Nontoxic concentrations of PEGylated graphene nanoribbons for selective cancer cell imaging and photothermal therapy

Reduced graphene oxide nanoribbons functionalized by amphiphilic polyethylene glycol (rGONR-PEG) were applied to attach arginine-glycine-aspartic acid (RGD)-based peptide and cyanine dye 3 (cy3) for targeting alpha(v)beta(3) integrin receptors on human glioblastoma cell line U87MG and its selective fluorescence imaging, respectively. The rGONR-PEG suspension with a concentration of 100 mu g mL(-1) showed similar to 14 and 2.4-fold higher near infrared (NIR) absorption at 808 nm than GONR (with dimensions of similar to 80 nm x 1 mu m) and rGO-PEG sheets (with lateral dimensions of similar to 2 mu m), respectively. The rGONR-PEG-cy3-RGD exhibited highly efficient NIR photothermal therapy performance (concentrations >= 1.0 mu g mL(-1) resulted in >= 97% cell destruction in vitro under 7.5 W cm(-2) NIR irradiation for 8 min). However, the rGONR-PEG exhibited concentration-dependent cyto- and genotoxicity, so that it initiated at 1.0 mu g mL(-1) and presented strong effects at concentrations >= 100 mu g mL(-1) (resulting in >72% cell destruction and >29% DNA fragmentation after 24 h in the dark). Therefore, the concentration of 1.0 mu g mL(-1) (with <11% cell destruction and 7% DNA fragmentation) is the most effective concentration which can present low cyto- and especially geno-toxic effects. This work can provide insights for simultaneously efficient and biocompatible applications of nano-sized graphene in future photothermal nanotherapy.