minimum distance between CsPbBr3 QDs and RhB molecules. This study provides a strategy for achieving efficient FRET research and further promotes the development of applications based on halide perovskite molecular systems.

Construction of nanohybrid Tb@CDs/GSH-CuNCs as a ratiometric probe to detect phosphate anion based on aggregation-induced emission and FRET mechanism.

The simple preparation of a nanohybrid of terbium-doped carbon dots/glutathione-capped copper nanoclusters (Tb@CDs/GSH-CuNCs) was for the first time developed for ratiometric detection of phosphate anion (Pi). Blue-emission of Tb@CDs can trigger non-luminescence of GSH-CuNCs for aggregation-induced emission (AIE) performance due to the strong reserved coordination capacity of Tb3+. Thus, Tb@CDs/GSH-CuNCs rapidly generated dual-emission signals at 630 nm and 545 nm by directly mixing the two individual materials via the AIE effect, alongside fluorescence resonance energy transfer (FRET) process. However, by the introduction of Pi, both AIE and FRET processes were blocked because of the stronger binding affinity of Tb3+ and Pi than that of Tb3+ and -COOH on Tb@CDs, thus realizing successful ratiometric detection of Pi. The linear concentration range was 0-16 μM, with the limit of detection (LOD) of 0.32 μM. The proposed method provided new ideas for designing nanohybrid of CDs and nanoclusters (MNCs) as ratiometric fluorescent probes for analytical applications.

Tunable Fluorescence and Morphology of Aggregates Built from a Mechanically Bonded Amphiphilic Bistable [2]Rotaxane.

Advanced Organic Chemical Materials Co-constructed Mechanically bonded amphiphiles (MBAs), also known as mechanically interlocked molecules (MIMs), have emerged as an important kind of functional building block for the construction of artificial molecular machines and soft materials. Herein, a novel MBA, i. e., bistable [2]rotaxane H2 was designed and synthesized. In the solution state, H2 demonstrated pH and metal ion-responsive emissions due to the presence of a distance-dependent photoinduced electron transfer (PET) process and the fluorescence resonance energy transfer (FRET) process, respectively. Importantly, the amphiphilic feature of H2 has endowed it with unique self-assembly capability, and nanospheres were obtained in a mixed H2 O/CH3 CN solvent. Moreover, the morphology of H2 aggregates can be tuned from nanospheres to vesicles due to the pH-controlled shuttling motion-induced alternation of H2 amphiphilicity. Interestingly, larger spheres with novel pearl-chain-like structures from H2 were observed after adding stoichiometric Zn2+ . In particular, H2 shows pH-responsive emissions in its aggregation state, allowing the visualization of the shuttling movement by just naked eyes. It is assumed that the well-designed [2]rotaxane, and particularly the proposed concept of MBA shown here, will further enrich the families of MIMs, offering prospects for synthesizing more MIMs with novel assembly capabilities and bottom-up building dynamic smart materials with unprecedented functions.

Dynamic Assembly‐Induced Time‐Resolved Optical Switches for Rewritable Advanced Information Encryption

AbstractThe development of photocontrolled assembly of smart materials with time‐dependent optical characteristics is a promising strategy to fabricate multiple optical materials for advanced information encryption. Herein, this work reports the integration of photochoromic spiropyran and square‐planar platinum(II) as a photocontrolled switching motif that endows the materials with dynamic assembly‐induced optical characteristics. Importantly, the time‐resolved multilevel optical switching processes have been achieved based on the synergism of the reversible photochoromism and fluorescence resonance energy transfer (FRET) processes through regulating the intramolecular isomerization and intermolecular self‐assembly processes. The excellent temporal multicolor features promote the photocontrolled switches as a promising candidate for time‐resolved confidential materials including multilevel displays and dynamic 4 dimension (4D) codes, with the achievement of relative encrypted data that can only be identified at a specified time. This synergistical strategy for constructing advanced materials provides an inspiring guidance for information encryption with higher security requirements.

Fluorometric Assay of Tyrosinase and Atrazine Based on the Use of Carbon Dots and the Inhibition of Tyrosinase Activity.

Sensitive and convenient strategy of tyrosinase (TYR) and its inhibitor atrazine is in pressing demand for essential research as well as pragmatic application. In this work, an exquisite label-free fluorometric assay with high sensitivity, convenience and efficiency was described for detecting TYR and the herbicide atrazine on the basis of fluorescent nitrogen-doped carbon dots (CDs). The CDs were prepared via one-pot hydrothermal reaction starting from citric acid and diethylenetriamine. TYR catalyzed the oxidation of dopamine to dopaquinone derivative which could quench the fluorescence of CDs through a fluorescence resonance energy transfer (FRET) process. Thus, a sensitive and selective quantitative evaluation of TYR can be constructed on the basis of the relationship between the fluorescence of CDs and TYR activity. Atrazine, a typical inhibitor of TYR, inhibited the catalytic activity of TYR, leading to the reduced dopaquinone and the fluorescence was retained. The strategy covered a broad linear range of 0.1-150 U/mL and 4.0-80.0 nM for TYR and atrazine respectively with a low detection limit of 0.02 U/mL and 2.4 nM/mL. It is also demonstrated that the assay can be applied to detect TYR and atrazine in spiked complex real samples, which provides infinite potential in application of disease monitoring along with environmental analysis.

Redox‐Modulated Circularly Polarized Luminescence in Chiral Photonic Films Derived from Cellulose Nanocrystals and Polyoxometalate

AbstractAchieving smart circularly polarized luminescence (CPL) materials with large luminescence dissymmetry factor (glum) is in high demand for potential technological applications in the chiroptical fields. Herein, a series of chiral photonic crystals (CPCs) derived from cellulose nanocrystals (CNCs) and photosensitive inorganic polyoxometalates (POMs) through an evaporation‐induced self‐assembly strategy are reported. The photonic bandgaps (PBGs) of CPC films are well regulated by controlling the amount of doped POMs, yielding the tunable right‐handed CPL emission with tailored glum. By locating the maximum emission peak of POMs at the center of the PBG of CPC films, the composite shows remarkable CPL performance with a |glum| value up to 0.53. Furthermore, the CPL can be reversibly switched on/off through a fluorescence resonance energy transfer (FRET) process controlled by alternate UV irradiation reduction and air oxidation. The CPC films hold the great promise as next‐generation chiroptical memory devices.

An ICT-FRET-based ratiometric fluorescent probe for hydrogen polysulfide based on a coumarin-naphthalimide derivative

Hydrogen polysulfide (H2Sn, n > 1), as one of the important members of reactive sulfur species (RSS), plays a vital part in the processes of both their physiology and pathology. In this work, a ratiometric fluorescent probe for H2Sn had been designed and prepared based on the combination mechanism of intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET). The probe chose a coumarin derivative as the energy donor, a naphthalimide derivative as the energy acceptor and 2-fluoro-5-nitrobenzoate as the H2Sn recognition group. When H2Sn was not present in the system, the ICT process of the naphthalimide acceptor was inhibited and the FRET process from the coumarin donor to the naphthalimide acceptor was turned off. When H2Sn was added, both ICT and FRET occurred due to the nucleophilic substitution-cyclization reactions between the probe and hydrogen polysulfide. In addition, the ratio value of the emission intensities at 550 nm and 473 nm (I550 nm/I473 nm) of this probe had a good linear relationship with H2Sn concentration in the range of 6.0 × 10-7-5.0 × 10-5 mol·L-1, and a detection limit of 1.8 × 10-7 mol·L-1 was obtained. The developed probe had high selectivity and sensitivity, as well as good biocompatibility. Additionally, the probe had been used to successfully image both indigenous and exogenous hydrogen polysulfide in A549 cells using confocal microscope.

Synthesis, photophysical, and photochemical properties of functional molecules based on a novel zinc(II) phthalocyanine-1,8-naphthalimide skeleton

Designing multifunctional photosensitizers with high efficiency has been significant in the molecular engineering field. In this work, we designed a novel molecular skeleton with a bi-chromophore, in which four 4-substituted-1,8-naphthalimide fluorophores were introduced as energy pumps to the zinc(II) phthalocyanine photosensitive group. Four peripherally symmetrical 4-NH-substituted-1,8-naphthalimide functionalized zinc(II) phthalocyanine molecules (NAZP1, NAZP2, NAZP3, NAZP4) were synthesized and characterized. The photophysical and photochemical properties of the molecules were investigated. The novel molecules showed dual-channel absorption and emission features of both chromophores. The fluorescence resonance energy transfer (FRET) process from 1,8-naphthalimide to zinc(II) phthalocyanine was verified by the spectral overlap and theoretical calculations. NAZP1 had higher FRET efficiency than the other three molecules. The singlet oxygen quantum yields of NAZP1, NAZP2, NAZP3, and NAZP4 in DMF were 0.84, 0.60, 0.68, and 0.73 respectively, being higher than the unsubstituted ZnPc. The introduction of four 1,8-naphthalimide energy pumps greatly improved the photophysical and photochemical properties of zinc(II) phthalocyanine, being hopeful in developing high-performance photosensitizers.

A novel fluorescent strategy for Golgi protein 73 determination based on aptamer/nitrogen-doped graphene quantum dots/molybdenum disulfide @ reduced graphene oxide nanosheets.

The effective detection of biomarkers associated with hepatocellular carcinoma (HCC) is of great importance. Golgi protein 73 (GP73), a serum biomarker of HCC, has better diagnostic value than Alpha-fetoprotein (AFP) has been reported. In this paper, highly accurate fluorescence sensing platform for detecting GP73 was constructed based on fluorescence resonance energy transfer (FRET), in which nitrogen-doped graphene quantum dots (NGQDs) labelling with GP73 aptamer (GP73Apt) was used as fluorescence probe, and molybdenum disulfide @ reduced graphene oxide (MoS2@RGO) nanosheets was used as fluorescent receptors. MoS2@RGO nanosheets can quench the fluorescence of NGQDs-GP73Apt owing to FRET mechanisms. In the presence of GP73, the NGQDs-GP73Apt specifically bound with GP73 to from the deployable structures, making NGQDs-GP73Apt far away from MoS2@RGO nanosheets, blocking the FRET process, resulting in fluorescence recovery of NGQDs-GP73Apt. Under optimal conditions, the recovery intensity of fluorescence in the detection system is linearly related to the concentration of GP73 in the range of 5ng/mL - 100ng/mL and the limit of detection is 4.54ng/mL (S/N=3). Moreover, detection of GP73 was performed in human serum samples with good recovery (97.21-100.83%). This platform provides a feasible method for the early diagnosis of HCC, and can be easily extended to the detection of other biomarkers.

A smartphone-based ratiometric fluoroprobe based on blue-red dual-emission signals of thiochrome and copper nanoclusters for sensitive assay of metam-sodium in cucumbers

It is of great importance to develop the highly efficient fluorescence strategy for rapid/sensitive detection of metam-sodium (MES) in evaluating its residual safety, especially in fresh vegetables. Herein, we prepared an organic fluorophore (thiochrome, TC) and glutathione-capped copper nanoclusters (GSH-CuNCs), and their combination (TC/GSH-CuNCs) was sucessfully employed as a ratiometric fluoroprobe by means of the blue-red dual emission. The fluorescence intensities (FIs) of TC decreased upon the addition of GSH-CuNCs via the fluorescence resonance energy transfer (FRET) process. When fortified at the constant levels of GSH-CuNCs and TC, MES substantially reduced the FIs of GSH-CuNCs, while this was not the case in the FIs of TC except for the prominent red-shift of ∼30 nm. Compared to the previous fluoroprobes, the TC/GSH-CuNCs based fluoroprobe supplied wider linear range of 0.2–500 μM, lower detection limit (60 nM), and satisfactory fortification recoveries (80–107%) for MES in the cucumber samples. Based on the fluorescence quenching phenomenon, a smartphone application was used to output RGB values of the captured images for the colored solution. The smartphone-based ratiometric sensor could be utilized for the visual fluorescent quantitation of MES by virtue of the R/B values in cucumbers, which gave linear range (1–200 μM) and LOD (0.3 μM). By means of blue-red dual-emission fluorescence, the smartphone-based fluoroprobe provides a cost-effective, portable and reliable avenue for the on-site, rapid and sensitive assay of MES's residues in complex vegetable samples.

Smartphone-Aided Fluorescence Detection of Cardiac Biomarker Myoglobin by a Ratiometric Fluorescent AuNCs-QDs Nanohybrids Probe with High Sensitivity.

Simple and sensitive detection of cardiac biomarkers is of great significance for early diagnosis and prevention of acute myocardial infarction (AMI). Here, a ratiometric fluorescent nanohybrids probe (AuNCs-QDs) was synthesized through the coupling of bovine serum albumin-functionalized gold nanoclusters (AuNCs) with CdSe/ZnS quantum dots (QDs) to realize simple and sensitive detection of cardiac biomarker myoglobin (Mb). The AuNCs-QDs probe shows pink fluorescence under UV light, with two emission peaks at 468nm and 630nm belonging to QDs and AuNCs, respectively. Importantly, the presence of Mb caused fluorescence quenching of the blue-emitting QDs, thereby inhibiting the fluorescence resonance energy transfer (FRET) process between QDs and AuNCs, and reducing the fluorescence intensity ratio (F468/F630) of AuNCs-QDs probe effectively. As the concentration of Mb increases, the ratiometric fluorescent probe also exhibits a visible fluorescence color change. The detection limit was as low as 4.99μg/mL, and the response of the probe to Mb showed a good linear relationship up to 0.52mg/mL. Moreover, the probe has excellent specificity for Mb. Besides, the AuNCs-QDs has been applied to detect Mb of urine samples. More importantly, we also developed an AuNCs-QDs probe modified smartphone-aided paper-based strip for on-site monitoring of Mb. As far as we know, this is the first report of a smartphone-aided paper-based strip for on-site quick monitoring of Mb, which provides a useful approach for AMI biomarker monitoring and may can be extended to other medical diagnostics.

Photo-Stimuli-Responsive Dual-Emitting Luminescence of Spiropyran-Encapsulated Metal-Organic Framework for Dynamic Information Encryption.

The development of photo-stimuli-responsive luminescent materials is essential to address emerging demands in encryption security. Here, we report a novel photo-stimuli-responsive dual-emitting luminescent material ZJU-128⊃SP (SP = spiropyran), which was obtained by encapsulating spiropyran molecule into a cadmium-based metal-organic framework (MOF), [Cd3 (TCPP)2 ]·4DMF·4H2 O (ZJU-128, H4 TCPP = 2,3,5,6-tetrakis (4-carboxyphenyl)pyrazine). This MOF/dye composite ZJU-128⊃SP exhibits a blue emission from ligand of ZJU-128 at 447nm and a red emitting around 650nm of spiropyran. Utilizing the photoisomerization of spiropyran from ring-closed to ring-open form under UV light irradiation, significant fluorescence resonance energy transfer process between ZJU-128 and spiropyran is achieved. As a result, the blue emission of ZJU-128 is gradually decreased while the red emission of spiropyran increased. This dynamic fluorescent behavior can fully recover to original state when exposed to visible light (> 405nm). By taking advantage of the time-dependent fluorescence, dynamical anti-counterfeiting pattern and multiplexed coding are successfully developed based on ZJU-128⊃SP film. This work provides an inspiring point for the design of information encryption materials with higher security requirements. This article is protected by copyright. All rights reserved.

Diverse Fluorescence Resonance Energy Transfer Processes Originating from the Conformational Heterogeneity of the Calcium Indicator Yellow Cameleon YC3.60.

By combining time-resolved fluorescence spectroscopy and molecular biology, we have clearly elucidated the fluorescence mechanism of yellow cameleon YC3.60. YC3.60 is one of the most widely used fundamental calcium ion indicator proteins and is a tandem protein consisting of cyan fluorescent protein, calmodulin, and yellow fluorescent protein. Our results show that the conformational heterogeneity of YC3.60 leads to multiple FRET (fluorescence resonance energy transfer) processes occurring in a variety of structures. In the presence of calcium ions, FRET occurs in 75% of all YC3.60 molecules, and the intramolecular FRET faster than 20 ps is dominant among the three different FRET processes. Even in the absence of calcium ions, FRET occurs in 28% of YC3.60, where intra- and intermolecular FRET with a time constant of 160 ps is dominant among the four different FRET processes. YC3.60 with the immature chromophore, which is 25% of the total, would result in lower contrast on imaging. Conformational heterogeneity arises from the specific association of the two fluorescent proteins. It was clearly shown that the association of fluorescent proteins has a significant impact on the fluorescence mechanism. These observations lead to the promotion of research that elucidates the relationship between the higher-order structure and function of proteins.

Rapid and Ultrasensitive Fluorescence Sensing Platform Based on Nanometer-Sized Metal–Organic Frameworks for Transgenic CaMV 35S Promoter Detection

Rapid and sensitive identification of genetically modified organisms (GMOs) is urgent for food safety and people health. Herein, a rapid and ultrasensitive fluorescence sensing platform is developed based on the single-strand DNA-labeled FAM dye (FAM-ssDNA) and nanometer-sized Fe-metal–organic framework (Fe-MOF), Fe-MIL-88. Fe-MIL-88 possesses a large specific surface area, remarkable preferential combining capacity with ssDNA versus dsDNA, and great quenching ability. FAM-ssDNA probes are elaborately designed as facile fluorescent probes to be fully complementary with the target of cauliflower mosaic virus 35S promoter (CaMV 35S), which can be absorbed to the surface of Fe-MIL-88 through π–π stacking and electrostatic interaction. The results indicate that the quenching ability of Fe-MIL-88 is attributed to the combination of photoinduced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes. Benefiting from the distinguishable ability of Fe-MIL-88, the fluorescent biosensor exhibits a satisfactory linear range from 5 pM to 50 nM and a low limit of detection (LOD) down to 0.184 pM. Also, the operation time was less than 1 h. Furthermore, the sensor also performs well in the anti-interference test and real sample test. Importantly, the sensing platform is equipped with easier operation without any complicated and difficult immobilization steps. Therefore, the sensor owns cheering potential for the detection of GMOs.