Limits...
Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions

View Article: PubMed Central - PubMed

ABSTRACT

New ionophores are essential for advancing the art of selective ion sensing. Metal-organic supercontainers (MOSCs), a new family of biomimetic coordination capsules designed using sulfonylcalix[4]arenes as container precursors, are known for their tunable molecular recognition capabilities towards an array of guests. Herein, we demonstrate the use of MOSCs as a new class of size-selective ionophores dedicated to electrochemical sensing of molecular ions. Specifically, a MOSC molecule with its cavities matching the size of methylene blue (MB+), a versatile organic molecule used for bio-recognition, was incorporated into a polymeric mixed-matrix membrane and used as an ion-selective electrode. This MOSC-incorporated electrode showed a near-Nernstian potentiometric response to MB+ in the nano- to micro-molar range. The exceptional size-selectivity was also evident through contrast studies. To demonstrate the practical utility of our approach, a simulated wastewater experiment was conducted using water from the Fyris River (Sweden). It not only showed a near-Nernstian response to MB+ but also revealed a possible method for potentiometric titration of the redox indicator. Our study thus represents a new paradigm for the rational design of ionophores that can rapidly and precisely monitor molecular ions relevant to environmental, biomedical, and other related areas.

No MeSH data available.


(a) Schematic representation of the 1-Co MMM ISE device, (b) Sensitivity of 1-Co MMM ISE to MB+, TBA+, and K+, and (c) response curves of 1-Co MMM ISE to MB+ and TBA+.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5385547&req=5

f2: (a) Schematic representation of the 1-Co MMM ISE device, (b) Sensitivity of 1-Co MMM ISE to MB+, TBA+, and K+, and (c) response curves of 1-Co MMM ISE to MB+ and TBA+.

Mentions: For the initial potentiometric study, a conventional ISE with an inner filling solution was chosen because it has proven to be extremely versatile and can be easily set up in the laboratory31. The potential (Ewe) of the conventional 1-Co MMM ISE was recorded versus a standard Ag/AgCl reference electrode as depicted in Fig. 2a. The potentiometric results of the 1-Co MMM ISE shown in Fig. 2b give a near-Nernstian response to [MB+] with a slope of 56.8 ± 2.5 mV/p[MB+] and a detection limit of ~300 nM. As described above and previously confirmed by single-crystal X-ray diffraction analysis, 1-Co possesses endo- (Ø ~1.7 nm) and exo-(Ø ~0.74 nm) cavities that determine its ion-capture properties. The sizes of these cavities fit nicely with the dimensions of MB+ that has a length of 1.6 nm and a width of 0.7 nm33. Thus, the MB cation can orientate itself to fit into the endo-cavity by length and the exo-cavity by width. While the binding affinity towards the endo- and exo- cavities may differ, the effect should not alter the sensitivity as described by the Nernst equation2021. The ideal dimensional match of MB+ with the MOSC cavities enables the size-selective potentiometric response to MB+. This result provides clear evidence for the use of 1-Co as an ionophore and its direct implementation in ISE sensors.


Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions
(a) Schematic representation of the 1-Co MMM ISE device, (b) Sensitivity of 1-Co MMM ISE to MB+, TBA+, and K+, and (c) response curves of 1-Co MMM ISE to MB+ and TBA+.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385547&req=5

f2: (a) Schematic representation of the 1-Co MMM ISE device, (b) Sensitivity of 1-Co MMM ISE to MB+, TBA+, and K+, and (c) response curves of 1-Co MMM ISE to MB+ and TBA+.
Mentions: For the initial potentiometric study, a conventional ISE with an inner filling solution was chosen because it has proven to be extremely versatile and can be easily set up in the laboratory31. The potential (Ewe) of the conventional 1-Co MMM ISE was recorded versus a standard Ag/AgCl reference electrode as depicted in Fig. 2a. The potentiometric results of the 1-Co MMM ISE shown in Fig. 2b give a near-Nernstian response to [MB+] with a slope of 56.8 ± 2.5 mV/p[MB+] and a detection limit of ~300 nM. As described above and previously confirmed by single-crystal X-ray diffraction analysis, 1-Co possesses endo- (Ø ~1.7 nm) and exo-(Ø ~0.74 nm) cavities that determine its ion-capture properties. The sizes of these cavities fit nicely with the dimensions of MB+ that has a length of 1.6 nm and a width of 0.7 nm33. Thus, the MB cation can orientate itself to fit into the endo-cavity by length and the exo-cavity by width. While the binding affinity towards the endo- and exo- cavities may differ, the effect should not alter the sensitivity as described by the Nernst equation2021. The ideal dimensional match of MB+ with the MOSC cavities enables the size-selective potentiometric response to MB+. This result provides clear evidence for the use of 1-Co as an ionophore and its direct implementation in ISE sensors.

View Article: PubMed Central - PubMed

ABSTRACT

New ionophores are essential for advancing the art of selective ion sensing. Metal-organic supercontainers (MOSCs), a new family of biomimetic coordination capsules designed using sulfonylcalix[4]arenes as container precursors, are known for their tunable molecular recognition capabilities towards an array of guests. Herein, we demonstrate the use of MOSCs as a new class of size-selective ionophores dedicated to electrochemical sensing of molecular ions. Specifically, a MOSC molecule with its cavities matching the size of methylene blue (MB+), a versatile organic molecule used for bio-recognition, was incorporated into a polymeric mixed-matrix membrane and used as an ion-selective electrode. This MOSC-incorporated electrode showed a near-Nernstian potentiometric response to MB+ in the nano- to micro-molar range. The exceptional size-selectivity was also evident through contrast studies. To demonstrate the practical utility of our approach, a simulated wastewater experiment was conducted using water from the Fyris River (Sweden). It not only showed a near-Nernstian response to MB+ but also revealed a possible method for potentiometric titration of the redox indicator. Our study thus represents a new paradigm for the rational design of ionophores that can rapidly and precisely monitor molecular ions relevant to environmental, biomedical, and other related areas.

No MeSH data available.