Bio-medical materials and engineering最新文献

Background: A combination of synthetic porous materials and BMP-2 has been used to promote fracture healing. For bone healing to be successful, it is important to use growth factor delivery systems that enable continuous release of BMP-2 at the fracture site. We previously reported that in situ-formed gels (IFGs) consisting of hyaluronan (HyA)-tyramine (TA), horseradish peroxidase and hydrogen peroxide enhance the bone formation ability of hydroxyapatite (Hap)/BMP-2 composites in a posterior lumbar fusion model.

Objective: We examined the effectiveness of IFGs-HyA/Hap/BMP-2 composites for facilitating osteogenesis in refractory fracture model mice.

Methods: After establishing the refractory fracture model, animals were either treated at the site of fracture with Hap harboring BMP-2 (Hap/BMP-2) or IFGs-HyA with Hap harboring BMP-2 (IFGs-HyA/Hap/BMP-2) (n = 10 each). Animals that underwent the fracture surgery but did not receive any treatment were considered the control group (n = 10). We determined the extent of bone formation at the fracture site according to findings on micro-computed tomography and histological studies four weeks following treatment.

Results: Animals treated with IFGs-HyA/Hap/BMP-2 demonstrated significantly greater bone volume, bone mineral content and bone union than those treated with vehicle or IFG-HyA/Hap alone.

Conclusions: IFGs-HyA/Hap/BMP-2 could be an effective treatment option for refractory fractures.

Background: Advances in bone tissue engineering offer novel options for the regeneration of bone tissue. In the current clinical treatment, the method of accelerating bone tissue regeneration rate by promoting early angiogenesis has been widely accepted.

Objective: This study aimed to develop a long-acting slow-release system using the pro-angiogenic drug tetramethylpyrazine (TMPZ) and pro-osteogenic drug icariin (ICA), which can be administered locally to achieve the sequential release of TMPZ and ICA for better clinically efficiency in the treatment of bone defects.

Methods: This study aimed to prepare microspheres with a core-shell structure using two polymers, poly lactic-co-glycolic acid and silk fibroin, by coaxial electrostatic spraying. Based on the therapeutic model for bone defects, the pro-angiogenic drug TMPZ and pro-osteogenic drug ICA were encapsulated in the shell and core layers of the microspheres, respectively. Subsequently, TMPZ and ICA were released sequentially to promote early angiogenesis and late osteogenesis, respectively, at the site of the bone defect. The optimal preparation parameters for preparing the drug-loaded microspheres were identified using the univariate controlled variable method. Additionally, microsphere morphology and core-shell structure, such as physical properties, drug-loading properties, in vitro degradation and drug release patterns, were characterised using scanning electron microscope and laser scanning confocal microscopy.

Results: The microspheres prepared in this study were well-defined and had a core-shell structure. The hydrophilicity of the drug-loaded microspheres changed compared to the no-load microspheres. Furthermore, in vitro results indicated that the drug-loaded microspheres with high encapsulation and loading efficiencies exhibited good biodegradability and cytocompatibility, slowly releasing the drug for up to three months.

Conclusion: The development of the drug delivery system with a dual-step release mechanism has potential clinical applications and implications in the treatment of bone defects.

Background: Modulation of macrophage polarization is required for effective tissue repair and regenerative therapies. Therapeutic modulation of macrophages from an inflammatory M1 to a fibrotic M2 phenotype could help in diseases, such as chronic wounds, which are stalled in a prolonged and heightened inflammatory stage within the wound healing process.

Objective: This study evaluates the efficiency of a pullulan/gelatin nanofiber scaffold loaded with retinoic acid (RA) and adipose-derived mesenchymal stem cells (ASCs) to modulate M1 to M2 anti-inflammatory transition.

Methods: Scaffolds were fabricated by electrospinning, and crosslinked using ethylene glycol diglycidyl ether (EGDE). Exposure of RA and/or ASCs to cultured macrophages have been shown to promote M1 to M2 transition. Pullulan was chosen as a scaffold material due to its ability to quench reactive oxygen species, key signaling molecules that play an important role in the progression of inflammation, as well as for its excellent mechanical properties. Gelatin was chosen as an additional scaffold component due to the presence of cell-binding motifs and its biocompatibility. Scaffold compositions examined were 75:25 and 50:50, pullulan:gelatin. The scaffolds were crosslinked in 1:70 and 1:50 EGDE:EtOH. The scaffold composition was determined via FTIR. For the present study, the 75:25 pullulan:gelatin crosslinked with 1:70 EGDE:EtOH, forming nanofibers 328 ± 47.9 nm (mean ± SD) in diameter, was chosen as the scaffold composition due to its lower degradation and release rate, which allows a sustained delivery of RA.

Results: The scaffold composition degraded to approximately 80% after 14 days, with approximately 38% of the drug released after 7 days. THP-1 monocytic cells were induced into a M1 macrophage phenotype through stimulation with lipopolysaccharide (LPS) and gamma interferon (IFN-γ). These M1 macrophages were the exposed to scaffolds loaded with RA and ASCs, to induce differentiation to an M2 phenotype.

Conclusion: Gene expression quantitation by qPCR showed a reduction of M1 biomarkers, tumor necrosis factor alpha (TNFα) and interleukin 1β (IL1β), and an increase of M2 biomarker CCL22 after 2 days of exposure, suggesting successful M1 to M2 transition.

Background: Calcium phosphate cements (CPCs) are biocompatible materials that have been evaluated as scaffolds in bone tissue engineering. At present, the stem cell density of inoculation on CPC scaffold varies.

Objective: The aim of this study is to analyze the effect of seeding densities on cell growth and osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) on a calcium phosphate cements (CPCs) scaffold.

Methods: BMMSCs derived from minipigs were seeded onto a CPC scaffold at three densities [1 million/mL (1M), 5 million/mL (5M) and 25 million/mL 25M)], and cultured for osteogenic induction for 1, 4 and 8 days.

Results: Well adhered and extended BMMSCs on the CPC scaffold showed significantly different proliferation rates within each seeding density group at different time points (P < 0.05). The number of live cells per unit area in 1M, 5M and 25M increased by 3.5, 3.9 and 2.5 folds respectively. The expression of ALP peaked at 4 days post inoculation with the fold-change being 2.6 and 2.8 times higher in 5M and 25M respectively as compared to 1M. The expression levels of OC, Coll-1 and Runx-2 peaked at 8 days post inoculation.

Conclusions: An optimal seeding density may be more conducive for cell proliferation, differentiation, and extracellular matrix synthesis on scaffolds. We suggest the optimal seeding density should be 5 million/mL.

Background: Suprahyoid muscles behavior during the tongue lifting movement has not yet been elucidated.

Objective: The purpose of this study was to investigate the potential of elastography imaging to examine developmental oral dysfunction in children and oral hypofunction in older adults using sonography.

Methods: Tongue pressure was measured using a manometer with a probe. The tongue pressure was measured with simultaneously scanning the geniohyoid muscle (GHM) and the anterior belly of the digastric muscle (DGM) using sonographic elastography. Sagittal images of the GHM and coronal images of the DGM were used for the strain ratio measurement. The strain ratio of the muscles was measured three times for each subject with the tongue pressure values of 0-30 kPa.

Results: The strain ratio of the GHM were higher than those of the DGM at tongue pressure of 10, 20 and 30 kPa. The strain ratio of the GHM increased as the tongue pressure increased in all participants. In contrast, the strain ratio of the DGM tended to slowly decrease as tongue pressure increased in female participants.

Conclusion: Sonographic elastography is useful for visual and quantitative evaluation of elastic properties in suprahyoid muscles during tongue lifting movements.

Background: It is of great significance to understand the effect of the different corrosion behaviors of magnesium (Mg) alloys manufactured using different casting methods and implanted with different methods on the long-term implantation to expand the application of Mg-based biomedical implants.

Objective: The effects of four different casting and rolling speeds on the microstructure of an Mg-rare earth (Mg-Re) alloy were analyzed using electron backscatter diffraction (EBSD).

Method: Four Mg alloys were obtained using vertical two-roll casting (TRC) at 10 m/min, 16 m/min, 24 m/min, and 30 m/min, and their microstructure, corrosion behavior and bone reaction in vivo were studied.

Results: The corrosion resistance of the alloy increases with an increase in casting speed and finer grain size of the cast-rolled parts. The Mg-Re alloys with TRC-10 m/min and TRC-30 m/min were selected for animal experiments. The two Mg alloys were made into metal rods and inserted into the rat femur to simulate the effect of Mg-Re on femoral healing under an injury condition. The rods were implanted for a long time to judge the effects of the Mg-Re alloy on the body. The TRC-30 m/min implants obtained highly mature new bone tissue in the case of bone injury.

Conclusion: The in vivo experiments showed that the corrosion resistance of the TRC-30 m/min implant was better than that of the TRC-10 m/min implant. After 32 weeks of implantation, there were no pathological changes in the liver, heart, or kidney of rats in the TRC-30 m/min group, and the cell structure was normal.

Background: Percutaneous kyphoplasty (PKP) or percutaneous vertebroplasty (PVP) are commonly employed for Kummell's disease in stages II-III; however, these techniques produce some complications.

Objective: To compare the clinical efficacy and imaging results of percutaneous vertebroplasty + bone cement-augmented short-segment pedicle screw fixation (PSPVP) versus transpedicular intracorporeal bone grafting + pedicle screw fixation (PSIBG) in the treatment of stage II-III Kummell's disease.

Methods: A total of 69 patients admitted between November 2017 and March 2021 were included in this study; 36 of these were treated with PSPVP, and 33 were treated with PSIBG. Patients in the two groups were compared in terms of perioperative, follow-up, and imaging data.

Results: No statistically significant differences were found between the two groups in terms of operation duration (P > 0.05). However, the PSPVP group was superior to the PSIBG group in terms of incision length, intraoperative blood loss, and length of stay (P < 0.05). All patients were followed up for more than 12 months. The VAS score, height of anterior vertebral margin, kyphosis Cobb angle, wedge angle of the affected vertebra at seven days after surgery and last follow-up, and the ODI index at the last follow-up of the two groups were significantly improved compared with figures before surgery (P < 0.05). Compared with values before surgery, no statistically significant differences were found in the height of the posterior vertebral margin in the PSPVP group at seven days after surgery and at the last follow-up (P > 0.05). There were also no statistically significant differences in the VAS score, ODI index, kyphosis Cobb angle, and wedge angle of the affected vertebra between the two groups at corresponding time points (P > 0.05). The heights of the anterior and posterior vertebral margins in the PSIBG group were better than those in the PSPVP group after surgery and at the last follow-up (P < 0.05). In the PSPVP group, a pedicle screw fracture occurred in one patient two months after surgery, while an upper adjacent vertebral fracture occurred in one patient eight months after surgery.

Conclusion: Both PSPVP and PSIBG can achieve good early clinical efficacy in the treatment of stage II-III Kummell's disease, with PSPVP being relatively less invasive while producing a poorer orthopedic effect and more complications than PSIBG.

Background: Although the internal fixation technique for scoliosis is effective, there is a great risk of nail placement in actual operation.

Objective: To compare the effects of three different nail placement strategies on LenkeC patients with scoliosis under cyclic loading.

Methods: Firstly, the finite element model was established by using CT scanning images and X-ray images of patients with LenkeC scoliosis. Secondly, the validity of the model was verified. Finally, the harmonic response analysis and transient dynamic analysis were carried out.

Results: The results showed that the maximum amplitude of each vertebral body appeared in the Z direction at the third natural frequency and the amplitudes of each corresponding vertebral body were very close under three kinds of nail placement. Under different nail placement methods, the uneven distribution of nails would make the model produce obvious stress concentration, but the principal stress of vertebral body and nail rod was far lower than its own yield strength. This showed that under the axial cyclic load, the vertebral bodies of scoliosis tended to have larger impact in Z direction. From the point of view of dynamics, it was feasible to reduce a certain number of nails in operation.

Conclusion: This paper revealed that it was feasible to reduce a certain number of nails during surgery.

Background: Hydrogel is a three-dimensional structure that has the potential to absorb and retain water within the mesh of its porous network structure. Currently hydrogels made from natural biopolymers are preferred in the discipline of biomedical applications because of their blood compatibility, adhesion of platelets and protein binding, ease of administration and delivery of ingredients to the place of action.

Objective: The aim of this work was to prepare a hydrogel from natural biopolymers and evaluate its blood compatibility, swelling nature, prolonged degradation and morphological features in order to further recommend its clinical use.

Methods: To prepare hydrogels, different combinations of gelatin, dialyzed SF, curcumin and N, N methylene bisacrylamide (MBA) were evenly mixed on a magnetic stirrer. After an hour of the gelation process it was kept in a refrigerator at 4 °C. For the characterization and biocompatibility studies of hydrogel, the swelling test and biodegradation analysis, SEM, FTIR, in vitro coagulation tests, total serum albumin and cholesterol level analysis were applied.

Results: Injectable hydrogels were successfully made with significantly correlated combinations of polymers. The analysis of physiochemical biocompatibility studies and morphological characterization were done effectively.

Conclusion: The results of the study indicate that hydrogels made from natural biopolymers are a potential source and suitable matrices with excellent biocompatible nature acting as a useful device in delivering drugs.

Background: Pain related to the sacroiliac joint (SIJ) accounts for low back pain in 15%-30% of patients. One of the most common treatment options is the use of pelvic belts. Various types of pelvic belts exist; however, the mechanisms underlying treatment and their effectiveness remain unclear to date.

Objective: To analyze stress distribution in the pelvis when a pelvic rubber belt or a padded pelvic belt is applied, to assess the effectiveness of treatment from a numerical biomechanical perspective.

Methods: The pressure distribution at the pelvic belts was measured using a device and subsequently modeled with the finite element method of a pelvis with soft tissues. The stress environment when wearing a pelvic belt in a double-leg stance was simulated.

Results: With the application of pelvic belts, the innominate bone rotated outward, which was termed an out-flare. This caused the SIJ to compress and cause reduction in sacrotuberous, sacrospinous, interosseous, and posterior sacroiliac ligament loading. Padded pelvic belts decreased the SIJ displacement to a greater extent than in pelvic rubber belts.

Conclusion: Pelvic belts aid in compressing the SIJ and reduce its mobility.