ABSTRACT
The most important biosystems that sustain life are closely associated with natural feedback system functions such as homeostasis. For example, hormone release from secretory cells is regulated by physiological cycles or specific input signals. In such natural feedback systems, cell membranes perceive specific ions or biological molecules like hormones, and induce conformational changes or rearrangements of their biomolecules to allow them to function biologically. A natural feedback system consists of a sensor to sense a stimulus as a signal, a processor to judge the magnitude of the signal, and an effector to alter function in direct response to the stimulus. In biomolecules, cell, and various biological systems, the functions of the sensor, processor, and effector are associated through hierarchical structures on the basis of covalent or noncovalent bonds. Therefore, combining their functions in polymeric
materials can lead to mimicking the natural feedback systems. Such mimicking will be an integral part of the next generation of biomaterials and drug delivery systems.
