This study presents the synthesis and biological applications of nano-graphene oxide (NGO), a single-layer graphene oxide sheet with lateral dimensions down to a few nanometers. The researchers developed functionalization chemistry to improve the solubility and compatibility of NGO in biological environments. They obtained size-separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions, which is used for live cell imaging in the near-infrared (NIR) with little background. The researchers also found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug, onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Due to its small size, intrinsic optical properties, large specific surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological and medical applications. The study describes the synthesis of graphene oxide (GO) using a modified Hummers method, followed by pegylation with polyethylene glycol (PEG) star-polymers to improve solubility and stability. The researchers developed a density gradient ultracentrifugation method to separate the NGO–PEG sheets by size, which allowed them to investigate the photoluminescence properties of NGO. They found that the different sized NGO sheets exhibited similar optical absorbance, photoluminescence, and photoluminescence excitation (PLE) spectra, suggesting the presence of small conjugated aromatic domains on the NGO sheets. The researchers also explored using NGO as a vehicle to transport the aromatic drug doxorubicin (DOX) into cancer cells. They found that DOX could be loaded onto NGO via simple π-stacking and released in response to changes in the chemical environment, such as acidic conditions. The drug release was pH-dependent, which could be exploited for drug delivery applications since the micro-environments in the extracellular tissues of tumors and intracellular lysosomes and endosomes are acidic. The researchers demonstrated the potential of NGO–PEG-antibody/drug conjugates for selective killing of cancer cells in vitro. They found that the conjugates could selectively bind to B-cell lymphoma cells and deliver the drug to them, resulting in significant cell growth inhibition. The study highlights the promising applications of graphene materials in biological and medical areas due to their multifunctional properties, including biocompatibility, photoluminescence, and drug loading and delivery.This study presents the synthesis and biological applications of nano-graphene oxide (NGO), a single-layer graphene oxide sheet with lateral dimensions down to a few nanometers. The researchers developed functionalization chemistry to improve the solubility and compatibility of NGO in biological environments. They obtained size-separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions, which is used for live cell imaging in the near-infrared (NIR) with little background. The researchers also found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug, onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Due to its small size, intrinsic optical properties, large specific surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological and medical applications. The study describes the synthesis of graphene oxide (GO) using a modified Hummers method, followed by pegylation with polyethylene glycol (PEG) star-polymers to improve solubility and stability. The researchers developed a density gradient ultracentrifugation method to separate the NGO–PEG sheets by size, which allowed them to investigate the photoluminescence properties of NGO. They found that the different sized NGO sheets exhibited similar optical absorbance, photoluminescence, and photoluminescence excitation (PLE) spectra, suggesting the presence of small conjugated aromatic domains on the NGO sheets. The researchers also explored using NGO as a vehicle to transport the aromatic drug doxorubicin (DOX) into cancer cells. They found that DOX could be loaded onto NGO via simple π-stacking and released in response to changes in the chemical environment, such as acidic conditions. The drug release was pH-dependent, which could be exploited for drug delivery applications since the micro-environments in the extracellular tissues of tumors and intracellular lysosomes and endosomes are acidic. The researchers demonstrated the potential of NGO–PEG-antibody/drug conjugates for selective killing of cancer cells in vitro. They found that the conjugates could selectively bind to B-cell lymphoma cells and deliver the drug to them, resulting in significant cell growth inhibition. The study highlights the promising applications of graphene materials in biological and medical areas due to their multifunctional properties, including biocompatibility, photoluminescence, and drug loading and delivery.