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| 2. |
- Echeverri Correa, Estefania, et al.
(författare)
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Decreasing the dissolution rate of silicon nitride coatings for spinal implants by the addition of Fe and C
- 2022
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Konferensbidrag (refereegranskat)abstract
- Spinal implants have been used for several decades to relieve pain and stabilise the spine, however an increase in the life span of implants is required due to younger and more active patients requiring spinal surgery. Silicon nitride-based coatings have been suggested as an alternative to metallic implants to reduce the release of detrimental ion and particles. However, due to the coating’s dissolution in the presence of water, reducing the dissolution rate by altering the coating composition is of high interest to ensure an adequate lifetime. The aim of this study was to investigate the dissolution rate of silicon nitride coatings containing Fe and C and the effect of the ions released on in vitro neural cell response. SiFeCN coatings were deposited by reactive sputtering using a combinatorial approach for efficient testing of different compositions. Compositional gradients were obtained for the investigated elements. SEM of the coated samples after exposure to cell media displayed stronger signs of dissolution on the SiN reference than the alloyed coatings. The addition of Fe and C decreased the ion release of the coating itself compared to the SiN coating. Indirect biocompatibility tests suggested that microglial cell viability was comparable to that of CoCrMo reference samples and SiN coatings. In conclusion, the results indicate the possibility of decreasing the dissolution rate of SiN coatings by the addition of Fe and C, while maintaining the biocompatibility as confirmed by the cytotoxicity tests on neural cells. Therefore, SiFeCN coatings merit further investigation for use in spinal implants. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 812765 and from the European Union’s Seventh Framework Programme (FP7/2007-2013), grant agreement GA-310477(LifeLongJoints).
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| 3. |
- Echeverri Correa, Estefania, et al.
(författare)
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Dissolution Behaviour and Biocompatibility of Combinatorially Sputtered SiFeCN Coatings for Spinal Implants
- 2022
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION One of the main limiting factors to the life span of spinal implants is the release of detrimental ions and particles, which are typically produced by wear and corrosion1,2. One suggested approach to overcome these issues is the use of silicon nitride-based coatings on metallic implants because of their low wear rates and their ability to slowly dissolve in aqueous solutions into biocompatible ions only, which could be advantageous in terms of limiting the effects of wear debris and ion release3. A previous study found that alloying the silicon nitride coating with Fe and C did not have a negative effect on mechanical properties nor biocompatibility in a direct contact in vitro test4. However, the dissolution behaviour of the coatings remains to be investigated. Furthermore, due to the close proximity to nerve tissues in spinal implants, the effect of the ions released on the neural tissue is a concern. The present study aimed to study the dissolution behaviour and in vitro neural cell response of SiFeCN coatings. A combinatorial approach was used for efficient screening of different compositions. EXPERIMENTAL METHODS SiFeCN coatings were deposited on CoCr disc substrates by reactive sputtering in an in-house built equipment, allowing for combinatorial processes, using Si, Fe and C solid targets. Nitrogen was supplied as a reactive gas. The coatings were characterized in 9 points using x-ray photoelectron spectroscopy (XPS), vertical scanning interferometry (VSI) and scanning electron microscopy (SEM). The points were placed in a 3x3 grid with 22.5 mm between each point. The dissolution behaviour was evaluated by exposing the coated samples to cell media for 14 days. The obtained extracts were diluted (1:32, 1:48, 1:64 and 1:80 dilution) and used to measure ion levels with inductively coupled plasma (ICP-OES) and to assess indirect biocompatibility in vitro using the MTT assay and glial cells. RESULTS AND DISCUSSION The XPS results showed compositional gradients of Si ranging between 36.4-47.3 at.%, Fe 1.4-9.3 at.% and C 4.5-13.9 at.% with average surface roughness, Sa, of 7.4 to 11.1 nm, similar to SiN and CoCr reference materials. SEM after exposure displayed signs of dissolution with visibly increased porosity for the coated samples. The SiN reference also showed substantial changes to the surface. The ICP results (Figure 1) showed a reduction in Co ions from the substrate in the coated samples compared to uncoated. Moreover, the addition of Fe and C decreased the ion release from the coating compared to the SiN reference coating. Extract biocompatibility tests suggested that glial cells tolerated the extracts and their dilutions obtained from the coated samples in a dose- dependent manner and the cell viability was comparable to that of the uncoated CoCr and SiN coating. CONCLUSIONS The findings from this study suggest that using iron and carbon as alloying elements in silicon nitride coatings has the potential to reduce ion release from a metallic substrate and lower the dissolution rate of the coating, while having a comparable cell response to that of the CoCr and SiN control materials. Therefore, SiFeCN coatings merit further investigation as a future option for spinal implants. REFERENCES 1.Shimamura Y. et al., Spine. 33(4):351–355, 2008 2.Vicars R. et al., Comprehensive Biomaterials II. (pp. 246–264), 20173. Pettersson M. et al., ACS Biomaterials Science and Engineering. 2(6):998–1004, 20164. Skjöldebrand C. et al., Materials (Basel). 13(9):1–16, 2020 ACKNOWLEDGMENTS This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 812765 and from the European Union’s Seventh Framework Programme (FP7/2007-2013), grant agreement GA-310477(LifeLongJoints).
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| 4. |
- Echeverri Correa, Estefania, et al.
(författare)
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Fe and C additions decrease the dissolution rate of silicon nitride coatings and are compatible with microglial viability in 3D collagen hydrogels
- 2023
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Ingår i: Biomaterials Science. - : Royal Society of Medicine Press. - 2047-4830 .- 2047-4849. ; 11:9, s. 3144-3158
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride (SiN) coatings may reduce unwanted release of metal ions from metallic implants. However, as SiN slowly dissolves in aqueous solutions, additives that reduce this dissolution rate would likely increase the lifetime and functionality of implants. Adding iron (Fe) and carbon (C) permits tuning of the SiN coatings’ mechanical properties, but their effect on SiN dissolution rates, and their capacity to reduce metal ion release from metallic implant substrates, have yet to be investigated. Such coatings have recently been proposed for use in spinal implants; therefore, it is relevant to assess their impact on the viability of cells expected at the implant site, such as microglia, the resident macrophages of the central nervous system (CNS). To study the effects of Fe and C on the dissolution rate of SiN coatings, compositional gradients of Si, Fe and C in combination with N were generated by physical vapor deposition onto CoCrMo discs. Differences in composition did not affect the surface roughness or the release of Si, Fe or Co ions (the latter from the CoCrMo substrate). Adding Fe and C reduced ion release compared to a SiN reference coating, which was attributed to altered reactivity due to an increase in the fraction of stabilizing Si–C or Fe–C bonds. Extracts from the SiN coatings containing Fe and C were compatible with microglial viability in 2D cultures and 3D collagen hydrogels, to a similar degree as CoCrMo and SiN coated CoCrMo reference extracts. As Fe and C reduced the dissolution rate of SiN-coatings and did not compromise microglial viability, the capacity of these additives to extend the lifetime and functionality of SiN-coated metallic implants warrants further investigation.
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| 5. |
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| 6. |
- Echeverri Correa, Estefania, et al.
(författare)
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Reducing the dissolution rate of silicon nitride coatings for spinal implants using Fe and C as alloying elements
- 2023
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: Wear and corrosion may lead to a release of particles and ions from spinal implants, which is a concern because of their potentially detrimental effect on the life span of the implant [1]. Silicon nitride-based coatings have been suggested as an option to reduce the release of metal ions from an implant. In addition, any particles produced will slowly dissolve, releasing only biocompatible ions [2]. It is of high interest to reduce the dissolution rate of the coating to ensure an adequate lifetime [3]. The present study aimed to assess the effect of Fe and C additions to silicon nitride coatings in terms of dissolution rate as well as the impact of the released ions on the in vitro neural cell response.METHODS: Using a combinatorial approach, SiFeCN coatings were deposited on CoCr disc substrates by reactive sputtering in an in-house built equipment. The coatings were characterized in 9 points using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The dissolution behaviour was evaluated by exposing the coated samples to cell media for 14 days. The obtained extracts were used to measure ion release with inductively coupled plasma - optical emission spectrometry (ICP-OES) and to assess cell viability of microglia (C8-B4 cell line) using the MTT assay. RESULTS: The XPS results showed compositional gradients of Si ranging from 35.0 to 47.3 at.%, Fe from 1.4 to 9.3 at.% and C from 4.5 to 13.9 at.%. SEM of focused ion beam (FIB) cross-sections revealed coating thicknesses between 427-534 nm. SEM of the coating after exposure showed substantial signs of dissolution with visibly increased porosity for the SiN coating, while the SiFeCN coatings appeared less affected. SiFeCN coatings appeared more affected by dissolution for increasing Si contents. The estimated dissolution rate of the SiN coating was 8.3 nm/day, while the rate of SiFeCN coatings was 5.2-6.8 nm/day. The ICP results showed a reduction in Co ions from the substrate in the coated samples compared to uncoated CoCr. Moreover, the levels of detected Si ions were lower for the SiFeCN compared to SiN reference. Indirect biocompatibility tests suggested that microglia cell viability was comparable for the SiFeCN coatings, the uncoated CoCr and the SiN coating.DISCUSSION & CONCLUSIONS: The compositional gradients influenced the thickness of the coating, giving a slight thickness increase in the coatings with the increment of Si content. In addition, the ICP results showed the capability of the coating to act as a barrier to the release of ions from the substrate. Furthermore, the presence of Fe and C in the coating causes a decrease in the ion release from the coating, indicative of a lower dissolution rate, which was supported by the thickness measurements. The findings from this study indicate that using Fe and C as alloying elements can lower the dissolution rate of the silicon nitride-based coating while showing positive indications of biocompatibility on neural cells. Therefore, SiFeCN coatings merit further investigation as a future option for spinal implants.REFERENCES: 1Y. Shimamura et al (2008) Spine. 33:351–355. 2M. Pettersson et al (2016) ACS Biomater. Sci. Eng. 2:998–1004. 3C. Skjöldebrand et al (2022) Biomater Sci, 10:3757–3769.ACKNOWLEDGEMENTS: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 812765 and from the European Union’s Seventh Framework Programme (FP7/2007-2013), grant agreement GA-310477(LifeLongJoints).
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| 7. |
- Geissel, Felix J., et al.
(författare)
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Nanostructured Ag-Bioglass Implant Coatings with Antibacterial and Osteogenic Activity
- 2023
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Ingår i: Advanced Materials Interfaces. - : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Bone implant failure due to aseptic loosening and biofilm infections is an increasing healthcare problem. Implants may be coated with nanoparticles to avoid bacterial colonization and promote osseointegration. However, these nanocoatings often require long, expensive, and complex manufacturing routes with limited clinical translation potential. Here, a multifunctional nanoparticle coating consisting of silver (Ag) and bioglass (BG) is investigated to overcome current limitations by providing synchronously antibacterial and osteogenic effect. Flame spray pyrolysis (FSP) is exploited as a scalable and reproducible process to synthesize large quantities of nanoparticles and deposit them on titanium (Ti) substrates. The deposited nanocoatings show a homogeneous morphology and biomineralize after soaking in simulated body fluid (SBF), while their adhesion on Ti substrates is promoted by in situ flame annealing. The Ag+ ion release from Ag containing BG samples inhibits Staphylococcus aureus biofilm formation up to 3 log units, while the osteogenic responses of pre-osteoblastic cells directly grown on AgBG samples show similar levels of alkaline phosphatase activity, calcium and collagen production when compared to pure Ti. The inexpensively synthesized multifunctional AgBG nanostructured implant coatings exert a high bioactivity and antibacterial response while maintaining high biocompatibility. The insights of this study can direct the development of multifunctional implant coatings.
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| 8. |
- Hulsart Billström, Gry, 1982-
(författare)
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Bone Regeneration with Cell-free Injectable Scaffolds
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bone is a remarkable multifunctional tissue with the ability to regenerate and remodel without generating any scar tissue. However, bone loss due to injury or diseases can be a great challenge and affect the patient significantly. Autologous bone grafting is commonly used throughout the world. Autograft both fills the void and is bone inductive, housing the particular cells that are needed for bone regeneration. However, a regenerative complement to autograft is of great interest as the use of biomaterials loaded with bioactive molecules can avoid donor site morbidity and the problem of a limited volume of material. Two such regenerative products that utilise bone morphogenetic protein (BMP)-7 and -2 have been used for more than a decade clinically. Unfortunately, several side effects have been reported, such as severe swelling due to inflammation and ectopic bone formation. Additionally, the products require open surgery and use of supra physiological doses of the BMPs due to poor localisation and retention of the growth factor. The purpose of this thesis was to harness the strong inductive capacity of the BMP-2 by optimising the carrier of this bioactive protein, thereby minimising the side effects that are associated with the clinical products and facilitating safe and localised bone regeneration. We focused on an injectable hyaluronan-based carrier developed through polymer chemistry at the University of Uppsala. The strategy was to use the body’s own regenerative pathway to stimulate and enhance bone healing in a manner similar to the natural bone-healing process. The hyaluronan-based carrier has a similar composition to the natural extracellular matrix and is degraded by resident enzymes. Earlier studies have shown improved properties when adding hydroxyapatite, a calcium phosphate that constitutes the inorganic part of the bone matrix. In Paper I, the aim was to improve the carrier by adding other forms of calcium phosphate. The results indicated that bone formation was enhanced when using nano-sized hydroxyapatite. In Paper II, we discovered the importance of crushing the material, thus enhancing permeability and enlarging the surface area. We wished to further develop the carrier system, but were lacking an animal model with relatively high throughput, facilitated access, paired data, and we were also committed to the 3Rs of refinement, reduction, and replacement. To meet these challenges, we developed and refined an animal model, and this is described in Paper III. In Paper IV, we sought to further optimise the biomaterial properties of the hydrogel through covalent bonding of bisphosphonates to the hyaluronan hydrogel. This resulted in exceptional retention of the growth factor BMP-2. In Paper V, SPECT/PET/µCT was combined as a tri-modal imaging method to allow visualisation of the biomaterial’s in situ action, in terms of drug retention, osteoblast activity and mineralisation. Finally, in Paper VI the correlation between existing in vitro results with in vivo outcomes was observed for an array of biomaterials. The study identified a surprisingly poor correlation between in vitro and in vivo assessment of biomaterials for osteogenesis.
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| 9. |
- Hulsart Billström, Gry, 1982-, et al.
(författare)
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In vivo safety assessment of a bio-inspired bone adhesive
- 2020
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Ingår i: Journal of materials science. Materials in medicine. - : SPRINGER. - 0957-4530 .- 1573-4838. ; 31:2
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Tidskriftsartikel (refereegranskat)abstract
- A new class of materials, bone adhesives, could revolutionise the treatment of highly fragmented fractures. We present the first biological safety investigation of a bio-inspired bone adhesive. The formulation was based upon a modified calcium phosphate cement that included the amino acid phosphoserine. This material has recently been described as substantially stronger than other bioresorbable calcium phosphate cements. Four adhesive groups with the active substance (phosphoserine) and two control groups without phosphoserine were selected for in vitro and in vivo biocompatibility testing. The test groups were subject for cell viability assay and subcutaneous implantation in rats that was followed by gene expression analysis and histology assessment after 6 and 12 weeks. All adhesive groups supported the same rate of cell proliferation compared to the alpha-TCP control and had viability between 45-64% when compared to cell control. There was no evidence of an increased immune response or ectopic bone formation in vivo. To conclude, this bio-inspired bone adhesive has been proven to be safe, in the present study, without any harmful effects on the surrounding soft tissue.
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