Bio-Medical Materials and Engineering - Volume 31, issue 3

Authors: Zhang, Yi | Zhao, Zhao | Xu, Hui-jie | He, Chong | Peng, Hao | Gao, Zhan | Xu, Zhi-yong

Article Type: Research Article

Abstract: BACKGROUND: Snoring source analysis is essential for an appropriate surgical decision for both simple snorers and obstructive sleep apnea/hypopnea syndrome (OSAHS) patients. OBJECTIVE: As snoring sounds carry significant information about tissue vibrations within the upper airway, a new feature entitled compressed histogram of oriented gradients (CHOG) is proposed to recognize vibration patterns of the snoring source acoustically by compressing histogram of oriented gradients (HOG) descriptors via the multilinear principal component analysis (MPCA) algorithm. METHODS: Each vibration pattern corresponds to a sole or combinatorial vibration among the four upper airway soft tissues of soft palate, lateral pharyngeal …wall, tongue base, and epiglottis. 1037 snoring events from noncontact sound recordings of 76 simple snorers or OSAHS patients during drug-induced sleep endoscopy (DISE) were evaluated. RESULTS: With a support vector machine (SVM) as the classifier, the proposed CHOG achieved a recognition accuracy of 89.8% for the seven observable vibration patterns of the snoring source categorized in our most recent work. CONCLUSION: The CHOG outperforms other single features widely used for acoustic analysis of sole vibration site. Show more

Keywords: Snoring source analysis, vibration pattern recognition, compressed histogram of oriented gradients, multilinear principal component analysis

DOI: 10.3233/BME-201086

Citation: Bio-Medical Materials and Engineering, vol. 31, no. 3, pp. 143-155, 2020

Authors: Nagayama, Kazuaki | Nishimiya, Kouhei

Article Type: Research Article

Abstract: BACKGROUND: Vascular smooth muscle cells (VSMCs) are one of the main components of arterial walls and actively remodel the arterial walls in which they reside through biomechanical signals applied to themselves. Contractile or differentiated VSMCs have been observed in normal blood vessels. In pathological vascular conditions, they become dedifferentiated from contractile to non-contractile or synthetic cells, and a similar change is observed when VSMCs are placed in culture conditions. The mechanisms regulating VSMC differentiation remain unclear at this stage. OBJECTIVE: In this paper we investigated the effects of substrate stiffness on the morphology, intercellular tension, and differentiation of …VSMCs. METHODS: Rat VSMCs were cultured on polyacrylamide (PA) gels, with elastic moduli of 15 kPa, 40 kPa, and 85 kPa, and PDMS substrate with elastic modulus of 1 MPa, and their morphology, intercellular tension, and contractile differentiation were assessed. RESULTS: Using fluorescence microscope image-based analysis and nano-indentation imaging with atomic force microscopy, we found that cell spreading and stiffening were induced by substrate stiffening in VSMCs. Interestingly, VSMCs on PA gel substrates with medium stiffness (40 kPa) showed significant elongation and shape polarization, and their 𝛼-SMA with F-actin cytoskeleton expression ratio was significantly higher than those of cells on other substrates. CONCLUSION: The results indicate an existing optimal substrate stiffness for promoting VSMC differentiation, and also indicate that cell shape polarization might be a key factor for VSMC differentiation. Show more

Keywords: Cell biomechanics, mechanobiology, substrate stiffness, smooth muscle cell differentiation, atomic force microscopy (AFM)

DOI: 10.3233/BME-201087

Citation: Bio-Medical Materials and Engineering, vol. 31, no. 3, pp. 157-167, 2020

Authors: Mitoh, Ayumi | Suebe, Yuto | Kashima, Tadashi | Koyabu, Etaro | Sobu, Eiji | Okamoto, Eiji | Mitamura, Yoshinori | Nishimura, Ikuya

Article Type: Research Article

Abstract: BACKGROUND: Thrombus formation and hemolysis are important factors in developing blood pumps and mechanical heart valve prostheses. These phenomena are induced by flow properties. High shear stress induces platelet and red cell damage. Computational fluid dynamics (CFD) analysis calculates shear stress of fluid and particle pathlines of blood cells. OBJECTIVE: We studied blood cell damage in a blood pump by using CFD analysis and proposed a method for estimating blood damage. METHODS: We analyzed a pulsatile blood pump that was developed as a totally implantable left ventricular assist system at Tokai University. Shear stress on …blood cells throughout pulsatile blood pumps were analyzed using CFD software. RESULTS: Based on the assumption that the effect of shear stress on platelets is accumulated along the trace, we proposed a method for estimating blood damage using the damage parameter D . Platelet damage parameter is calculated regardless of the division time 𝛥t which is dependent on the calculation time step. The results of the simulations are in good agreement with Giersiepen’s equation obtained from the experiments. CONCLUSION: The history of shear stress on a particle was calculated using CFD analysis. The new damage parameter D yields a value close to that of Giersiepen’s equation with small errors. Show more

Keywords: Computational fluid dynamics (CFD), shear stress, thrombus formation, hemolysis, blood pump

DOI: 10.3233/BME-201088

Citation: Bio-Medical Materials and Engineering, vol. 31, no. 3, pp. 169-178, 2020

Authors: Zhang, Yichen | Luo, Yunhua

Article Type: Research Article

Abstract: BACKGROUND: It is well known that there is a relationship between bone strength and the forces that are daily applied to the bone. However, bone is a highly heterogeneous material and it is still not clear how mechanical variables regulate the distribution of bone mass in a femur. METHODS: We studied the role of four mechanical variables, i.e. principal tensile/compressive stress, von Mises stress, and strain energy density (SED), in the regulation of bone mineral density (BMD) distribution in the human femur. The actual BMD in a femur was extracted from quantitative computed tomography (QCT) and used as …a reference for comparison. A finite element model of the femur was constructed from the same set of QCT scans and then used in iterative simulations of femur remodeling under stance and walking loading. The finite element model was initially assigned a homogeneous BMD distribution. During the remodeling, femur BMD was locally modified according to one of the four mechanical variables. The simulations were stopped when BMD change in two consecutive iterations was adequately small. The four simulated BMD patterns were then compared with the actual BMD. RESULTS: It was found that the BMD pattern regulated by SED had the best similarity with the actual BMD. The medullary canal was successfully reproduced by simulated remodeling, indicating that in addition to its biological functions, the medullary canal has important biomechanical functions. CONCLUSIONS: Both the actual and simulated BMD distributions showed that the proximal femur has much lower BMD than the femur shaft, which may explain why hip fractures most often occur at the proximal femur. Show more

Keywords: Wolff’s law, bone mineral density (BMD), bone remodeling, mechanical stimulus, finite element simulation

DOI: 10.3233/BME-206000

Citation: Bio-Medical Materials and Engineering, vol. 31, no. 3, pp. 179-190, 2020

Authors: Montaño, C.J. | Campos, T.P.R. | Lemos, B.R.S. | Yoshida, M.I. | Almeida, N.G.S. | Aguilar, M.T.P. | Lima, C.V.

Article Type: Research Article

Abstract: OBJECTIVE: The main goal of this study was to examine the influence of hydroxyapatite (HAp) macroaggreate concentrations on thermal and mechanical properties of radioactive bone cement and to study the relation of glass transition T g with its mechanical properties. METHODS: The bone cement as (1-x)PMMA-xHAp binary system was prepared in six [x ] distinct concentration parameters of 0.0 up to 0.5. The HAp was synthesized using a solgel procedure following calcination by thermal treatment. The composite was prepared in cold based (non-radioactive) mixing polymethyl methacrylate (PMMA) and HAp. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) …and mechanical compressive strength (CS) were used to measure the thermal and mechanical properties. RESULTS: The DSC and TGA thermal profiles in function to concentration parameter [x ] were presented. The CS lies in a range of 3.71–7.37 MPa and the glass transition temperature T g = 126.27 °C. There was a direct relationship between the PMMA-HAp thermoplastic properties with mechanical and thermal properties in function of HAp concentrations. CONCLUSION: The specific PMMA-HAp composite, with a concentration ratio of 1:1 and HAp thermal treatment at the T g , provides a material with a compression strength of 7.37 MPa and a suitable amount of porous similar to a trabecular bone, possible to apply in bone cement implants, regardless of whether they are radioactive or not. Show more

Keywords: Bone cement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), glass transition, compressive strength

DOI: 10.3233/BME-206001

Citation: Bio-Medical Materials and Engineering, vol. 31, no. 3, pp. 191-201, 2020