ABSTRACT
Nanoscale systems have recently received tremendous attention, particularly in the field of biomedical research. Although drug molecules can be manipulated to improve their properties at drug discovery stage, the compatible drug delivery strategies have to be applied to facilitate the clinical applications and achieve the desirable therapeutic outcomes. Therapeutic or imaging agents can be encapsulated into the inner layer or core of nanoparticles or absorbed on the surface of nanoparticles via various mechanisms. The idea of the stimuli-responsive drug delivery comes from the fact of abnormalities in the diseased tissues or cells. Significant alterations in the physiological condition are often the vital hallmarks for certain diseases, such as cancer and inflammatory diseases, rendering them attractive targets for designing stimuli-responsive systems. Enzymes play significant roles in biological processes due to their exceptional specificity and outstanding catalytic properties. Hypoxia, widely existing in various pathological conditions, is considered a hallmark of ischemic diseases, including ischemic heart disease, limb, and stroke.
