Force modeling for needle insertion into soft tissue based on mechanical properties and geometric parameters

The force model during needle insertion into soft tissue is important for accurate percutaneous intervention.In this paper,a force model for needle insertion into a tissue- equivalent material is presented and a series of experiments are conducted to acquire data from needle soft- tissue interaction process.In order to build a more accurate insertion force model,the interaction force between a surgical needle and soft tissue is divided into three parts:stiffness force,friction force,and cutting force.The stiffness force is modeled on the basis of contact mechanics model.The friction force model is presented using a modified Winkler' s foundation model.The cutting force is viewed as a constant depending on a given tissue.The proposed models in the paper are established on the basis of the mechanical properties and geometric parameters of the needle and soft tissue.The experimental results illustrate that the force models are capable of predicting the needle-tissue interaction force.The force models of needle insertion can provide real-time haptic feedback for robot-assisted procedures,thereby improving the accuracy and safety of surgery.

Reduced graphene oxide-grafted bovine serum albumin/bredigite nanocomposites with high mechanical properties and excellent osteogenic bioactivity for bone tissue engineering

The optimization of the scaffolds to provide a suitable matrix and accelerate the regeneration process is vital for bone tissue engineering.However,poor mechanical and biological characteristics remain the primary challenges that must be addressed.For example,although bredigite(Br)has shown great potential for application in bone tissue engineering,it easily fails in replacement.In the present work,these challenges are addressed by reinforcing the Br matrix with nanosheets of graphene oxide(rGO)that have been reduced by bovine serum albumin(BSA)in order to enhance the mechanical properties and biological behavior.The reduction of graphene oxide by BSA improves the water stability of the nanosheets and provides an electrostatic interaction between theBSA-rGO nanosheets and theBr particles.The high thermal conductivity of theBSA-rGO nanosheets decreases the porosity of the Br by transferring heat to the core of the tablet.Furthermore,the addition of BSA-rGO nanosheets into the Br matrix enhances the adhesion of G-292 cells on the surface of the tablets.These findings suggest that the tablet consisting of BSA-rGO-reinforced Br has encouraging potential for application in bone tissue engineering.

Physical and Mechanical Properties of Antifungal Ionic Liquid-Incorporated Dental Tissue Conditioner

Denture stomatitis and fungal infection are commonly found in long-time denture wearer. Ionic liquids have been used as plasticizer and also possess antimicrobial activity. In this study, ionic liquid in form of 1-Decyl-3-methy-limidazolium chloride was incorporated into tissue conditioner (GC Soft-liner TM) to improve antifungal activity. Physical and mechanical properties were evaluated. Compliance was carried out using penetration test according to ISO 10139-1. Weight change, water absorption and solubility were determined by weight measurement. Conventional and nystatin-incorporated tissue conditioner served as controls. Results showed that ionic liquid-incorporated tissue conditioner significantly decreased fungal formation, both in material suspension and on material surface. The penetration depth of all groups tended to reduce over time with no significant difference at each time point. After water immersion, ionic liquid- and nystatin-incorporated tissue conditioner gained weight while conventional group showed weight loss. The percentage of water absorption of conventional group was significantly lower than ionic liquid and nystatin group, while the percentage of water solubility of nystatin group was significantly higher than others. Our work indicated that antifungal ionic liquid-incorporated tissue conditioner met the standard criteria in terms of material compliance. However, further studies including dynamic viscoelastic property are needed before clinical trial or application.

General Theory of Body Contouring: 2. Modulation of Mechanical Properties of Subcutaneous Fat Tissue

Subcutaneous white adipose tissue (sWAT) can be described micromechanically as a foam structure. It is shown that according to this model, mechanical stiffness of this tissue is primarily dependent on the average cell size and is almost independent of the dispersion of cell sizes in a local adipocytes’ population. Whereas the influence of natural fat renewal process with a rate of 10% per year must be of minor importance for mechanical properties of sWAT, induced adipocytes’ death can substantially reduce local sWAT stiffness. The sWAT which contains two or more different subpopulations of adipocytes of varying sizes with a spatially clustered structure can demonstrate significant inhomogeneity of their mechanical properties when compared with those of sWAT consisting of a single population of adipocytes. It is proposed that this effect may be an important pathophysiological feature of cellulite. Transformation of the cell shape from quasispherical to wrinkled or elliptical forms makes adipocytes more susceptible to thermo-mechanical stress reducing the strain needed to achieve the local plastic deformation. These mechanical features of sWAT are essential for understanding the mechanisms of different non-invasive and minimal invasive body contouring procedures.

Additive manufacturing of biodegradable magnesium-based materials:Design strategies,properties,and biomedical applications

Magnesium(Mg)-based materials are a new generation of alloys with the exclusive ability to be biodegradable within the human/animal body.In addition to biodegradability,their inherent biocompatibility and similar-to-bone density make Mg-based alloys good candidates for fabricating surgical bioimplants for use in orthopedic and traumatology treatments.To this end,nowadays additive manufacturing(AM)along with three-dimensional(3D)printing represents a promising manufacturing technique as it allows for the integration of bioimplant design and manufacturing processes specific to given applications.Meanwhile,this technique also faces many new challenges associated with the properties of Mg-based alloys,including high chemical reactivity,potential for combustion,and low vaporization temperature.In this review article,various AM processes to fabricate biomedical implants from Mg-based alloys,along with their metallic microstructure,mechanical properties,biodegradability,biocompatibility,and antibacterial properties,as well as various post-AM treatments were critically reviewed.Also,the challenges and issues involved in AM processes from the perspectives of bioimplant design,properties,and applications were identified;the possibilities and potential scope of the Mg-based scaffolds/implants are discussed and highlighted.

Structural properties of scaffolds:Crucial parameters towards stem cells differentiation

Tissue engineering is a multidisciplinary field that applies the principles of engineering and life-sciencesfor regeneration of damaged tissues. Stem cells have attracted much interest in tissue engineering as a cell source due to their ability to proliferate in an undifferentiated state for prolonged time and capability of differentiating to different cell types after induction. Scaffolds play an important role in tissue engineering as a substrate that can mimic the native extracellular matrix and the properties of scaffolds have been shown to affect the cell behavior such as the cell attachment, proliferation and differentiation. Here, we focus on the recent reports that investigated the various aspects of scaffolds including the materials used for scaffold fabrication, surface modification of scaffolds, topography and mechanical properties of scaffolds towards stem cells differentiation effect. We will present a more detailed overview on the effect of mechanical properties of scaffolds on stem cells fate.

Virtual Biopsy and Physical Characterization of Tissues, Biofilms, Implants and Viscoelastic Liquids Using Vibrational Optical Coherence Tomography

Tissue biopsies and implant analysis during animal testing or clinical studies are a requirement for development of new surgical materials and procedures. In this paper we report the use of vibrational OCT (VOCT) to evaluate the viscoelastic behavior of tissues, polymeric materials, biofilms, and viscoelastic solutions of macromolecules. Our results suggest that VOCT is a useful technique to characterize the behavior of cellular tissues and biofilms, polymeric implant materials and viscoelastic solutions used in medicine. It is demonstrated that the modulus and resonant frequency squared per unit thickness is a feature that can be used to characterize a variety of tissues. Further work is needed to understand the generalized behavior of synthetic polymers and viscoelastic solutions.

天然高分子基角膜修复材料力学性能研究进展

由于盲人数量庞大、可供移植的捐赠角膜供不应求,人工角膜逐渐成为研究热点,但人工角膜常因力学性能不足而发生植片撕裂,为克服这一问题,国内外研究者开展了一系列研究工作尝试改善人工角膜的力学性能。文章针对胶原蛋白、明胶、丝素蛋白以及壳聚糖这4类常见的天然高分子基角膜修复材料的力学性能相关进展进行了总结。结果发现,通过光交联、热交联等物理方法,1-乙基-3-(3-二甲基氨基丙基)碳二亚胺(EDC)/N-羟基琥珀酰亚胺(NHS)交联、京尼平或戊二醛交联等化学方法以及其他复合方法都可以显著提升角膜材料的力学性能,但这些方法仍存在一些不足之处。因此,进一步开发高质量人工角膜至关重要,文章通过归纳总结希望能够为角膜修复材料的力学性能提升研究提供一些参考和思路。

基于Langer线的穿刺体位对肿瘤化疗患者输液港难免性医用黏胶相关皮肤损伤的预防效果研究

目的探究基于Langer线的无损伤针穿刺体位对肿瘤化疗患者输液港难免性黏胶相关皮肤损伤的预防效果。方法通过平行胸部Langer线对床头抬高60~90°和平卧位穿刺进行皮肤软组织力学、表皮屏障功能理论分析,然后选取2019年5月至2020年5月南京医科大学第一附属医院肿瘤科79例植入胸壁输液港、既往应用Ⅳ3000及液体敷料皮肤保护性屏障仍出现输液港黏胶相关性皮肤损伤的患者为研究对象。采用前瞻性自身前后对照,干预前采用平卧位穿刺,干预后床头抬高60~90°穿刺,比较两种穿刺体位对输液港黏胶相关性皮肤损伤预防效果和带针期间舒适度的影响。结果干预后患者输液港黏胶相关性皮肤相关性损伤总发生率较干预前显著降低(P<0.001),机械性损伤发生率、接触性皮炎发生率较干预前显著降低(均P<0.05),输液港带针期间舒适度较干预前明显提高(P<0.001),且不增加患者穿刺时的疼痛感(P=0.692)。结论床头抬高60~90°穿刺可降低肿瘤化疗患者输液港难免性黏胶相关皮肤损伤,提高患者带针期间的舒适度。

SEBS凝胶的创伤弹道特性

苯乙烯-乙烯-丁烯-苯乙烯(Styrene Ethylene Butylene Styrene,SEBS)嵌段共聚物与白油混合制成的凝胶拥有与弹道明胶类似的性质,且相比于弹道明胶,具有良好的温度稳定性、优异的透明度和耐老化性能。为了研究SEBS凝胶替代弹道明胶进行创伤弹道试验的可行性,对其力学特性进行全面测量。采用万能材料试验机和改进的霍普金森压杆对4种质量分数(15%、20%、25%和30%)SEBS凝胶进行准静态和动态力学特性的测试,研究共聚物含量对凝胶力学性能的影响,并与10%和20%弹道明胶力学性能进行对比,以确定与弹道明胶力学性能最为接近的质量分数。采用5.8 mm步枪弹直接侵彻3种质量分数(15%、20%和25%)SEBS凝胶,通过高速摄影机拍摄弹丸运动姿态和靶标内瞬时空腔演化过程,并与侵彻10%质量分数弹道明胶试验结果进行对比。试验结果表明:准静态压缩下10%弹道明胶的应力-应变曲线介于15%和20%SEBS凝胶之间,20%弹道明胶的应力-应变曲线介于20%和25%SEBS凝胶之间,高应变率下20%和30%SEBS凝胶力学特性分别与10%和20%弹道明胶接近;15%SEBS凝胶的最大空腔直径与10%弹道明胶最为接近,但空腔的膨胀和收缩速度高于弹道明胶;所得研究成果可为SEBS凝胶替代弹道明胶作为新的软组织替代物提供数据支撑。

Carbon nanotubes-reinforced polylactic acid/hydroxyapatite porous scaffolds for bone tissue engineering

In the field of bone defect repair,critical requirements for favorable cytocompatibility and optimal mechanical properties have propelled research efforts towards the development of composite materials.In this study,carbon nanotubes/polylactic acid/hydroxyapatite(CNTs/PLA/HA)scaffolds with different contents(0.5,1,1.5 and 2 wt.%)of CNTs were prepared by the thermally induced phase separation(TIPS)method.The results revealed that the composite scaffolds had uniform pores with high porosities over 68%and high through performances.The addition of CNTs significantly enhanced the mechanical properties of resulted PLA/HA,in which the 1.5 wt.%CNTs/PLA/HA composite scaffold demonstrated the optimum mechanical behaviors with the bending elastic modulus of(868.5±12.34)MPa,the tensile elastic modulus of(209.51±12.73)MPa,and the tensile strength of(3.26±0.61)MPa.Furthermore,L929 cells on the 1.5 wt.%CNTs/PLA/HA scaffold displayed good spreading performance and favorable cytocompatibility.Therefore,it is expected that the 1.5 wt.%CNTs/PLA/HA scaffold has potential applications in bone tissue engineering.

脑组织热-力耦合行为综述

脑组织是由固相与液相组成的饱和含液多孔材料,固、液、生理环境(尤其温度)之间相互作用,具体表现为脑组织内部温度场、渗流场、应力场相互影响的热-力耦合行为,故阐明脑组织的热-力耦合行为是理解大脑功能和疾病病理的关键.该文首先介绍了脑组织的传热学和力学性质,重点关注实验测量及应变率和温度的影响;其次,总结了描述脑组织热-力耦合行为的数理模型,包括力学模型、传热学模型和热-力耦合模型;最后,对该重要学科交叉领域进行了总结和展望.

水凝胶:口腔颌面部组织缺损修复中的作用与问题

背景:水凝胶因优越的机械及生物性能在生物医学领域占据独特优势,已成为研究热点。目前水凝胶相关研究涉及组织工程和创口敷料等方面。目的:综述水凝胶的优势性能与在口腔颌面部缺损修复领域中的应用研究进展,探讨水凝胶目前在应用推广中的局限以及在此领域所面临的挑战,为未来研究方向提供新思路。方法:利用计算机检索Pub Med、中国知网、万方数据库发表的相关文献,检索词为“水凝胶,口腔颌面部缺损,机械性能,组织工程,创口敷料”“hydrogel,oral and maxillofacial defects,mechanical properties,guided tissue regeneration,wound dressing”。通过阅读文题和摘要进行初步筛选,排除与文章主题不相关的文献,根据纳入标准和排除标准,最终纳入108篇文献进行结果分析。结果与结论:(1)水凝胶具有良好的生物学活性、机械可控性及刺激响应等优势性能。(2)聚合物、金属和陶瓷联合制备的水凝胶复合物具有适当的机械性能、生物降解性以及可控的释放速率,契合颌面骨组织工程的需求。(3)纤维蛋白基水凝胶可填充穿过神经缺损区域的中空神经导管并促进轴突再生和生长从而恢复颌面神经功能。(4)控制纳米材料和水凝胶的相互作用可以改善肌纤维定向结构的形成以促进颌面肌组织再生。(5)多糖水凝胶,因具有控制药物递送和携带生物活性分子等作用,并且与其他材料联合应用可以产生与细胞外基质相匹配的最佳支架,因此逐渐成为修复不规则牙周缺损的首选。(6)磷酸钙或碳酸钙基水凝胶中填充不规则形状或精细的组织缺损并使牙体硬组织再矿化,自组装水凝胶制备简便且生物活性优良。(7)唾液腺来源的细胞外基质样凝胶有望参与许多唾液腺疾病的治疗。(8)水凝胶可作为伤口敷料结合生物黏合剂、脱细胞生物材料、抗微生物和抗氧化剂或干细胞等而被广泛用于治疗各种伤口。(9)纤维蛋白基水凝胶在口腔颌面部缺损修复中最具潜力,其具有优良的生物相容性、柔韧性和可塑性,可与细胞、细胞外基质蛋白和各种生长因子结合,能够促进间充质干细胞的成骨分化、轴突的再生与生长、血管生成、肌管分化、唾液腺组织再生和牙周组织再生,在口腔颌面部缺损组织的修复中具有广泛前景。然而其治疗效果取决于所携带物质的功能,复杂的制备工艺、安全性和长期疗效以及口腔颌面特殊的解剖结构是阻碍推广的难题,这也为未来的研究提供了方向。

Laser Powder Bed Fusion-built Ti6Al4V Bone Scaffolds Composed of Sheet and Strut-based Porous Structures: Morphology, Mechanical Properties, and Biocompatibility

Laser powder bed fusion(L-PBF)-built triply periodic minimal surface(TPMS)structures are designed by implicit functions and are endowed with superior characteristics,such as adjustable mechanical properties and light-weight features for bone repairing;thus,they are considered as potential candidates for bone scaffolds.Unfortunately,previous studies have mainly focused on different TPMS structures.The fundamental understanding of the differences between strut and sheet-based structures remains exclusive,where both were designed by one formula.This consequently hinders their practical applications.Herein,we compared the morphology,mechanical properties,and biocompatibility of sheet and strut-based structures.In particular,the different properties and in vivo bone repair effects of the two structures are uncovered.First,the morphology characteristics demonstrate that the manufacturing errors of sheet-based structures with diverse porosities are comparable,and semi-melting powders as well as the ball phenomenon are observed;in comparison,strut-based samples exhibit cracks and thickness shrinking.Second,the mechanical properties indicate that the sheet-based structures have a greater elastic modulus,energy absorption,and better repeatability compared to strut-based structures.Furthermore,layer-by-layer fracturing and diagonal shear failure modes are observed in strut-based and sheet-based structures,respectively.The in vivo experiment demonstrates enhanced bone tissues in the strut-based scaffold.This study significantly enriches our understanding of TPMS structures and provides significant insights in the design of bone scaffolds under various bone damaging conditions.

Biomechanical Properties and Modeling of Skin with Laser Influence

This paper studied experimentally and theoretically the biomechanical properties of skin with laser influence. Different types of tensile tests of the porcine skin in vitro were conducted to study effect of the laser, tensile strength, stress-strain relationship, influence of skin's anisotropy and different regions, repetitive loading and stress-relaxation. A modeling of skin was developed according to the experimental results. The modeling provided insights into the important structure-function relationship in skin tissue with the laser effect. The nonlinear and anisotropic mechanical responses of skin are largely due to varying degree of fiber undulation which is effected by laser and outside forces. By introducing the laser factor into the constitutive modeling, the skin's biomechanical properties and the mechanism of the skin repair with laser were discussed.

利用一维Fung模型探讨长宽比对兔腹部皮肤单轴拉伸力学特性的影响

目的 从实验方法学角度研究不同的长宽比对皮肤条状试样单轴拉伸力学特性的影响。方法 以新西兰大白兔腹部皮肤为研究对象,取其从头到脚(0°)和与之垂直(90°)的两个方向,获取长宽比从2∶1~6∶1的多个条状试样,进行单轴拉伸测试至试样破坏。经过实验数据处理,得到兔腹部皮肤单轴拉伸的Kirchhoff应力-Green应变数据,利用一维Fung模型S=cEexp(αE~2)对其进行拟合,从而得到相应的材料参数c、α,并对参数进行统计学分析。结果 两个方向上c值差异不明显(P=0.151),α值差异比较大(P=0.001)。两个方向上不同长宽比兔腹部试样参数c、α无显著性差异(P>0.05)。结论 在2∶1~6∶1长宽比范围内,兔腹部皮肤试样不同长宽比对单轴拉伸力学特性无影响。

碳纳米管在组织工程修复中的作用与优势

背景:近来年,碳纳米管材料因其独特的结构及材料特性而备受关注,将其作为组织工程材料在组织修复中的研究逐渐深入,在动物体内已取得良好的修复效果。目的:综述碳纳米管作为组织工程材料的特性及碳纳米管用于组织工程修复中的研究进展。方法:应用计算机检索万方医学网、中国知网、维普、Web of Science和PubMed数据库中的相关文献,中文检索词为“碳纳米管、复合材料、组织工程、组织修复”,英文检索词为“carbon nanotubes,composite materials,tissue engineering,tissue repair”,最终纳入75篇文献进行归纳总结。结果与结论:①碳纳米管主要分为由单层管状石墨烯形成的单壁碳纳米管和由多个同心管状石墨烯层组成的多壁碳纳米管,通过修饰改性碳纳米管以及调节浓度使含有碳纳米管的复合支架材料获得更好导电性、机械性能、生物相容性及生物降解性。②通过促进蛋白质吸附、调控电信号转导通路及机械转导信号通路可以促进细胞增殖、分化、黏附等行为及提高细胞活性,从而促进骨重塑及整合、改善神经及心肌功能、加速缺损修复促进组织再生,且在体内无不良反应。③目前的研究表明碳纳米管复合材料能够完全修复临界大块骨缺损,达到自体移植相似的神经修复效果及使得受损心肌的生理心肌传导速度完全恢复。因此,碳纳米管作为新型生物材料在组织工程修复领域中具有巨大的潜力。④碳纳米管在组织修复领域的相关研究尚处于体外实验或动物实验水平,基于碳纳米管的复合材料要从实验研究走向临床实践还需要克服很多困难,如碳纳米管的毒理学评价、有效性评价等需后续研究进一步完善,而碳纳米管的直径、长度、纯度及复合材料的制备方法等参数与组织修复相关通路的联系需要进一步研究。

Scaffold-based tissue engineering strategies for soft-hard interface regeneration

Repairing injured tendon or ligament attachments to bones(enthesis)remains costly and challenging.Despite superb surgical management,the disorganized enthesis newly formed after surgery accounts for high recurrence rates after operations.Tissue engineering offers efficient alternatives to promote healing and regeneration of the specialized enthesis tissue.Load-transmitting functions thus can be restored with appropriate biomaterials and engineering strategies.Interestingly,recent studies have focused more on microstructure especially the arrangement of fibers since Rossetti successfully demonstrated the variability of fiber underspecific external force.In this review,we provide an important update on the current strategies for scaffold-based tissue engineering of enthesis when natural structure and properties are equally emphasized.We firstly described compositions,structures and features of natural enthesis with their special mechanical properties highlighted.Stimuli for growth,development and healing of enthesis widely used in popular strategies are systematically summarized.We discuss the fabrication of engineering scaffolds from the aspects of biomaterials,techniques and design strategies and comprehensively evaluate the advantages and disadvantages of each strategy.At last,this review pinpoints the remaining challenges and research directions to make breakthroughs in further studies.

天然血管基质/聚己内酯复合血管支架的制备与性能表征

将脱细胞血管基质(decellularized vascular matrix,DVM)与聚己内酯(Polycaprolactone,PCL)相复合,得到的复合支架能保留天然血管基质的血管诱导再生特性,克服降解过快的不足,扩大其在组织工程领域的应用范围。将新鲜的猪主动脉经脱细胞、脱脂等一系列处理后得到DVM粉末,再将其经酶解得到脱细胞血管基质凝胶(decellularized vascular matrix gel,DVMG),将用冰醋酸配置的PCL溶液与DVMG按照不同比例混合,将混合溶液反复包裹模具,室温中冷却后得到不同组的复合血管支架。共制备出4组DVMG/PCL的支架材料,通过扫描电子显微镜(scanning electron microscope,SEM)观察发现支架表面较为均匀,截面结构有明显孔隙,利于细胞黏附与迁移。通过力学拉伸实验检测PCL支架、DVMG∶PCL分别为1∶1,1.5∶1,5∶1的各组支架的拉伸模量值依次为49.00±9.52 MPa,46.29±3.08 MPa,38.77±2.07 MPa和31.18±2.80 MPa。体外降解实验显示:4组支架材料均有一定的降解能力,降解速率与DVMG的含量有关,说明改变DVMG与PCL的比例可以制备出不同力学性能、降解性能的复合血管支架。相较于单纯的PCL支架,复合支架中DVMG的含量越高,支架的刚度越低,降解速率越快,DVMG/PCL支架的整体性能得到一定改善。研究结果对于进一步扩大DVM和DVMG的应用范围,改善高分子材料的生物学响应性能具有参考价值。

仿胶原纤维屈曲结构PPDO纤维膜的制备及性能

为获得仿胶原纤维屈曲结构的组织工程支架,选用聚对二氧环己酮(PPDO)制备静电纺取向纤维膜,用热乙醇溶液对纤维膜进行卷曲处理以获得屈曲结构,同时利用化学反应的气体产物进行蓬松处理以增大纤维间隙,从而更好地模拟细胞外基质的结构形态。通过对4种不同结构的PPDO纤维膜进行性能测试与表征,评估蓬松卷曲PPDO纤维膜的性能特点。结果表明,相比PPDO取向纤维,蓬松卷曲PPDO纤维膜的水接触角由(125.26±2.33)°减小至(93.16±7.06)°,纵向拉伸强度由(4.13±0.28)MPa增大至(5.31±0.32)MPa,横向拉伸强度从(0.18±0.01)MPa增大至(0.25±0.02)MPa,细胞增殖率仍大于80%,说明其亲水性和拉伸性能得到明显改善,且纤维膜具有优异的生物相容性,证实其具有巨大的组织工程应用潜力。