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A protein – dye hybrid system as a narrow range tunable intracellular pH sensor † † Electronic supplementary information (ESI) available: Figures depicting various photophysical properties, cytotoxicity studies and confocal fluorescence images. See DOI: 10.1039/c6sc02659a Click here for additional data file.

View Article: PubMed Central - PubMed

ABSTRACT

Accurate monitoring of pH variations inside cells is important for the early diagnosis of diseases such as cancer. Even though a variety of different pH sensors are available, construction of a custom-made sensor array for measuring minute variations in a narrow biological pH window, using easily available constituents, is a challenge. Here we report two-component hybrid sensors derived from a protein and organic dye nanoparticles whose sensitivity range can be tuned by choosing different ratios of the components, to monitor the minute pH variations in a given system. The dye interacts noncovalently with the protein at lower pH and covalently at higher pH, triggering two distinguishable fluorescent signals at 700 and 480 nm, respectively. The pH sensitivity region of the probe can be tuned for every unit of the pH window resulting in custom-made pH sensors. These narrow range tunable pH sensors have been used to monitor pH variations in HeLa cells using the fluorescence imaging technique.

No MeSH data available.


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The mode of interaction of SqNPs with BSA at different pH conditions: BSA protein contains several amino acids having different nucleophilic functional groups. SqNPs interact with BSA differently with respect to pH variation at different BSA–SqNP compositions.
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sch1: The mode of interaction of SqNPs with BSA at different pH conditions: BSA protein contains several amino acids having different nucleophilic functional groups. SqNPs interact with BSA differently with respect to pH variation at different BSA–SqNP compositions.

Mentions: The role of the ratio between BSA and SqNPs on the pH response is explained based on the pH dependent reactivity of various functional groups in the protein (Scheme 1). At lower pH, the thiol group of BSA is less reactive towards the SqNPs and the interaction is exclusively noncovalent as indicated by the turn-on emission at 700 nm. In this case, a large amount of BSA is required for the emission response to become saturated. As the pH of the medium is increased, the thiol group of BSA becomes increasingly reactive towards the SqNPs, triggering the emission at 480 nm with a relatively lower amount of the protein. At pH > 8.0, in addition to the thiol group, the other nucleophilic groups of BSA also become reactive towards the Sq dyes and the interaction becomes exclusively covalent. Thus, at higher pH, a single protein can be covalently labeled with more than one dye molecule.26 Thus, the maximum fluorescence response at 480 nm occurs even with a lower amount of the protein. In all these cases, the protein facilitates the disassembly of SqNPs. The optimum amount of protein required for the complete disassembly of SqNPs at different pH values was determined by DLS analysis (Fig. S13†).


A protein – dye hybrid system as a narrow range tunable intracellular pH sensor † † Electronic supplementary information (ESI) available: Figures depicting various photophysical properties, cytotoxicity studies and confocal fluorescence images. See DOI: 10.1039/c6sc02659a Click here for additional data file.
The mode of interaction of SqNPs with BSA at different pH conditions: BSA protein contains several amino acids having different nucleophilic functional groups. SqNPs interact with BSA differently with respect to pH variation at different BSA–SqNP compositions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5134758&req=5

sch1: The mode of interaction of SqNPs with BSA at different pH conditions: BSA protein contains several amino acids having different nucleophilic functional groups. SqNPs interact with BSA differently with respect to pH variation at different BSA–SqNP compositions.
Mentions: The role of the ratio between BSA and SqNPs on the pH response is explained based on the pH dependent reactivity of various functional groups in the protein (Scheme 1). At lower pH, the thiol group of BSA is less reactive towards the SqNPs and the interaction is exclusively noncovalent as indicated by the turn-on emission at 700 nm. In this case, a large amount of BSA is required for the emission response to become saturated. As the pH of the medium is increased, the thiol group of BSA becomes increasingly reactive towards the SqNPs, triggering the emission at 480 nm with a relatively lower amount of the protein. At pH > 8.0, in addition to the thiol group, the other nucleophilic groups of BSA also become reactive towards the Sq dyes and the interaction becomes exclusively covalent. Thus, at higher pH, a single protein can be covalently labeled with more than one dye molecule.26 Thus, the maximum fluorescence response at 480 nm occurs even with a lower amount of the protein. In all these cases, the protein facilitates the disassembly of SqNPs. The optimum amount of protein required for the complete disassembly of SqNPs at different pH values was determined by DLS analysis (Fig. S13†).

View Article: PubMed Central - PubMed

ABSTRACT

Accurate monitoring of pH variations inside cells is important for the early diagnosis of diseases such as cancer. Even though a variety of different pH sensors are available, construction of a custom-made sensor array for measuring minute variations in a narrow biological pH window, using easily available constituents, is a challenge. Here we report two-component hybrid sensors derived from a protein and organic dye nanoparticles whose sensitivity range can be tuned by choosing different ratios of the components, to monitor the minute pH variations in a given system. The dye interacts noncovalently with the protein at lower pH and covalently at higher pH, triggering two distinguishable fluorescent signals at 700 and 480 nm, respectively. The pH sensitivity region of the probe can be tuned for every unit of the pH window resulting in custom-made pH sensors. These narrow range tunable pH sensors have been used to monitor pH variations in HeLa cells using the fluorescence imaging technique.

No MeSH data available.


Related in: MedlinePlus