title: Biological relevance of oxidative debris present in as-prepared graphene oxide.
abstract: The influence of oxidative debris (OD) present in as-prepared graphene oxide (GO) suspensions on proteins and its toxicity to human embryonic kidney cells (HEK-293T) are reported here. The OD was removed by repeated washing with aqueous ammonia to produce the corresponding base-washed GO (bwGO). The loading (w/w) of bovine serum albumin (BSA) was increased by 85% after base washing, whereas the loading of hemoglobin (Hb) and lysozyme (Lyz), respectively, was decreased by 160% and 100%. The secondary structures of 13 different proteins bound to bwGO were compared with the corresponding proteins bound to GO using the UV circular dichroism spectroscopy. There was a consistent loss of protein secondary structure with bwGO when compared with proteins bound to GO, but no correlation between either the isoelectric point or hydrophobicity of the protein and the extent of structure loss was observed. All enzymes bound to bwGO and GO indicated significant activities, and a strong correlation between the enzymatic activity and the extent of structure retention was noted, regardless of the presence or absence of OD. At low loadings (<100 μg/mL) both GO and bwGO showed excellent cell viability but substantial cytotoxicity (~40% cell death) was observed at high loadings (>100 μg/mL). In control studies, OD by itself did not alter the growth rate even after a 48-h incubation. Thus, the presence of OD in GO played a very important role in controlling the chemical and biological nature of the protein-GO interface and the presence of OD in GO improved its biological compatibility when compared to bwGO.
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060 ; Department of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060 ; The Institute of Material Science, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: Ajith
authors.initials: A
authors.lastname: Pattammattel
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060 ; Department of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: Christina L
authors.initials: CL
authors.lastname: Williams
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: Paritosh
authors.initials: P
authors.lastname: Pande
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: William G
authors.initials: WG
authors.lastname: Tsui
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: Ashis K
authors.initials: AK
authors.lastname: Basu
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060 ; Department of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060 ; The Institute of Material Science, University of Connecticut, 55 North Eagleville Road, Unit 3060⍰, Storrs, CT 06269-3060.
authors.forename: Challa Vijaya
authors.initials: CV
authors.lastname: Kumar