the interactions of dendrimers with biological systems, such as amine-terminal modified dendrimers which have a propensity to interact with cell membranes with anionic charge. Certain in vivo studies have shown polycationic dendrimers to be cytotoxic through membrane permeabilization, a phenomenon that could be partially mitigated via addition of PEGylation caps on amine groups, resulting in lower cytotoxicity and lower red blood cell hemolysis. Additionally, studies have found that PEGylation of dendrimers results in higher drug loading, slower drug release, longer circulation times in vivo, and lower toxicity in comparison to counterparts without PEG modifications. Numerous targeting moieties have been used to modify dendrimer biodistribution and allow for targeting to specific organs. For example, folate receptors are overexpressed in tumor cells and are therefore promising targets for localized drug delivery of chemotherapeutics. Folic acid conjugation to PAMAM dendrimers has been shown to increase targeting and decrease off-target toxicity while maintaining on-target cytotoxicity of chemotherapeutics such as methotrexate, in mouse models of cancer. Antibody-mediated targeting of dendrimers to cell targets has also shown promise for targeted drug delivery. As epidermal growth factor receptors (EGFRs) are often overexpressed in brain tumors, EGFRs are a convenient target for site-specific drug delivery. The delivery of boron to cancerous cells is important for effective neutron capture therapy, a cancer treatment which requires a large concentration of boron in cancerous cells and a low concentration in healthy cells. A boronated dendrimer conjugated with a monoclonal antibody drug that targets EGFRs was used in rats to successfully deliver boron to cancerous cells. Modifying nanoparticle dendrimers with peptides has also been successful for targeted destruction of colorectal (HCT-116) cancer cells in a co-culture scenario. Targeting peptides can be used to achieve site- or cell-specific delivery, and it has been shown that these peptides increase in targeting specificity when paired with dendrimers. Specifically, gemcitabine-loaded YIGSR-CMCht/PAMAM, a unique kind of dendrimer nanoparticle, induces a targeted mortality on these cancer cells. This is performed via selective interaction of the dendrimer with laminin receptors. Peptide dendrimers may be employed in the future to precisely target cancer cells and deliver chemotherapeutic agents. The cellular uptake mechanism of dendrimers can also be tuned using chemical targeting modifications. Non-modified PAMAM-G4 dendrimer is taken up into activated microglia by fluid phase endocytosis. Conversely, mannose modification of hydroxyl PAMAM-G4 dendrimers was able to change the mechanism of internalization to mannose-receptor (CD206) mediated endocytosis. Additionally, mannose modification was able