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 ανβ3 integrin receptors on human glioblastoma cell line U87MG and its selective fluorescence imaging, respectively. The rGONR–PEG suspension with a concentration of 100 μg mL−1 showed ∼14 and 2.4-fold higher near infrared (NIR) absorption at 808 nm than GONR (with dimensions of ∼80 nm × 1 μm) and rGO–PEG sheets (with lateral dimensions of ∼2 μm), respectively. The rGONR–PEG–cy3–RGD exhibited highly efficient NIR photothermal therapy performance (concentrations ≥1.0 μg 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 geno-toxicity, so that it initiated at 1.0 μg mL−1 and presented strong effects at concentrations ≥100 μg mL−1 (resulting in >72% cell destruction and >29% DNA fragmentation after 24 h in the dark). Therefore, the concentration of 1.0 μg 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.