Polyethylene Glycol Density and Length Affects Nanoparticle Uptake by Cancer Cells

is most important because NPs should not be cleared from the body before its interaction with tumor tissue. To achieve favorable blood circulation times and cancer cell targeting, various NP sizes, shapes and surfaces have been studied [1720]. For example, gold NPs (GNPs) whose surface was modified with folic acid was found to target cancer cells versus healthy cells as it was found to deliver doxorubicin more effectively to HeLa cells in comparison to MDCK cells [21]. Similarly, magnetic iron oxide NPs that targeted urokinase plasminogen activator receptors were found effective for drug delivery and imaging of cells that over expressed such receptors [22,23]. However, prior to cancer cell targeting, long blood circulation times must be achieved so that NPs may enter tumor tissue to begin with. This is achieved by surface modification of NPs with polyethylene glycol (PEG) or PEGylation, as found in numerous in vivo studies [11,15,16,18,19,24-28].