Does nutrition affect bone porosity and mineral tissue distribution in deer antlers? The relationship between histology, mechanical properties and mineral composition

It is well known that porosity has an inverse relationship with the mechanical properties of bones. We examined cortical and trabecular porosity of antlers, and mineral composition, thickness and mechanical properties in the cortical wall. Samples belonged to two deer populations: a captive population of an experimental farm having a high quality diet, and a free-ranging population feeding on plants of lower nutritive quality. As shown for minerals and mechanical properties in previous studies by our group, cortical and trabecular porosity increased from the base distally. Cortical porosity was always caused by the presence of incomplete primary osteons. Porosity increased along the length of the antler much more in deer with lower quality diet. Despite cortical porosity being inversely related to mechanical properties and positively with K, Zn and other minerals indicating physiological effort, it was these minerals and not porosity that statistically better explained variability in mechanical properties. Histochemistry showed that the reason for this is that Zn is located around incomplete osteons and also in complete osteons that were still mineralizing, whereas K is located in non-osteonal bone, which constitutes a greater proportion of bone where osteons are incompletely mineralized. This suggests that, K, Zn and other minerals indicate reduction in mechanical performance even with little porosity. If a similar process occurred in internal bones, K, Zn and other minerals in the bone may be an early indicator of decrease in mechanical properties and future osteoporosis. In conclusion, porosity is related to diet and physiological effort in deer.     

多孔钛孔隙率和孔隙尺寸对其力学性能及细胞相容性的影响

目的研究多孔钛孔隙率和孔隙尺寸对其力学性能及细胞黏附与增殖的影响,为临床应用提供依据。方法调整加入造孔剂的粒径及质量分数,粉末冶金法制备12组不同孔隙结构的多孔钛,金相显微镜观察其孔隙特征,计算孔隙率及平均孔隙尺寸。万能材料试验机测定其屈服强度、弹性模量及弯曲强度。筛选力学参数与人皮质骨匹配的多孔钛,CCK-8法测定其MC3T3-E1细胞黏附及增殖活性。结果随着多孔钛孔隙率增大,其屈服强度由406.0 MPa降至52.9 MPa,弹性模量由18.2 GPa降至3.5 GPa,弯曲强度从327.2 MPa降至50.6 MPa。多孔钛孔隙率和孔隙尺寸对其屈服强度、弹性模量及弯曲强度均有影响(P<0.05)。MC3T3-E1细胞在多孔钛表面的早期黏附吸光度值低于致密纯钛和塑料培养板对照组(P<0.05),但细胞在前者的增殖活性显著高于后者(P<0.05)。结论在本实验研究范围内,当孔隙率为43.1%～53.3%、且孔隙尺寸为154.8～191.6μm时,多孔钛的力学性能与人骨接近,且有利于成骨细胞增殖。     

High-impact strength acrylic denture base material processed by autoclave

PurposeTo investigate the effect of two different cycles of autoclave processing on the transverse strength, impact strength, surface hardness and the porosity of high-impact strength acrylic denture base material.MethodsHigh Impact Acryl was the heat-cured acrylic denture base material included in the study. A total of 120 specimens were prepared, the specimens were grouped into: control groups in which high-impact strength acrylic resins processed by conventional water-bath processing technique (74 °C for 1.5 h then boil for 30 min) and experimental groups in which high-impact strength acrylic resins processed by autoclave at 121 °C, 210 kPa .The experimental groups were divided into (fast) groups for 15 min, and (slow) groups for 30 min. To study the effect of the autoclave processing (Tuttnauer 2540EA), four tests were conducted transverse strength (Instron universal testing machine), impact strength (Charpy tester), surface hardness (shore D), and porosity test. The results were analyzed to ANOVA and LSD test.ResultsIn ANOVA test, there were highly significant differences between the results of the processing techniques in transverse, impact, hardness, and porosity test. The LSD test showed a significant difference between control and fast groups in transverse and hardness tests and a non-significant difference in impact test and a highly significant difference in porosity test; while, there were a highly significant differences between control and slow groups in all examined tests; finally, there were a non-significant difference between fast and slow groups in transverse and porosity tests and a highly significant difference in impact and hardness tests.ConclusionsIn the autoclave processing technique, the slow (long) curing cycle improved the tested physical and mechanical properties as compared with the fast (short) curing cycle. The autoclave processing technique improved the tested physical and mechanical properties of High Impact Acryl.     

The effect of scaffold macroporosity on angiogenesis and cell survival in tissue-engineered smooth muscle

Angiogenesis and survival of cells within thick scaffolds is a major concern in tissue engineering. The purpose of this study is to increase the survival of intestinal smooth muscle cells (SMCs) in implanted tissue-engineered constructs. We incorporated 250-μm pores in multi-layered, electrospun scaffolds with a macroporosity ranging from 15% to 25% to facilitate angiogenesis. The survival of green fluorescent protein (GFP)-expressing SMCs was evaluated after 2 weeks of implantation. Whereas host cellular infiltration was similar in scaffolds with different macroporosities, blood vessel development increased with increasing macroporosity. Scaffolds with 25% macropores had the most GFP-expressing SMCs, which correlated with the highest degree of angiogenesis over 1 mm away from the outermost layer. The 25% macroporous group exceeded a critical threshold of macropore connectivity, accelerating angiogenesis and improving implanted cell survival in a tissue-engineered smooth muscle construct.     

Degradation resistance of ormocer- and dimethacrylate-based matrices with different filler contents

Objectives

To investigate the influence of matrix and filler content on degradation resistance of an experimental pure-ormocer and an dimethacrylate-based composite derived from a commercially available material.

Materials and methods

A dimethacrylate- Grandio (GR) and a model pure ormocer-based-matrix ORMOCER (ORM) were used. Each material had three different types according to their filler content (% w/w): regular (87% and 86%), flowable (80% and 79%) and fissure sealer (70% and 69%) for GR and ORM respectively. Disc-shaped (1 mm thickness × 10 mm diameter) samples were prepared for each material (n = 6). Water sorption and solubility tests were adapted from ISO4049. To evaluate porosity, specimens were scanned at a resolution of 19.4 μm and 3D reconstructions were made. The volume ratio of pores in the specimens were calculated and expressed as percentages. The results were submitted to 2-way ANOVA (factors: matrix and filler content) and Tukey post-hoc statistic test (p = 0.05).

Results

Filler content influenced the water sorption for the ormocer-matrix and the water solubility for the dimethacrylates. ORMOCER regular was a less porous material compared to flowable and sealer formulations. On the other hand, the filler content had no effect on porosity for Grandio.

Conclusion

Modifications made in the pure ormocer-matrix formulation were not significantly important to produce a more water-stable material compared to the dimethacrylate-matrix composite materials.     

多孔细菌纤维素-聚乳酸乙醇酸复合支架制备及性能研究

目的制备多孔细菌纤维素(Bacterial Cellulose,BC)-聚乳酸乙醇酸(Poly Lactic-co-gly-colic acid,PLGA)复合支架及研究其相关性能。方法溶液浇铸/粒子沥滤技术制备多孔BC-PLGA复合支架并检测相关理化性能(抗张强度、断裂伸长率、吸水率和孔隙率)。然后接种成骨样细胞MG-63体外培养,通过扫描电镜(SEM)观测细胞生长状况;四甲基偶氮唑盐比色法(MTT)分析支架浸提液毒性。结果多孔BC-PLGA支架抗拉强度为(9.8536±0.9155)N/mm2,伸长率为(596.16±81.51)%,孔隙率为(65.11±5.72)%,吸水率为(69.42±5.13)%;扫描电镜和MTT法检测结果显示支架无细胞毒性,对MG-63细胞具有良好的亲和性及增殖活性。结论多孔BC-PLGA复合支架具备良好的理化性能和生物相容性,有望用作组织工程支架材料。     

The influence of porosity and the nature of the charge storage capacitance on the impedance behaviour of electropolymerized polyaniline films

Impedance spectra of electropolymerized polyaniline films were analysed by the theory of the impedance of macrohomogeneous porous electrodes. Specific ohmic and charge transfer resistivities were calculated, and their potential and pH dependence is discussed in terms of structural changes of the polymer during redox and protonation processes. Furthermore it is shown that a correct understanding of the high frequency limit of the impedance is achieved only if the porosity is implemented and thus the discrepancies inherent in the inappropriate assumption of a compact polymer film are avoided. Another not well understood electrochemical phenomenon of conducting polymers is the apparently capacitive current plateau in the cyclic voltammogram and the large series ac capacitance. It will be demonstrated that this supposed `capacitive' behaviour is related to continuous faradaic charge transfer at potentials beyond the first oxidation wave in the cyclic voltammogram.     

Contribution of high resolution peripheral quantitative CT to the management of bone and joint diseases

Many imaging modalities have been described to diagnose and monitor osteoporosis (OP), osteoarthritis and inflammatory rheumatic diseases. Over the last ten years, High Resolution peripheral Quantitative Computerized Tomography (HR-pQCT) was shown to be a precise and non invasive technique to study bone and joint diseases in clinical research. It allows the study of both cortical and trabecular bone microarchitecture at the distal tibia and radius, and further applications have been developed such as the study of mechanical properties by the finite element analysis. Thus, in case-control and cross-sectional studies, microarchitecture parameters discriminated fractured individuals independently of areal BMD. Also, microstructure parameters can predict incident fracture in postmenopausal women. In metabolic diseases associated with bone fragility, HR-pQCT may also be used to explore bone changes. In joint disease studies, HR-pQCT was a remarkable tool to assess bone erosion and joint space narrowing at the hand. This article gives an overview of this imaging technique.     

A biodegradable vascularizing membrane: a feasibility study

Regenerative medicine and in vivo biosensor applications require the formation of mature vascular networks for long-term success. This study investigated whether biodegradable porous membranes could induce the formation of a vascularized fibrous capsule and, if so, the effect of degradation kinetics on neovascularization. Poly(l-lactic acid) (PLLA) and poly(dl-lactic-co-glycolic) acid (PLGA) membranes were created by a solvent casting/salt leaching method. Specifically, PLLA, PLGA 75:25 and PLGA 50:50 polymers were used to vary degradation kinetics. The membranes were designed to have an average 60mum pore diameter, as this pore size has been shown to be optimal for inducing blood vessel formation around nondegradable polymer materials. Membrane samples were imaged by scanning electron microscopy at several time points during in vitro degradation to assess any changes in pore structure. The in vivo performance of the membranes was assessed in Sprague-Dawley rats by measuring vascularization within the fibrous capsule that forms adjacent to implants. The vascular density within 100microm of the membranes was compared with that seen in normal tissue, and to that surrounding the commercially available vascularizing membrane TheraCyte. The hemoglobin content of tissue containing the membranes was measured by four-dimensional elastic light scattering as a novel method to assess tissue perfusion. Results from this study show that slow-degrading membranes induce greater amounts of neovascularization and a thinner fibrous capsule relative to fast degrading membranes. These results may be due both to an initially increased number of macrophages surrounding the slower degrading membranes and to the maintenance of their initial pore structure.     

Hydration and N-acetyl-l-cysteine alter the microstructure of human nail and bovine hoof: Implications for drug delivery

This work aimed to (a) characterize the microstructure and porosity of human nail and bovine hoof by mercury intrusion porosimetry and SEM image analysis, (b) study the effects of hydration and of N-acetyl-l-cysteine treatment on the microstructure of both membranes, and (c) determine whether the microstructural modifications were associated with changes in drug penetration measured by standard diffusion studies. Bovine hoof surface is more porous than nail surface although there were no differences between the mean surface pore sizes. Hydration and N-acetyl-l-cysteine increased the roughness and apparent surface porosity, and the porosity determined by mercury intrusion porosimetry of both membranes. Pore-Cor^TM was used to generate tridimensional structures having percolation characteristics comparable to nail and hooves. The modeled structures were horizontally banded having an inner less-porous area which disappeared upon treatment. Treatment increased the predicted permeability of the simulated structures. Triamcinolone permeation increased significantly for hooves treated N-acetyl-l-cysteine, i.e., the membranes for which microstructural and permeability changes were the largest. Thus, microstructural changes determined via mercury intrusion porosimetry and subsequently modeled by Pore-Cor^TM were related to drug diffusion. Further refinement of the technique will allow fast screening of penetration enhancers to be used in ungual drug delivery.