Supramolecular hydrogel exhibiting four basic logic gate functions to fine-tune substance release

Abstract

Logic-gate operations displaying macroscopic outputs are promising systems for the development of intelligent soft materials that can perform effective functions in response to various input patterns. A supramolecular hydrogel comprising the phosphate-type hydrogelator 1 exhibits macroscopic gel-sol behavior in response to four distinct input stimuli: temperature, pH, Ca(2+), and light. We characterized this performance through microscopic, spectroscopic, and rheological measurements. On the basis of its multiple-stimulus responsiveness, we constructed gel-based supramolecular logic gates from hydrogelator 1 that demonstrated AND, OR, NAND, and NOR types of stimulus-responsive gel-sol behavior in the presence of various combinations of the four stimuli. Implementation of such logic-gate functions into semiwet soft materials (e.g., supramolecular hydrogels) is an important step toward the design of controlled drug delivery and release systems. Indeed, we demonstrate herein that one of our gel-based supramolecular logic gates is capable of holding and releasing bioactive substances in response to logic triggers. Furthermore, combining our supramolecular gel-based AND logic gate with a photoresponsive supramolecular gel could temporarily modulate the release rate of the bioactive substance.