“…This characteristic is globally recognized as an advantageous opportunity to promote passive tumor accumulation of nanoparticles and to facilitate their cellular uptake, depending on the nanoparticles physicochemical properties [148,149]. Moreover, compared to healthy tissues, tumor microenvironment has unique physicochemical features, including hypoxia, slightly acidic pH, active efflux pumps, hyperthermia and overexpression of several molecular biomarkers [150,151,152]. Considering this, a locally triggered drug release from nanosystems may be promoted by taking advantage of these intrinsic tumor biological peculiar conditions (e.g., pH, temperature and enzymes) or through the application of external stimuli (e.g., light, electric fields, magnetic fields or ultrasound) [144,152,153,154,155,156,157].…”