Pub Date : 2024-11-13DOI: 10.1016/j.jmbbm.2024.106816
Takashi Inagaki, Jeonghyun Kim, Maeda Eijiro, Takeo Matsumoto
Spheroid culture, where cells are aggregated three-dimensionally, is expected to have applications as a model that better recapitulates invivo environment beyond two-dimensional environments. When human mesenchymal stem cells are subjected to spheroid culture in the presence of osteogenesis supplements, the gene expression of osteocyte differentiation marker is greatly increased within a short period compared to two-dimensional culture. However, how such alterations may be reflected to mechanical properties of the spheroid remains unknown. In this study, using a uniaxial compression system, we evaluated the macroscopic mechanical properties of human mesenchymal stem cell-derived spheroids including viscoelastic behavior. The Young's modulus of spheroids cultured for 2 days was about 18 kPa, whereas that of individual cells is around 1–10 kPa. We also found that creep behavior of the spheroid was greater in 50% strain compression beyond 10 or 30% strain, indicating that they are viscoelastic materials. Upon release from compression, the spheroids tended to revert to their original shape through elastic deformation. However, spheroids in which actin filament formation was inhibited exhibited a remarkably greater plastic deformation, suggesting that the actin filaments play a crucial role in the elastic behavior of spheroids. By understanding the mechanical properties and behavior of spheroids, it provides a framework for predicting and manipulating the development of tissues and organs in the field of morphogenesis.
{"title":"Macroscopic creep behavior of spheroids derived from mesenchymal stem cells under compression","authors":"Takashi Inagaki, Jeonghyun Kim, Maeda Eijiro, Takeo Matsumoto","doi":"10.1016/j.jmbbm.2024.106816","DOIUrl":"10.1016/j.jmbbm.2024.106816","url":null,"abstract":"<div><div>Spheroid culture, where cells are aggregated three-dimensionally, is expected to have applications as a model that better recapitulates <em>in</em> <em>vivo</em> environment beyond two-dimensional environments. When human mesenchymal stem cells are subjected to spheroid culture in the presence of osteogenesis supplements, the gene expression of osteocyte differentiation marker is greatly increased within a short period compared to two-dimensional culture. However, how such alterations may be reflected to mechanical properties of the spheroid remains unknown. In this study, using a uniaxial compression system, we evaluated the macroscopic mechanical properties of human mesenchymal stem cell-derived spheroids including viscoelastic behavior. The Young's modulus of spheroids cultured for 2 days was about 18 kPa, whereas that of individual cells is around 1–10 kPa. We also found that creep behavior of the spheroid was greater in 50% strain compression beyond 10 or 30% strain, indicating that they are viscoelastic materials. Upon release from compression, the spheroids tended to revert to their original shape through elastic deformation. However, spheroids in which actin filament formation was inhibited exhibited a remarkably greater plastic deformation, suggesting that the actin filaments play a crucial role in the elastic behavior of spheroids. By understanding the mechanical properties and behavior of spheroids, it provides a framework for predicting and manipulating the development of tissues and organs in the field of morphogenesis.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106816"},"PeriodicalIF":3.3,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.jmbbm.2024.106814
Dylan B. Crocker, Ozan Akkus, Clare M. Rimnac
Sequential irradiation has been advocated for mitigating the reduction in fatigue properties of tendon compared to a single dose. However, to our knowledge, its capability of mitigating fatigue losses in bone is unknown. Recently, we reported that sequential irradiation did not mitigate losses in high-cycle S-N fatigue life of cortical bone at 15 kGy; however, it is unclear if sequential irradiation provides a benefit to fatigue crack propagation resistance. Our previous study also showed that radiation-induced collagen chain fragmentation and crosslinking increased from 0 to 15 kGy, suggesting that both likely contribute to the reduction in high-cycle S-N fatigue life within this dose range. Our objectives were: 1) to evaluate the fatigue crack propagation resistance of cortical bone and the effect of radiation on fracture plane damage zone thickness (DZT) at the crack tip in the dose range of 0–15 kGy, and 2) to evaluate whether sequential irradiation at 15 kGy mitigates the loss of fatigue crack propagation resistance of cortical bone compared to a single irradiation dose. Compact tension specimens from four male donor femoral pairs (ages 21–61 years old) were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and a 15 kGy sequential irradiation dose of 5 kGy sequentially irradiated with 10 kGy) and subjected to fatigue crack propagation testing (n = 3–4 specimens per group) where fatigue crack growth rate da/dN and cyclic stress intensity factor ΔK were determined. Following testing, specimens were bulk stained in basic fuchsin, embedded in poly(methylmethacrylate), sectioned, and mounted on acrylic slides to evaluate fracture plane DZT at known crack lengths. Sections were then imaged with a fluorescence microscope, and fracture plane DZT was measured using ImageJ (n = 3–4 specimens per group) and analyzed as a function of ΔK. We observed a decrease in fatigue crack propagation resistance at 15 kGy compared to doses of 10 kGy or lower (p ≤ 0.013). Fracture plane DZT decreased overall with increasing radiation dose from 0 to 15 kGy. Sequential irradiation offered no improvement in fatigue crack propagation resistance (p = 0.98). Radiation-induced collagen chain fragmentation and crosslinking in this dose range likely contribute to a decrease in energy dissipation capability with increasing radiation dose. Other alternative radiation sterilization methods besides sequential irradiation may be warranted to mitigate radiation-induced tissue damage and extend the functional lifetime of structural cortical bone allografts.
{"title":"Sequential irradiation does not improve fatigue crack propagation resistance of human cortical bone at 15 kGy","authors":"Dylan B. Crocker, Ozan Akkus, Clare M. Rimnac","doi":"10.1016/j.jmbbm.2024.106814","DOIUrl":"10.1016/j.jmbbm.2024.106814","url":null,"abstract":"<div><div>Sequential irradiation has been advocated for mitigating the reduction in fatigue properties of tendon compared to a single dose. However, to our knowledge, its capability of mitigating fatigue losses in bone is unknown. Recently, we reported that sequential irradiation did not mitigate losses in high-cycle S-N fatigue life of cortical bone at 15 kGy; however, it is unclear if sequential irradiation provides a benefit to fatigue crack propagation resistance. Our previous study also showed that radiation-induced collagen chain fragmentation and crosslinking increased from 0 to 15 kGy, suggesting that both likely contribute to the reduction in high-cycle S-N fatigue life within this dose range. Our objectives were: 1) to evaluate the fatigue crack propagation resistance of cortical bone and the effect of radiation on fracture plane damage zone thickness (DZT) at the crack tip in the dose range of 0–15 kGy, and 2) to evaluate whether sequential irradiation at 15 kGy mitigates the loss of fatigue crack propagation resistance of cortical bone compared to a single irradiation dose. Compact tension specimens from four male donor femoral pairs (ages 21–61 years old) were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and a 15 kGy sequential irradiation dose of 5 kGy sequentially irradiated with 10 kGy) and subjected to fatigue crack propagation testing (n = 3–4 specimens per group) where fatigue crack growth rate da/dN and cyclic stress intensity factor ΔK were determined. Following testing, specimens were bulk stained in basic fuchsin, embedded in poly(methylmethacrylate), sectioned, and mounted on acrylic slides to evaluate fracture plane DZT at known crack lengths. Sections were then imaged with a fluorescence microscope, and fracture plane DZT was measured using ImageJ (n = 3–4 specimens per group) and analyzed as a function of ΔK. We observed a decrease in fatigue crack propagation resistance at 15 kGy compared to doses of 10 kGy or lower (p ≤ 0.013). Fracture plane DZT decreased overall with increasing radiation dose from 0 to 15 kGy. Sequential irradiation offered no improvement in fatigue crack propagation resistance (p = 0.98). Radiation-induced collagen chain fragmentation and crosslinking in this dose range likely contribute to a decrease in energy dissipation capability with increasing radiation dose. Other alternative radiation sterilization methods besides sequential irradiation may be warranted to mitigate radiation-induced tissue damage and extend the functional lifetime of structural cortical bone allografts.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106814"},"PeriodicalIF":3.3,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-09DOI: 10.1016/j.jmbbm.2024.106811
Bingbing An , Tiange Zhou , Yalin Li
The Bouligand structure represents helicoidal stacking of aligned fibers; such a structure is widely observed in biological composites. Despite the progress in characterization of toughening caused by Bouligand arrangement of fibers, the inelastic deformation mechanisms of this structure remain elusive. In this study, we carry out calculations for plastic deformation of Bouligand structure, crossed-lamellar structure and the single lamellar structure. It is found that the single lamellar structure and crossed-lamellar structure can undergo necking, while in the Bouligand structure, plastic strain localization bands develop, which is accompanied by plastic rotating of fibers, lamellar twisting and lamellar delamination. Compared with crossed-lamellar structure, the Bouligand structure exhibits lower plastic energy dissipation. However, the Bouligand pattern can activate delamination of lamellae, generating high level of damage energy dissipation. The plastic deformation of Bouligand structure depends on the fracture properties of interface between adjacent lamellae. It is identified that the plastic dissipation of Bouligand structure increases with increasing cohesive strength of lamellar interface, and dominant shear bands emerge in the case of weak lamellar interface. The high strength of lamellar interface plays a role in promoting twisting of lamellae. We have further revealed the effect of the thickness of individual lamella on plastic deformation of the Bouligand structure. The thick lamella is capable of suppressing plastic strain localization in Bouligand structure, thereby giving rise to high plastic dissipation. The findings of this study shed new light on the development of bioinspired Bouligand-type materials.
{"title":"Plastic strain localization in Bouligand structures","authors":"Bingbing An , Tiange Zhou , Yalin Li","doi":"10.1016/j.jmbbm.2024.106811","DOIUrl":"10.1016/j.jmbbm.2024.106811","url":null,"abstract":"<div><div>The Bouligand structure represents helicoidal stacking of aligned fibers; such a structure is widely observed in biological composites. Despite the progress in characterization of toughening caused by Bouligand arrangement of fibers, the inelastic deformation mechanisms of this structure remain elusive. In this study, we carry out calculations for plastic deformation of Bouligand structure, crossed-lamellar structure and the single lamellar structure. It is found that the single lamellar structure and crossed-lamellar structure can undergo necking, while in the Bouligand structure, plastic strain localization bands develop, which is accompanied by plastic rotating of fibers, lamellar twisting and lamellar delamination. Compared with crossed-lamellar structure, the Bouligand structure exhibits lower plastic energy dissipation. However, the Bouligand pattern can activate delamination of lamellae, generating high level of damage energy dissipation. The plastic deformation of Bouligand structure depends on the fracture properties of interface between adjacent lamellae. It is identified that the plastic dissipation of Bouligand structure increases with increasing cohesive strength of lamellar interface, and dominant shear bands emerge in the case of weak lamellar interface. The high strength of lamellar interface plays a role in promoting twisting of lamellae. We have further revealed the effect of the thickness of individual lamella on plastic deformation of the Bouligand structure. The thick lamella is capable of suppressing plastic strain localization in Bouligand structure, thereby giving rise to high plastic dissipation. The findings of this study shed new light on the development of bioinspired Bouligand-type materials.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106811"},"PeriodicalIF":3.3,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142640296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-09DOI: 10.1016/j.jmbbm.2024.106792
Piotr Pańtak , Joanna P. Czechowska , Adelia Kashimbetova , Ladislav Čelko , Edgar B. Montufar , Łukasz Wójcik , Aneta Zima
Bone cements are the subject of intensive research, primarily due to their versatility and the increasing importance for personalized medicine. In this study, novel hybrid self-setting scaffolds, based on calcium phosphates and natural polymers, were fabricated using the robocasting technique. Additionally, the influence of two different silane coupling agents, tetraethyl orthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS), on the physicochemical and biological properties of the obtained materials was thoroughly investigated. The chemical and phase compositions (XRF, XRD, FTIR), setting process, rheological properties, mechanical strength, microstructure (SEM), and chemical stability in vitro were comprehensively examined. The use of silane coupling agents improved compressive strength of the scaffolds from 5.20 to 9.26 MPa. The incorporation of citrus pectin into the liquid phase of the materials, along with the use of a hybrid hydroxyapatite-chitosan powder, not only facilitated the development of printable pastes suitable for robocasting but also enhanced the physicochemical properties of the robocasted scaffolds. The results presented in this study underscore the beneficial influence of silane coupling agents on the characteristics of calcium phosphate-based bone scaffolds. Developed robocasted scaffolds hold great potential for applications in the field of bone tissue engineering and personalized medicine. Further in vitro and in vivo studies are necessary to validate their suitability for clinical applications.
{"title":"Improving the processability and mechanical strength of self-hardening robocasted hydroxyapatite scaffolds with silane coupling agents","authors":"Piotr Pańtak , Joanna P. Czechowska , Adelia Kashimbetova , Ladislav Čelko , Edgar B. Montufar , Łukasz Wójcik , Aneta Zima","doi":"10.1016/j.jmbbm.2024.106792","DOIUrl":"10.1016/j.jmbbm.2024.106792","url":null,"abstract":"<div><div>Bone cements are the subject of intensive research, primarily due to their versatility and the increasing importance for personalized medicine. In this study, novel hybrid self-setting scaffolds, based on calcium phosphates and natural polymers, were fabricated using the robocasting technique. Additionally, the influence of two different silane coupling agents, tetraethyl orthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS), on the physicochemical and biological properties of the obtained materials was thoroughly investigated. The chemical and phase compositions (XRF, XRD, FTIR), setting process, rheological properties, mechanical strength, microstructure (SEM), and chemical stability <em>in vitro</em> were comprehensively examined. The use of silane coupling agents improved compressive strength of the scaffolds from 5.20 to 9.26 MPa. The incorporation of citrus pectin into the liquid phase of the materials, along with the use of a hybrid hydroxyapatite-chitosan powder, not only facilitated the development of printable pastes suitable for robocasting but also enhanced the physicochemical properties of the robocasted scaffolds. The results presented in this study underscore the beneficial influence of silane coupling agents on the characteristics of calcium phosphate-based bone scaffolds. Developed robocasted scaffolds hold great potential for applications in the field of bone tissue engineering and personalized medicine. Further <em>in vitro</em> and <em>in vivo</em> studies are necessary to validate their suitability for clinical applications.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106792"},"PeriodicalIF":3.3,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142640292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.jmbbm.2024.106809
Kelli Nunes Monteiro , Rafaela Paschoalin Nigro , Raul Campos Costa , Bruno de Oliveira Macedo , Stéphanie Soares Favero , Ranulfo Benedito de Paula Miranda , Estevam Augusto Bonfante , Paulo Francisco Cesar
The objective was to evaluate the effect of material (four monolithic zirconia) and surface condition [glazed (G) versus polished after simulation of occlusal adjustment (GAP)] on roughness and volumetric wear (VW) of dental zirconia after chewing simulation (CS). Zirconia specimens (ZS) were fabricated with an approximate diameter of 12.0 mm and a thickness of 1.0 mm. The four types of monolithic zirconia utilized were Prettau 4 Anterior (PA), Lava Plus (LP), Cercon hT (hT), and Cercon xT (xT). All specimens were coated with a thin and uniform layer of Prettau Plus glaze. Additionally, half of the ZS underwent a simulation of occlusal adjustment followed by clinical polishing. The sliding wear test was performed using a chewing simulator set at 30 N, 2 Hz, and 500,000 cycles, employing steatite specimens (SS) to simulate opposing dentition. ZS and SS underwent topographic analysis through optical profilometry to assess volumetric wear (VW) and surface roughness. The average roughness values (μm) of the zirconia ranged from 0.38h (PA-G before CS) to 2.55a (PA-GAP after CS), while for the antagonist the values ranged from 1.3b (LP-G before CS) to 2.6a (PA-GAP after CS). The VW values (mm3) of the ZS ranged from 0.7b (LP-G) to 2.5a (LP-GAP), while for the antagonist the values ranged from 0.17a (xT-GAP) to 0.33a (LP-G). The CS increased the roughness of all materials tested, regardless of the surface condition. The glazed condition showed lower roughness than the glazed/occlusal adjustment/polishing condition before the CS for three zirconia (PA, LP and xT) and after the CS for all materials. The surface condition did not significantly influence volumetric wear (VW) for three materials (PA, hT, and xT); however, for the Lava Plus (LP) group, the glazed condition resulted in reduced VW. The VW of the SS was unaffected by the material type or surface condition. In summary, zirconia specimens that underwent occlusal adjustment followed by repolishing demonstrated increased surface roughness compared to the glazed ones, while their wear behavior varied depending on the type of zirconia used.
{"title":"Effect of occlusal adjustment and subsequent repolishing on the surface roughness and volumetric wear of different types of glazed monolithic zirconia after chewing simulation","authors":"Kelli Nunes Monteiro , Rafaela Paschoalin Nigro , Raul Campos Costa , Bruno de Oliveira Macedo , Stéphanie Soares Favero , Ranulfo Benedito de Paula Miranda , Estevam Augusto Bonfante , Paulo Francisco Cesar","doi":"10.1016/j.jmbbm.2024.106809","DOIUrl":"10.1016/j.jmbbm.2024.106809","url":null,"abstract":"<div><div>The objective was to evaluate the effect of material (four monolithic zirconia) and surface condition [glazed (G) versus polished after simulation of occlusal adjustment (GAP)] on roughness and volumetric wear (VW) of dental zirconia after chewing simulation (CS). Zirconia specimens (ZS) were fabricated with an approximate diameter of 12.0 mm and a thickness of 1.0 mm. The four types of monolithic zirconia utilized were Prettau 4 Anterior (PA), Lava Plus (LP), Cercon hT (hT), and Cercon xT (xT). All specimens were coated with a thin and uniform layer of Prettau Plus glaze. Additionally, half of the ZS underwent a simulation of occlusal adjustment followed by clinical polishing. The sliding wear test was performed using a chewing simulator set at 30 N, 2 Hz, and 500,000 cycles, employing steatite specimens (SS) to simulate opposing dentition. ZS and SS underwent topographic analysis through optical profilometry to assess volumetric wear (VW) and surface roughness. The average roughness values (μm) of the zirconia ranged from 0.38<sup>h</sup> (PA-G before CS) to 2.55<sup>a</sup> (PA-GAP after CS), while for the antagonist the values ranged from 1.3<sup>b</sup> (LP-G before CS) to 2.6<sup>a</sup> (PA-GAP after CS). The VW values (mm<sup>3</sup>) of the ZS ranged from 0.7<sup>b</sup> (LP-G) to 2.5<sup>a</sup> (LP-GAP), while for the antagonist the values ranged from 0.17<sup>a</sup> (xT-GAP) to 0.33<sup>a</sup> (LP-G). The CS increased the roughness of all materials tested, regardless of the surface condition. The glazed condition showed lower roughness than the glazed/occlusal adjustment/polishing condition before the CS for three zirconia (PA, LP and xT) and after the CS for all materials. The surface condition did not significantly influence volumetric wear (VW) for three materials (PA, hT, and xT); however, for the Lava Plus (LP) group, the glazed condition resulted in reduced VW. The VW of the SS was unaffected by the material type or surface condition. In summary, zirconia specimens that underwent occlusal adjustment followed by repolishing demonstrated increased surface roughness compared to the glazed ones, while their wear behavior varied depending on the type of zirconia used.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106809"},"PeriodicalIF":3.3,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142635301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polyvinyl alcohol (PVA) is a biocompatible biopolymer with superior dimensional and mechanical stability when compared to naturally available biomaterials such as collagen and gelatin. Furthermore, PVA in hydrogel form behaves non-linearly during mechanical loading, generating a response like soft biological tissues. Generally, PVA hydrogels are fabricated using freeze-thaw cycles (FTCs) and changing the number of FTCs gives control over its mechanical properties. Porosity of the hydrogel is another important factor which determines its mechanical properties and is also evident in biological soft tissues. Incorporating macro-pores in PVA hydrogels substantially reduces the stiffness of the material and can mimic some porous tissues such as lung, liver, bone marrow, kidneys, and penile tissues (corpus cavernosa and spongiosum). Within this study, we developed macro-porous PVA hydrogels using the freeze-thaw process followed by particulate leaching of sacrificial 3D-printed and milled PVA (m-PVA) filler particles. This fabrication method enables control over the porosity in macro-porous PVA hydrogels, which is crucial not only for tuning mechanical properties but also for mimicking the structure of spongy tissues, such as liver tissue and corpus cavernosum in the penis, for example. We investigated the level of porosity in the specimen using optical microscopy to understand the distribution of the pores and the pore size. The tunability of the mechanical properties of PVA hydrogels is a key finding of this study and is achieved using three factors: (i) weight percentage of sacrificial fillers, (ii) number of FTCs and (iii) concentration of PVA. These macro-porous PVA specimens have wide ranging biomedical applications as biological soft tissue analogues, or tissue engineering scaffolds, where the PVA hydrogel can be tuned to match the mechanical properties of these soft biological tissues.
{"title":"Tailoring the mechanical properties of macro-porous PVA hydrogels for biomedical applications","authors":"Shirsha Bose , Majid Akbarzadeh Khorshidi , Caitríona Lally","doi":"10.1016/j.jmbbm.2024.106787","DOIUrl":"10.1016/j.jmbbm.2024.106787","url":null,"abstract":"<div><div>Polyvinyl alcohol (PVA) is a biocompatible biopolymer with superior dimensional and mechanical stability when compared to naturally available biomaterials such as collagen and gelatin. Furthermore, PVA in hydrogel form behaves non-linearly during mechanical loading, generating a response like soft biological tissues. Generally, PVA hydrogels are fabricated using freeze-thaw cycles (FTCs) and changing the number of FTCs gives control over its mechanical properties. Porosity of the hydrogel is another important factor which determines its mechanical properties and is also evident in biological soft tissues. Incorporating macro-pores in PVA hydrogels substantially reduces the stiffness of the material and can mimic some porous tissues such as lung, liver, bone marrow, kidneys, and penile tissues (corpus cavernosa and spongiosum). Within this study, we developed macro-porous PVA hydrogels using the freeze-thaw process followed by particulate leaching of sacrificial 3D-printed and milled PVA (m-PVA) filler particles. This fabrication method enables control over the porosity in macro-porous PVA hydrogels, which is crucial not only for tuning mechanical properties but also for mimicking the structure of spongy tissues, such as liver tissue and corpus cavernosum in the penis, for example. We investigated the level of porosity in the specimen using optical microscopy to understand the distribution of the pores and the pore size. The tunability of the mechanical properties of PVA hydrogels is a key finding of this study and is achieved using three factors: (i) weight percentage of sacrificial fillers, (ii) number of FTCs and (iii) concentration of PVA. These macro-porous PVA specimens have wide ranging biomedical applications as biological soft tissue analogues, or tissue engineering scaffolds, where the PVA hydrogel can be tuned to match the mechanical properties of these soft biological tissues.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106787"},"PeriodicalIF":3.3,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-05DOI: 10.1016/j.jmbbm.2024.106795
Daniel P. Pearce, Michael Chiariello, Colleen M. Witzenburg
Planar biaxial testing offers a physiologically relevant approach for mechanically characterizing thin deformable soft tissues, but often relies on erroneous assumptions of uniform strain fields and negligible shear strains and forces. In addition to the complex mechanical behavior exhibited by soft tissues, constraints on sample size, geometry, and aspect ratio often restrict sample shape and symmetry. Using simple PDMS gels, we explored the unknown and unquantified effects of sample shape asymmetry on planar biaxial testing results, including shear strain magnitudes, shear forces measured at the sample’s boundary, and the homogeneity of strains experienced at the center of each sample. We used a combination of finite element modeling and experimental validation to examine PDMS gels of varying levels of asymmetry, allowing us to identify effects of sample shape without confounding factors introduced by the nonlinear, spatially variable, and anisotropic properties of soft tissues. Both biaxial simulations and experiments, which showed strong agreement, revealed that sample shape asymmetry led to significantly larger shear strains, shear forces, and overestimation of principal stresses. Excluding these shear forces resulted in an underestimation of shear moduli during inverse mechanical characterizations. Even in the simplest of deformable biomaterials, sample shape asymmetry should be avoided as it can induce drastic increases in shear strains and shear forces, invalidating traditional planar biaxial testing analyses. Alternatively, sample shape asymmetry may be exploited to generate more robust estimates of constitutive parameters in more complex materials, which could lead to a refined understanding and inference of mechanical behavior.
{"title":"Asymmetric sample shapes complicate planar biaxial testing assumptions by intensifying shear strains and stresses","authors":"Daniel P. Pearce, Michael Chiariello, Colleen M. Witzenburg","doi":"10.1016/j.jmbbm.2024.106795","DOIUrl":"10.1016/j.jmbbm.2024.106795","url":null,"abstract":"<div><div>Planar biaxial testing offers a physiologically relevant approach for mechanically characterizing thin deformable soft tissues, but often relies on erroneous assumptions of uniform strain fields and negligible shear strains and forces. In addition to the complex mechanical behavior exhibited by soft tissues, constraints on sample size, geometry, and aspect ratio often restrict sample shape and symmetry. Using simple PDMS gels, we explored the unknown and unquantified effects of sample shape asymmetry on planar biaxial testing results, including shear strain magnitudes, shear forces measured at the sample’s boundary, and the homogeneity of strains experienced at the center of each sample. We used a combination of finite element modeling and experimental validation to examine PDMS gels of varying levels of asymmetry, allowing us to identify effects of sample shape without confounding factors introduced by the nonlinear, spatially variable, and anisotropic properties of soft tissues. Both biaxial simulations and experiments, which showed strong agreement, revealed that sample shape asymmetry led to significantly larger shear strains, shear forces, and overestimation of principal stresses. Excluding these shear forces resulted in an underestimation of shear moduli during inverse mechanical characterizations. Even in the simplest of deformable biomaterials, sample shape asymmetry should be avoided as it can induce drastic increases in shear strains and shear forces, invalidating traditional planar biaxial testing analyses. Alternatively, sample shape asymmetry may be exploited to generate more robust estimates of constitutive parameters in more complex materials, which could lead to a refined understanding and inference of mechanical behavior.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106795"},"PeriodicalIF":3.3,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142607305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-05DOI: 10.1016/j.jmbbm.2024.106799
Zhongheng Yang , Sen Zhang , Mingfeng Wang , Jiao Yan , Tao Yan , Zengqian Liu , Qiang Wang , Zhe Yi , Yuzhong Gao
Enhancement of the mechanical and biological properties of dental restoration materials is of significant importance. Drawing inspiration from the architecture and mechanical properties of natural nacre, we employed a low-cost accumulative rolling process to develop resin-ceramic composites with suitable hardness and high toughness. Plate-like aluminum oxide powder with diameters of 5–10 μm and nano-zinc oxide (ZnO) with antibacterial properties were mixed as the ceramic phase of the composite. Aluminum oxide ceramic plates were stacked using an accumulative rolling process to achieve a consistent orientation, followed by sintering to obtain porous ceramic scaffolds. The ceramic scaffolds were subsequently immersed in methyl methacrylate resin to complete the fabrication of the biomimetic composites. The mechanical and biological properties of the composites were comprehensively tested. The composites had a suitable hardness (1.09–1.63 GPa), excellent flexural strength (156.7–167.8 MPa), and fracture toughness (KIC = 2.66–3.59 MPa m1/2). Biomimetic composites are expected to mitigate the wear of natural teeth without developing fractures or deformations, while also exhibiting excellent cytocompatibility and antibacterial activity. This study investigated the factors influencing crack propagation in fracture tests and provided insights into enhancing the toughness of dental restorative materials. The biomimetic resin-ceramic composites containing Zn developed in this study have the potential to be used as functional dental restoration materials.
{"title":"Exploring the mechanical and biological properties of a resin-ceramic composite with biomimetic nacre structure containing zinc used for prosthodontics","authors":"Zhongheng Yang , Sen Zhang , Mingfeng Wang , Jiao Yan , Tao Yan , Zengqian Liu , Qiang Wang , Zhe Yi , Yuzhong Gao","doi":"10.1016/j.jmbbm.2024.106799","DOIUrl":"10.1016/j.jmbbm.2024.106799","url":null,"abstract":"<div><div>Enhancement of the mechanical and biological properties of dental restoration materials is of significant importance. Drawing inspiration from the architecture and mechanical properties of natural nacre, we employed a low-cost accumulative rolling process to develop resin-ceramic composites with suitable hardness and high toughness. Plate-like aluminum oxide powder with diameters of 5–10 μm and nano-zinc oxide (ZnO) with antibacterial properties were mixed as the ceramic phase of the composite. Aluminum oxide ceramic plates were stacked using an accumulative rolling process to achieve a consistent orientation, followed by sintering to obtain porous ceramic scaffolds. The ceramic scaffolds were subsequently immersed in methyl methacrylate resin to complete the fabrication of the biomimetic composites. The mechanical and biological properties of the composites were comprehensively tested. The composites had a suitable hardness (1.09–1.63 GPa), excellent flexural strength (156.7–167.8 MPa), and fracture toughness (K<sub>IC</sub> = 2.66–3.59 MPa m<sup>1/2</sup>). Biomimetic composites are expected to mitigate the wear of natural teeth without developing fractures or deformations, while also exhibiting excellent cytocompatibility and antibacterial activity. This study investigated the factors influencing crack propagation in fracture tests and provided insights into enhancing the toughness of dental restorative materials. The biomimetic resin-ceramic composites containing Zn developed in this study have the potential to be used as functional dental restoration materials.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106799"},"PeriodicalIF":3.3,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142635304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-04DOI: 10.1016/j.jmbbm.2024.106800
Fei Sun , Libing Xu , Jianmin Han , Hai Xu , Xinchang Li , Zeng Lin
The connection structure of zirconia dental implants significantly influences their biomechanical behavior and plays a crucial role in the overall service performance of the implant system. This study aims to compare the stress distribution of zirconia implants featuring various internal connection structures under different working conditions. Four distinct types of connection structures were designed for zirconia dental implants: triangular, quadrilateral, hexagonal, and hexalobular plus connections. Additionally, the finite element method was employed to analyze these structures under three working conditions: a static load test model, a bone level model, and a torsion model. Results indicated that in the static load test model, the hexagonal structure experienced the highest stress value at 1284.9 MPa due to its thin neck wall, whereas the hexalobular plus connected implant exhibited the lowest stress value at 1252.9 MPa. In the bone level model, the triangular connection structure demonstrated poor stress distribution for cortical bone and cancellous bone at 69.606 MPa and 7.8191 MPa, respectively. Conversely, the hexalobular plus connection yielded superior stress results for cortical bone and cancellous bone, with values of 66.24 MPa and 5.1327 MPa, respectively. In the torsion model, the hexalobular plus-connected implant exhibits the highest stress value at 237.6 MPa, while maintaining the smallest force transmission angle. Therefore, given that the abutment necessitates a greater range of installation angles and improved torque transmission, the hexalobular plus connection structure may represent the optimal choice.
{"title":"Effect of the connection structure of zirconia dental implants on biomechanical properties","authors":"Fei Sun , Libing Xu , Jianmin Han , Hai Xu , Xinchang Li , Zeng Lin","doi":"10.1016/j.jmbbm.2024.106800","DOIUrl":"10.1016/j.jmbbm.2024.106800","url":null,"abstract":"<div><div>The connection structure of zirconia dental implants significantly influences their biomechanical behavior and plays a crucial role in the overall service performance of the implant system. This study aims to compare the stress distribution of zirconia implants featuring various internal connection structures under different working conditions. Four distinct types of connection structures were designed for zirconia dental implants: triangular, quadrilateral, hexagonal, and hexalobular plus connections. Additionally, the finite element method was employed to analyze these structures under three working conditions: a static load test model, a bone level model, and a torsion model. Results indicated that in the static load test model, the hexagonal structure experienced the highest stress value at 1284.9 MPa due to its thin neck wall, whereas the hexalobular plus connected implant exhibited the lowest stress value at 1252.9 MPa. In the bone level model, the triangular connection structure demonstrated poor stress distribution for cortical bone and cancellous bone at 69.606 MPa and 7.8191 MPa, respectively. Conversely, the hexalobular plus connection yielded superior stress results for cortical bone and cancellous bone, with values of 66.24 MPa and 5.1327 MPa, respectively. In the torsion model, the hexalobular plus-connected implant exhibits the highest stress value at 237.6 MPa, while maintaining the smallest force transmission angle. Therefore, given that the abutment necessitates a greater range of installation angles and improved torque transmission, the hexalobular plus connection structure may represent the optimal choice.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106800"},"PeriodicalIF":3.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142607372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-03DOI: 10.1016/j.jmbbm.2024.106797
Baki Aksakal , Zehra Kaplan , Kadir Turhan
The influence of plasticizer glycerol (GLY) on the mechanical, structural, and thermal properties of silk fibroin (SF)/sodium alginate (SA) biocomposite films was investigated in detail. As the SF/SA ratio increased up to 65%, the SF content significantly improved the Tensile strength (σT), Young's modulus (Ey) but reduced the elongation at break (εb). To modify and enhance the elasticity and flexibility of the biocomposite films, the GLY as a plasticizer was used at different ratio from 20 to 50% for each SF/SA biocomposite films. Although the extensibility of the films was improved greatly with increasing GLY ratio, σT and Ey reduced significantly. The effect was observed more apparently for the GLY ratio starting from 35%. It was also shown that crystallinity index in the Amide I region increased as the SF/SA ratio increased to 65%. Increasing SF content improved the thermal stability of the SF/SA biocomposites. The XRD results showed that crystallinity was increased as SF/SA ratio increased. Stress-relaxation of SF/SA (30%) biocomposite films plasticized with GLY revealed that each kind of plasticized films showed a viscoelastic behavior and a fast relaxation in the first stage (1–2 min) of the processes and then continued slowly. The GLY increased the extensibility and elasticity limit of the SF/SA (30%) composite films. During the strain recovery processes, the plasticized composite films recovered completely in a quite shorter time than that of unplasticized films. It was observed higher the GLY content, the recovery times became shorter.
{"title":"The influence of plasticizer on the mechanical, structural, thermal and strain recovery properties following stress-relaxation process of silk fibroin/sodium alginate biocomposites for biomedical applications","authors":"Baki Aksakal , Zehra Kaplan , Kadir Turhan","doi":"10.1016/j.jmbbm.2024.106797","DOIUrl":"10.1016/j.jmbbm.2024.106797","url":null,"abstract":"<div><div>The influence of plasticizer glycerol (GLY) on the mechanical, structural, and thermal properties of silk fibroin (SF)/sodium alginate (SA) biocomposite films was investigated in detail. As the SF/SA ratio increased up to 65%, the SF content significantly improved the Tensile strength (σ<sub>T</sub>), Young's modulus (E<sub>y</sub>) but reduced the elongation at break (ε<sub>b</sub>). To modify and enhance the elasticity and flexibility of the biocomposite films, the GLY as a plasticizer was used at different ratio from 20 to 50% for each SF/SA biocomposite films. Although the extensibility of the films was improved greatly with increasing GLY ratio, σ<sub>T</sub> and E<sub>y</sub> reduced significantly. The effect was observed more apparently for the GLY ratio starting from 35%. It was also shown that crystallinity index in the Amide I region increased as the SF/SA ratio increased to 65%. Increasing SF content improved the thermal stability of the SF/SA biocomposites. The XRD results showed that crystallinity was increased as SF/SA ratio increased. Stress-relaxation of SF/SA (30%) biocomposite films plasticized with GLY revealed that each kind of plasticized films showed a viscoelastic behavior and a fast relaxation in the first stage (1–2 min) of the processes and then continued slowly. The GLY increased the extensibility and elasticity limit of the SF/SA (30%) composite films. During the strain recovery processes, the plasticized composite films recovered completely in a quite shorter time than that of unplasticized films. It was observed higher the GLY content, the recovery times became shorter.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"161 ","pages":"Article 106797"},"PeriodicalIF":3.3,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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