Novel styryldehydropyridocolinium derivative as turn-on fluorescent probe for DNA detection

Accepted Manuscript Title: Novel styryldehydropyridocolinium derivative as turn-on fluorescent chemosensor for DNA detection Author: Lifang Chang Chang Liu Song He Yan Lu Siwen Zhang Liancheng Zhao Xianshun Zeng PII: DOI: Reference:

S0925-4005(14)00628-5 http://dx.doi.org/doi:10.1016/j.snb.2014.05.089 SNB 16963

To appear in:

Sensors and Actuators B

Received date: Revised date: Accepted date:

27-2-2014 14-5-2014 19-5-2014

Please cite this article as: http://dx.doi.org/10.1016/j.snb.2014.05.089 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Novel styryldehydropyridocolinium derivative as turn-on fluorescent chemosensor for DNA detection

a

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Lifang Chang,a Chang Liu,a Song He,a Yan Lu,a Siwen Zhang,a Liancheng Zhaoa,b and Xianshun Zeng*a Key Laboratory of Display Materials & Photoelectric Devices, Ministry of Education, School of Materials Science &

Engineering, Tianjin University of Technology, Tianjin 300384, China. Fax: +86-22-60215226; E-mail: [email protected]. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.

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Abstract

Novel styryldehydropyridocolinium derivative L was prepared and found to have low fluorescence

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quantum yield in water; however, upon addition of DNA, the fluorescence intensity increased by a factor of 60-fold. Meanwhile, it also showed rapid cellular uptake properties in cell imaging due to its cationic

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structure favored for cell membrane permeability.

Keywords: Fluorescence spectroscopy; Sensor; Dye; DNA; Cell staining

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1. Introduction

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Due to their functions are still obscured in complicated bio-systems, DNAs are one of the key conundrums that scientists are confronted with them for a long time.1 Therefore, small molecular

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chemosensors with a special signal reporting unit that bind to DNA via intercalative, electrostatic and groove binding interactions have attracted much attention.2 These chemosensors demonstrate a variety of possible applications ranging from pharmaceuticals to tools for molecular biology, as well as probes for electron and/or energy transfer, or even gene modulators.2 From the viewpoint of the structural feature of the chemosensors, most of them are planar polycyclic π-conjugated aromatic heterocycles, which can intercalate between two adjacent base pairs in duplex DNA via an optimized π-π interactions.3 With respect to such chemosensors, positively charged heterocycles are the most favorable families. It is believed that the electrostatic energy between DNA and positively charged chemosensors plays an important role in the stabilization of the interactions. It is not only favorable for binding to nucleic acids, but also beneficial to the intercalation process.4 Thus, a number of positively charged dyes, such as quinolizinium, benzooxazolinium, benzothiazolinium and acridizinium derivatives have been successfully developed as powerful fluorescent chemosensors for DNA detection,5 and quadruplex-specific probes.6 Since the

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understanding of DNA organization and function in vivo need the chemosensors with the nature of high quantum yield, large storks shift and high membrane permeability to obtain high signal to nose ratio,7 the discovery of DNA-selective chemosensors and probes with such nature is important for DNA detection and in vivo imaging.

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Previously, our group had developed a series of polycharged fluorescent polymers for DNA detection via electrostatic interactions between DNA and the positively charged polymers.8 As a continuous project

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for DNA probe development, we reported herein, a small molecular styryl dye, namely 2-p-dimethylaminostyryl-3-methyldehydropyridocolinium chloride L as a DNA-selective chemosensor

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(Scheme 1). Though this type of dyes has been reported over 60 years,9 the optical properties of them are under development.10 It is well known that asymmetric cyanine dyes, such as styrylindolium,11

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styrylquinolinium dyes etc are normally with the nature of large storks shift (normally over 100 nm) which are very important factors to eliminate the background interferences for live-cell imaging.12 At the same

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time, they usually showed a lower quantum yield (normally < 0.01) in aqueous solution due to the mobility around the etheno bridge connecting the electron-donating and electron-accepting moieties of the dyes.

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Therefore, we proposed that styryldehydropyridocolinium derivatives may show a significant optical property changes before and after binding with biomacromolecules. As predicted, L exhibited very weak

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fluorescence in sodium phosphate buffer, and showed excellent turn-on effect upon binding with calf

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thymus DNA (DNA). Meanwhile, it also showed rapid cellular uptake within one hour due to its positively charged structure favored for cell membrane permeability.

2. Experimental 2.1. Materials

All solvents and reagents (analytical grade and spectroscopic grade) were obtained commercially and

used without further purification unless otherwise mentioned. Calf thymus DNA and bovine pancreatic deoxyribonuclease I (DNase І, 2000 units/mg) were purchased from Beijing Dingguo Biotech Co. Ltd. The DNA concentration per nucleotide was determined by absorption spectroscopy by using the molar absorption coefficient (ε = 6600 M-1 cm-1) at 260 nm. Sodium phosphate buffer solution (pH = 7.4) was used for all experiments.

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2.2. Apparatus NMR spectra were recorded on a Bruker spectrometer at 400 (1H NMR) MHz and 100 (13C NMR) MHz. Chemical shifts (δ values) were reported in ppm down field from internal Me4Si (1H and 13C NMR).

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High-resolution mass spectra (HRMS) were acquired on an Agilent 6510 Q-TOF LC/MS instrument (Agilent Technologies, Palo Alto, CA) equipped with an electrospray ionization (ESI) source. Elemental analyses were performed on a Vanio-EL elemental analyzer (Analysensystem GmbH, Germany). UV

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absorption spectra were recorded on a UV-2550 UV-VIS spectrophotometer (Shimadzu, Japan).

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Fluorescence measurements were performed using an F-4600 fluorescence spectrophotometer (Hitachi, Japan) equipped with a plotter unit and a quartz cell (1 cm × 1 cm). The excitation and emission slit widths

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were 5 nm and 5 nm, respectively. The excitation wavelength was set in 500 nm. Melting points were recorded on a RY-2 Melting Point Analyzer (Analytical Instrument Factory, Tianjin) and are uncorrected.

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Cell image was performed on a Confocal Laser Scanning Microscope FV-1000 (Olympus, Japan).

2.3. Preparation and characterization of the chemosensor L N

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i)

N Cl-

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N Cl-

L

1

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Scheme 1. Synthesis of chemosensor L. i) p-N,N-dimethylaminobenzaldehyde, ethanol and piperidine refluxed for 72 h under nitrogen atmosphere.

Synthesis of 2,3-dimethyldehydroquinolizinium Chloride 1. To a 100 mL flask, dibutylamine

(1.290 g) was added to a solution of N-(ethoxycarbonylmethyl)-2-methyl-pyridinium chloride (2.157 g, 0.01 mol) and diacetyl (0.900 g, 0.01 mol) in ethanol (95%, 20 mL). The reaction mixture was refluxed for 1 h. Then, the solvent was removed to dryness. The residue was washed with ether and acetone. The solid product was recrystallized from ethanol/ether. The product was obtained as pale yellow powder in 48% yield (0.926 g), mp: 280-282 oC. HRMS: m/z [M-Cl]+ = 158.0964; Calcd: 158.0964; 1H NMR (DMSO-d6, 400 MHz, ppm): 9.35 (s, 1H), 9.23 (d, J = 8.8 Hz, 1H), 8.45 (s, 1H), 8.41 (d, J = 8.8 Hz, 1H), 8.27 (t, J = 7.8 Hz, 1H), 8.0 (t, J = 7.8 Hz, 1H), 2.59 (s, 3H), 2.48 (s, 3H); 13C NMR (DMSO, 400 MHz, ppm): 149.9, 140.8, 135.7, 135.2, 134.7, 134.0, 125.8, 125.1, 122.7, 19.5, 16.5. Synthesis of 2-p-dimethylaminostyryl-3-methyldehydropyridocolinium chloride L. To a 50 mL reactor,

was

charged

2,3-dimethyldehydroquinolizinium

chloride

1

(0.099

g,

0.5

mmol),

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p-N,N-dimethylaminobenzaldehyde (0.095 g, 0.6 mmol), ethanol (5 mL), piperidine (20 µL). The reaction mixture was refluxed for 72 h under nitrogen atmosphere. The reaction mixture was condensed to dryness. The residue was recrystallized from methanol. L was obtained as deep red powder in 26% yield (0.042 g); mp: 268-270 oC. HRMS: m/z [M-Cl]+ = 289.1703; Calcd: 289.1699; 1H NMR (400 MHz, DMSO-d6, ppm):

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9.19 (s, 1H), 9.03 (d, J = 6.8 Hz, 1H), 8.80 (s, 1H), 8.28 (d, J = 8.8 Hz, 1H), 8.13 (t, J = 7.8 Hz, 1H), 7.82 (t, J = 8.8 Hz, 1H), 7.78 (d, J = 16.0 Hz, 1H), 7.64 (d, J = 8.4 Hz, 2H), 7.19 (d, J = 16.0 Hz, 1H), 6.77 (d, J

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= 8.4 Hz, 2H), 3.01 (s, 6H), 2.60 (s, 3H); 13C NMR (100 MHz, DMSO-d6, ppm): 152.4, 147.6, 141.9, 140.9, 135.8, 135.78, 135.6, 132.7, 130.7, 126.9, 124.1, 122.6, 119.2, 115.7, 112.8, 17.8; Anal. Calcd. for

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C20H21ClN2·H2O: C 70.06; H 6.76; N 8.17; Found: C 69.93%, H 7.05%, N 7.97%.

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2.4. Sample preparation

All spectroscopic experiments were carried out in buffer solution at 25 ◦C. The stock solution of the

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chemosensor L (2.0 × 10-3 M) was diluted to 10.0 µM or 20 µM in buffer solution.

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2.5. The fluorescence quantum yield (FLQY)

Abs B × F1 × λexB × η1 Φ1 = Φ B × 2 Abs1 × FB × λex1 × η B 2

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The FLQY of the sample (Φ1) was calculated according to the following equation:

Where Φ1, ΦB are the quantum yields of the sample and the standard; AbsB, Abs1 stand for the absorbance at the exciting wavelength; F1, FB are the integration area; λexB, λex1 are the exciting wavelength; η1, ηB are the refractive indexes.

When the wavelength at which both absorption curves of the standard and a sample intersect is chosen as the excitation wavelength of the standard and the sample. Here, rhodamine B was used as the standard, and 500 nm as the excitation wavelength, so the equation is

Φ1 = Φ B ×

F1 × η1

2

FB × η B

2

3. Results and discussion 3.1 synthesis of L

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The

synthesis

of

chemosensor

L,

N-(ethoxycarbonylmethyl)-2-methylpyridinium

chloride.

Scheme The

1,

began

with

intermediate

material

2,3-dimethyldehydroquinolizinium chloride 1 was obtained in 48% yield by the condensation of N-(ethoxycarbonylmethyl)-2-methylpyridinium chloride with 2,3-butanedione through a modified

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Westphal reaction.13 Then, L was facilely obtained as a deep red powder by the condensation of 1 with

spectroscopy, mass-spectrometric data, and elemental analyses.

C NMR

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3.2 Spectroscopic properties of L and its optical responses to DNA

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4-N,N-dimethylaminobenzaldehyde in 26% yield. The structure of L was confirmed by 1H and

The optical properties of L were firstly elucidated by electronic absorption spectroscopy in the

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absence and presence of several of anions in sodium phosphate buffer (2 mM, pH = 7.4). L exhibited a maximum absorption band at 433 nm (ε = 3.06 × 104 M-1 cm-1) that matched with those of classical π-π*

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transitions of styrylindolium dyes.11 (Fig. S1). Upon the addition of 30.0 equivalents of ATP, Br-, Cl-, F-, H2PO4-, HCO3-, HSO4-, I-, P2O74-, and DNA (10 equivalents) into the yellow solutions of L, only DNA

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immediately induced a pink color change and a new red-shifted absorption band (effects evidencing binding to DNA) with the absorption maximum at 463 nm. However, no obvious colour changes arose

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from the addition of other anions, only with the absorbance increase or diminish to some extent at 433 nm.

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Thus, the prominent features of DNA-induced characteristic colour changes indicated that L can serve as selective visible color and fluorescence chemosensor for DNA detection (Fig. 1).

Fig. 1. Photograph of L (10 µM) in the presence of various anions (30.0 equiv.) and DNA (10 equiv.) in sodium phosphate buffer. Color a) and fluorescence (λex = 365 nm) b) changes in the presence of various anions and DNA. From left to right: ATP, Br-, Cl-, F-, H2PO4-, DNA, HCO3-, HSO4-, I-, P2O74-, and L.

To elucidate the binding modes between L and DNA, a continuous titration experiment of L with DNA was carried out. Upon addition of DNA (0-0.5 equiv.) (Fig. 2a), the absorption at 433 nm decreased gradually. Then, the absorption curve increased steadily and saturated at about the addition of 2 equivalent 5

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of DNA. Meanwhile, a bathochromic shift of 30 nm was observed at this stage. The result suggested that two modes of binding occurred with the increasing amount of DNA concentrations. At low DNA-to-L ratios, both intercalation and groove binding occurred at the same time.14 The groove binding mode was gradually converted to intercalation mode with the increasing amount of DNA and it converted completely

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to the intercalation mode at high DNA-to-L ratios (> 2). To further elucidate the binding modes between L and DNA, the melting experiments also were carried out to confirm the DNA binding abilities of L to DNA.

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In the presence and absence of L, the helix melting temperatures were recorded by monitoring the absorbance of DNA bases at 260 nm as a function of temperature. The results showed that the melting

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temperature of DNA (56.5 oC) increased by 14.4 oC at 1:7.6 ratio of [L]/[DNA] (Fig. 2b), suggested that the

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binding mode of L with DNA is intercalation at lower [L]/[DNA] ratios.4

Fig. 2. a) UV-vis titration spectra of L (20 μM) with increasing amounts of DNA (0-49.2 equiv) in 2 mM sodium phosphate

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buffer (pH = 7.4). b) Thermal denaturation curves of DNA (25 μM) in 2 mM sodium phosphate buffer, pH =7.4, in the absence (●) and presence of L (■) at a CL/CDNA = 1/7.6.

To obtain a fully understanding of the optical properties of L and those in the presence of an

incremental amount of DNA concentrations, the fluorometric titration of L by DNA was carried out in sodium phosphate buffer solution. As shown in Fig. 3a, the free chemosensor L showed a very low fluorescence at 635 nm (ΦFL = 0.0145), which supports the hypotheses that the low fluorescence intensity of L is the result of conformational changes in the excited state. The intrinsic low ΦFL of the free chemosensor L is of pivotal importance for fluorescent detection. The fluorometric titration reaction curves displayed a steady and smooth increase at 629 nm with the addition of DNA (inset in Fig. 3a). A significant fluorescence enhancement with a turn-on ratio about 60-fold was triggered upon addition of 50 equivalents of DNA. The fluorescent quantum yield (ΦF) of L was increased to 0.869 in the presence of 50 equivalents of DNA, indicated that the mobility around the etheno bridge of the dye 6

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was strongly restricted. A Job’s plot yielded from fluorescent emission titrations showed a DNA-to-L in 2:1 ratios (Fig. S2).15 The bonding association constant was calculated as 4.27 × 107 M-2 (R = 0.9996) by using nonlinear least-square analysis in a 1:2 L-to-DNA ratio (Fig. S3), which was comparable with those of EB and its derivatives (with binding constants among 104 - 105 M range).4b As can be see from

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Inset in Fig. 3, the changes of DNA-dependent fluorescence intensity at 629 nm followed by a sigmoid curve. The linear range of L for DNA detection can be separated in two parts, namely, 0 - 2 × 10-6 M (R =

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0.998) and 1.5 × 10-5 - 1.85 × 10-4 M (R = 0.997) (Fig. S4b and S4c). The detection limit was estimated to be 7.56 × 10-7 M (detection limit = 3σbi/m) (Fig. S4b).16 By comparison, the detection limit was also

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measured under the same conditions for the detection of DNA with EB (Fig. S4a). The linear range of EB for DNA detection was 0 - 2 × 10-5 M (R = 0.991) and with the detection limit of 3.08 × 10-7 M.

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Thus, the detection limits of L and EB for DNA detections showed the same order of magnitude under

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the same conditions.

Fig. 3. a) Fluorimetric titration of DNA (0-54 equiv.) to L (5 μM) in 2 mM sodium phosphate buffer (pH = 7.4); Inset: the fluorescence intensity at 629 nm of L as a function of the DNA concentration. Excitation wavelength λex = 500 nm, slit 5.0. b) Plot of fluorescence intensity (629 nm) against 1/T of L (10 μM) in the presence of 10 equiv of DNA upon addition of 1 equiv DNase І.

Probe L was then utilized successfully as fluorescent sensor for monitoring the activity of bovine

pancreatic deoxyribonuclease I (DNase І). The addition of DNase І in mixture of L and DNA solutions resulted in rapid diminution of the fluorescence intensity at 629 nm, which indicated the regeneration of the free chemosensor L (Fig. 3b). Meanwhile, the pink solution turned out to be slight green again. Within 2 h, the hydrolysis of DNA catalyzed by DNase I was completed. These results indicated that L can be used to monitor the deoxyribonuclease activity and hydrolysis process.

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To explore further the utility of L as a DNA-selective chemosensor, we evaluated the response of the chemosensor L to other anions, such as Br-, Cl-, F-, HCO3-, HSO4-, I-, ATP, ADP, AMP, UMP, RNA. Among the anions examined, L only showed a selective fluorescence increase (ca. 24-fold) positioned at 629 nm upon addition 10 equivalents of DNA (Fig. 4). However, the addition of other anions (30 equiv.) has no

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enhancement. Thus, L can function as a DNA-selective fluorescent chemosensor.

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obvious effect on the fluorescence emission, except that RNA (30 equiv.) had 4.6-fold fluorescence

Fig. 4. Fluorescence spectra of L (10 μM) in the presence of several anions (10 equiv for ct-DNA and 30 equiv for other

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anions). Inset: histogram representing the fluorescence enhancement and quenching of L in the present of various anions. 1:

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L ; 2: L + ATP; 3: L + Br-; 4: L + Cl-; 5: L + DNA; 6: L + F-; 7: L + HCO3-; 8: L + HSO4-; 9: L + I-; 10: L + ADP; 11: L + AMP; 12: L + UMP; 13: L + RNA in PBS buffer. λex = 500 nm, slit 5.0, 5.0.

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It is well known that ethidium bromide (EB) has been developed as powerful fluorescent probes that light up upon intercalative binding to duplex DNA. It is interesting to compare the properties of L with that of EB under the same conditions. Upon addition of 10 equivalents of DNA to the sodium phosphate buffer solutions of EB, an increase of the florescent emission positioned at 602 nm with an enhancement factor of 8.6-fold was observed. However, the florescent enhancement at 629 nm was found to be 28.5-fold for L under the same conditions (Fig. S5). The results suggested that the turn-on property of L is much more efficient than that of the widely used EB. Meanwhile, upon addition 1 equivalent of EB to an equilibrated L + DNA solution or addition of L to an equilibrated EB + DNA solution, they yielded almost the same results, namely they showed a new emission peak at 615 nm (Fig. S5). The results indicated that both the chemosensor L and EB can intercalative binding to duplex DNA.4c

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Fig. 5. Electrophoresis image of the interactions between L and DNA (500 ng) at increasing concentration. The DNA/L ratio

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is 500, 1000, 5000, 10000, 20000 for lane 1 to lane 5, respectively. Lane 6 is the reference GoldenviewTM with DNA.

3.3 Electrophoresis assay

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Next, electrophoresis assay was performed to investigate the intercalation properties between the chemosensor L and DNA. As shown in Fig. 5, the mobility of DNA was not affected by the intercalation of

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the chemosensor L, which showed the same mobility as that stained by GoldenviewTM. However, higher concentrations of the dye led to a fluorescence self-quenching effect. The results indicated that the

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chemosensor L can intercalate to DNA base pairs, and can potentially be used as an indicator for DNA

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staining in electrophoresis analysis.

Fig. 6. PC12 cells treated with 0.5 µM L. Top panels: a) PC12 cells stained with 0.5 µM solution of L PBS buffer for 40 min at 37 °C shown in Fall channel; b) Brightfield transmission image; c) The overlay image of a and b. Bottom panels: d) PC12 cells stained with 0.5 µM solution of L PBS buffer for 60 min at 37 °C shown in Fall channel; e) Brightfield transmission image; h) The overlay image of d and e.

3.4. Live-cell staining properties Since the positively charged structure of L is favorable for cell membrane permeability, we then investigated the cellular uptake properties of L in a PC-12 cell line by using confocal fluorescent microscopy. Fig. 6 demonstrated that L has high cell permeability. For example, live cells incubated with L

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generate high levels of intracellular fluorescence, indicating that L has high cell permeability. Meanwhile, L exhibited rapid cellular uptake within 1 h. As depicted in Fig. 6c and f, the overlay of fluorescence and bright-field images revealed that the brightness of fluorescence signals within the nucleus is obviously higher than the perinuclear area of the cytosol after one hour incubation. These results demonstrated that L

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might be used for imaging of nucleic acids within cells.

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4. Conclusions

In conclusion, the preparation of a novel styryldehydropyridocolinium derivative L was described.

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The photophysical and biological properties of L were investigated. The intrinsically weak fluorescence of the free chemosensor exhibits promising properties for DNA detection. Due to torsional restriction of the

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excited state when confined by a tightly intercalative binding, it showed a significantly selective fluorescent turn-on effect with DNA among the various anions examined. Meanwhile, it showed fluorescent quenching

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changes with DNase I. Furthermore, it also showed rapid cellular uptake properties for its cationic structure favored for cell membrane permeability. With smart structural design, we anticipate that this type of dyes

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Acknowledgments

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has ideal properties to be used as DNA-selective “light-up probes”.

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We gratefully acknowledge the Natural Science Foundation of China (NNSFC 21272172, 20972111), the Program for New Century Excellent Talents in University (NCET-09-0894 and NCET-12-1066) and the Natural Science Foundation of Tianjin (12JCZDJC21000).

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at

doi:10.1016/j.snb.aaa.aa.aaa

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aggregation-induced emission of conjugated poly(pyridinium salt)s, Polym. Chem. 4 (2013) 4045. (b) F. Han, Y. Lu, Q. Zhang, J. Sun, X. Zeng, C. Li, Homogeneous and sensitive DNA detection based on polyelectrolyte

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complexes of cationic conjugated poly(pyridinium salt)s and DNA, J. Mater. Chem. 22 (2012) 4106. A. Richards, T.S. Stevens, Sythesis and properties of dehydropyridocolinium salts, J. Chem. Soc. 25 (1958) 3067.

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10 E. Maçôas, G. Marcelo, S. Pinto, T. Cañeque, A.M. Cuadro, J.J. Vaquerob, J.M.G. Martinho, A V-shaped cationic dye for nonlinear optical bioimaging, Chem. Commun. 47 (2011) 7374.

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11 (a) J. Chang, Y. Lu, S. He, C. Liu, L. Zhao, X. Zeng, Efficient fluorescent chemosensors for HSO4- based on a strategy of anion-induced rotation-displaced H-aggregates, Chem. Commun. 49 (2013) 6259. (b) C. Liu, Y. Lu, S. He, Q. Wang, L. Zhao, X. Zeng, The nature of the styrylindolium dye: transformations among its monomer, aggregates and water adducts, J. Mater. Chem. C, 1 (2013) 4770. (c) Q. Liu, C. Liu, S. He, Y. Lu, L. Zhao, X. Zeng, Tunable PET processes by intercalation of cationic styryl dye in DNA and its application as efficient turn-on fluorescent probe for silver ions, RSC Advance, 4(2014) 14361. 12 (a) H. Özhalici-Ünal, C.L. Pow, S.A. Marks, L.D. Jesper, G.L. Silva, N.I. Shank, E.W. Jones, J.M. Burnette III, P.B. Berget, B.A. Armitage, A rainbow of fluoromodules: a promiscuous scFv protein binds to and activates a diverse set of fluorogenic cyanine dyes, J. Am. Chem. Soc. 130 (2008) 12620. (b) A.S. Brown, L.M. Bernal, T.L. Micotto, E.L. Smith, J.N. Wilson, Fluorescent neuroactive probes based on stilbazolium dyes, Org. Biomol. Chem. 9 (2011) 2142. (c) P.R. Bohländer, H.A. Wagenknecht, S. Affiliations, Synthesis and evaluation of cyanine–styryl dyes with enhanced photostability for fluorescent DNA staining, Org. Biomol. Chem., 11 (2013) 7458.

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living cells, Org. Biomol. Chem. 8 (2010) 3751.

16 M. Shortreed, R. Kopelman, M. Kuhn, B. Hoyland, Fluorescent fiber-optic calcium for physiological measurement, Anal.

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Chem. 48 (1996) 1414.

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Biographies Lifang Chang is a postgraduate student of School of Materials Science & Engineering at Tianjin University of Technology. Chang Liu received her Master’s degree (2013) from Tianjin University of Technology. At present she is a PHD student in School of Materials Science & Engineering at Harbin Institute of Technology.

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Song He graduated from College of Chemistry at Jilin University. She received her Master’s degree (2001) from Nankai University and PhD (2007) from Hongkong University. At present she is a lecturer in School of Materials Science & Engineering at Tianjin University of Technology.

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Yan Lu graduated from College of Chemistry at Xuzhou Normal University (1998). She received her PhD from Nankai University in June 2004. At present she is a professor in School of Materials Science & Engineering at Tianjin University of mechanism investigation in biological, medical, and chemical systems.

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Technology. Her current research interests are focused on the polymer-based recognition, assembling, and the related

Siwen Zhang graduated from College of Physics at Nankai University (2005). She received her Master’s degree (2008) and PhD (2011) from Nankai University. At present she is a lecturer in School of Materials Science & Engineering at Tianjin

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University of Technology.

Liancheng Zhao is a professor in School of Materials Science & Engineering at Harbin Institute of Technology. In 2003, he became an academician of Chinese Academy of Engineering. His current research interests include the development of

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fluorescent sensors and biosensors etc.

Xianshun Zeng received his Master’s degree (1995) and PhD (2001) from Nankai University. He is currently a professor in School of Materials Science & Engineering at Tianjin University of Technology. His research interests are focused on the

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molecular recognition and the related mechanism investigation in biological, medical, and chemical systems.

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Novel styryldehydropyridocolinium derivative as turn-on fluorescent chemosensor for DNA detection

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Lifang Chang, Chang Liu, Song He, Yan Lu, Siwen Zhang, Liancheng Zhao and Xianshun Zeng

A novel cationic styryl dye with innate nature of low quantum yield and large stokes shift in water was prepared.

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It showed a large fluorescence enhancement upon binding to DNA and rapid cellular uptake properties in cell

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imaging.

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