Quantitative analysis of BMP-2 derived peptides covalently grafted to oxidized detonation nanodiamonds

In order to deploy detonation nanodiamonds (NDs) in nanomedicine and drug delivery applications, fundamental understanding of their surface chemistry and drug loading capacity is highly desirable. Herein, bone morphogenetic protein 2 (BMP-2) derived peptides have been successfully grafted onto NDs using carbodiimide crosslinker chemistry. Initially, functional surface groups of wet- and dry-oxidized NDs were compared using infrared and mass spectroscopy. Dry-oxidized NDs exhibit the highest amount of carboxylic acid derivatives with a surface loading of 0,113 mmol/g after air annealing at 415 °C for 5 hours determined by mass spectroscopy. Compared to wet-oxidation the dry-oxidation process shows a two-fold increased amount of carbonyl compounds deduced from infrared spectroscopy. Crosslinking of the carboxylic acid derivatives to the primary amines of BMP-2 derived peptides is feasible in the range of 30-96 % total binding efficacy. 1:1 and 5:1 ND-peptide ratios were utilized to study the binding efficacy of NDs using fluorescence spectroscopy. The chemisorption of BMP-2 derived peptides onto NDs reveals superior binding efficacy and results in reproducible amounts of tethered bioactive molecules.