Optimal structural characteristics of bone tissue engineering scaffolds from bionics and PSO-BP-NSGA III integrated algorithm

Gene-mediated Restoration of Normal Myofiber Elasticity in Dystrophic Muscles

Bimodal structured Ti-base alloy with large elasticity and low Young's modulus

Bioelectronics are a crucial means for biomedical diagnosis and therapeutic, as they seamlessly interface with biological tissues. Biomaterials-based ionic hydrogels have been recognized as ideal electrode materials for bioelectronics. However, biomaterials-based ionic hydrogels suffer from low ionic conductivity and high Young's modulus, which limit their performance in electrophysiological monitoring. Here, we developed a biomaterials-based ionic hydrogel inspired by the ion channel receptor in neuron membranes, and this bio-inspired hydrogel (BIH) offers a high ionic conductivity and low Young's modulus simultaneously. By mimicking the ion-accelerating function of ion channel receptors in neuron membranes, the sulfonate groups and quaternary ammonium groups on zwitterionic side chains of poly(sulfobetaine methacrylate) (pSBMA) construct artificial ion channels to accelerate cation and anion transport in BIH, respectively. The brush-like polymer structure of the pSBMA reduce chain entanglement and substantially lower the Young's modulus of BIH. Compared with other reported biomaterials-based ionic hydrogels, the BIH simultaneously possesses higher ionic conductivity (7.04 S m-1) and lower Young's modulus (7.2 kPa). The BIH also has excellent interfacial adhesion with tissues resulting from electrostatic interactions. Owing to the high conductivity and low Young's modulus, the BIH has a lower interfacial impedance with tissues that that of commercial electrodes, and the good adhesive property of BIH ensures its interfacial stability with tissues when collecting electrophysiological signals. The BIH is capable of collecting high-quality both epidermal and in vivo electrophysiological signals, and the signal-to-noise ratio (SNR) of electrocardiogram (ECG) and electromyogram (EMG) signals are significantly higher than those of commercial electrodes. Such an BIH with biomimetic ion channels and low Young's modulus could provide new insights into the rational design of biomaterials-based ionic hydrogels for bioelectronics.

Titanium Alloys

Objective: To investigate the influence of porosity and Young's modulus of gelatin methacrylate anhydride (GelMA) hydrogels on the biological behavior of mouse bone marrow mesenchymal stem cells (BMSCs), and to provide a theoretical basis for the development of tissue engineering scaffolds for skin wound repair. Methods: This study was an experimental study. GelMA hydrogels that were prepared by photo-crosslinking 50 g/L GelMA solution for 30 and 60 seconds and 150 g/L GelMA solution for 30 and 60 seconds, were designated respectively as low-concentration short-time group, low-concentration long-time group, high-concentration short-time group, and high-concentration long-time group. The porosity of the 4 groups of hydrogels after freeze-drying for 48 hours was measured and calculated using Image J 1.54 software. The Young's modulus of the 4 groups of hydrogels was detected using a Young's modulus tester. The correlation between the porosity and Young's modulus was evaluated and a predictive model between them was established. The remaining mass percentages of the 4 groups of hydrogels after soaking in phosphate buffered saline for 7 days were calculated. BMSCs were isolated from the femurs of 10 C57BL/6 mice aged 1 day of unknown sex. Cell-loaded GelMA hydrogels were prepared by mixing BMSCs with 50 g/L GelMA solution and photo-crosslinking for 30 and 60 seconds, and by mixing BMSCs with 150 g/L GelMA solution and photo-crosslinking for 30 and 60 seconds, and were designated respectively as low-concentration short-time cell-loaded group, low-concentration long-time cell-loaded group, high-concentration short-time cell-loaded group, and high-concentration long-time cell-loaded group. The cell survival in the 4 cell-loaded groups of hydrogels after 7 days of culture was detected using a live/dead cell kit, and the cell survival rate was calculated. After 10 days of osteogenic induction culture of the hydrogels in the 4 cell-loaded groups, the mRNA expressions of osteogenic-related factors Runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP), and stemness-related factors SRY-box transcription factor 2 (Sox2) and Nanog in the cells were detected by real-time fluorescence quantitative reverse transcription polymerase chain reaction; the protein expressions of Runx2 and Nanog in the cells were detected by immunofluorescence method. Except for the protein expression (qualitative observation), the sample size of each group for the other indicators was three. Results: The porosity of hydrogels in low-concentration short-time group, low-concentration long-time group, high-concentration short-time group, and high-concentration long-time group after freeze-drying for 48 hours decreased successively, being (92.7±0.9)%, (85.0±1.8)%, (68.6±1.2)%, and (56.3±5.8)%, respectively; the Young's modulus increased successively, being (5.933±0.020), (7.803±0.089), (20.772±0.106), and (22.498±0.060) kPa, respectively. Except for the Young's modulus of hydrogels between the high-concentration long-time group and high-concentration short-time group (P>0.05), the pairwise comparisons of hydrogel porosity or Young's modulus among the remaining groups showed statistically significant differences (P<0.05). The porosity and Young's modulus of the hydrogels were significantly negatively correlated (R2=0.91, P<0.05), and a linear equation predictive model between them was established accordingly. After soaking for 7 days, the remaining mass percentages of hydrogels in low-concentration long-time group, high-concentration short-time group, and high-concentration long-time group were significantly higher than that in low-concentration short-time group (P<0.05), and the remaining mass percentage of hydrogels in high-concentration long-time group was significantly higher than that in low-concentration long-time group (P<0.05). After 7 days of culture, a large number of live cells was observed in the 4 cell-loaded groups of hydrogels, and there was no statistically significant difference in the overall comparison of cell survival rate among the groups (P>0.05). After 10 days of osteogenic induction culture, the mRNA expressions of Runx2 and ALP in the cells of hydrogels in high-concentration long-time cell-loaded group were significantly higher than those in the other three cell-loaded groups (P<0.05), and the mRNA expressions of Sox2 and Nanog in the cells of hydrogels in low-concentration short-time cell-loaded group were significantly higher than those in the other three cell-loaded groups (P<0.05); the protein expression of Runx2 in the cells of hydrogels in high-concentration long-time cell-loaded group was the highest, and the protein expression of Nanog in the cells of hydrogels in low-concentration short-time cell-loaded group was the highest. Conclusions: The porosity and Young's modulus of GelMA hydrogel synergistically regulate the biological behavior of mouse BMSCs, where high porosity and low Young's modulus are conducive to maintaining stemness, while low porosity and high Young's modulus drive osteogenic differentiation.

ObjectiveTo investigate the Young's modulus value of infraspinatus tendons using shear wave elastography (SWE) technique in normal adults, and to analyze the influence of gender, postures, exercise, and dominant side on Young's modulus of infraspinatus tendons.MethodsThis is a prospective cross‐sectional study. From January 2019 to July 2020, 14 healthy subjects were identified, including seven males and seven females aged between 24 to 34, with a mean age of 27.67 ± 3.08 years. The Young's modulus of their infraspinatus tendons was measured by two operators using SWE in neutral and maximum external rotation positions of both sides before exercise and the dominant side after exercise. The Young's modulus values in different sexes, different postures, before vs after exercise, and dominant vs non‐dominant side were statistically analyzed.ResultsAll 14 subjects completed the data collection process. The mean Young's modulus values of infraspinatus tendon for dominant sides in neutral position were 33.04 ± 3.01 kPa for males and 28.76 ± 3.09 kPa for females. And for non‐dominant sides in the neutral position, the values were 33.02 ± 2.38 kPa for males and 28.86 ± 2.47 kPa for females. In the maximum external rotation position, the values for dominant sides were 50.19 ± 4.86 kPa for males and 42.79 ± 4.44 kPa for females, and for non‐dominant sides were 50.95 ± 3.24 kPa for males and 42.42 ± 3.66 kPa for females. After exercise, the mean Young's modulus values of infraspinatus tendon for dominant sides in neutral position were 54.56 ± 3.76 kPa for males and 46.66 ± 5.99 kPa for females. And for the maximum external rotation position, the values were 59.13 ± 3.78 kPa for males and 54.49 ± 5.67 kPa for females. The Young's modulus of infraspinatus tendon in the neutral and maximum external rotation positions showed statistically significant differences in males and females, as well as before and after exercise (P < 0.05). However, the difference in Young's modulus between the dominant and non‐dominant sides was not statistically significant (P > 0.05). Intergroup reliability between both operators was excellent (ICC > 0.85).ConclusionThere are gender‐related differences and post‐exercise increase in Young's modulus, yet such a difference cannot be witnessed between the dominant and non‐dominant sides.

High strength and Young's modulus of wet-coagulated bodies is key to the success of a direct coagulation casting (DCC) process. The yield strength and Young's modulus of wet-coagulated alumina bodies prepared at various concentrations of ammonium poly(acrylate) dispersant and MgO coagulating agent has been evaluated. The yield strength and Young's modulus of the wet-coagulated bodies, prepared at a MgO concentration equivalent to react with the dispersant, increased with an increase in the dispersant concentration due to the binding of alumina particles by the Mg-poly(acrylate) formed by the reaction between the dispersant and MgO. Addition of MgO higher than the equivalent amount to react with the dispersant increased the yield strength, Young's modulus, and brittleness of the wet-coagulated bodies. This is due to a combination of an increase in the cohesive force between particles and a decrease in homogeneity of the particle network in the wet-coagulated body induced by heterocoagulation of alumina and MgO particles having opposite surface charges. The high yield strength (up to 472 kPa) and Young's modulus (up to 110 MPa) achieved would facilitate easy and successful removal of the wet-coagulated bodies even from intricate shape molds.

Effect of stress-induced α″ martensite on Young's modulus of β Ti–33.6Nb–4Sn alloy

Experimental studies of carbon nanotubes (CNTs) obtained through different synthesis routes show considerable variability in their mechanical properties. The strongest CNTs obtained so far had a high Young's modulus of 1 TPa but could only be produced in gram scale quantities. The synthesis by catalytic chemical vapor deposition, a method that holds the greatest potential for large-scale production, gives CNTs with a high defect density. This leads to low Young's modulus values below 100 GPa for multiwall CNTs. Here we performed direct measurements of the mechanical properties of catalytically grown CNTs with only a few walls and find a Young's modulus of 1 TPa. This high value is confirmed for CNTs grown under two different growth conditions where the synthesis parameters such as the hydrocarbon source, catalyst material, and the synthesis temperature were varied. The results indicate that the observed difference in the Young's modulus for the catalytically grown CNTs with high and low numbers of walls is probably related to the growth mechanism of CNT.

Here, a new technology was developed to selectively produce areas of high and low surface Young's modulus on biomedical polymer films using micropatterns. First, an elastic polymer film was adhered to a striped micropattern to fabricate a micropattern-supported film. Next, the topography and Young's modulus of the film surface were mapped using atomic force microscopy. Contrasts between the concave and convex locations of the stripe pattern were obvious in the Young's modulus map, although the topographical map of the film surface appeared almost flat. The concave and convex locations of a polymer film supported by a different micropattern also contrasted clearly. The resulting Young's modulus map showed that the Young's modulus was higher at convex locations than at concave locations. Hence, regions of high and low stiffness can be locally generated based on the shape of the micropattern supporting the film. When cells were cultured on the micropattern-supported films, NIH3T3 fibroblasts preferentially accumulated in convex regions with high Young's moduli. These findings demonstrate that this new technology can regulate regions of high and low surface Young's modulus on a cellular scaffold with high planar resolution, as well as providing a method for directing cellular patterning. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 976-985, 2018.

Despite the importance of single-crystal elastic constants of β-phase titanium alloys in understanding their low Young's modulus—a property crucial for many applications, such data are often difficult to obtain when the alloy composition is close to the instability limit of the β phase, where the presence of α" martensite precludes the fabrication of β-phase single crystal. In the present study, we extracted the single-crystal elastic constants of such a β-phase titanium alloy with low Young's modulus, Ti-36Nb-5Zr (wt. %), from polycrystalline specimens by using an in-situ synchrotron X-ray diffraction technique. It is indicated that the low Young's modulus of the alloy originates from the anomalously low shear modulus C44 as well as the low shear modulus C′, which is different from a common viewpoint that the Young's modulus of β-phase titanium alloys is dominantly controlled by the C′. This suggests that low C44 is an important contributor to low Young's modulus for instable β-phase titanium alloys.

Mechanical compatibility of titanium implants in hard tissues

Optimizing the cell compatibility and mechanical properties in TiZrNbTa medium-entropy alloy/β-Ti composites through phase transformation

Planar auxeticity from elliptic inclusions

The optimal Young's modulus of material of orthopedic devices for fracture treatment is still unknown. The purpose of present study was to evaluate the impacts of intramedullary nails composed of a titanium alloy with low Young's modulus, on accelerating fracture healing compared with stainless steel with high Young's modulus. A β-type TiNbSn alloy with a low Young's modulus close to that of human cortical bone was developed for clinical application. TiNbSn alloy with a Young's modulus of 45 GPa and stainless steel with a Young's modulus of 205 GPa were compared, with respect to the impacts on fracture healing. Fracture and fixation using intramedullary nail were performed on the right tibiae of C57BL/6 mice. The assessment of bone healing was performed via micro-computed tomography, histomorphometry, and quantitative reverse transcription polymerase chain reaction. In micro-computed tomography, larger bone volumes were observed in the fracture callus treated with TiNbSn alloy in comparison with those treated with stainless steel. Histological assessments confirmed accelerated cartilage absorption and new bone formation in the TiNbSn alloy group compared with the stainless steel group. The expression of Col1a1, Runx2, Dkk1, and Acp5 was higher in the TiNbSn alloy group, while that of Col2a1 and Col10a1 was lower in the late phase. The present study demonstrated that the fixation by intramedullary nails with TiNbSn alloy offered an accelerated fracture healing with promotion of bone formation via increased Runx2 expression. TiNbSn alloy might be a promising material for fracture treatment devices.