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"Turn-on" fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules.

Ang CY, Tan SY, Lu Y, Bai L, Li M, Li P, Zhang Q, Selvan ST, Zhao Y - Sci Rep (2014)

Bottom Line: Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process.A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids.This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
A "turn-on" thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

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(A) Kinetic measurements of the ZG-20 NPs with and without (Blank) various thiol compounds. λex = 330 nm, λem = 477 nm. (B) Fluorescence spectra of ZG-20 NPs (λex = 330 nm) after incubation with and without (Blank) various thiol compounds (5 mM). Prescan curve refers to the fluorescence spectrum of the NPs before the incubation, and Blank curve means that the fluorescence spectrum of the NPs was recorded after the same incubation time without the addition of thiol compounds.
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f4: (A) Kinetic measurements of the ZG-20 NPs with and without (Blank) various thiol compounds. λex = 330 nm, λem = 477 nm. (B) Fluorescence spectra of ZG-20 NPs (λex = 330 nm) after incubation with and without (Blank) various thiol compounds (5 mM). Prescan curve refers to the fluorescence spectrum of the NPs before the incubation, and Blank curve means that the fluorescence spectrum of the NPs was recorded after the same incubation time without the addition of thiol compounds.

Mentions: In order to further probe the reaction kinetics of NPs with various thiol compounds, we carried out the time-dependent fluorescence measurements of the NP solution with the incubation of various thiols at pH 7.4 and 37°C over a period of 3 h (Figure 4A). The results of the kinetic experiments show that the treatment of the NPs with various thiol compounds induces the enhancement of the fluorescence at 477 nm under the excitation of 330 nm. DTT led to the highest rate of response, followed by Cys, Hcy and GSH. In addition, a blank run where no additive was added into the NP solution during the incubation period was performed as a control. In the control case, there was no increase in the fluorescence intensity at 477 nm over 3 h, while a decrease in the fluorescence intensity was observed. We speculated that the decrease in the fluorescence intensity was a result of the hydrolysis of the carbonate group on the 7th position of the coumarin molecule. In the initial state, electron-withdrawing carbonate group exhibits an inductive effect on the PySSCou molecule, contributing to the slight inhibition of the PET process to the pyridine group. The unstable carbonate group is prone to hydrolyze, converting into electron-donating phenoxide anion. The resulted phenoxide anion further promotes the PET process, which leads to the decrease of the fluorescence for the blank experiment. The presence of the carbonate group in the PySSCou molecule has two reasons. One is for synthesis reason that the incorporation of the carbonate group prevents the nucleophilic attack of the phenoxide group onto the 4-nitrophenyl chloroformate unit. The second reason is to employ it as a normalization signal during all the kinetic studies. It was observed from the kinetic studies that all the kinetic curves begin at the same starting point, having absolute fluorescence intensity at about 40 a.u. This observation indicates that all the kinetic experiments were conducted with the same initial NP concentration. At the end of the kinetic experiments, the fluorescence spectra of the NPs were recorded under the excitation wavelength of 330 nm (Figure 4B). Initially quenched fluorescence of probe-integrated NPs showed a fluorescence enhancement upon the reactions with various thiol compounds. In addition, kinetic studies were also performed using the naked PySSCou molecule and a same trend of reactivity was observed (Figure S4 in the SI).


"Turn-on" fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules.

Ang CY, Tan SY, Lu Y, Bai L, Li M, Li P, Zhang Q, Selvan ST, Zhao Y - Sci Rep (2014)

(A) Kinetic measurements of the ZG-20 NPs with and without (Blank) various thiol compounds. λex = 330 nm, λem = 477 nm. (B) Fluorescence spectra of ZG-20 NPs (λex = 330 nm) after incubation with and without (Blank) various thiol compounds (5 mM). Prescan curve refers to the fluorescence spectrum of the NPs before the incubation, and Blank curve means that the fluorescence spectrum of the NPs was recorded after the same incubation time without the addition of thiol compounds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231329&req=5

f4: (A) Kinetic measurements of the ZG-20 NPs with and without (Blank) various thiol compounds. λex = 330 nm, λem = 477 nm. (B) Fluorescence spectra of ZG-20 NPs (λex = 330 nm) after incubation with and without (Blank) various thiol compounds (5 mM). Prescan curve refers to the fluorescence spectrum of the NPs before the incubation, and Blank curve means that the fluorescence spectrum of the NPs was recorded after the same incubation time without the addition of thiol compounds.
Mentions: In order to further probe the reaction kinetics of NPs with various thiol compounds, we carried out the time-dependent fluorescence measurements of the NP solution with the incubation of various thiols at pH 7.4 and 37°C over a period of 3 h (Figure 4A). The results of the kinetic experiments show that the treatment of the NPs with various thiol compounds induces the enhancement of the fluorescence at 477 nm under the excitation of 330 nm. DTT led to the highest rate of response, followed by Cys, Hcy and GSH. In addition, a blank run where no additive was added into the NP solution during the incubation period was performed as a control. In the control case, there was no increase in the fluorescence intensity at 477 nm over 3 h, while a decrease in the fluorescence intensity was observed. We speculated that the decrease in the fluorescence intensity was a result of the hydrolysis of the carbonate group on the 7th position of the coumarin molecule. In the initial state, electron-withdrawing carbonate group exhibits an inductive effect on the PySSCou molecule, contributing to the slight inhibition of the PET process to the pyridine group. The unstable carbonate group is prone to hydrolyze, converting into electron-donating phenoxide anion. The resulted phenoxide anion further promotes the PET process, which leads to the decrease of the fluorescence for the blank experiment. The presence of the carbonate group in the PySSCou molecule has two reasons. One is for synthesis reason that the incorporation of the carbonate group prevents the nucleophilic attack of the phenoxide group onto the 4-nitrophenyl chloroformate unit. The second reason is to employ it as a normalization signal during all the kinetic studies. It was observed from the kinetic studies that all the kinetic curves begin at the same starting point, having absolute fluorescence intensity at about 40 a.u. This observation indicates that all the kinetic experiments were conducted with the same initial NP concentration. At the end of the kinetic experiments, the fluorescence spectra of the NPs were recorded under the excitation wavelength of 330 nm (Figure 4B). Initially quenched fluorescence of probe-integrated NPs showed a fluorescence enhancement upon the reactions with various thiol compounds. In addition, kinetic studies were also performed using the naked PySSCou molecule and a same trend of reactivity was observed (Figure S4 in the SI).

Bottom Line: Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process.A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids.This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
A "turn-on" thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

Show MeSH
Related in: MedlinePlus