Bio-medical materials and engineering最新文献

Background: There are many reasons that could lead to finger joint arthroplasty, and the most familiar reason is osteoarthritis. Silicone finger joint are the most commonly used implants. However, these implants might fracture with time and cause wear which will lead to chronic inflammation and synovitis for the patient and then implant failure.

Objective: The aim of this study is to improve the design of the silicone finger joint and simulate the different designs using finite element analysis (FEA) simulation.

Method: Three different designs were drawn and FEA has been used in this study using Solidworks software. The first design is the silicone finger joint design without any modification, the second one is modified design with added ribs to the junction of distal stem and hinge and the third design was added filler material inside the body of the artificial joint. An axial force with 625 N that was applied on the upper part of the distal stem which is nearly represents the maximum value of the grip strength for normal males.

Results: The results showed improvement on the design in which the concentrated stress at the junction of the distal stem and hinge of the design was distributed. In addition, the Von Mises stress was stable for the modified design with added ribs and the added filler material designs after 15°.

Conclusion: The design modification could improve the stress distribution and stability of the artificial finger joint and increase the lifetime expectancy of these implants.

Background: Myocardial infarction is a serious clinical disease with high mortality and poor prognosis. Cardiomyocytes (CMs) have limited regeneration abilities after ischemic injury. Their growth and differentiation can be enhanced by contact co-culture with stem cells.

Objective: The aim was to study the contact co-culture of Dil-labeled bone marrow mesenchymal stem cells (BMSCs) and CMs for inducing differentiation of CMs from stem cells for treating myocardial infarction.

Methods: After contact co-culture, the differentiation of BMSCs into CMs was analyzed qualitatively by detecting myocardial markers (cardiac troponin T and α-smooth muscle actin) using immunofluorescence and quantitatively using flow cytometry. To examine the mechanism, possible gap junctions between BMSCs and CMs were analyzed by detecting gap junction protein connexin 43 (C×43) expression in BMSCs using immunofluorescence. The functionality of gap junctions was analyzed using dye transfer experiments.

Results: The results revealed that BMSCs in contact with CMs exhibited myocardial markers and a significant increase in differentiation rate (P < 0.05); they also proved the existence and function of gap junctions between BMSCs and CMs.

Conclusions: It was shown that contact co-culture can induce Dil-labeled BMSCs to differentiate into CM-like cells and examined the principle of gap junction-mediated signaling pathways involved in inducing stem cells to differentiate into cardiomyocytes.

Background: Collagen production in fibroblasts is important for skin tissue repair. Cell-adhesive Arg-Gly-Asp (RGD) peptides immobilized on scaffolds stimulate fibroblast collagen production, but RGD peptides in solution exhibit opposite effects. Transgenic silkworm technology enables the design of fusion positions for RGD peptides in silk fibroin molecules. The effect of RGD-fused silk fibroin in solution on fibroblast cell activity remains unclear.

Objective: To clarify the effects of RGD peptides fused to silk fibroin heavy (H)-chain or light (L)-chain on fibroblast proliferation and collagen production when RGD-fused silk fibroin proteins were added to the culture medium.

Methods: Silk fibers with RGD-fused H-chains (H-RGD) or L-chains (L-RGD) were degummed, dissolved, and dialyzed to prepare H-RGD or L-RGD aqueous solutions, respectively. These solutions were added to the fibroblast medium, and their proliferation and collagen production were quantified.

Results: Both L- and H-RGD stimulated fibroblast proliferation at a similar level, even in a solution format, but L-RGD promoted fibroblast collagen production significantly, indicating the synergistic effect of the native H-chain and RGD-fused L-chain.

Conclusion: RGD-fused silk fibroin in solution stimulated fibroblast proliferation and collagen production, depending on the fusion position of the peptides.

Background: Atherosclerosis is one of the main causes of vertebral artery stenosis, which reduces blood supply to the posterior circulation, resulting in cerebral infarction or death.

Objective: To investigate stenosis rates and locations on the development of vertebral artery plaques.

Methods: Stenosis models with varying degrees and positions of stenosis were established. The stenosis area was comprehensively analyzed using multiphase flow numerical simulation. Wall shear stress (WSS), blood flow velocity, and red blood cell (RBC) volume fraction were calculated.

Results: Blood flow velocity in 30-70% stenosis of each segment tended to increase significantly higher than normal. Downstream of 50% stenosis exhibited turbulent flow; downstream of 70% displayed reflux. Severe stenosis increases the WSS and distribution area. The mixed area of high and low WSS appeared downstream of the stenosis. The RBC volume fraction at the stenosis increased (maximum value: 0.487 at 70% stenosis in the V4), which was 1.08 times the normal volume fraction. Turbulent and backflow regions exhibited complex RBC volume fraction distributions.

Conclusion: Flow velocity, WSS, and RBC volume fraction at the stenosis increase with stenosis severity, increasing plaque shedding. Narrow downstream spoiler and reflux areas possess low WSS and high erythrocyte volume fractions, accelerating plaque growth.

Background: Pulmonary artery stenosis is a serious threat to people's life and health.

Objective: The hydrodynamic mechanism of pulmonary artery stenosis is investigated.

Methods: Numerical analysis of hemodynamics in pulmonary artery stenosis using computational fluid dynamics techniques is performed. An idealized model of pulmonary artery stenosis is established, and the model is divided into main pulmonary artery, right and left pulmonary arteries, and their branches. The sections at different positions are intercepted to study the distribution trend of maximum velocity, pressure and wall shear stress.

Results: The numerical simulation results show that the pressure drop at both ends of the narrow area is large. High velocity and wall shear stress exist in the center of stenosis, and the wall shear stress at the distal end of stenosis gradually decreases, resulting in endothelial dysfunction.

Conclusions:  To some extent, this study helps clinicians make diagnosis and treatment plans in advance and improve prognosis. This method could be used in the numerical simulation of practical models.

Background: The necessity to manufacture scaffolds with superior capabilities of biocompatibility and biodegradability has led to the production of extracellular matrix (ECM) scaffolds. Among their advantages, they allow better cell colonization, which enables its successful integration into the hosted tissue, surrounding the area to be repaired and their formulations facilitate placing it into irregular shapes. The ECM from porcine urinary bladder (pUBM) comprises proteins, proteoglycans and glycosaminoglycans which provide support and enable signals to the cells. These properties make it an excellent option to produce hydrogels that can be used in regenerative medicine.

Objective: The goal of this study was to assess the biocompatibility of an ECM hydrogel derived from the porcine urinary bladder (pUBMh) in vitro using fibroblasts, macrophages, and adipose-derived mesenchymal stem cells (AD-MCSs), as well as biocompatibility in vivo using Wistar rats.

Methods: Effects upon cells proliferation/viability was measured using MTT assay, cytotoxic effects were analyzed by quantifying lactate dehydrogenase release and the Live/Dead Cell Imaging assay. Macrophage activation was assessed by quantification of IL-6, IL-10, IL-12p70, MCP-1, and TNF-α using a microsphere-based cytometric bead array. For in vivo analysis, Wistar rats were inoculated into the dorsal sub-dermis with pUBMh. The specimens were sacrificed at 24 h after inoculation for histological study.

Results: The pUBMh obtained showed good consistency and absence of cell debris. The biocompatibility tests in vitro revealed that the pUBMh promoted cell proliferation and it is not cytotoxic on the three tested cell lines and induces the production of pro-inflammatory cytokines on macrophages, mainly TNF-α and MCP-1. In vivo, pUBMh exhibited fibroblast-like cell recruitment, without tissue damage or inflammation.

Conclusion: The results show that pUBMh allows cell proliferation without cytotoxic effects and can be considered an excellent biomaterial for tissue engineering.

Background: During gait, healthy knee coronal kinematics of each bony axis and lower extremity alignment are important because they could be useful as reference data for several surgeries and provide clarification of the etiology of diseases around the knee in healthy participants; however, it remains unknown.

Objective: The objective of this study was to clarify the kinematics of lower extremity alignment and the bony axes relative to the ground during gait, focused on the coronal plane, in healthy individuals by applying our unique three-dimensional (3D) motion analysis.

Methods: The study included 21 healthy individuals, including 9 healthy females and 12 healthy males with an average age of 36 ± 17 years. Knee kinematics were calculated in a gait analysis by combining the data from a motion-capture system and a 3D lower-extremity alignment assessment system on biplanar long-leg radiographs by using a 3D-2D registration technique. The main kinematic parameters were the dynamic position change relative to the ground, applying the femoral anatomical axis (FAA), tibial anatomical axis (TAA), and dynamic alignment in the coronal plane during the stance phase of gait.

Results: The average changes in FAA, TAA, and dynamic varus alignment were 3.7° ± 1.2°, 3.5° ± 0.8°, and 3.0° ± 1.2°, respectively. The TAA tilted laterally during the loading response and a plateau area appeared afterwards; the FAA gradually inclined laterally until the terminal stance phase, and the dynamic alignment showed varus angular change during the loading response.

Conclusions: The tibia and femur were found to change approximately 2-5° of the position of the bony axes relative to the ground. In terms of clinical relevance, our findings can be used to clarify the etiology of diseases around the knee joint and as reference data for surgeries.

Background: In the preventive treatment protocol, providing remineralization of the tissue in demineralized dentin caries is an important step.

Objective: In this in vitro study, the effectiveness of remineralization agents in natural caries-affected dentin (NCAD) were investigated.

Methods: Forty caries slices were prepared from permanent molar dentin with International Caries Detection and Assessment System (ICDAS 2) (Code 3). The interventions with 8 days pH cycling were as follows: Deionized water (DW); 5% Sodium Fluoride (5% NaF) Varnish; Casein Phosphopeptide-Amorphous Calcium Fluoride Phosphate (CPP-ACFP); Calcium Glyserophosphate (CaGP) + Magnesium (Mg) + Xylitol. DIAGNOdent (Laser Fluorescence, LF), Surface Microhardness (SMH), and X-ray Fluorescence (XRF) Spectroscopy measurements were calculated before and after pH cycling.

Results: LF values decreased between 5% NaF, CCP-ACFP and CaGP. NCAD treated with 5% NaF, CaGP and CCP-ACFP exhibited statistically higher hardness compared to the control group. After 5% NaF application, SMH values were significantly higher than the others. There was no statistically significant difference between baseline and after pH cycling hardness of the control group. After cycling, XRF showed that Ca and P concentrations were increased in all groups.

Conclusion: The application of agents used in the study could be recommended and promoted as a treatment option of caries dentin for conventional management of caries.

Background: Magnesium (Mg) enhances the bone regeneration, mineralization and attachment at the tissue/biomaterial interface.

Objective: In this study, the effect of Mg on mineralization/osseointegration was determined using (Ti,Mg)N thin film coated Ti6Al4V based plates and screws in vivo.

Methods: TiN and (Ti,Mg)N coated Ti6Al4V plates and screws were prepared using arc-PVD technique and used to fix rabbit femur fractures for 6 weeks. Then, mineralization/osseointegration was assessed by surface analysis including cell attachment, mineralization, and hydroxyapatite deposition on concave and convex sides of the plates along with the attachment between the screw and the bone.

Results: According to Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analyses; cell attachment and mineralization were higher on the concave sides of the plates from both groups in comparison to the convex sides. However, mineralization was significantly higher on Mg-containing ones. The mean gray value indicating mineralized area after von Kossa staining was found as 0.48 ± 0.01 and 0.41 ± 0.04 on Mg containing and free ones respectively. Similarly, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analyses showed that hydroxyapatite growth was abundant on the Mg-containing and concave sides of the plates. Enhanced mineralization and strong attachment to bone were also detected in EDS and SEM analyses of Mg-containing screws.

Conclusion: These findings indicated that (Ti,Mg)N coatings can be used to increase attachment at the implant tissue interface due to accelerated mineralization, cell attachment, and hydroxyapatite growth.

Background: Mesenchymal stem cell (MSC)-based therapies offer potential for bone repair. MSC spheroid cultures may harbor enhanced therapeutic potential over MSC monolayers through increased secretion of trophic factors. However, the impact of spheroid size on trophic factor expression is unclear.

Objective: We investigated the effect of spheroid size on trophic factor-related gene expression.

Methods: KUM10, a murine MSC line was used. RNA-seq was used to screen the transcriptional profiles of MSC monolayer and spheroid cultures. Differentially expressed genes identified in RNA-seq were evaluated by q-PCR in cultures of 5 × 104 (S group), 5 × 105 (M group), 5 × 106 (L group) cells/well.

Results: Comparison of expression levels between KUM10 monolayer and spheroid cultures identified 2140 differentially expressed genes, of which 1047 were upregulated and 1093 were downregulated in KUM10 spheroids. Among these, 12 upregulated genes (Bmp2, Fgf9, Fgf18, Ngf, Pdgfa, Pdgfb, Tgfb1, Vegfa, Vegfc, Wnt4, Wnt5a, Wnt10a) were associated with secretory growth factors. Of these, expression of Fgf9, Fgf18, Vegfa and Vegfc was elevated in the L group, and Pdgfb and Tgfb1 was elevated in the S group.

Conclusions: Spheroid size may impact trophic factor expression. Our results will be useful for future studies assessing the utility of MSC spheroids for treating bone injury.