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Biomolecule Functionalization of Diamond Surfaces for Implant Applications - A Theoretical Study
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a promising material with unique chemical properties. In this thesis, nano-scale diamond quantum size effects were investigated using several chemical property indicators. The results show that the chemical properties are strongly dependent on size for film thicknesses smaller than 1 nm (1D), and for nanodiamond particle diameters less than 2 nm (3D). When the sizes exceed these ranges there are no longer any quantum effects.

The influence of surface termination coverage on the surface chemical properties has been calculated for the 2×1 reconstructed diamond (100) surface and for the diamond (111) surface. The terminating species included COOH and NH2 groups, which both are beneficial for the immobilization of biomolecules. The results of the calculations show that it is energetically possible to terminate the diamond surfaces up to 100% with NH2, while it is only possible to cover the surfaces up to 50% with COOH species. The reason for the latter result is most probably the larger sterical hindrance amongst the adsorbates. Both types of termination species were shown to influence the diamond surface electronic properties (e.g., HOMO/LUMO levels).

In order to extend the diamond utility for biomedical applications, especially implant design, interactions of various growth factors with the diamond surfaces were also simulated. For non-solvent diamond-biomolecule systems, the results show that adhesion affinities are strongly dependent on biomolecule molecular weights. When including a water based solvent in the systems, the results show good physisorption affinities between proteins and diamond. Proteins structures, before and after physisorption, were visualized, and further investigated with respect to electrostatic properties and functional groups. By comparing the biomolecular structural changes during the adhesion processes, it can be concluded that both the general structures, as well as the binding pocket structures, were kept intact after the adhesion to the diamond surfaces (regardless of the adhesion affinities). In addition, the surface electronic potential distributions were maintained, which indicate preserved biomolecule functionalities.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1210
Keyword [en]
Diamond, Biomolecules, Functionalization, VEGF, BMP2, Fibronectin, Chitosan, Heparin, RGD peptide, Angiopoietin, Theoretical
National Category
Medical Materials Theoretical Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-236957ISBN: 978-91-554-9118-5 (print)OAI: oai:DiVA.org:uu-236957DiVA: diva2:766008
Public defence
2015-01-28, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Projects
Vascubone
Available from: 2015-01-07 Created: 2014-11-25 Last updated: 2015-02-03
List of papers
1. Effect of diamond surface modification by biomolecular adhesion – a quantum mechanical study
Open this publication in new window or tab >>Effect of diamond surface modification by biomolecular adhesion – a quantum mechanical study
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The diamond material possesses very attractive properties, such as superior electronic properties (when doped), biocompatibility, chemical inertness, in addition to a controllable surface termination. All resulting (and interesting) properties of a terminated diamond surface, make it clear that surface termination is very important for especially those applications in which diamond can function in the field of implant materials.

The present theoretical work has been focused on the combined effect of diamond surface planes and termination, on the adhesion of important biomolecules for bone regeneration and vascularization [Arginine-Glycine-Aspartic acid (RGD), Chitosan, Heparin, Bone Morphogenetic Protein 2 (BMP2), Angiopoietin 1(AGP1), Fibronectin and Vascular Endothelial Growth Factor (VEGF)]. The calculated results, using predominantly force field calculations, show that the binding (non-covalent) of the biomolecules are in proportion with their molecular weights. Three groups of biomolecules were observed for both the diamond (100)-2x1 and (111) planes. The largest BMP2 molecule showed the strongest binding. The weakest binding was presented by the smaller polypeptides: RGD, Chitosan and Heparin. Finally, the third group, with adhesion energies somewhere in between the other two groups, included VEGF, Fibronectin and Angiopoietin. Moreover, the terminated diamond (111) surfaces were generally observed to display a larger binding of the biomolecules, relative to diamond (100)-2x1. In addition, a predominant variation in adhesion energy for the various termination species was observed for the various biomolecules within the present study.

Keyword
Diamond; Theory; Biomolecules
National Category
Manufacturing, Surface and Joining Technology Medical Materials
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-236954 (URN)
Projects
Vascubone
Funder
EU, FP7, Seventh Framework Programme, 242175
Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2015-02-03
2. Theoretical Study of Size Effects on Surface Chemical Properties for Nanoscale Diamond Particles
Open this publication in new window or tab >>Theoretical Study of Size Effects on Surface Chemical Properties for Nanoscale Diamond Particles
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 45, 26061-26069 p.Article in journal (Refereed) Published
Abstract [en]

Nanodiamond has displayed some unique physical and chemical properties compared to bulk diamond, which broadens its applications in various areas. However, a more detailed picture of nanodiamond quantum confinements is still missing from a theoretical point of view. This investigation presents a study where the effects of one-dimension (i.e., diamond thin films) and three-dimension (i.e., nanodiamond particles) confinement on surface reactivity, and properties, have been calculated using density functional theory (DFT) and tight binding density functional theory (DFTB) methods. Surface specific parameters like (i) surface C–H bond length, (ii) atomic charges, (iii) H adsorption energy, (iv) highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), (v) band gap, and (vi) Fukui functions were thereby carefully calculated and compared. For both the one-dimensional diamond thin films of different surface planes, quantum confinements have strong influences on these factors from thickness of 0.2 to ∼1 nm, while for thin films thicker than 1 nm, the values stabilize around a plateau value. For three-dimensional situations, these factors were found to change within a range of nanodiamond diameter of 0.4 to ∼2 nm, followed by oscillations around specific values as well. These results reveal that nanoscale diamond quantum confinements exist for a nanodiamond particle of a diameter smaller than 2 nm, but not for larger particle sizes. It must here be stressed that all surface specific parameters did independently show the existence of the here presented size ranges for quantum confinement.

Place, publisher, year, edition, pages
Washington, D.C.: American Chemical Society (ACS), 2014
Keyword
Nano-scale diamond, DFTB, Nanodiamond
National Category
Nano Technology
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-236449 (URN)10.1021/jp507421u (DOI)000344978000029 ()
Projects
Vascubone
Funder
EU, FP7, Seventh Framework Programme, 242175
Available from: 2014-11-19 Created: 2014-11-19 Last updated: 2017-12-05Bibliographically approved
3. Protein Functionalized Diamond Surfaces in a Water Solvent – A Theoretical Approach
Open this publication in new window or tab >>Protein Functionalized Diamond Surfaces in a Water Solvent – A Theoretical Approach
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In order to improve the performances of a diamond-based implant material, surface functionalization with different proteins is a promising approach. The main goal of the present study has been to theoretically investigate the diamond functionalization by physisorption of different proteins onto different surface planes. The protein candidates selected are growth factors which can promote cell adhesion and growth, and subsequent vascularization surrounding the implanted materials. They include Bone Morphogenetic Protein 2 (BMP2), Vascular Endothelial Growth Factor (VEGF), Fibronectin (FN), and Angiopoietin (AGP). Moreover, it is well-known that diamond surface properties are strongly dependent on diamond surface planes and surface terminations. Therefore, the following two different diamond surface planes [diamond (100)-2x1 and diamond (111)], and four different kinds of terminations species (H, OH, COOH and NH2), where used in the present study. The results from force-field calculations show that the surface wettability is crucial for the protein adhesion onto the diamond surfaces, and the different proteins possess distinct preferences for diamond surface planes and terminations. For the identification of protein functionality, the atomic structures, in addition to corresponding electrostatic maps, were also visualized in the comparison of protein structures before and after adhesion to the diamond surfaces. It could be concluded that the protein structures and binding pocket electrostatic distributions are maintained as a result of the functionalization process, regardless of adhesion energy strength. These results provide a solid base for experimental protein functionalization of the diamond surfaces.  

Keyword
Diamond, Functionalization, BMP2, Angiopoietin, Fibronectin, VEGF
National Category
Medical Materials Manufacturing, Surface and Joining Technology
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-236955 (URN)
Projects
Vascubone
Funder
EU, FP7, Seventh Framework Programme, 242175
Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2015-02-03
4. Process of Diamond Surface Termination by Carboxylic and Amino groups – A Quantum Mechanics Approach
Open this publication in new window or tab >>Process of Diamond Surface Termination by Carboxylic and Amino groups – A Quantum Mechanics Approach
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The main goal with the present work has been to study the possibility and thermodynamical stability for a sequential termination with either carboxylic groups (COOH), or amino groups (NH2), from an initially H-terminated diamond (111), or diamond (100)-2x1 surface. When sequentially substituting the H species with COOH groups, the total energy of adsorption onto the diamond (100)-2x1 surface was observed to drop from -5.45 eV (6.25%) to -26.22 eV (50%).  It was not possible to cover the surface with COOH species at a higher surface coverge. For the diamond (111) surface, the corresponding adsorption energy was calculated as -5.10 eV (6.25%) to -20.03 eV (50%). The values in parentheses are the COOH surface coverages. These values show that it is energetically preferable to terminate both types of surface planes to 50%. For NH2, it was observed possible to terminate both types of surface planes up to 100% coverage. The total adsorption energies went from -3.83 eV (6.25%) to -45.84 eV (100%) for the diamond (100)-2x1 surface, and from -3.61 eV (6.25%) to -39.91 eV (100%) for the diamond (111) surface.

In order to follow the individual bond energy variations with variations in surface coverage, the averaged adsorption energies have also been calculated. As expected, the lowest COOH coverage resulted in the energetically most preferable adsorption energies [(-5.45 eV for diamond (100)-2x1, and -5.10 eV for diamond (111)]. The corresponding situation for the NH2 group was identical for the diamond (111) surface only, with the lowest surface leading to the most preferable adsorption situation (-3.61 eV for the first NH2 group). For the situation with diamond (100)-2x1, a continuous decrease in average adsorption energy was obtained when going from the lowest surface energy of 6.25 % (-3.83 eV) up to 43.75% (-3.95 eV). Hence, there is a thermodynamically preference for diamond (100)-2x1 to be terminated with NH2 groups for higher concentration up to 43.75%.

Partial Density of States were calculated with the purpose to analyse the COOH-induced surface electronic properties, The results showed that NH2 groups will contribute to the shift of the LUMO or HOMO energy levels. As a result, this will lead to a decrease in the HOMO-LUMO gaps, being valid for both diamond surface planes. Moreover, partially filled states were observed in the HOMO-LUMO gaps for COOH-terminated diamond (100)-2x1 surface, as well as for both COOH- and NH2-terminated diamond (111) surfaces. These specific types of surface terminations thereby display surface conductivities, which were not observed for 100% H-terminated surfaces. 

Keyword
Carboxylic, Amino, Theory, Diamond
National Category
Materials Engineering
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-236956 (URN)
Projects
Vascubone
Funder
EU, FP7, Seventh Framework Programme, 242175
Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2015-02-03

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