Activatable fluorescent probes for imaging and diagnosis of rheumatoid arthritis

Rheumatoid arthritis(RA)is a systemic autoimmune disease that is primarily manifested as synovitis and polyarticular opacity and typically leads to serious joint damage and irreversible disability,thus adversely affecting locomotion ability and life quality.Consequently,good prognosis heavily relies on the early diagnosis and effective therapeutic monitoring of RA.Activatable fluorescent probes play vital roles in the detection and imaging of biomarkers for disease diagnosis and in vivo imaging.Herein,we review the fluorescent probes developed for the detection and imaging of RA biomarkers,namely reactive oxygen/nitrogen species(hypochlorous acid,peroxynitrite,hydroxyl radical,nitroxyl),pH,and cysteine,and address the related challenges and prospects to inspire the design of novel fluorescent probes and the improvement of their performance in RA studies.

Hydroxylated graphene quantum dots as fluorescent probes for sensitive detection of metal ions

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.

Synthesis of 3-hydroxyflavone fluorescent probes and study of their fluorescence properties

Direct measurement of dipole potential in biological membranes has been impossible and 3-hydroxyflavones(3HFs) have allowed detection of changes in dipole potential in biological systems.In the present study,sixteen derivatives of 3HF with aliphatic hydrocarbon chains of different lengths at 4′-position and 6-position were synthesized.The basic fluorescence properties of 3HFs are maintained in all the probes in terms of strong blue shift in maximum fluorescence emission wavelength and>100 fold increase in quantum yield in organic solvents and in dioleoylphosphatidylcholine(DOPC) small unilamellar vesicles(SUV) in comparison to in aqueous Hepes buffer(15 mmol/L,pH 7.4).More importantly,the ability of the new compounds to report dipole potential changes in biological systems are also maintained,since all the new probes showed spectrum properties that are similar to yet different from that of F4N1,which potentially may allow more sensitive measurement of the dipole potential change in membranes.

STRUCTURAL INVESTIGATION OF A NEW POLYORGANOSILOXANE CONTAINING NANOTUBULAR CAVITIES USING ORGANIC FLUORESCENT PROBES

Fluorescent molecules - p-dimethylaminobenzonitrile (DMABN) and trans-stilbene (TSB ) - were used as probes to investigate the inner structure of the nanotubular cavities contained in a new polyorganosiloxane (POS) which was prepared by the hydrosilylation coupling reaction of cis-isotactic ladderlike polyvinylsilsesquioxane (Vi-T) with 1,1,3,3-tetramethyldisiloxane (H-MM) as coupling agent in the presence of catalyst dicyclopentadienyldichloroplatinum (Cp2PtCl2). The results from FTIR spectra and fluorescence spectra in combination with molecular simulation reveal that the cross-section of the nanotubular cavity is nearly rectangular in shape, and is about 0.62 nm in width and about 0.38 nm in height. This work gains in-depth knowledge into the inner structure of the nanotubular cavities of POS and furthermore provides a guide to the selection of proper guest molecules in constructing functional supramolecular clathrate based upon POS.

Synthesis and Spectral Characterization of Novel Sulfhydryl-reactive Benzimidazole Fluorescent Probes

Three sulfhydryl-reactive fluorescent probes, which contain 2-（1H-benzoimidazol-2-yl）-phenol and maleimide group, were synthesized and their structures were characterized by IR and ^1H NMR. Their photo-physical properties and the specificity to sulfhydryl group in the 2-mercapto-ethanol as well as the L-cysteine adducts were indicated by fluorescence intensity. Preliminary tests revealed that the probes could react selectively with the cysteine molecules, suggesting that these probes might be generally useful in biomedical researches.

Responsive mechanism and molecular design of di-2-picolylamine-based two-photon fluorescent probes for zinc ions

The properties of one-photon absorption（OPA）, emission and two-photon absorption（TPA） of a di-2-picolylaminebased zinc ion sensor are investigated by employing the density functional theory in combination with response functions.The responsive mechanism is explored. It is found that the calculated OPA and TPA properties are quite consistent with experimental data. Because the intra-molecular charge transfer（ICT） increases upon zinc ion binding, the TPA intensity is enhanced dramatically. According to the model sensor, we design a series of zinc ion probes which differ by conjugation center, acceptor and donor moieties. The properties of OPA, emission and TPA of the designed molecules are calculated at the same computational level. Our results demonstrate that the OPA and emission wavelengths of the designed probes have large red-shifts after zinc ions have been bound. Comparing with the model sensor, the TPA intensities of the designed probes are enhanced significantly and the absorption positions are red-shifted to longer wavelength range. Furthermore, the TPA intensity can be improved greatly upon zinc ion binding due to the increased ICT mechanism. These compounds are potential excellent candidates for two-photon fluorescent zinc ion probes.

Recent progress on fluorescent probes for viruses

Viruses are ubiquitous in human life. Some viruses can be used as vectors of genetic engineering and specific pesticides. Other viruses trigger a variety of diseases in humans, animals and plants, resulting in high infection rates and mortality. Therefore, convenient, accurate and rapid detection of viruses is of great significance for the diagnosis and treatment of subsequent diseases. In contrast to traditional methods of detection, which rely on time-consuming and complex techniques such as polymerase chain reaction (PCR), fluorescent probes and imaging methods generate real-time results, with high specificity, and have been widely used in viral detection. In this review, the application of viral fluorescent probes in analyzing the molecular structure, detection and biological imaging is discussed. In particular, we categorized the probes based on their specificity for human and plant viruses, reviewing the latest findings and analyzing their limitations. The potential of fluorescent molecular probes in the treatment of viral disease and environmental analysis, and their possible combinations with protein and immune technology are discussed.

Fluorescent Probes for Cysteine and Cysteine Oxidation Imaging

Cysteine is an important regulator of redox processes.Due to the nucleophilic and oxidative sensitivity,cysteine residues in proteins can be oxidized by intracellular reactive oxygen species(ROS),which can lead to protein structural and functional changes.Hence,the development of fluorescent probes to image cysteine and cysteine oxidation is of great significance for the study of redox homeostasis in living system.In this review,the development of fluorescent probes for imaging cysteine and cysteine oxidation was summarized.Moreover,we further analyzed defects of the reported fluorescent probes and made suggestions for the future development of fluorescent probes.We expect that this review can not only provide a deeper understanding of the role of cysteine and cysteine oxidation in oxidative stress,but also broaden the application of fluorescent probes in imaging cysteine and cysteine oxidation.

Design and applications of carbon dots-based ratiometric fluorescent probes:A review

Ratiometric fluorescence(FL)probes can eliminate the background interference and provide more accurate detection results than single emission intensity-based nanoprobes.Recently,carbon dots(CDs)-based ratiometric FL probes have received extensive research attention due to their excellent biocompatibility,water solubility,and multi-emission capabilities.In this review,we firstly summarize the construction strategies of CDs-based ratiometric FL probes,including physical mixing,nanohybrid,and dual-emitting CDs strategies.Additionally,we classify the sensing types of CDs-based ratiometric FL probes into five categories according to the difference in spectral variation caused by analytes:“single-response-ON”,“single-response-OFF”,“doubleresponses-ON”,“double-responses-OFF”,and“double-responses-Reverse”types.Finally,a thorough overview of CDs-based ratiometric FL probe applications in ions,molecules,pH,and temperature sensing is provided.We believe this review can show the latest research progress of CDs-based ratiometric FL sensing fields and provide perspectives on future developments for the construction of CDs-based ratiometric FL probes and their potential applications.

Environmentally sensitive fluorescent probes with improved properties for detecting and imaging PDEδ in live cells and tumor slices

Kirsten rat sarcoma viral oncogene homolog(KRAS)-phosphodiesterase-delta(PDEδ)is a promising target for antitumor drug discovery.Herein,highly efficient and environmentally sensitive fluorescent probes of PDEδ(DS-Probes)were rationally designed.As compared with the reported PDEδprobes,DS-Probes showed higher binding affinity and selectivity,which were able to conveniently and efficiently label PDEδin live cells as well as tumor tissues.Therefore,these fluorescent probes are expected to facilitate PDEδ-based mechanism elucidation,drug discovery and pathologic diagnosis.

Fluorescent probes for glucolipid metabolism of bacterial cell wall

Cell wall is a basic component of bacteria that promotes bacteria to adapt the complicated environment as well as play an essential role in antimicrobial resistance.The structure of bacterial cell wall is remarkably rich,and some complex components,such as peptidoglycan,lipopolysaccharide,and peptidoglycan-arabinogalactan et al.,can only be found in bacteria.Furthermore,the biosynthesis and transfer of these glycolipids are indispensable for bacteria during cell elongation.And the process of biosynthesis and transfer are generally associated with metabolism and sophisticated enzyme mechanisms.However,how the metabolic process takes place,what role enzymes play in this process and how they function have been major concerns for scientists in this field.Numerous significant progresses on fluorescent probes and biological imaging bring opportunity for the studying of metabolism and enzyme mechanisms recently due to its non-invasive and high sensitivity.In this review,we focused on metabolic fluorescent probes for the detection of glycolipids in bacterial cell wall and highlighted the involving mechanisms and biological application.

Real-time in situ observation of P53-mediated cascade activation of apoptotic pathways with nucleic acid multicolor fluorescent probes based on symmetrical gold nanostars

T-2 toxin,one of the most dangerous natural pollutants,induces apoptosis through multiple pathways.Amongst,P53 mediated apoptosis pathway,an important collection of molecules,plays a key role in cell vital activity.Real-time monitoring of upstream and downstream activation relationships of P53 mRNA,Bax mRNA,and cytochrome c(Cyt c)in signaling pathways is of great significance for understanding the apoptotic machinery in human physiology.In this work,a novel nucleic acid multicolor fluorescent probe,based on silica-coated symmetric gold nanostars(S-AuNSs@SiO_(2)),was developed for highly sensitive in situ real-time imaging of P53 mRNA,Bax mRNA,and Cyt c during T-2 toxin-induced apoptosis.The nucleic acid chains modified with carboxyl groups were modified on the surface of S-AuNSs@SiO_(2)by amide reaction.The complementary chains of targeted mRNA and the aptamer of targeted Cyt c were modified with different fluorophores,respectively,and successfully hybridized on S-AuNSs@SiO_(2)surface.When targets were present,the fluorescent chains bound to the targets and detached from the material,resulting in the quenched fluorescence being revived.The probes based on S-AuNSs showed excellent performance is partly ascribed to the presence of 20 symmetric“hot spots”.Notably,the amide-bonded probe exhibited excellent anti-interference capability against biological agents(nucleases and biothiols).During the real-time fluorescence imaging of T-2 toxin-induced apoptosis,the corresponding fluorescence signals of P53 mRNA,Bax mRNA,and Cyt c were observed sequentially.Therefore,S-AuNSs@SiO_(2)probe not only provides a novel tool for real-time monitoring of apoptosis pathways cascade but also has considerable potential in disease diagnosis and pharmaceutical medical.

A ratiometric fluorescent probe for hypoxanthine detection in aquatic products based on the enzyme mimics and fluorescence of cobalt-doped carbon nitride

A ratiometric fluorescent probe for hypoxanthine(Hx)detection was established based on the mimic enzyme and fluorescence characteristics of cobalt-doped graphite-phase carbon nitride(Co doped g-C_(3)N_(4)).In addition to emitting strong fluorescence,the peroxidase activity of Co doped g-C_(3)N_(4)can catalyze the reaction of O-phenylenediamine and H_(2)O_(2)to produce diallyl phthalate which can emit yellow fluorescence at 570 nm.Through the decomposition of Hx by xanthine oxidase,Hx can be indirectly detected by the generating hydrogen peroxide based on the measurement of fluorescent ratio I(F_(570)/F_(370)).The linear range was 1.7-272.2 mg/kg(R^(2)=0.997),and the detection limit was 1.52 mg/kg(3σ/K,n=9).The established method was applied to Hx detection in bass,grass carp,and shrimp,and the data were verified by HPLC.The result shows that the established probe is sensitive,accurate,and reliable,and can be used for Hx detection in aquatic products.

A highly sensitive fluorescent probe RN-NA reveals peroxynitrite as a novel biomarker for primary open angle glaucoma

AIM:To directly quantify peroxynitrite(ONOO-)using a highly sensitive fluorescence resonance energy transfer probe RN-NA,investigate the association between ONOOand primary open angle glaucoma(POAG),and clarify whether RN-NA could be used as a potential tool for POAG diagnosis.METHODS:Plasma and aqueous humor(AH)samples were collected from POAG patients(n=100,age:59.70±6.87y)and age-related cataract(ARC)patients(n=100,age:61.15±4.60y)admitted to our hospital.Next,RN-NA was used to detect ONOO-in plasma and AH samples,and the relationship between ONOO-level and POAG was analyzed using binary logistic regression.Besides,Pearson correlation analysis was applied to characterize the correlation of the levels of ONOO-with the patients’age,intraocular pressure(IOP),and mean deviation of visual field testing.The ONOO-scavenger MnTMPyP was employed to treat the 3-morpholinosyndnomine(SIN-1)-induced ocular hypertension in mice(n=7,6-8wk).Finally,the IOP and ONOO-in both eyes were measured 30min after the last drug treatment.RESULTS:ONOO-levels of AH and plasma were significantly higher in the POAG group than in the ARC group(P<0.01).Additionally,ONOO-levels were closely correlated with POAG in a binary logistic regression analysis[odds ratio(OR)=1.008,95%confidence interval(CI):1.002-1.013,P<0.01 for AH;OR=1.004,95%CI:1.002-1.006,P<0.001 for plasma].Pearson correlation analysis showed that ONOO-levels in AH or plasma were positively associated with visual field defects(R=0.51,P<0.01 for AH;R=0.45,P<0.001 for plasma),and ONOO-levels in plasma and AH were correlated in the POAG group(R=0.69,P<0.001).However,administering MnTMPyP to mouse eyes reversed the elevated IOP caused by SIN-1(P<0.05).CONCLUSION:ONOO-levels in AH and plasma,detected by RN-NA,are significantly related to POAG and positively correlated with visual field defects in POAG patients.Hence,ONOO-is a potential biomarker of POAG,especially advanced POAG.Besides,anti-nitration compounds may be novel ocular hypotensive agents based on the animal study.

Recent advances in formaldehyde-responsive fluorescent probes

Formaldehyde, as one of the simplest reactive carbonyl species（RCS）, is regarded as a potential carcinogen and a sick house syndrome gas. Recent studies have shown that abnormally high levels of formaldehyde may result in cognitive decline and spatial memory deficits, asthmatic symptoms,Alzheimer＇s disease, and cancer. Due to the harmfulness of high levels of formaldehyde in nature and humans, it is of great significance to further elucidate the roles and functions of formaldehyde by a noninvasive detection approach. Fluorescence imaging has become a powerful and popular tool in monitoring bio-species owing to their high sensitivity and selectivity, excellent spatiotemporal resolution and non-invasion nature. Therefore, fluorescent probes are widely applied to track and detect formaldehyde in vitro and in vivo which have attracted more and more interest recently. This review focuses on various strategies to design the fluorescent probes for detecting formaldehyde based on different recognition groups.

Vinyl Groups Containing Tetraphenylethylene Derivatives as Fluorescent Probes Specific for Palladium and the Quenching Mechanism

We previously reported that a series of tetraphenylethylene(TPE)-containing all-hydrocarbon conjugated polymers exhibited a specific fluorescence quenching by palladium ions(Pd^(2+)).To understand the quenching mechanism,herein we investigate the quenching behaviors of three TPE derivatives in the presence of Pd^(2+).Each TPE derivative,consisting of TPE unit and terminal vinyl groups,shows an aggregation-induced emission(AIE)and its fluorescence turns off specifically to Pd^(2+).The sensitivity is enhanced with increasing numbers of vinyl groups in the molecules.By time-resolved fluorescence measurement,a dynamic quenching is observed where the fluorescence lifetime is reduced with Pd^(2+).Specifically,the quenching occurs via the electron transfer in the excited states,as suggested by the disappearance of the stimulated emission band in transient absorption spectra.A theoretical calculation on the excited states identifies intermolecular electron transfer from TPE derivatives to Pd,especially for electron-rich TPE derivative.The mechanism can be general for the design of novel AIE active chemosensors.

Recent advances in small molecule fluorescent probes for simultaneous imaging of two bioactive molecules in live cells and in vivo

The interrelationships and synergistic regulations of bioactive molecules play pivotal roles in physiological and pathological processes involved in the initiation and development of some diseases,such as cancer and neurodegenerative and cardiovascular diseases.Therefore,the simultaneous,accurate and timely detection of two bioactive molecules is crucial to explore their roles and pathological mechanisms in related diseases.Fluorescence imaging associated with small molecular probes has been widely used in the imaging of bioactive molecules in living cells and in vivo due to its excellent performances,including high sensitivity and selectivity,noninvasive properties,real-time and high spatial temporal resolution.Single organic molecule fluorescent probes have been successively developed to simultaneously monitor two biomolecules to uncover their synergistic relationships in living systems.Hence,in this review,we focus on summarizing the design strategies,classifications,and bioimaging applications of dual-response fluorescent probes over the past decade.Furthermore,future research directions in this field are proposed.

Recent progress in Michael addition-based fluorescent probes for sulfur dioxide and its derivatives

Sulfur dioxide（SO_2） is a harmful environmental pollutant. Inhaled SO_2 can be rapidly hydrated into its derivatives, bisulfite（HSO_3^-） and sulfite（SO_3^（2-））. SO_2 derivatives are well known as preservatives and antioxidants, which are used in food and beverages to prevent oxidation and bacterial growth. Although SO_2 can be endogenously generated in mammals and exhibits unique bioactivities in regulating cardiovascular function, excessive SO_2 and its derivatives have toxic effects on humans and animals for triggering adverse reactions and diseases. A large number of fluorescent probes for SO_2 and its derivatives have been designed and reported due to their high sensitivity and selectivity, high temporal and spatial resolution, non-invasive and non-destructive detection as well as real-time visualization in situ. In this review, we have summarized the recent progress of Michael addition-based fluorescent probes for SO_2 and its derivatives. These probes are categorized and concluded according to the different α,β-unsaturated compounds（i.e., Michael acceptors）. The design strategies, sensing performances, detection mechanisms and applications of these probes are discussed in detailed. Finally, a general overview about the design of probes for SO_2 and its derivatives is provided, which will facilitate the development of ideal probes for SO_2 and its derivatives.

Fluorescent probes for the detection of reactive oxygen species in human spermatozoa

Reactive oxygen species(ROS)production is a by-product of mitochondrial activity and is necessary for the acquisition of the capacitated state,a requirement for functional spermatozoa.However,an increase in oxidative stress,due to an abnormal production of ROS,has been shown to be related to loss of sperm function,highlighting the importance of an accurate detection of sperm ROS,given the specific nature of this cell.In this work,we tested a variety of commercially available fluorescent probes to detect ROS and reactive nitrogen species(RNS)in human sperm,to define their specificity.Using both flow cytometry(FC)and fluorescence microscopy(FM),we confirmed that MitoSOX™Red and dihydroethidium(DHE)detect superoxide anion(as determined using antimycin A as a positive control),while DAF-2A detects reactive nitrogen species(namely,nitric oxide).For the first time,we also report that RedoxSensor™Red CC-1,CellROX®Orange Reagent,and MitoPYl seem to be mostly sensitive to hydrogen peroxide,but not superoxide.Furthermore,mean fluorescence intensity(and not percentage of labeled cells)is the main parameter that can be reproducibly monitored using this type of methodology.

Recent development in fluorescent probes based on attacking of double bond and masking of functional group

The works on the procedure of fluorescent sensors for the detection of biological analytes are extremely momentous.Among diverse analytical approaches,fluorescence is the most eye-catching due to its high sensitivity,selectivity,rapidity,robustness,ease of measurement and non-destructive approaches.Herein,we show different fluorescent probes synthesized for estimation and detection of biological analytes(H_(2)S,SO_(3)^(2-)/HSO_(3)^(-),H_(2)O_(2),HOCl,HNO,ONOO^(-)).These probes were constructed by masking the functional groups (hydroxyl and amino) of fluorophore and formation of active C=C,C=N,C=O and N=N for specific analytes.In this review we concentrate on synthesis of the probe,their photophysical properties and applications to biological studies.