Fig. 2

Schematic mechanisms of targeted delivery based on BNPs. a BNPs loaded with drugs were injected into the organism intravenously. b The passive targeting of BNPs towards tumors through the EPR effect. As the leaky vasculature exists in tumor vessels, BNPs are allowed to pass through the pathophysiological walls rather than regular walls, leading to the accumulation of BNPs within the tumor due to the characteristic size, shape, surface charge of the nanoparticles. c Active targeting enables uptake of BNPs through the ligand-mediated pathway and stimulus-responsive pathway. Ligand-mediated targeting leverages the high expression of specific receptors on the surface of targeted cells by keeping them engaged with the targeting ligands. In the presence of intrinsic and/or extrinsic stimuli, BNPs attempt to accumulate in microenvironments of disease tissues and realize environment-responsive drug release