uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 131) Show all publications
van Dijk, N. P., Wu, D., Persson, C. & Isaksson, P. (2019). A global digital volume correlation algorithm based on higher-order finite elements: Implementation and evaluation. International Journal of Solids and Structures, 168, 211-227
Open this publication in new window or tab >>A global digital volume correlation algorithm based on higher-order finite elements: Implementation and evaluation
2019 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 168, p. 211-227Article in journal (Refereed) Published
Abstract [en]

We propose a DVC technique that is based on higher-order finite-element discretization of the displacement field and a global optimization procedure. We use curvature penalization to suppress non-physical fluctuations of the displacement field and resulting erroneous strain concentrations. The performance of the proposed method is compared to the commercial code Avizo using trabecular bone images and found to perform slightly better in most cases. In addition, we stress that the performance of a DVC method needs to be evaluated using double scans (zero strain), virtual deformation (imposed deformation) and real deformation. Double scans give insight into the presence of noise and artifacts whereas virtual deformation benchmarks allows evaluation of the performance without noise and artifacts. Investigation of the performance for actual deformed heterogeneous materials is needed for evaluation with noise, artifacts and non-zero strains. We show that both decreasing the resolution of the displacement field (increasing subvolume size) as well as (increasing) curvature penalization (regularization) have a similar effect on the performance of evaluated DVC methods: Decreasing the detrimental effect of noise, artifacts and interpolation errors, but also decreasing the sensitivity of a DVC method to displacement peaks, discontinuities and strain concentrations. The needed amount of regularization is a trade-off between accuracy and precision of the estimated strain fields and their resolution. The obtainable accuracy and precision of the estimated displacement fields are influenced by interpolation errors in the DVC procedure and the relative amount of detail, noise and artifacts in the images. Errors in the displacement field are typically magnified during the strain calculation. Based on the tests and subvolume sizes (16-50 voxels) in this study, the expected order of magnitude of the accuracy and precision is 0.1 micro-voxels and 1 milli-voxels for the displacements and 0.1 and 1 milli-strains of the strain fields. 

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Digital volume correlation, Accuracy, Precision, Benchmarks, Evaluation, Trabecular bone
National Category
Applied Mechanics
Identifiers
urn:nbn:se:uu:diva-387714 (URN)10.1016/j.ijsolstr.2019.03.024 (DOI)000469906300017 ()
Funder
Swedish Research Council, 2016-04608Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology
Available from: 2019-06-26 Created: 2019-06-26 Last updated: 2019-08-12Bibliographically approved
Diez-Escudero, A., Torreggiani, E., Di Pompo, G., Espanol, M., Persson, C., Ciapetti, G., . . . Ginebra, M.-P. (2019). Effect of calcium phosphate heparinization on the in vitro inflammatory response and osteoclastogenesis of human blood precursor cells. Journal of Tissue Engineering and Regenerative Medicine, 13(7), 1217-1229
Open this publication in new window or tab >>Effect of calcium phosphate heparinization on the in vitro inflammatory response and osteoclastogenesis of human blood precursor cells
Show others...
2019 (English)In: Journal of Tissue Engineering and Regenerative Medicine, ISSN 1932-6254, E-ISSN 1932-7005, Vol. 13, no 7, p. 1217-1229Article in journal (Refereed) Published
Abstract [en]

The immobilization of natural molecules on synthetic bone grafts stands as a strategy to enhance their biological interactions. During the early stages of healing, immune cells and osteoclasts (OC) modulate the inflammatory response and resorb the biomaterial, respectively. In this study, heparin, a naturally occurring molecule in the bone extracellular matrix, was covalently immobilized on biomimetic calcium-deficient hydroxyapatite (CDHA). The effect of heparin-functionalized CDHA on inflammation and osteoclastogenesis was investigated using primary human cells and compared with pristine CDHA and beta-tricalcium phosphate (beta-TCP). Biomimetic substrates led to lower oxidative stresses by neutrophils and monocytes than sintered beta-TCP, even though no further reduction was induced by the presence of heparin. In contrast, heparinized CDHA fostered osteoclastogenesis. Optical images of stained TRAP positive cells showed an earlier and higher presence of multinucleated cells, compatible with OC at 14 days, while pristine CDHA and beta-TCP present OC at 21-28 days. Although no statistically significant differences were found in the OC activity, microscopy images evidenced early stages of degradation on heparinized CDHA, compatible with osteoclastic resorption. Overall, the results suggest that the functionalization with heparin fostered the formation and activity of OC, thus offering a promising strategy to integrate biomaterials in the bone remodelling cycle by increasing their OC-mediated resorption.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
biomaterial, heparin, hydroxyapatite, inflammation, osteoclastogenesis
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-391031 (URN)10.1002/term.2872 (DOI)000475495400011 ()31050382 (PubMedID)
Funder
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), STINT-IG2011-2047
Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2019-08-19Bibliographically approved
Barba, A., Diez-Escudero, A., Espanol, M., Bonany, M., Maria Sadowska, J., Guillem-Marti, J., . . . Ginebra, M.-P. (2019). Impact of Biomimicry in the Design of Osteoinductive Bone Substitutes: Nanoscale Matters. ACS Applied Materials and Interfaces, 11(9), 8818-8830
Open this publication in new window or tab >>Impact of Biomimicry in the Design of Osteoinductive Bone Substitutes: Nanoscale Matters
Show others...
2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 9, p. 8818-8830Article in journal (Refereed) Published
Abstract [en]

Bone apatite consists of carbonated calcium-deficient hydroxyapatite (CDHA) nanocrystals. Biomimetic routes allow fabricating synthetic bone grafts that mimic biological apatite. In this work, we explored the role of two distinctive features of biomimetic apatites, namely, nanocrystal morphology (plate vs needle-like crystals) and carbonate content, on the bone regeneration potential of CDHA scaffolds in an in vivo canine model. Both ectopic bone formation and scaffold degradation were drastically affected by the nanocrystal morphology after intramuscular implantation. Fine-CDHA foams with needle-like nanocrystals, comparable in size to bone mineral, showed a markedly higher osteoinductive potential and a superior degradation than chemically identical coarse-CDHA foams with larger plate-shaped crystals. These findings correlated well with the superior bone-healing capacity showed by the fine-CDHA scaffolds when implanted intraosseously. Moreover, carbonate doping of CDHA, which resulted in small plate-shaped nanocrystals, accelerated both the intrinsic osteoinduction and the bone healing capacity, and significantly increased the cell-mediated resorption. These results suggest that tuning the chemical composition and the nanostructural features may allow the material to enter the physiological bone remodeling cycle, promoting a tight synchronization between scaffold degradation and bone formation.

Keywords
biomimetic, calcium phosphate, carbonated apatite, nanostructure, foaming, osteoinduction, osteogenesis
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-380465 (URN)10.1021/acsami.8b20749 (DOI)000460996900015 ()30740968 (PubMedID)
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Diez-Escudero, A., Liu, Y., Lançon, V., Widhe, M., Persson, C., Hedhammar, M. & Mestres, G. (2019). Recombinant silk with calcium phosphates as macroporous bone scaffolds. In: : . Paper presented at European Congress and Exhibition on advanced materials and processes (EUROMAT 2019), 1-5 September 2019, Stockholm, Sweden.
Open this publication in new window or tab >>Recombinant silk with calcium phosphates as macroporous bone scaffolds
Show others...
2019 (English)Conference paper, Oral presentation only (Refereed)
Keywords
Biomaterials, calcium phosphate cements, porosity
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-392965 (URN)
Conference
European Congress and Exhibition on advanced materials and processes (EUROMAT 2019), 1-5 September 2019, Stockholm, Sweden
Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2019-09-16Bibliographically approved
Bang, L. T., Filho, L., Engqvist, H., Xia, W. & Persson, C. (2019). Synthesis and assessment of metallic ion migration through a novel calcium carbonate coating for biomedical implants. Journal of Biomedical Materials Research. Part B - Applied biomaterials
Open this publication in new window or tab >>Synthesis and assessment of metallic ion migration through a novel calcium carbonate coating for biomedical implants
Show others...
2019 (English)In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981Article in journal (Refereed) Published
National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-395269 (URN)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-16
Luo, J., Faivre, J., Engqvist, H. & Persson, C. (2019). The Addition of Poly(Vinyl Alcohol) Fibers to Apatitic Calcium Phosphate Cement Can Improve Its Toughness. Materials, 12(9), Article ID 1531.
Open this publication in new window or tab >>The Addition of Poly(Vinyl Alcohol) Fibers to Apatitic Calcium Phosphate Cement Can Improve Its Toughness
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 9, article id 1531Article in journal (Refereed) Published
Abstract [en]

Calcium phosphate cements, and in particular hydroxyapatite cements, have been widely investigated for use as bone void fillers due to their chemical similarity to bone and related osteoconductivity. However, they are brittle, which limits their use to non-load-bearing applications. The aim of the current study was to improve the toughness of hydroxyapatite cements through fiber reinforcement. The effect of the addition of hydrophilic, poly(vinyl-alcohol) (PVA) fibers to hydroxyapatite cement was evaluated in terms of mechanical properties, including compressive strength, diametral tensile strength and toughness (work of fracture), as well as setting time, phase composition and cement morphology. The fiber reinforcement enhanced the fracture resistance of the hydroxyapatite cement, but also simultaneously reduced the compressive strength and setting time of the cements. However, cement with 5 wt % of fibers (of the powder component) could be considered a good compromise, with a compressive strength of 46.5 +/- 4.6 MPa (compared to 62.3 +/- 12.8 MPa of that without fibers), i.e., still much greater than that of human trabecular bone (0.1-14 MPa). A significantly higher diametral tensile strength (9.2 +/- 0.4 MPa) was found for this cement compared to that without fibers (7.4 +/- 1.5 MPa). The work of fracture increased four times to 9.1 +/- 1.5 kJ/m(2) in comparison to the pristine apatite. In summary, the hydroxyapatite cements could be reinforced by suitable amounts of PVA fibers, which resulted in enhancing the material's structural integrity and ductility, and increased the material's resistance to cracking.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
fiber reinforcement, apatite cement, poly(vinyl alcohol), composite, compressive strength, work of fracture, diametral tensile strength, toughness
National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-387969 (URN)10.3390/ma12091531 (DOI)000469757500172 ()31083315 (PubMedID)
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Tkachenko, S., Datskevich, O., Kulak, L., Persson, C. & Engqvist, H. (2019). The Effect of Al Addition on the Tribological Behavior of Ti-Si-Zr Alloys. Journal of tribology, 141(4), Article ID 041604.
Open this publication in new window or tab >>The Effect of Al Addition on the Tribological Behavior of Ti-Si-Zr Alloys
Show others...
2019 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 141, no 4, article id 041604Article in journal (Refereed) Published
Abstract [en]

While commercial biomedical titanium alloys present excellent biocompatibility and corrosion resistance, their poor wear resistance remains a major limitation. In this study, alloying with aluminum was used to improve the tribological performance of an experimental Ti-Si-Zr alloy. The effect of Al content on the alloy's microstructure and mechanical properties was evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers hardness measurements. Sliding wear testing was performed in a ball-on-disk setup, using stainless steel and silicon nitride counterparts and serum solution lubrication. Microstructural examinations showed that an increase in Al content induced a change from eutectic cell microstructure to regular near-equiaxed particles and produced a solid solution strengthening, increasing alloy's hardness. The adhesive tendencies of the alpha-Ti matrix to the counterpart dominated the frictional response, and a lower friction coefficient was found against silicon nitride compared to stainless steel. In wear tests against stainless steel counterparts, the alloys showed significantly higher wear rates than the CoCr and Ti-6Al-4V references due to severe abrasive wear, induced by the adhesion of titanium matrix to the counterpart. The Al addition had a positive effect on the wear resistance against silicon nitride due to the solid solution strengthening and the change in microstructure, which reduced the risk of brittle delamination. However, while this gave a trend for a lower wear rate against silicon nitride than the Ti-6Al-4V alloy, the wear rate was still approximately three times higher than that of CoCr.

Keywords
nonferrous metals, sliding wear, electron microscopy, hardness, two-body abrasion
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-379021 (URN)10.1115/1.4042098 (DOI)000459212000009 ()
Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-03-12Bibliographically approved
Filho, L. C., Schmidt, S., López, A., Cogrel, M., Leifer, K., Engqvist, H., . . . Persson, C. (2019). The Effect of Coating Density on Functional Properties of SiNx Coated Implants. Materials, 12(20), Article ID 3370.
Open this publication in new window or tab >>The Effect of Coating Density on Functional Properties of SiNx Coated Implants
Show others...
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 20, article id 3370Article in journal (Refereed) Published
Abstract [en]

Ceramic coatings may be applied onto metallic components of joint replacements for improved wear and corrosion resistance as well as enhanced biocompatibility, especially for metal-sensitive patients. Silicon nitride (SiNx) coatings have recently been developed for this purpose. To achieve a high coating density, necessary to secure a long-term performance, is however challenging, especially for sputter deposited SiNx coatings, since these coatings are insulating. This study investigates the time-dependent performance of sputter-deposited SiNx based coatings for joint applications. SiNx coatings with a thickness in the range of 4.3–6.0 µm were deposited by reactive high power impulse magnetron sputtering onto flat discs as well as hip heads made of CoCrMo. SiNx compositional analysis by X-ray photoelectron spectroscopy showed N/Si ratios between 0.8 and 1.0. Immersion of the flat disks in fetal bovine serum solution over time as well as short-term wear tests against ultra-high molecular weight polyethylene (UHMWPE) discs showed that a high coating density is required to inhibit tribocorrosion. Coatings that performed best in terms of chemical stability were deposited using a higher target power and process heating.

Keywords
silicon nitride, coating, reactive high-power impulse magnetron sputtering, wear, joint replacements
National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-396226 (URN)10.3390/ma12203370 (DOI)000498402100093 ()31618981 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, FP7-NMP-2012-310477
Available from: 2019-10-31 Created: 2019-10-31 Last updated: 2019-12-18Bibliographically approved
Filho, L., Schmidt, S., Leifer, K., Engqvist, H., Högberg, H. & Persson, C. (2019). Towards Functional Silicon Nitride Coatings for Joint Replacements. Coatings, 9(2), Article ID 73.
Open this publication in new window or tab >>Towards Functional Silicon Nitride Coatings for Joint Replacements
Show others...
2019 (English)In: Coatings, ISSN 2079-6412, Vol. 9, no 2, article id 73Article in journal (Refereed) Published
Abstract [en]

Silicon nitride (SiNx) coatings are currently under investigation as bearing surfaces for joint implants, due to their low wear rate and the good biocompatibility of both coatings and their potential wear debris. The aim of this study was to move further towards functional SiNx coatings by evaluating coatings deposited onto CoCrMo surfaces with a CrN interlayer, using different bias voltages and substrate rotations. Reactive direct current magnetron sputtering was used to coat CoCrMo discs with a CrN interlayer, followed by a SiNx top layer, which was deposited by reactive high-power impulse magnetron sputtering. The interlayer was deposited using negative bias voltages ranging between 100 and 900 V, and 1-fold or 3-fold substrate rotation. Scanning electron microscopy showed a dependence of coating morphology on substrate rotation. The N/Si ratio ranged from 1.10 to 1.25, as evaluated by X-ray photoelectron spectroscopy. Vertical scanning interferometry revealed that the coated, unpolished samples had a low average surface roughness between 16 and 33 nm. Rockwell indentations showed improved coating adhesion when a low bias voltage of 100 V was used to deposit the CrN interlayer. Wear tests performed in a reciprocating manner against Si3N4 balls showed specific wear rates lower than, or similar to that of CoCrMo. The study suggests that low negative bias voltages may contribute to a better performance of SiNx coatings in terms of adhesion. The low wear rates found in the current study support further development of silicon nitride-based coatings towards clinical application.

Keywords
silicon nitride, coating, reactive high-power impulse magnetron sputtering, wear, joint replacements
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-379945 (URN)10.3390/coatings9020073 (DOI)000460700700011 ()
Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-03-25Bibliographically approved
Luo, J., Engqvist, H. & Persson, C. (2018). A ready-to-use acidic, brushite-forming calcium phosphate cement. Acta Biomaterialia, 81, 304-314
Open this publication in new window or tab >>A ready-to-use acidic, brushite-forming calcium phosphate cement
2018 (English)In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 81, p. 304-314Article in journal (Refereed) Published
Abstract [en]

Premixed calcium phosphate cements have been developed to simplify the usage of traditional calcium phosphate cements and reduce the influence of the setting reaction on the delivery process. However, difficulties in achieving a good cohesion, adequate shelf life and sufficient mechanical properties have so far impeded their use in clinical applications, especially for the more degradable acidic calcium phosphate cements. In this study, a brushite cement was developed from a series of ready-to-use calcium phosphate pastes. The brushite cement paste was formed via mixing of a monocalcium phosphate monohydrate (MCPM) paste and a beta-tricalcium phosphate (beta-TCP) paste with good injectability and adequate shelf life. The MCPM paste was based on a water-immiscible liquid with two surfactants and the beta-Tcp paste on a sodium hyaluronate aqueous solution. The effect of citric acid as a retardant was assessed. Formulations with suitable amounts of citric acid showed good cohesion and mechanical performance with potential for future clinical applications. Statement of Significance Acidic calcium phosphate cements have attracted extensive attention as bone substitute materials due to their ability to resorb faster than basic calcium phosphate cements in vivo. However, traditionally, short working times and low mechanical strength have limited their clinical application. Premixed cements could simplify the clinical use as well as improve property reproducibility, but short shelf lives, low cohesion and low mechanical properties have restricted the development. In this study, an injectable ready-to-use two-phase system consisting of an MCPM paste and a beta-TCP paste was developed based on acidic cement. It shows good cohesion, compressive strength and adequate shelf life, which has the potential to be used in a dual chamber system for simplified and fast filling of bone defects in a minimally invasive manner. This will reduce surgery time, decrease the risk of contamination and ensure repeatable results.

Keywords
Ready-to-use, Acidic calcium phosphate cement, Brushite, Cohesion, Injectability, Shelf life
National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-372719 (URN)10.1016/j.actbio.2018.10.001 (DOI)000451937500024 ()30291976 (PubMedID)
Funder
Swedish Foundation for Strategic Research
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6663-6536

Search in DiVA

Show all publications