Browsing by Author "Seidenstuecker, Michael"

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Open Access
Adjustment of micro- and macroporosity of ß-TCP scaffolds using solid-stabilized foams as bone replacement
(2023) Dufner, Lukas; Oßwald, Bettina; Eberspaecher, Jan; Riedel, Bianca; Kling, Chiara; Kern, Frank; Seidenstuecker, Michael
To enable rapid osteointegration in bioceramic implants and to give them osteoinductive properties, scaffolds with defined micro- and macroporosity are required. Pores or pore networks promote the integration of cells into the implant, facilitating the supply of nutrients and the removal of metabolic products. In this paper, scaffolds are created from ß-tricalciumphosphate (ß-TCP) and in a novel way, where both the micro- and macroporosity are adjusted simultaneously by the addition of pore-forming polymer particles. The particles used are 10-40 wt%, spherical polymer particles of polymethylmethacrylate (PMMA) (Ø = 5 m) and alternatively polymethylsilsesquioxane (PMSQ) (Ø = 2 m), added in the course of ß-TCP slurry preparation. The arrangement of hydrophobic polymer particles at the interface of air bubbles was incorporated during slurry preparation and foaming of the slurry. The foam structures remain after sintering and lead to the formation of macro-porosity in the scaffolds. Furthermore, decomposition of the polymer particles during thermal debindering results in the formation of an additional network of interconnecting micropores in the stabilizing structures. It is possible to adjust the porosity easily and quickly in a range of 1.2-140 m with a relatively low organic fraction. The structures thus prepared showed no cytotoxicity nor negative effects on the biocompatibility.
Open Access
Biodegradable, antibacterial TCP implant coatings with magnesium phosphate‐based supraparticles
(2025) Lanzino, Maria Carolina; Höppel, Anika; Le, Long‐Quan R. V.; Morelli, Stefania; Killinger, Andreas; Rheinheimer, Wolfgang; Mayr, Hermann O.; Dembski, Sofia; Al‐Ahmad, Ali; Mayr, Moritz F.; Gbureck, Uwe; Seidenstuecker, Michael
This work highlights the potential of porous, bioactive coatings to advance implant technology and address critical clinical challenges. A key issue in implant coatings is to achieve the balance between infection prevention and successful osseointegration. Although titanium implants are widely used due to their mechanical strength and biocompatibility, their bioinert nature limits integration with bone tissue. To address these issues, porous calcium phosphate (CaP) coatings have been developed to enhance cell attachment and bone growth. However, CaP, especially in the widely used form of hydroxyapatite (HAp), has a low resorption rate, which often leads to prolonged coating stability and impairs natural bone remodeling. To overcome this limitation, magnesium phosphate (MgP), an underexplored but promising biomaterial with high biocompatibility and osteogenic potential, can be introduced. Another innovative strategy is the doping of biomaterials with antibacterial ions, among which copper (Cu) has attracted particular attention. The incorporation of Cu into the coating matrix can significantly reduce the risk of post‐operative infection while promoting angiogenesis, a key factor for rapid and stable implant integration. This study presents bone implant coatings composed of tricalcium phosphate (TCP) and Cu‐doped MgP clustered nanoparticles (supraparticles) fabricated via high‐velocity suspension flame spraying (HVSFS). This particle system addresses current challenges in bone tissue regeneration by synergistically combining the high biodegradability of MgP, the bone‐mimicking properties of CaP, and the antibacterial capabilities of Cu. In addition, the HVSFS process enables the creation of thin layers with porous microstructures. Biocompatibility of the prepared coatings was assessed using MG63 osteosarcoma cells, while the antibacterial efficacy was tested against Staphylococcus aureus and Escherichia coli . The incorporation of Cu‐doped MgP supraparticles (MgPCu and MgPCu HT) into TCP coatings resulted in high Cu release and pronounced antibacterial efficacy compared to the TCP reference, while the addition of Cu‐doped FT supraparticles (FTCu) led to high cell proliferation.
Open Access
Copper-enriched hydroxyapatite coatings obtained by high-velocity suspension flame spraying : effect of various gas parameters on biocompatibility
(2024) Le, Long-Quan R. V.; Lanzino, M. Carolina; Blum, Matthias; Höppel, Anika; Al-Ahmad, Ali; Killinger, Andreas; Gadow, Rainer; Rheinheimer, Wolfgang; Seidenstuecker, Michael
Hydroxyapatite (HAp)-coated bone implants are frequently used for orthopaedic or dental implants since they offer high biocompatibility and osteoconductivity. Yet, problems such as infections, e.g. periprosthetic joint infections, occur when implanting foreign material into the body. In this study, HAp coatings were produced via high-velocity suspension flame spraying (HVSFS). This method allows for the production of thin coatings. We investigated the effects of different gas parameters on the coating properties and on the biocompatibility, which was tested on the human osteosarcoma cell line MG63. Furthermore, Copper (Cu) was added to achieve antibacterial properties which were evaluated against standard microorganisms using the airborne assay. Three gas parameter groups (low, medium, and high) with different Cu additions (0 wt.%, 1 wt.% and 1.5 wt.%) were evaluated. Our findings show that porosity as well as hardness can be controlled through gas parameters. Furthermore, we showed that it is possible to add Cu through external injection. The Cu content in the coating as well as the release varies with different gas parameters. Both antibacterial efficacy as well as biocompatibility are affected by the Cu content. We could significantly reduce the amount of colony-forming units (CFU) in all coatings for E. coli , CFU for S. aureus was reduced by adding 1.5 wt.% of Cu to the coating. The biocompatibility testing showed a cytotoxicity threshold at a Cu-release of 14.3 mg/L in 120 hours. Based on our findings, we suggest medium gas parameters for HVSFS and the addition of 1 wt.% Cu to the coating. With these parameters, a reasonable antibacterial effect can be achieved while maintaining sufficient biocompatibility.
Open Access
Cu-doped calcium phosphate supraparticles for bone tissue regeneration
(2024) Höppel, Anika; Bahr, Olivia; Ebert, Regina; Wittmer, Annette; Seidenstuecker, Michael; Carolina Lanzino, M.; Gbureck, Uwe; Dembski, Sofia
Calcium phosphate (CaP) minerals have shown great promise as bone replacement materials due to their similarity to the mineral phase of natural bone. In addition to biocompatibility and osseointegration, the prevention of infection is crucial, especially due to the high concern of antibiotic resistance. In this context, a controlled drug release as well as biodegradation are important features which depend on the porosity of CaP. An increase in porosity can be achieved by using nanoparticles (NPs), which can be processed to supraparticles, combining the properties of nano- and micromaterials. In this study, Cu-doped CaP supraparticles were prepared to improve the bone substitute properties while providing antibacterial effects. In this context, a modified sol-gel process was used for the synthesis of CaP NPs, where a Ca/P molar ratio of 1.10 resulted in the formation of crystalline β-tricalcium phosphate (β-TCP) after calcination at 1000 °C. In the next step, CaP NPs with Cu 2+ (0.5-15.0 wt%) were processed into supraparticles by a spray drying method. Cu release experiments of the different Cu-doped CaP supraparticles demonstrated a long-term sustained release over 14 days. The antibacterial properties of the supraparticles were determined against Gram-positive ( Bacillus subtilis and Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria, where complete antibacterial inhibition was achieved using a Cu concentration of 5.0 wt%. In addition, cell viability assays of the different CaP supraparticles with human telomerase-immortalized mesenchymal stromal cells (hMSC-TERT) exhibited high biocompatibility with particle concentrations of 0.01 mg mL -1 over 72 hours.
Open Access
Effect of 20‐μm‐thin ceramic coatings of hydroxyapatite, bioglass, GB14 and β‐TCP with copper on the ingrowth behavior of femoral implants
(2025) Subkov, Eugen; Latorre, Sergio H.; Müller, Karola; Bagnavi, Anna; Krieg, Peter; Killinger, Andreas; Schmal, Hagen; Kubosch, Eva Johanna; Seidenstuecker, Michael
Aseptic loosening and infection are still the main reasons for revision surgery. The contact of the implant is made through the surface, which is coated with calcium phosphate ceramics for better integration into the bone. The aim of the present work is to optimize these coatings by making them thinner (20 μm) and doping them with copper to add antimicrobial functionality. Four different coating materials were used: hydroxyapatite, Bioglass, GB14, and beta tricalcium phosphate. The coatings were applied by high velocity suspension flame spraying. The titanium rods with the coatings were then implanted bilaterally into the femoral condyles in 144 New Zealand White rabbits, and ingrowth was evaluated after 2, 4, 6, 12, and 24 weeks. Biomechanical (previously published), histological, and histomorphometric analyses were conducted. Histologically, Cu‐doped HA, GB14, and β‐TCP showed normal ingrowth behavior, with the coating not completely degraded after 24 weeks and remaining in contact with the bone. Bioglass showed rapid degradation and calcium loss from the bone. However, no negative effect of Cu doping on bone cells (osteoblasts, osteocytes and connective tissue cells) was observed. Via histomorphometry, Bioglass showed low bone mineralization, while TCP, HA and GB14 revealed an increase in mineralization over time to values between 70%-95%. Comparable results were obtained with the undoped coatings. The bone‐coating contact was in a similar range to the mineralization because of the coating's incomplete degradation after 24 weeks. The thinner coating could also be applied to titanium rods of the same quality (as the titanium plates in Burtscher et al.) using HVFSF. In animal experiments, all rods, regardless of the coating, could be well inserted-there was no delamination. Histology and histomorphometry showed that BG was not suitable for long‐term coating as it had already degraded after 4 weeks and also caused calcium loss in the bone. The other coatings were clearly more suitable. However, we also found that still far too much coating remained after 24 weeks because it was too dense.
Open Access
Inverse 3D printing with variations of the strand width of the resulting scaffolds for bone replacement
(2021) Seidenstuecker, Michael; Schilling, Pia; Ritschl, Lucas; Lange, Svenja; Schmal, Hagen; Bernstein, Anke; Esslinger, Steffen
The objective of this study was to vary the wall thicknesses and pore sizes of inversely printed 3D molded bodies. Wall thicknesses were varied from 1500 to 2000 to 2500 µm. The pores had sizes of 500, 750 and 1000 µm. The sacrificial structures were fabricated from polylactide (PLA) using fused deposition modeling (FDM). To obtain the final bioceramic scaffolds, a water-based slurry was filled into the PLA molds. The PLA sacrificial molds were burned out at approximately 450 °C for 4 h. Subsequently, the samples were sintered at 1250 °C for at least 4 h. The scaffolds were mechanically characterized (native and after incubation in simulated body fluid (SBF) for 28 days). In addition, the biocompatibility was assessed by live/dead staining. The scaffolds with a strand spacing of 500 µm showed the highest compressive strength; there was no significant difference in compressive strength regardless of pore size. The specimens with 1000 µm pore size showed a significant dependence on strand width. Thus, the specimens (1000 µm pores) with 2500 µm wall thickness showed the highest compressive strength of 5.97 + 0.89 MPa. While the 1000(1500) showed a value of 2.90 + 0.67 MPa and the 1000(2000) of 3.49 + 1.16 MPa. As expected for beta-Tricalciumphosphate (β-TCP), very good biocompatibility was observed with increasing cell numbers over the experimental period.
Open Access
Smart thin porous calcium phosphate coatings for local antibiotic delivery
(2025) Le, Long-Quan R. V.; Lanzino, Maria Carolina; Höppel, Anika; Rech, Mirjam; Dembski, Sofia; Killinger, Andreas; Riedel, Bianca; Seidenstuecker, Michael
Objective. Implant failure after arthroplasty, primarily due to aseptic loosening or periprosthetic joint infection, remains a significant clinical problem. Bioactive ceramic coatings, such as β-tricalcium phosphate (β-TCP), enhance osseointegration and may reduce the risk of aseptic loosening. At the same time, localized antibiotic release from the implant surface represents a promising strategy to prevent early bacterial colonization. The aim of this study was to evaluate the feasibility of incorporating the heat-sensitive antibiotic vancomycin (VAN) into β-TCP coatings using high-velocity suspension flame spraying (HVSFS). Results. We successfully embedded VAN into β-TCP coatings by preparing suspensions containing VAN-loaded supraparticles as feedstock for the HVSFS process. High-performance liquid chromatography analysis confirmed that VAN maintained its chemical integrity during spraying, with spectra comparable to untreated controls, indicating no thermal degradation. The resulting multifunctional coatings therefore combined the osteoconductive potential of β-TCP with the antibacterial activity of VAN. These findings demonstrate that HVSFS is a viable technique for producing bioactive coatings that simultaneously promote bone integration and enable local antibiotic delivery, offering a potential strategy to mitigate both aseptic loosening and infection risks in arthroplasty.
Open Access
Suspension-sprayed calcium phosphate coatings with antibacterial properties
(2024) Lanzino, Maria Carolina; Le, Long-Quan R. V.; Höppel, Anika; Killinger, Andreas; Rheinheimer, Wolfgang; Dembski, Sofia; Al-Ahmad, Ali; Mayr, Hermann O.; Seidenstuecker, Michael
Prosthesis loosening due to lack of osteointegration between an implant and surrounding bone tissue is one of the most common causes of implant failure. Further, bacterial contamination and biofilm formation onto implants represent a serious complication after surgery. The enhancement of osteointegration can be achieved by using bioconductive materials that promote biological responses in the body, stimulating bone growth and thus bonding to tissue. Through the incorporation of antibacterial substances in bioconductive, biodegradable calcium phosphate (CaP) coatings, faster osteointegration and bactericidal properties can be achieved. In this study, Cu-doped CaP supraparticles are spray-dried and suspension-sprayed CaP ceramic coatings with antibacterial properties are prepared using high-velocity suspension flame spraying (HVSFS). The objective was to increase the coatings’ porosity and investigate which Cu-doped supraparticles have the strongest antibacterial properties when introduced into the coating layers. Biocompatibility was tested on human Osteosarcoma cells MG63. A porosity of at least 13% was achieved and the supraparticles could be implemented, enhancing it up to 16%. The results showed that the addition of Cu-doped supraparticles did not significantly reduce the number of viable cells compared to the Cu-free sample, demonstrating good biocompatibility. The antimicrobial activity was assessed against the bacterial strains Escherichia coli and Staphylococcus aureus , with Safe Airborne Antibacterial testing showing a significant reduction in both Gram-positive and Gram-negative strains on the Cu-doped coatings.
Open Access
Thin GB14 coatings on implants using HVSFS
(2024) Lanzino, Maria Carolina; Le, Long-Quan R. V.; Wilbig, Janka; Rheinheimer, Wolfgang; Seidenstuecker, Michael; Günster, Jens; Killinger, Andreas
Enhancing osseointegration, the process by which medical implants securely bond to bone, is crucial for improving patient outcomes in orthopedics and dental surgery. Calcium alkali orthophosphates, with their superior bioactivity, resorbability, and chemical resemblance to bone minerals, have emerged as promising candidates for implant coatings. These materials offer improved solubility and lower melting points due to the substitution of calcium with potassium and sodium, along with the addition of magnesium oxide. This study investigates GB14 calcium alkali orthophosphate coatings applied via High Velocity Suspension Flame Spraying (HVSFS), a technique that enables precise control over coating properties. A porosity target of >10% was set to promote bone growth, and we achieved porosities up to 13%, ensuring better cell penetration and stability at the implant-bone interface. Coatings were produced using different gas parameters and distances, with their microstructure and phase composition analyzed using scanning electron microscope (SEM), Vickers hardness testing and X-ray diffraction (XRD). Additionally, roughness and porosity were also assessed. Different coating’s microstructures were achieved by varying stand-off distance and gas parameters. Increasing stand-off distance while reducing gas stoichiometry enabled the production of calcium alkali orthophosphate coatings with fewer cracks, higher porosity and a hardness level comparable to that of state-of-the-art tricalcium phosphate (TCP) coatings. The sample with optimized properties in terms of achieved microstructure and topography was selected for in vitro testing using MG63 osteosarcoma cells to evaluate cell proliferation and adhesion. WST (I) assay, LDH assay, and live/dead staining confirmed the biocompatibility of the coatings, highlighting the potential of HVSFS to enhance osseointegration and outperform conventional methods in implantology. No relevant cytotoxicity could be shown and cells show a good proliferation over time. These results highlight thus the potential of HVSFS to produce thin, bioactive and resorbable coatings to enhance osseointegration.