Fluorescent Units Research Articles

Portable cell imprinted polymer-based microfluidic sensor for bacteria detection in real water

Cell-imprinted polymer (CIP) based optical biosensors have transformed point-of-care detection. However, challenges remain in their portability and detection sensitivity, time, and cost. Herein, we present an imprinted polymer-based low-cost microfluidic device integrated into a portable enclosure that enables rapid and sensitive bacteria detection in real water. A portable 3D-printed platform was custom-designed, housing all essential detection components, i.e., pumping and fluorescent imaging units and the microfluidic sensor. CIP coated magnetic microparticles (MPs) with affinity to bacteria were manipulated inside the magnetophoretic microfluidic device at an optimized flow rate of 0.01 mL/min for bacteria capturing. Fluorescent imaging pre- and post-bacteria capture facilitated quantification of fluorescence intensity changes as bacteria were trapped by the CIP-MPs. The sensor’s dose–response curve established limits of detection (LOD) and quantification (LOQ) at 8 × 103 and 6 × 105 CFU/mL, respectively, within a dynamic range of 103 to 109 CFU/mL. It specifically detected E. coli, distinguishing it from non-specific bacteria like Salmonella and Sarcina. In real pond water tests, our sensor detected 2 × 10⁶ CFU/mL, matching a central lab’s result of 2.33 × 10⁶ CFU/mL, demonstrating its effectiveness for real-water monitoring. While further enhancements are needed for improving the specificity in complex environmental matrices and broader bacterial strain detection, the sensor’s simplicity and portability highlight its potential for practical potential.

Robust Luminescent Pyrene-Based Metal-Organic Framework Hydrogel as a pH-Responsive Fluorescence Emitter for Sensitive Immunoassay of Cardiac Troponin I.

Despite many luminescent advantages including outstanding absorption coefficient and high quantum yield, pyrene and its derivatives have been suffering from a dramatic aggregation-caused quenching (ACQ) effect. Although the dramatic ACQ effect of pyrene-based fluorophores has been restrained in pyrene-doped metal-organic frameworks (MOFs), the low loading of fluorescent (FL) units substantially impedes the improved luminescent behaviors. Herein, pyrene-based MOFs hydrogel was synthesized with a high loading of pyrene as the unique organic linker blocks instead of a dopant in MOFs. The gel matrix contributed to rigidifying the location of the FL emitters and achieving intensive FL emission and high luminescent stability and therefore efficiently overcoming the ACQ effect. Furthermore, the protonation of pyrene in the MOFs hydrogel remarkably decreased the luminescent intensity, which endowed the FL hydrogel with highly pH-responsive activity in the broad range (pH 4-10). Interestingly, glucose oxidase was immobilized into ZIF-8 as a highly efficient luminescent quencher, which contributed to catalyzing the form of gluconic acid and thus drastically quenching the FL signal of the MOFs hydrogel. Furthermore, the emitter-quencher pair of pyrene-based MOFs hydrogel and glucose oxidase was successfully employed to develop an ultrasensitive FL immunoassay platform for cardiac troponin I (as a model analyte). The limit of detection for cardiac troponin I was 5.2 pg/mL (3σ). The proof-of-principle study demonstrated the thrilling auxiliary effect of tailorable MOFs hydrogel on boosting the feasibility of aqueous insoluble FL chromophores for trace analysis.

A Self‐Calibrating Sensing Platform Based on Amine‐Responsive Excitation Wavelength‐Dependent Fluorescent Polymers for Real‐Time and Visual Detection of Food Freshness

AbstractAccurate assessment of food freshness is critical to maintaining human health. However, the complex environment of food usually leads to false‐positive measurements result. Therefore, the development of sensing platforms with self‐calibration for accurate detection of food freshness in complex environments is essential. Here, using the green fluorescence‐emitting FITC‐ene and the red fluorescence‐emitting DBA‐ene‐Eu3+ as fluorescent units, fluorescent polymeric materials P1‐P4 with excitation wavelength‐dependent (254 and 365 nm, matched with standard UV lamp) emission are prepared. P1‐P4 responded rapidly to biogenic amines (BAs). Among them, P3 exhibits the widest linear range, and the most noticeable fluorescence color change (from orange‐red to yellow‐green) under 254 nm excitation and enhanced green fluorescence under 365 nm excitation. The changes of P3‐prepared labels at different excitation wavelengths can be utilized to rapidly evaluate the food's freshness. Furthermore, by using a smartphone to read the Red/Green/Blue values of the labels, the total volatile basic nitrogen (TVBN) values can be output to quantitatively evaluate the food freshness, and the output TVBN values at different excitation wavelengths are utilized for mutual calibration to improve the accuracy of the estimation results. This self‐calibrating sensing platform is fast and nondestructive, which provides an effective method for the accurate evaluation of food freshness.

Strategies for preparation of chitosan based water-soluble fluorescent probes to detect Cr3+ and Cu2+ ions

The low solubility of chitosan (CS) imposes adverse effects on its application. In this work, one of the aims is to improve the water solubility of CS. By introducing water-soluble side chains to CS, this aim was achieved. Besides, fluorescent moieties were incorporated into the side chains, the fluorescent copolymers were endowed with Cr3+ and Cu2+ ions recognition ability. Firstly, a reversible addition-fragmentation chain transfer polymerization (RAFT) reagent with naphthalimide units and CC groups was prepared. Water-soluble monomer methyl acrylic acid (MAA) was employed in the RAFT polymerization. Thus, water-soluble polymer with fluorescent unit and -C ≡ C on both ends of the polymer was obtained. They were introduced into CS, and the CS-based fluorescent copolymers were obtained eventually. The amount of MAA introduced could be tuned to obtain three side chains of different lengths. It was found that the more MAA was introduced, the better the solubility of CS-TP was. The detection limits (LOD) of Cr3+ and Cu2+ were 44.6 nM and 54.5 nM, respectively. The detection of Cr3+ and Cu2+ ions is further combined with a mobile APP to realize real-time, portable, and visual detection. And the application in the logic gate, a new detection platform, is prepared.

De Novo Glycan Display on Cell Surfaces Using HaloTag: Visualizing the Effect of the Galectin Lattice on the Lateral Diffusion and Extracellular Vesicle Loading of Glycosylated Membrane Proteins.

Glycans cover the cell surface to form the glycocalyx, which governs a myriad of biological phenomena. However, understanding and regulating glycan functions is extremely challenging due to the large number of heterogeneous glycans that engage in intricate interaction networks with diverse biomolecules. Glycocalyx-editing techniques offer potent tools to probe their functions. In this study, we devised a HaloTag-based technique for glycan manipulation, which enables the introduction of chemically synthesized glycans onto a specific protein (protein of interest, POI) and concurrently incorporates fluorescent units to attach homogeneous, well-defined glycans to the fluorescence-labeled POIs. Leveraging this HaloTag-based glycan-display system, we investigated the influence of the interactions between Gal-3 and various N-glycans on protein dynamics. Our analyses revealed that glycosylation modulates the lateral diffusion of the membrane proteins in a structure-dependent manner through interaction with Gal-3, particularly in the context of the Gal-3-induced formation of the glycan network (galectin lattice). Furthermore, N-glycan attachment was also revealed to have a significant impact on the extracellular vesicle-loading of membrane proteins. Notably, our POI-specific glycan introduction does not disrupt intact glycan structures, thereby enabling a functional analysis of glycans in the presence of native glycan networks. This approach complements conventional glycan-editing methods and provides a means for uncovering the molecular underpinnings of glycan functions on the cell surface.

Non-conventional exciplex system by leveraging zero-radius of intramolecular energy transfer mechanism: Seamless integration of p-host and fluorescent dopant for highly efficient OLEDs

A multi-component emissive layer (EML) composed of a mixture of p- and n-type hosts and a dopant is a widely used structure in organic light-emitting diodes (OLEDs) due to its high efficiency and operational stability. However, multi-component EML devices impose limitations such as difficulty in accurately controlling the mixing ratio and profiles in the manufacturing process, high costs, and complexity in the photophysical properties of the components.In this paper, a p-type host fused with a blue fluorescent dopant, 5,9-di([1,1′-biphenyl]-2-yl)-2′-(9H-carbazole-9-yl)3,7-dimethyl-5,5a,5a1,9,9a,16a-hexahydrospiro[5,9-diaza-16b-boraindeno[2,1-b]naphtho[1,2,3-fg]anthracene-11,9′-fluorene] (DABNA-Spiro-Cz), was designed and successfully synthesized to construct a novel EML structure. Completely fused within DABNA-Spiro-Cz, the p-type host and blue fluorescent dopant can independently perform their respective roles. An exciplex is formed between n-type host and p-type host unit in the DABNA-Spiro-Cz molecule and its energy is effectively transferred to the blue fluorescent dopant unit in DABNA-Spiro-Cz. In other words, a degree of freedom is earned from a conventional 3-component exciplex-dopant system. A high external quantum efficiency of 14.9 % was achieved thanks to “zero-radius of intramolecular energy transfer in exciplex (ZETPLEX)” system, which is completely non-conventional and novel. We believe the ZETPLEX mechanism opens a new era of designing emissive materials and paves a new way of constructing a novel EML and device architecture for highly efficient OLEDs.

Flow cytometry: Unravelling the real antimicrobial and antibiofilm efficacy of natural bioactive compounds

Flow cytometry (FCM) provides unique information on bacterial viability and physiology, allowing a real-time early warning antimicrobial and antibiofilm monitoring system for preventing the spread risk of foodborne disease. The present work used a combined culture-based and FCM approach to assess the in vitro efficacy of essential oils (EOs) from condiment plants commonly used in Mediterranean Europe (i.e., thyme EO, oregano EO, basil EO, and lemon EO) against planktonic and sessile cells of food-pathogenic Listeria monocytogenes 56 LY, and contaminant and alterative species Escherichia coli ATCC 25922 and Pseudomonas fluorescens ATCC 13525. Evaluation of the bacterial response to the increasing concentrations of natural compounds posed FCM as a crucial technique for the quantification of the live/dead, and viable but non-culturable (VBNC) cells when antimicrobial agents exert no real bactericidal action. Furthermore, the FCM results displayed higher numbers of viable bacteria expressed as Active Fluorescent Units (AFUs) with a greater level of repeatability compared with outcomes of the plate-count method. Overall, accurate counting of viable microbial cells is a critically important parameter in food microbiology, and flow cytometry provides an innovative approach with high-throughput potential for applications in the food industry as “flow microbiology”.

In Situ Quantitative Imaging of Plasma Membrane Stiffness in Live Cells Using a Genetically Encoded FRET Sensor.

Cell membrane stiffness is critical for cellular function, with cholesterol and sphingomyelin as pivot contributors. Current methods for measuring membrane stiffness are often invasive, ex situ, and slow in process, prompting the need for innovative techniques. Here, we present a fluorescence resonance energy transfer (FRET)-based protein sensor designed to address these challenges. The sensor consists of two fluorescent units targeting sphingomyelin and cholesterol, connected by a linker that responds to the proximity of these lipids. In rigid membranes, cholesterol and sphingomyelin are in close proximity, leading to an increased FRET signal. We utilized this sensor in combination with confocal microscopy to explore changes in plasma membrane stiffness under various conditions, including differences in osmotic pressure, the presence of reactive oxygen species (ROS) and variations in substrate stiffness. Furthermore, we explored the impact of SARS-CoV-2 on membrane stiffness and the distribution of ACE2 after attachment to the cell membrane. This tool offers substantial potential for future investigations in the field of mechanobiology.

Cholesterol-decorated porphyrin with circularly polarized luminescence: Design, synthesis and properties

Porphyrin was an excellent near-infrared dye but its rigid planar structure is not favorable for producing circularly polarized luminescence (CPL) property. Chirality transfer is an effective strategy to realize the CPL emission for achiral fluorescent unit. In this study, porphyrin derivatives with four cholesterol groups and dodecyl groups B4C and B4D were designed and synthesized. B4C and B4D exhibited good near-infrared emission in both solution and aggregated states. The solid film of B4C emitted strong left CPL fluorescence, while this CPL signal in mesomorphic film was stronger and switched to right CPL emission. The fluorescence dissymmetry factor (glum) of B4C was as high as 2.31×10−2. These results suggested the effective chirality transfer from cholesterol units to porphyrin units based on spiral columnar liquid crystalline stacking and the CPL signal of B4C was tunable by temperature, supplying a good way on design and synthesis of CPL material with tunable CPL signal based on achiral dyes.

Multi-functional fluorescent silicon elastomer cross-linked with AIE polymer by dynamic imine bond and its application in anti-counterfeiting

Fluorescent elastomer materials have received extensive attention due to their excellent optical performance, flexibility, and chemical stability in recent years, and demonstrate great application potentials in intelligent sensors, optoelectronic devices, medical equipment and other fields. Although the traditional method for constructing fluorescent elastomers by doping fluorescent small molecules is facile and universal, it also has limitations such as low luminous efficiency, uneven dispersion, poor stability and single function. In this work, an aggregation-induced emission (AIE) fluorescent polymer with aldehyde groups in side chain was synthesized and crosslinked with aminopropyl double capped polydimethylsiloxane (NH2-PDMS-NH2) through mild Schiff base reaction to construct a fluorescent elastomer. Compared with fluorescent small molecules, AIE polymers have superior fluorescence performance and can be flexibly designed according to demands. The dynamic imine bonds endow the as-obtained elastomers with self-healing and recycling properties, enabling rapid repair and remodeling at room temperature. Besides, the tensile and swelling properties of PDMS enable them to adjust the concentration of fluorescent units in the matrix under corresponding stimulus, thereby achieving tunable fluorescence emission. Taking advantage of the fluorescent elastomers, we prepared fluorescent anti-counterfeiting patterns that were hidden in daylight and visible under UV light, demonstrating the potential applications of the fluorescent elastomers in the fields of anti-counterfeiting and information encryption. This study also provides an alternative strategy for developing multifunctional fluorescent elastomers.

In vitro evaluation of shape-memory hydrogels for removable dental prostheses and optimization of phase-transition temperature for intraoral use

Removable dental prostheses require periodic relining with the loss of intaglio surface fit because of mucosal shape changes over time. Therefore, a new material with high adaptability to tissue changes over time would be beneficial. This study focused on a shape-memory gel (SMG) that softens when heated, retains its shape when cooled, and returns to its original shape when reheated. The purpose was to optimize SMG for intraoral use by controlling the ratio of 2 acrylate monomers and to evaluate the changes in the shape memory and physical properties of SMG with temperature and to evaluate biocompatibility. SMG specimens were synthesized using the following mixing ratios of 2 monomers, docosyl acrylate (DA) and stearyl acrylate (SA): 0:100, 25:75, 50:50, 75:25, and 100:0. SMG specimens were photopolymerized using a fluorescent light-polymerizing unit. To evaluate shape memory as a function of temperature, permanent deformation was measured based on the standardized compression set test for thermoplastic rubber. For evaluation of the physical properties and cytotoxicity, a 3-dimensionally printed denture base material was used as the control material. All assessments were compared between the groups by using 1-way analysis of variance followed by the Tukey-Kramer multiple comparison test (α=.05). SMGs with a higher amount of DA maintained their compressed shape at room and intraoral temperatures. However, the SMG matrices softened and recovered their original shapes above 60°C. SMGs showed Shore A hardness equivalent to that of the denture-base polymer material at intraoral temperatures because of the high phase-transition temperature. The low water solubility of SMGs supported the biocompatibility test results. SMG, in which the phase-transition temperature was controlled by mixing acrylate monomers with different melting points, exhibited shape memory in the intraoral environment. The results indicate the feasibility of applying SMG for the fabrication of removable dental prostheses because of its high adaptability to tissue changes over time and biocompatibility.

Visual monitoring of biocatalytic processes using small molecular fluorescent probes: strategies-mechanisms-applications.

Real-time monitoring of biocatalytic-based processes is significantly improved and simplified when they can be visualized. Visual monitoring can be achieved by integrating a fluorescent unit with the biocatalyst. Herein, we outline the design strategies of fluorescent probes for monitoring biocatalysis: (1) probes for monitoring biocatalytic transfer: γ-glutamine is linked to the fluorophore as both a recognition group and for intramolecular charge transfer (ICT) inhibition; the probe is initially in an off state and is activated via the transfer of the γ-glutamine group and the release of the free amino group, which results in restoration of the "Donor-π-Acceptor" (D-π-A) system and fluorescence recovery. (2) Probes for monitoring biocatalytic oxidation: a propylamine is connected to the fluorophore as a recognition group, which cages the hydroxyl group, leading to the inhibition of ICT; propylamine is oxidized and subsequently β-elimination occurs, resulting in exposure of the hydroxyl group and fluorescence recovery. (3) Probes for monitoring biocatalytic reduction: a nitro group attached to a fluorophore as a fluorescence quenching group, this is converted to an amino group by catalytic reduction, resulting in fluorescence recovery. (4) Probes for monitoring biocatalytic hydrolysis: β-D-galactopyranoside or phosphate acts as a recognition group attached to hydroxyl groups of the fluorophore; the subsequent biocatalytic hydrolysis reaction releases the hydroxyl group resulting in fluorescence recovery. Following these 4 mechanisms, fluorophores including cyanine, coumarin, rhodamine, and Nile-red, have been used to develop systems for monitoring biocatalytic reactions. We anticipate that these strategies will result in systems able to rapidly diagnose and facilitate the treatment of serious diseases.

Effects of substitution and conjugation on photophysical properties of ESIPT-based fluorophores with the core of 4-aminophthalimide

4-Aminophthalimide is a highly fluorescent signaling unit with excellent photophysical properties and wide application foregrounds. Based on this, a range of theoretical investigations are conducted on the fluorescent probe (E)-5-((2-hydroxybenzylidene) amino) isoindoline-1, 3-dione (HID) with the core of 4-aminophthalimide using density functional theory (DFT) and time-containing density functional theory (TD-DFT) methods in this paper. The optimized configurations, vertical excitation and emission energies, electronic characteristics and excited-state intramolecular proton transfer (ESIPT) behaviors of the probe HID are discussed in detail. Furthermore, to enhance the luminescent properties of HID, five novel compounds have been designed based on the structure of HID by introducing amino, methoxy and naphthalene groups (–NH2, –OMe and C10H8). Our work thoroughly explores how the property and position of substituents and conjugation affect photophysical characteristics and ESIPT processes. We find that the ESIPT dynamics can be modulated by the substitution and conjugation effects. Specifically, the introduction of amino and methoxy groups at the ortho-position and the introduction of the naphthalene group promote the ESIPT behavior of HID1, whereas the introduction of amino and methoxy groups at the meta-position exhibits the contrary impact. Therefore, we boldly infer that the introduction of electron-donating groups in the ortho-position and the introduction of the conjugated group make the ESIPT process more effortless to occur, whereas the introduction of substituents with opposing natures in the meta-position makes the ESIPT process more difficult to occur. In addition, the ionization potentials (IP), electron affinities (EA) and reorganization energies (λh and λe) of molecules are calculated to assess their potential as luminescent materials. Our work not only reveals the luminescence and ESIPT mechanism of the probe HID1, but also proposes to modulate the ESIPT process through the substitution and conjugation effects. In particular, the designed molecules have better photoelectric properties as a result of their red-shifted absorption and fluorescence spectra, smaller energy gaps, larger transferred charges and greater charge transferred distances, which offers some valuable ideas for the experimental development of more efficient organic luminescent materials with ESIPT properties.

Tri-Allelic Autosomal STR Patterns Observed in Pakistani Population during Forensic Case Work

The tri-allelic pattern is a genotyping abnormality that can be observed during routine short tandem repeat (STR) profiling in the field of forensic science. Fourteen tri-allelic patterns have been observed in nine different loci during routine forensic casework consisting of 20,000 STR profiles. All these 20,000 STR unrelated profiles were profiled using AmpFlSTR Identifiler Plus® and Global Filer® kits. Tri-allelic patterns can be divided into two types based on RFUs (relative fluorescent units) in peaks of three component alleles. Unequal RFUs of all three peaks are observed in the Type-I pattern, whereas in the Type-II pattern, RFUs of all three peaks are nearly equal. A total of nine novel tri-allelic genotypes were observed out of 20,000 unrelated individuals in the Pakistani population. All of these forensic cases belonged to the Type-I pattern which means that the sum of the height of two smaller peaks is nearly equal to the height of the third larger peak. The frequency of occurrence for all these patterns was compared with already reported data. In this study, eight novel tri-allelic patterns have been reported which are not listed in the National Institute of Standards and Technology (NIST) database as well as in any published article.

2D Hierarchical Microbarcodes with Expanded Storage Capacity for Optical Multiplex and Information Encryption.

The design of nanosegregated fluorescent tags/barcodes by geometrical patterning with precise dimensions and hierarchies could integrate multilevel optical information within one carrier and enhance microsized barcoding techniques for ultrahigh-density optical data storage and encryption. However, precise control of the spatial distribution in micro/nanosized matrices intrinsically limits the accessible barcoding applications in terms of material design and construction. Here, crystallization forces are leveraged to enable a rapid, programmable molecular packing and rapid epitaxial growth of fluorescent units in 2D via crystallization-driven self-assembly. The fluorescence encoding density, scalability, information storage capacity, and decoding techniques of the robust 2D polymeric barcoding platform are explored systematically. These results provide both a theoretical and an experimental foundation for expanding the fluorescence storage capacity, which is a longstanding challenge in state-of-the-art microbarcoding techniques and establish a generalized and adaptable coding platform for high-throughput analysis and optical multiplexing.

A hydrogen-bonded organic framework containing fluorescent carbazole and responsive pyridyl units for sensing organic acids

Hydrogen-bonded organic frameworks (HOFs) are a promising candidate for optical sensing, but the lack of effective design strategies poses significant challenges to the construction of HOFs for organic acid sensing. In this work, the first HOF for organic acid sensing is reported by constructing a multiple-pyridine carbazole-based dense HOF, namely HOF-FJU-206, from a tripyridine-carbazole molecular 3,6-bis(pyridin-4-yl)-9-(4-(pyridin-4-yl)phenyl)-9H-carbazole (CPPY) with carbazole center for luminescence, pyridyl sites for its responsive of hydrogen proton, and narrow channels in the dense framework for the diffusion of hydrogen protons. HOF-FJU-206 exhibits differential responsively fluorescence sensing and recovery properties to formic, acetic, and propionic acids with different molecular sizes and pKa value (acid dissociation constant). The dissociation degree of various acids can be determined by analyzing the slope of changes in both peak wavelength and intensity of in-situ fluorescence, which easily enables the dual-corrective recognition of different acids. The varying degree of protonation at pyridine sites is proved to be the reason for differential sensing of various acids, as demonstrated by 1H NMR spectra, X-ray photoelectron spectroscopy (XPS) characterization, and modeling studies.

Ultrabright Acrylic Polymers with Tunable Fluorescence Enabled by Imprisoning Single TICT Probe.

Bright and colorful fluorescent polymers are ideal materials for a variety of applications. Although polymers could be made fluorescent by physical doping or chemical binding of fluorescent units, it is a great challenge to get colorful and highly emissive polymers with a single fluorophore. Here the development of a general and facile method to synthesize ultrabright and colorful polymers using a single twisted intramolecular charge transfer (TICT) probe is reported. By incorporating polymerizable, highly fluorescent, and environmental sensitive TICT probe, a series of colorful acrylic polymers (emission from 481 to 543nm) with almost 100% fluorescence quantum yields are prepared. Like the solvatochromic effect, functional groups within side chains of acrylic polymers (including alkyl chain, tetrahydrofurfuryl group, and hydroxyl group) provide varied environmental polarity for the incorporated fluorophore, resulting in a series of colorful polymeric materials. Benefiting from the excellent photophysical properties, the polymers show great potential in encryption, cultural relics protection, white light-emitting diode bulb making, and fingerprint identification.

Dynamics of Active Fluorescent Units (AFU) and Water Activity (aw) Changes in Probiotic Products-Pilot Study.

The flow cytometry method (FCM) is a widely renowned practice increasingly used to assess the microbial viability of probiotic products. Additionally, the measurement of water activity (aw) can be used to confirm the presence of viable cells in probiotic products throughout their shelf lives. The aim of this study was to investigate the correlation between changes in aw and variations in active fluorescent units (AFU), a unit commonly used in flow cytometry method, during the aging of probiotic products containing freeze-dried bacteria. We controlled the stability of probiotic products for bacterial counts (using ISO 19344 method) and aw levels in commercially available capsules containing freeze-dried bacteria such as Lactobacillus sp. or combinations of Lactobacillus sp. and Bifidobacterium sp. in standard conditions (25 ± 2 °C and 60% relative humidity) over a period of 24 months. During this time, the bacterial contents decreased by 0.12 Log10 in the single-strain product, by 0.16 Log10 in the two-strain product and by 0.26 Log10 in the multi-strain product. With the increase in aw, the number of bacteria decreased but the aw at the end point of the stability study did not exceed 0.15 in each of the three tested products. FCM combined with aw is a prospective analysis that can be used to assess the stability of probiotic products, both for its ability to detect bacterial viability and for practical (analysis time) and economic reasons.

A large Stokes shift and emission shift ratiometric mitochondria-targeted fluorescent probe for sensing HClO with an ESIPT-ICT integrated platform

Hypochlorous acid (HClO) is regarded as a significant oxidative stress marker and plays key factor in various pathological and physiological processes. However, the overexpression of HClO is relation to variety of diseases due to cellular damage and oxidative stress. Studies have described that the HClO level in mitochondria is crucial to maintain the normal function of mitochondrial. Herein, we presented a simple mitochondria-targeted fluorescent probe (BA-MR), which consists of the benzothiazole dye as the fluorescent signaling unit, the methyl thioether as the HClO recognition group, and the imine pyridinium salt moiety as the mitochondria targeting group. The free probe BA-MR possessed a super large Stokes shift (260 nm) and displayed a red fluorescent at 600 nm. Upon addition of HClO, the methyl thioether of BA-MR was oxidezed exclusively into a sulfoxide group, thereby leading to the generation of compound BAO-MR with a prominent blueshift of emission at 450 nm. As expected,the probe displayed highly sensitive and selective fluorescence response to HClO with fast response (120 s) and a low detection limit (86 nM). Importantly, the newly-synthesized probe was displayed to have low cytotoxicity, and could be successfully used to imaging HClO in mitochondria, which demonstrated the probe BA-MR can act as an effective tool for researching HClO-related physiological and pathological processes.

Linkages Make a Difference in the Photoluminescence of Covalent Organic Frameworks

AbstractCovalent organic frameworks (COFs) with structural designability and tunability of photophysical properties enable them to be a promising class of organic luminescent materials by incorporating well‐designed fluorescent units directly into the periodic skeletons. The photophysical properties of COFs are mainly affected by the structural features, which determine the conjugation degree, charge delocalization ability, and exciton dynamics of COFs. To understand the relationship between COF structures and their photophysical properties, two COFs with the same pyrene chromophore units but different linkages (imine or vinylene) were designed and synthesized. Interestingly, different linkages endow COFs with huge differences in solid‐state photoluminescence quantum yield (PLQY) for imine‐ and vinylene‐linked pyrene‐based COFs, which possess PLQY values of 0.34 % and 15.43 %, respectively. The femtosecond‐transient absorption spectra and time‐dependent density functional theory reveal the different charge‐transfer pathways in imine‐ and vinylene‐linked COFs, which influence the exciton relaxation way and fluorescence intensity. In addition, an effective white‐light device was obtained by coating the vinylene‐linked COF on a light‐emitting diode strip.