Biofunctionalization of annealed nanodiamonds

In the last decades nanodiamonds have received special attention from the scientific community as a new carbon material with unique properties. Along with the macrosize diamond, those nanoparticles exhibit an exceptional hardness and sp3-core whereas, the size allows different applications. Among others they can be applied in new composites, lubrication oils, polishing and electronic materials, and drug delivery, biolabeling and bioimaging systems. To improve biocompatibility of diamond nanocrystals the surface functionalization is a favorable solution. The nanodiamonds the authors used were obtained by detonation synthesis and for this possess several functional groups on the surface. Further modifications require a homogeneous surface. In this approach a thermal methodology was used to remove the functional groups in order to produce an uniform carbon surface. The chosen biomolecules were phenylalanine, glutathione, biotin and O-phosphorylethanolamine to increase the biological suitability. The thermal annealing process was performed at three different temperatures: 750 °C, 900 °C and 1100 °C, under nitrogen flow to prevent oxidation. In the end of the procedure, samples were characterized by infrared spectroscopy, thermogravimetric analysis and transmission electron microscopy. The results revealed a significant decrease in functional groups for all temperatures. At 1100 °C onion like carbon can be identified in our sample, proving of a successful graphitization of the nanodiamonds. For biofunctionalization different approaches were applied: 1) carboxylation and further peptide bonding; 2) hydroxylation, silanization and further peptide bonding; 3) click chemistry, as depicted in figure 2. Success of the modification is verified by infrared spectroscopy and thermogravimetric analysis which evidence the success of the surface modification

Detonation nanodiamonds biofunctionalization and immobilization to titanium alloy surfaces as first steps towards medical application

Due to their outstanding properties nanodiamonds are a promising nanoscale material in various applications such as microelectronics, polishing, optical monitoring, medicine and biotechnology. Beyond the typical diamond characteristics like extreme hardness or high thermal conductivity, they have additional benefits as intrinsic fluorescence due to lattice defects without photobleaching, obtained during the high pressure high temperature process. Further the carbon surface and its various functional groups in consequence of the synthesis, facilitate additional chemical and biological modification. In this work we present our recent results on chemical modification of the nanodiamond surface with phosphate groups and their electrochemically assisted immobilization on titanium-based materials to increase adhesion at biomaterial surfaces. The starting material is detonation nanodiamond, which exhibits a heterogeneous surface due to the functional groups resulting from the nitrogen-rich explosives and the subsequent purification steps after detonation synthesis. Nanodiamond surfaces are chemically homogenized before proceeding with further functionalization. Suspensions of resulting surface-modified nanodiamonds are applied to the titanium alloy surfaces and the nanodiamonds subsequently fixed by electrochemical immobilization. Titanium and its alloys have been widely used in bone and dental implants for being a metal that is biocompatible with body tissues and able to bind with adjacent bone during healing. In order to improve titanium material properties towards biomedical applications the authors aim to increase adhesion to bone material by incorporating nanodiamonds into the implant surface, namely the anodically grown titanium dioxide layer. Differently functionalized nanodiamonds are characterized by infrared spectroscopy and the modified titanium alloys surfaces by scanning and transmission electron microscopy. The process described shows an adsorption and immobilization of modified nanodiamonds on titanium; where aminosilanized nanodiamonds coupled with O-phosphorylethanolamine show a homogeneous interaction with the titanium substrate