Aggregation-Induced Emission Active Metal-Free Chemosensing

Subscriber access provided by UNIV NEW ORLEANS

Article

AIE Active Metal-Free Chemosensing Platform for Highly Selective Turn-ON Sensing and Bioimaging of Pyrophosphate Anion Abhijit Gogoi, Sandipan Mukherjee, Aiyagari Ramesh, and Gopal Das Anal. Chem., Just Accepted Manuscript • Publication Date (Web): 10 Jun 2015 Downloaded from http://pubs.acs.org on June 10, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

AIE Active Metal-Free Chemosensing Platform for Highly Selective Turn-ON Sensing and Bioimaging of Pyrophosphate Anion Abhijit Gogoi,a Sandipan Mukherjee,b Aiyagari Ramesh*b and Gopal Das*a a

Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India. Fax: + 91 361 2582349; Tel: +91 3612582313; E-mail: [email protected]. b Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India. Fax: + 91 361 2582249; Tel: +91 3612582205; E-mail: [email protected]. ABSTRACT: We report the synthesis of a metal-free chemosensor for highly selective sensing of PPi anion in physiological medium. The novel phenylbenzimidazole functionalized imine containing chemosensor (L) could sense PPi anion through ‘turn-on’ colorimetric and fluorimetric responses in a very competitive environment. The overall sensing mechanism is based on the aggregation-induced emission (AIE) phenomenon. Moreover, a real time in-field device application was demonstrated by sensing PPi in paper strips coated with L. Interestingly, detection of intracellular PPi ions in model human cells could also be possible by fluorescence microscopic studies without any toxicity to these cells.

■ INTRODUCTION Anions are ubiquitous in nature and play critical roles in many biological and environmental processes, so the selective detection of a certain anion is of vital importance1-3 In this context, sensing of pyrophosphate (PPi) anion is of particular interest due to its germane role in many cellular and metabolic processes.4-6 PPi is known to form by ATP hydrolysis under cellular conditions, and it plays a central role in important biochemical pathways such as DNA polymerization and synthesis of cyclic adenosine monophosphate (c-AMP) catalyzed by DNA polymerase and adenylate cyclase, respectively.7-9 Furthermore, recent studies have highlighted the emerging role of PPi as an important biomarker for several ailments.10-13 Consequently, specific recognition and sensing of the PPi anion in physiological conditions is highly desirable. However, owing to its high solvation energy (∆Gº = - 465 KJ mol-1) in water 14-15 and low solubility of most of the organic probes designed for PPi sensing, bulk of the studies are confined to organic or mixed aqueous medium.16-17 To circumvent this problem, in the recent years, certain metal complexes, mostly of Zn(II), Cd(II) or Cu(II), have been used for PPi sensing.18-23 Such studies are based on the strong interaction of PPi with the metal–chemosensor ensemble, which in turn alters the coordination environment of the metal ion and triggers a measurable response. This kind of indirect anion sensing system is likely to compromise with the sensitivity of detection. However, this bottleneck can perhaps be overcome by developing a metal-free sensor, which enables direct sensing of anion. Amongst the various approaches for PPi detection,24-27 fluorescence-based sensing has emerged as a rational option, as it is rapid, highly sensitive, easy to handle and amicable to in vitro and in vivo applications such as cell imaging.28 In order to harness the potential of a PPi sensor in the biological mi-

lieu, it is critical that the developed sensor functions in an aqueous medium. Further, owing to the complexity of biological samples and the possibility of signal interference from non-specific molecules, the target analyte is often detected using high concentrations of the sensor. However, in this backdrop, sensing may be impeded as it has been shown previously that increasing the concentration of the sensor may lead to an aggregation-caused quenching (ACQ) phenomenon.29-30 The development of certain organic dye molecules that exhibit aggregation-induced emission (AIE) has emerged as a viable option to prevail over this limitation.31-32 Thus, considerable efforts have been made in the development of such AIE-active fluorescent probes in the last decade. But, most of the AIE probes are highly conjugated molecules33-35 whose synthesis encompasses multiple steps. Thus, there is a need to develop facile routes for synthesizing simpler probes as evident from the literature.36-39 Some polymer based chemosensors also elicit high selectivity for PPi.40-43 Based on the aforementioned rational and the need to sense PPi in physiological conditions and the cellular environment, in the present study, a dipodal benzimidazolefunctionalized sensor was developed, which was AIE-active and could directly sense PPi without any metal-mediator through an enhanced ‘turn-on’ fluorescence emission. The developed sensor was highly selective towards PPi with nanomolar level of detection limit in physiological medium. Interestingly, the sensor could readily detect inherent PPi levels in HeLa cells as evidenced in cellular imaging studies.

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 8

Scheme 1. Synthetic scheme of the chemosensor L.

bated with 2.5 µM L and again washed to remove excess probe and the image of the cells was acquired as described previously. Subsequently, a 50 µM solution of calcium chloride was added to the same cells containing L and incubated for 1 h to facilitate intracellular formation of L-PPi complex. The cells were then washed thrice with sterile PBS and then the image of the cells was acquired using a fluorescence microscope as described earlier.

■ EXPERIMENTAL SECTION

■ RESULT AND DISCUSSION

Synthesis of L. [2,6-bis-((4-(1H-benzo[d]imidazol2-yl)phenyl)imino) methyl)-4 methyl phenol] Condensation of 2,6-Diformyl-4-methylphenol with 4-(1Hbenzo[d]imidazol-2-yl)aniline for 4 hours gives reddish type precipitate, which after column chromatography gives L ( Scheme 1). The chemical structure was fully characterized with 1H NMR, 13C NMR and mass analysis. 1 H NMR of L (400 MHz, DMSO-d6): 10.216 (s, 2H), 8.008(d, 4H), 7.851-7.818 (s, 2H), 7.764-7.710(m, 2H), 7.472(d, 2H), 6.769(s, 4H), 2.332 (s, 3H). 13C NMR: 192.25, 154.09, 149.81, 137.30, 131.47, 129.85, 128.81, 125.15, 1253.34, 122.55, 113.63, 113.11, 107.93, 19.55. ESI-MS (positive mode, m/z) Calculated [L + H+] = 459.1062, found mass: 459.1042. General Procedure for UV−Vis and Fluorescence Measurement. Stock solutions of various anions (1 × 10−3 mol L−1) were prepared with ultrapure water. A stock solution of L (5 × 10−3 mol L−1) was prepared in DMF. For the selectivity study, L’s solutions were then diluted to 10 × 10−6 mol L−1 in the required experimental medium. The fluorescence quantum yield in solution and in powder was measured using quinine sulfate as reference and with an integration sphere, respectively. In titration experiments, a quartz optical cell of 1 cm path length was filled with a 2.0 mL solution of L to which the ion stock solutions were gradually added using a micropipette. For fluorescence measurements, excitation wavelength was at 430 nm, and emission was acquired from 450 nm to 700 nm. Aggregation Studies. Studies on aggregation of the ligand and ligand-PPi complex were pursued through dynamic light scattering (DLS), atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). The detailed experimental procedures are described in the supporting information. Cell Imaging Studies. HeLa cells (human cervical carcinoma cells) were initially cultured in a 25 cm2 tissue culture flask containing DMEM medium supplemented with 10% FBS, penicillin (100 µ g mL−1) and streptomycin (100 µ g mL−1) in a CO2 incubator. Prior to cell imaging studies, HeLa cells were seeded into a 6 well plate and grown in DMEM medium at 37°C till 80% confluency in a CO2 incubator. Subsequently, the cells were washed thrice with sterile phosphate buffered saline (PBS), incubated with 2.5 µM L in DMEM at 37° C for 1 h in a CO2 incubator and followed by image acquisition using a fluorescence microscope (Eclipse Ti-U, Nikon, USA) with blue filter that allowed green light emission. The cells were further incu-

Design principle The design principle of the PPi sensor working on aggregation induced emission principle should encompass the following cardinal features: (1) The probe should be an aromatic system with extended conjugation with the possibility of ππ stacking and (2) it should possess sufficient convergent Hbond donor sites for efficient anion coordination. Based on the above rational, we have synthesized a benzimidazolefunctionalized imine-based chemosensor (L) bearing phenolic OH and benzimidazole NH as H-bond donors. The imine functionality and the benzimidazole functionality are intended to increase the π electron density and also the extent of π delocalization in the system. AIE phenomenon The photophysical properties of the chemosensor were elucidated by UV/Vis absorption and fluorescence emission study in various solvents. For this, a stock solution of L was prepared in DMSO (5.0 mM) and diluted accordingly with the experimental solutions. As depicted in Figure 1, the chemosensor L (10 µM) was practically non-emissive in THF, but weakly fluorescent in some other polar solvents such as methanol, acetonitrile and others. (Supporting Information, Figure S1). However, the aqueous solution of the chemosensor, which is a poor solvent for L, was strongly emissive at ∼530 nm with a Stokes shift of 125 nm.44 (λex = 430 nm, slit = 2nm / 2nm), which suggested the possibility of aggregation induced emission (AIE) phenomenon. To elucidate the AIE process, L’s emission intensity was recorded with increasing water fraction in THF. As evident in Figure 1A, the solution was very weakly emissive upto fw = 90 %. However, further increase in the water content lead to a remarkable increase in emission intensity. At 99 vol% fw, the emission intensity of solution was nearly 9.0 times than that at fw = 0% (Figure 1B). Furthermore, a light green fluorescence of the solution was apparent under a 365 nm UV lamp (Figure 1B, inset). The AIE activity of L was also observed in acetonitrile solution with progressive addition of water, wherein the fluorescence intensity increased linearly with increasing fraction of water (Supporting Information, Figure S2).

2


Page 3 of 8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. AFM images of L in A) water. FESEM images of L in B) DMSO and C) water. The concentration of L used in each case is 10 µM. Figure 1. A) Fluorescence intensity changes of the chemosensor (L, 10 µM) with increasing water fraction in THF. B) A plot of intensity (I530 nm) versus fraction of water (fw) content in THFwater mixture. Inset of panel B: Fluorescent images of L with fw = 0 and fw = 99 and the corresponding color changes on TLC plates observed under the 365 nm UV lamp (λex = 430 nm, slit 2/2 nm).

A close inspection of the receptor design revealed that it was very flexible and can adopt various conformations through several possible combinations for C-C or even C=N imine bond rotations/isomerization.44 These rotations or conformational changes leads to the non-radiative deactivation of the excited state, which perhaps accounts for the weak fluorescence of the probe in THF. However, as the chemosensor is insoluble in water, addition of higher water fraction triggers aggregation of L, wherein the intermolecular and intramolecular hydrogen bonding between various H-donors and Hacceptors in the chemosensor would be the driving force. These interactions lock the conformation and thus, the restriction of intramolecular rotation (RIR) around single bond finally leads to fluorescence enhancement. Given that aggregation of L is the plausible reason for fluorescence enhancement, it was anticipated that L would be strongly fluorescent in viscous solvents, which are known to hinder intramolecular rotation. Prominent fluorescence emission spectra of L recorded in glycerol (Supporting Information, Figure S1A) supported this premise. Subsequently, solution of L was spotted on filter a paper and on one of the spot, THF was added and on the other water was added. Following drying, the spot in THF displayed bluish-violet fluorescence, whereas the aqueous spot exhibited yellowish like fluorescence under the 365 nm UV lamp (Figure 1B, inset). This also validated the aggregation caused fluorescence emission behavior of L. However, naked eye observation indicated that the aqueous L solution was transparent and macroscopically homogeneous with no visible precipitation, which perhaps suggests the formation of sub-micron aggregates in solution. Formation of smaller aggregates was also supported by the changes in absorption spectra of L in water. The probe L exhibited an absorption maximum at 325 nm and a hump at 375 nm in THF whereas, in water the absorption maxima was slightly blue shifted to 321 nm along with a broad hump like peak around 439 nm (Supporting Information, Figure S1B). The weak absorption peaks at 321 nm or 325 nm can be attributed to the ππ* transition of benzimidazole-benzene.36 Upon close inspection a trailing trace beyond 500 nm was observed, which suggested light scattering or Mie effect originating from the smaller aggregates present in the solution (Supporting Information, Figure S1B).

In order to ascertain the formation of nano-aggregates of L in aqueous medium, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) analysis were pursued. AFM analysis of a 10 µM aqueous solution of L revealed the formation of aggregates of average particle size ranging from 40-50 nm (Figure 2A). This was corroborated by FESEM, wherein the fibril-like shape of L in DMSO (Figure 2B) was observed to transform into block-shaped aggregates of particle size 50-60 nm in case of a 10 µM aqueous solution of L (Figure 2C). Collectively, these results strongly suggest aggregation of the probe molecules in water.

Anion sensing behavior It has been reported that the AIE nature of a chromophore can be tuned by guest molecules.45-48 In the present study, the chemosensor L has potential anion binding sites (NH and OH). Hence, it was pertinent to scrutinize its anion sensing aptitude in water. To this end, changes in the UV-visible spectra of a 10 µM aqueous solution of L was recorded upon addition of 10 equivalents of sodium or tetrabutyl salts of various anions such as F-, Cl-, Br-, I-, NO3-, OAc- (CH3CO2-), HSO4-, SO42-, ClO4- and PPi. Interestingly, a distinct change in the UV-visible spectra was observed only after addition of pyrophosphate anion (PPi), which lead to the emergence of new absorption peaks at 270 nm and 439 nm (Supporting Information, Figure S3). These spectral changes were accompanied by a distinct visual change in the color of the solution of the probe L from colorless to faint yellowish in case of the interaction of L with PPi (Supporting Information, Figure S3, inset). This visual color change was encouraging as it rendered facile naked eye detection of PPi in water. Further inspection of the UV-Vis spectra after the addition of PPi anion revealed the formation of isosbestic points at 266 nm, 321 nm and 391 nm, which indicate the formation of a new species. It may also be mentioned that addition of PPi induced further aggregation, which was evident from the trailing UV-visible trace of the probe solution in presence of PPi (Supporting Information, Figure S3B, inset). Our next endeavour was to determine the selectivity and sensitivity of L towards PPi for which fluorescence-based experiments were pursued.

3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3. A) Fluorescence emission spectra of L (10 µM) with incremental concentration of PPi. (λex = 430 nm, slit = 2 nm/2 nm). B) AFM and C) FESEM images of L after PPi addition.

Upon addition of increasing concentrations of PPi, the fluorescence intensity of L increased systematically to attain a magnitude, which was nearly 17 times more than the probe alone at 530 nm (Figure 3A). The L-PPi solution also exhibited intense yellowish-green like fluorescence when observed under the 365 nm UV lamp (Inset, Figure 3A). The steep enhancement in the fluorescence emission intensity of the aforesaid solution suggested the possibility that PPi promoted further aggregation of the probe L, whose magnitude was higher than that observed in case of aggregation of L in aqueous medium alone. This tenet was validated by AFM and FESEM analysis of L-PPi complex, which indicated the formation of aggregates (Figure 3B-3C), whose average particle size (130170 nm) appeared to be greater than that of L alone in water (Figure 2A, 2C). Job’s plot analysis suggested that L and PPi form a 1:1 host guest complex (Supporting Information, Figure S4A). The apparent binding constant as calculated by B-H plot was 4.2×105 M-1 (Supporting Information, Figure S4B). The limit of detection (LOD) of L for PPi was 1.67 nM, with a signal: noise ratio of 3:1 (Supporting Information, Figure S5).

Figure 4. A) Fluorescence emission changes of L (10 µM) after addition of various anion (10 equv.) in water. B) Selectivity of L for PPi in presence of various anions (10 equv.).

This detection limit of PPi compares well with those reported in previous studies (Supporting Information, Table S1). The specificity of L towards PPi was verified in solution–based experiments wherein other tested anions such as F-, Cl-, Br-, I-, NO3-, OAc-, HSO4-, SO42-, ClO4-, H2PO4-, PO43- HPO42-, ADP, and AMP etc. caused no change to the emission spectra of L. However, a prominent enhancement in the emission intensity of L was also recorded in presence of ATP (Figure 4A). Com-

Page 4 of 8

petitive binding studies were also carried out with these anions by mixing 10 equivalents of the aforesaid anions to a solution of L containing 1.0 equv. of PPi (Figure 4B). It is significant to mention that the PPi-induced manifold enhancement of the emission intensity of L remained almost unaffected by these anions, which indicated the strong selectivity of the developed sensor for PPi. We have also tested some biologically relevant anions such as citrate, tartrate, succinate and oxalate for possible interference. Interestingly, none of the aforesaid anions caused any significant change in the fluorescence emission intensity of L (Supporting Information, Figure S6). The chemosensor could also detect PPi in a mixed aqueous medium and caused similar changes. Prior to PPi addition, L in a 1:1 (v/v) MeCN-5.0 mM HEPES buffer (pH~7.4) mixture exhibited weak fluorescence. However, addition of 10 equiv. of PPi resulted in strong fluorescence at 530 nm (Supporting Information, Figure S7). It can be construed that the higher MeCN content in this experimental solution prevented the L molecules to aggregate, which resulted in comparatively weak fluorescence emission of the solution. However, presence of PPi perhaps triggered the aggregation of L molecules, which resulted in enhanced fluorescence emission (Supporting Information, Figure S7). Other anions failed to produce similar optical signal with L under similar experimental conditions. It may be mentioned here that even in pure dry acetonitrile medium (fw = 0), PPi-induced aggregation of the probe was observed (Supporting Information, Figure S8). Ca2+ has a high affinity for PPi and is known to form a strong complex with the same. It was thus envisaged that addition of Ca2+ is likely to disrupt the L-PPi ensemble owing to strong Ca2+-PPi interactions and this would also provide strong evidence for the involvement of PPi in inducing aggregation and thereby enhancing the fluorescence emission intensity of L manifold. As anticipated, upon addition of Ca2+, the solution turned colourless and the fluorescence diminished considerably, which implies the involvement of PPi in the enhancement of fluorescence emission (Supporting Information, Figure S9)

Scheme 2. The proposed binding of L with PPi leading to aggregate formation.

UV-vis and fluorescence-based studies indicated that the initial aggregation induced emission of L in water was further magnified with the addition of PPi. This suggested that addition of PPi would lead to the generation of comparatively larger aggregates in aqueous medium. This was corroborated by FESEM and AFM analysis, as discussed earlier. Further, dynamic light scattering (DLS) measurement showed an average

4


Page 5 of 8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


particle size of 258 nm (PdI = 0.554, Supporting Information, Figure S10) in a 10 µM solution of L in water interacted with 10 equiv. of pyrophosphate anion. Collectively, all these evidences support the PPi-induced aggregation of L in aqueous medium probably through the involvement of OH and NH groups (Scheme 2).

Paper strip-based detection of PPi For practical application of a chemosensor, it is preferable to perform the detection on solid supports in order to circumvent the involvement of complex and expensive equipment and render the detection rapid and facile. To this end filter papers were soaked with the chemosensor solution and checked for fluorescence and colorimetric changes following addition of aqueous pyrophosphate solution. Interaction with PPi anion resulted in a light yellowish color on the filter paper, which could be readily deciphered with naked eye (Figure 5A). Furthermore, under a 365 nm UV lamp, the faint bluish-green L-impregnated paper emitted strong yellowish-green like fluorescence following PPi addition. Similar changes were also observed on the silica plates (Figure 5B, inset).

Considering the non-toxic nature of L as well as L-PPi ensemble, it was envisaged that the probe could be used for detecting intracellular PPi through imaging studies. To this end, when L was added to HeLa cells at 2.5 µM followed by an incubation for 1 h, it was observed that the cellular fluorescence was negligible (Figure 6A). However, on further addition of 2.5 µM L, a prominent green fluorescence could be detected in the cells (Figure 6B). These results suggested that the probe L facilitated sensing of the inherent PPi levels present in the cell. On careful observation, intracellular clusters emitting intense green fluorescence could be deciphered in some cells, which perhaps represent intracellular aggregates of L-PPi complex. Interestingly, subsequent addition of Ca2+ to HeLa cells resulted in a dramatic quenching of the fluorescence of HeLa cells (Figure 6C), which further supported the relevance of PPi in inducing aggregation of the probe, and consequently manifold increase in the fluorescence exhibited by HeLa cells.

Figure 5. Paper strip test of L with different concentrations of PPi. Visual color changes of L after PPi addition A) in day light and B) under 365 nm UV lamp. Inset of panel B: The color change experiment on TLC plates after PPi addition.

Detection of intracellular PPi by imaging Pyrophosphate (PPi) has emerged as an anion of significant biological relevance as it has been shown to have a profound role in several cellular processes.10-13 This has spurred considerable interest amongst analytical chemists to design chemosensors that can be deployed for PPi sensing in the cellular milieu. In the present study, the excellent selectivity of the probe L for PPi and its strong fluorescence in aqueous medium suggested that the probe could perhaps be used for bio-imaging of intracellular pyrophosphate. An important prerequisite for this endeavour was to ascertain the cytotoxic potential of the probe. To that end, the well-established MTTbased cytotoxicity assay on HeLa cell line (human cervical carcinoma cells) were carried out. Interestingly, even at very high concentrations of the probe or probe-PPi complex (60 µM) the viability of the cells was as high as 80% (Supporting Information, Figure S11).

Figure 6. Fluorescence microscope images of HeLa cells incubated with (a) probe L (2.5 µM) only, (b) probe L (subsequent addition of 2.5 µM) and (c) Ca2+ (50 µM) following addition of L.

■ CONCLUSION In conclusion, we have developed a promising AIE active chemosensor for the selective ‘switch-on’ colorimetric and fluorimetric detection of pyrophosphate anion in physiological medium. Interaction with the PPi anion boosted the fluorescence through aggregation, which is well supported by FESEM, AFM and DLS experiments. The high sensitivity for the PPi anion is observed both in aggregated as well as nonaggregate (solution) form of the chemosensor. Importantly, the PPi selectivity does not alter even in the presence of higher concentration of other competing anions, including biologically relevant anions. Finally, based on the non-toxic nature of the probe, the PPi-induced enhanced fluorescence emission

5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

could be garnered to ascertain inherent levels of PPi produced in live HeLa cells.

■ ASSOCIATED CONTENT Supporting Information 1 H MNR, 13C NMR, emission spectra, absorption spectra and the details of the synthetic procedures. This material is available free of charge via the Internet at http://pubs.acs.org.

■ AUTHOR INFORMATION Prof. Aiyagari Ramesh; Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India. Fax: + 91 361 2582249; Tel: +91 3612582205; Email: [email protected]. Prof. Gopal Das; Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India. Fax: + 91 361 2582349; Tel: +91 3612582313; E-mail: [email protected]

■ ACKNOWLEDGMENT The authors thank CSIR (01/2727/13/EMR-II), Science & Engineering Research Board (SR/S1/OC-62/2011) and Department of Biotechnology (BT/01/NE/PS/08), India for financial support and CIF, IIT Guwahati for providing instrument facilities. AG and SM acknowledge IIT Guwahati for research fellowship.

■ SUPPORTING INFORMATION Additional details of a complete description of chemicals, materials, instrumentation, method, characterization. This information is available free of charge via the Internet at http://pubs.acs.org/.

■ REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Gale, P. A. Chem. Soc. Rev. 2010, 39, 3746-3771. Wenzel, M. J.; Hiscock, R.; Gale, P. A. Chem. Soc. Rev. 2012, 41, 480-520. Gale, P. A.; Busschaert, N.; Haynes, C. J. E.; Karagiannidis, L. E.; Kirby, I. L. Chem. Soc. Rev. 2014, 43, 205-241. Kim, S. K.; Lee, D. H.; Hong, J.-I.; Yoon, J. Acc. Chem. Res. 2009, 42, 23-31. Hargrove, A. E.; Nieto, S.; Zhang, T.; Sessler, J. L.; Anslyn, E. V. Chem. Rev. 2011, 111, 6603-6782. Bencini, A.; Bartoli, F.; Caltagirone, C.; Lippolis, V. Dyes Pigm. 2014, 110, 169-192. Lipscombe, W. N.; Strater, N. Chem. Rev. 1996, 96, 2375-2434. Caswell, A.; Guilland-Cumming, D. F.; Hearn, P. R.; McGuire, M. K.; Russell, R. G. Ann. Rheum. Dis. 1983, 42, 27-37. Ronaghi, M.; Karamohamed, S.; Pettersson, B.; Uhlen, M.; Nyren, P. Anal. Biochem. 1996, 242, 84-89. Timms, A. E.; Zhang, Y.; Russell, R. G. G.; Brown, M. A. Rheumatology 2002, 41, 725-729. Xu, S.; He, M.; Yu, H.; Cai, X.; Tan, X.; Lu, B.; Shu, B. Anal Biochem. 2001, 299, 188-193. Doherty, M.; Belcher, C.; Rehan, M.; Jones, A.; Ledingham, J. Ann. Rheum. Dis. 1996, 55, 432-436. Terkeltaub, R. A. Am. J. Physiol. Cell Phydiol. 2001, 281, C1C11. Marcus, Y. J. Chem. Soc., Farady Trans. 1991, 87, 2995.

Page 6 of 8

15. Colvin, M. E.; Evleth, E.; Akacem, Y. J. Am. Chem. Soc. 1995, 117, 4357-4362. 16. Caltagirone, C.; Bazzicalupi, C.; Isaia, F.; Light, M. E.; Lippolis, V.; Montis, R.; Murgia, S.; Olivari, M.; Picci, G. Org. Biomol. Chem. 2013, 11, 2445-2451. 17. Sokkalingam, P.; Kim, D. S.; Hwang, H.; Sessler, J. L.; Lee, C.H. Chem. Sci. 2012, 3, 1819-1824. 18. Zeng, Z.; Torriero, A. A.; Bond, A. M.; Spiccia, L. Chem. –Eur. J. 2010, 16, 9154-9163. 19. Shao, N.; Wang, H.; Gao, X.; Yang, R.; Chan, W. Anal. Chem. 2010, 82, 4628-4636. 20. Yu, W.; Qiang, J.; Yin, J.; Kambam, S.; Wang, F.; Wang, Y.; Chen, X. Org. Lett. 2014, 16, 2220-2223. 21. Ngo, H. T.; Liu, X.; Jolliffe, K. A. Chem. Soc. Rev. 2012, 41, 4928-4965. 22. Bhowmik, S.; Ghosh, B. N.; Marjomäki, V.; Rissanen, K. J. Am. Chem. Soc. 2014, 136, 5543-5546. 23. Lee, S.; Yuen, K. K. Y.; Jolliffe, K. A.; Yoon, J. Chem. Soc. Rev. 2015, 44, 1749-1762. 24. Quinlan, E.; Matthews, S. E.; Gunnlaugsson, T. J. Org. Chem. 2007, 72, 7497-7503. 25. Shin, I.-S.; Bae, S. W.; Kim, H.; Hong, J.-I. Anal. Chem. 2010, 82, 8259-8265. 26. Su, X.; Zhang, C.; Xiao, X.; Xu, A.; Xu, Z.; Zhao, M. Chem. Commun. 2013, 49, 798-800. 27. Lee, D. H.; Kim, S. Y.; Hong, J.-I. Angew. Chem., Int. Ed. 2004, 43, 4777-4780. 28. Schaferling, M. Angew. Chem., Int. Ed. 2012, 51, 3532-3554. 29. Lemmer, U.; Heun, S.; Mahrt, R. F.; Scherf, U.; Hopmeier, M.; Siegner, U.; Gobel, E. O.; Mullen, K.; Bassler, H. Chem. Phys. Lett. 1995, 240, 373-378. 30. J. B. Birks, Photophysics of Aromatic Molecules, Wiley, London, 1970. 31. Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.; Kwok, H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001, 1740-1741. 32. Tang, B. Z.; Zhan, X.; Yu, G.; Lee, P. P. S.; Liu, Y.; Zhu, D. J. Mater. Chem. 2001, 11, 2974-2978. 33. Tong, H.; Dong, Y.; Hong, Y.; Haeussler, M.; Lam, J. W. Y.; Sung, H. H. Y.; Yu, X.; Sun, J.; Williams, I. D.; Kwok, H. S.; Tang, B. Z. J. Phys. Chem. C 2007, 111, 2287-2294. 34. Zeng, Q.; Li, Z.; Dong, Y.; Di, C.; Qin, A.; Hong, Y.; Ji, L.; Zhu, Z.; Jim, C. K. W.; Yu, G.; Li, Q.; Li, Z.; Liu, Y.; Qin, J.; Tang, B. Z. Chem. Commun. 2007, 70-72. 35. Dong, Y.; Lam, J. W. Y.; Qin, A.; Liu, J.; Li, Z.; Tang, B. Z.; Sun, J.; Kwok, H. S. Appl. Phys. Lett. 2007, 91, 011111-011113. 36. Wang, L.; Shen, Y.; Yang, M.; Zhang, X.; Xu, W.; Zhu, Q.; Wu, J.; Tian, Y.; Zhou, H. Chem. Commun. 2014, 50, 8723-8726. 37. Liu, G.; Yang, M.; Wang, L.; Zheng, J.; Zhou, H.; Wua, J.; Tiana, Y. J. Mater. Chem. C 2014, 2, 2684-2691. 38. Yang, M.; Zhang, Y.; Zhu, W.; Wang, H.; Huang, J.; Cheng, L.; Zhou, H.; Wu, J.; Tian, Y. J. Mater. Chem. C 2015, 3, 19942002. 39. Samanta, S.; Goswami, S.; Hoque, Md. N.; Ramesh, A.; Das, G. Chem. Commun. 2014, 50, 11833-11836. 40. Zhao, X.; Liu, Y.; Schanze, K. S. Chem. Commun. 2007, 2914– 2916. 41. Zhao, X.; Schanze, K. S. Chem. Commun. 2010, 46, 6075–6077. 42. Guo, Z.; Zhu, W.; Tian, H. Macromolecules 2010, 43, 739-744. 43. Bao, Y.; Wang, H.; Li, Q.; Liu, B.; Li, Q.; Bai, W.; Jin, B.; Bai, R. Macromolecules 2012, 45, 3394-3401. 44. Cao, Y.; Yang, M.; Wang, Y.; Zhou, H.; Jun, Z.; Zhang, X.; Wu, J.; Tiana, Y.; Wud, Z. J. Mater. Chem. C 2014, 2, 3686-3694. 45. Maity, A.; Ali, F.; Agarwalla, H.; Anothumakkool, B.; Das, A. Chem. Commun. 2015, 51, 2130-2133. 46. Gao, C.; Gao, G.; Lan, J.; You, J. Chem. Commun. 2014, 50, 5623-5625.

6


Page 7 of 8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


47. Chang, J.; Lu, Y.; He, S.; Liu, C.; Zhaoab, L.; Zeng, X. Chem. Commun. 2013, 49, 6259-6261. 48. Gui, S.; Huang, Y.; Hu, F.; Jin, Y.; Zhang, G.; Yan, L.; Zhang, D.; Zhao, R. Anal. Chem. 2015, 87, 1470-1477.

7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 8

For TOC only

8


Aggregation-Induced Emission Active Metal-Free Chemosensing

Recommend Documents