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Chemomechanical Polymers as Sensors and Actuators for Biological and Medicinal Applications.

Schneider HJ, Kato K, Strongin RM - Sensors (Basel) (2007)

Bottom Line: Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate.Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer.The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles.

View Article: PubMed Central - PubMed

Affiliation: FR Organische Chemie der Universität des Saarlandes, D-66041 Saarbrücken, Germany.

ABSTRACT
Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any measuring devices, transducers or power supplies. Until recently the most often used of these materials responded to changes in pH. Chemists are now increasingly using supramolecular recognition sites in materials, which are covalently bound to the polymer backbone. This allows one to use a nearly unlimited variety of guest (or effector) compounds in the environment for a selective response by automatically triggered size changes. This is illustrated with non-covalent interactions of effectors comprising of metal ions, isomeric organic compounds, including enantiomers, nucleotides, aminoacids, and peptides. Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate. This concept is particularly fruitful with effector compounds such as peptides, which only trigger size changes if, e.g. copper ions are present in the surroundings. Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer. The most promising application is the selective interaction of covalently fixed boronic acid residues with glucose, which renders itself not only for sensing, but eventually also for delivery of drugs such as insulin. The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles. Of particular interest is the sensitivity increase which can be reached by downsizing the particle volume.

No MeSH data available.


Expansions (in % volume) triggered by nucleotides UMP and AMP and phosphate (0.1 M) at different pH values; chemomechanical polymer I [39a].
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f21-sensors-07-01578: Expansions (in % volume) triggered by nucleotides UMP and AMP and phosphate (0.1 M) at different pH values; chemomechanical polymer I [39a].

Mentions: Saturation-type profiles as function of the effector concentration can be expected until all binding sites of a chemomechanical polymer are occupied, unless abrupt phase transitions occur. Figure 5 [39b] illustrates in the case of polymer I that such isotherm-like curves can be observed, unless the cooperativity effects discussed below play a role. The curves exhibit only approximately normal saturation isotherms, but allow one to infer the affinity of an effector towards the polymer. The data is analogous to that used to derive apparent association constants of related host-guest complexes in aqueous solution. Thus, the apparent binding constant K e.g. for AMP under the conditions in Scheme 7 is approximately 20 M-1, roughly comparable to K values reported in homogenous solutions for the interaction of AMP and ethylenediamine-type host compounds.[59] From the first part of the characteristically discontinuous concentration profiles observed when using transition metal ion effectors [60] and the maximum expansions reached there one can estimate affinities which are, as expected, much higher than for AMP. For example, Cu(II) ions have an apparent K value around 105 to 106 M-1. However, the profiles not only depend on the presence of additional salts or buffers, but also show a lag period before swelling begins (Figure 5). In contrast, UV/vis measurements show absorption begins to occur at concentrations which are too low to induce gel expansion. The expansion starts at a concentration at which presumably the effector starts to move inside the gel after initially saturating the surface.


Chemomechanical Polymers as Sensors and Actuators for Biological and Medicinal Applications.

Schneider HJ, Kato K, Strongin RM - Sensors (Basel) (2007)

Expansions (in % volume) triggered by nucleotides UMP and AMP and phosphate (0.1 M) at different pH values; chemomechanical polymer I [39a].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3814870&req=5

f21-sensors-07-01578: Expansions (in % volume) triggered by nucleotides UMP and AMP and phosphate (0.1 M) at different pH values; chemomechanical polymer I [39a].
Mentions: Saturation-type profiles as function of the effector concentration can be expected until all binding sites of a chemomechanical polymer are occupied, unless abrupt phase transitions occur. Figure 5 [39b] illustrates in the case of polymer I that such isotherm-like curves can be observed, unless the cooperativity effects discussed below play a role. The curves exhibit only approximately normal saturation isotherms, but allow one to infer the affinity of an effector towards the polymer. The data is analogous to that used to derive apparent association constants of related host-guest complexes in aqueous solution. Thus, the apparent binding constant K e.g. for AMP under the conditions in Scheme 7 is approximately 20 M-1, roughly comparable to K values reported in homogenous solutions for the interaction of AMP and ethylenediamine-type host compounds.[59] From the first part of the characteristically discontinuous concentration profiles observed when using transition metal ion effectors [60] and the maximum expansions reached there one can estimate affinities which are, as expected, much higher than for AMP. For example, Cu(II) ions have an apparent K value around 105 to 106 M-1. However, the profiles not only depend on the presence of additional salts or buffers, but also show a lag period before swelling begins (Figure 5). In contrast, UV/vis measurements show absorption begins to occur at concentrations which are too low to induce gel expansion. The expansion starts at a concentration at which presumably the effector starts to move inside the gel after initially saturating the surface.

Bottom Line: Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate.Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer.The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles.

View Article: PubMed Central - PubMed

Affiliation: FR Organische Chemie der Universität des Saarlandes, D-66041 Saarbrücken, Germany.

ABSTRACT
Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any measuring devices, transducers or power supplies. Until recently the most often used of these materials responded to changes in pH. Chemists are now increasingly using supramolecular recognition sites in materials, which are covalently bound to the polymer backbone. This allows one to use a nearly unlimited variety of guest (or effector) compounds in the environment for a selective response by automatically triggered size changes. This is illustrated with non-covalent interactions of effectors comprising of metal ions, isomeric organic compounds, including enantiomers, nucleotides, aminoacids, and peptides. Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate. This concept is particularly fruitful with effector compounds such as peptides, which only trigger size changes if, e.g. copper ions are present in the surroundings. Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer. The most promising application is the selective interaction of covalently fixed boronic acid residues with glucose, which renders itself not only for sensing, but eventually also for delivery of drugs such as insulin. The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles. Of particular interest is the sensitivity increase which can be reached by downsizing the particle volume.

No MeSH data available.