基于BioMEMS微柱矩阵的细胞牵引力测量

本文综述了基于生物微机电系统 (BioMEMS) 微柱矩阵的细胞牵引力测量方法。细胞牵引力对于许多生物学过程非常关键,决定着许多细胞功能,包括细胞迁移、细胞外基质构建、信号传导等。细胞通过纳牛顿量级的牵引力使细胞外基质局部变形来探测其机械顺从性。精确测量细胞牵引力大小及分布对细胞生物学、组织工程等生物医学研究具有重要意义。BioMEMS 的进步使高深宽比聚二甲基硅氧烷 (PDMS) 微柱矩阵被开发出来作为传感器用来探测细胞纳牛力学及在体外研究细胞的机械性质。细胞贴附在微柱矩阵顶端,并且在多个柱顶端间延展迁移,这个过程会造成微柱发生如垂直悬臂梁般的弯曲形变。采用这种致密、垂直、离散微柱矩阵结构替代传统测量的连续介质,通过对微柱形变的显微图像处理,细胞牵引力可以被直接定性定量测量,精度可以达到数十 nN/?m 量级。首先简要总结了传统细胞牵引力测量方法,接下来着重于基于 BioMEMS 微柱矩阵的测量方法,论述了其原理、制作工艺、表面处理及细胞实验等。最后对微柱矩阵结构的坍塌问题进行了讨论。     

微悬臂梁阵列在细胞牵引力测量中的应用

精确测量细胞牵引力的大小及分布对细胞生物学、组织工程等研究具有重要意义。近年来,基于生物微机电系统技术制作的高深宽比聚;甲基硅氧烷（PDMS）微悬臂梁阵列作为细胞牵引力测量传感器受到广泛关注。不同于传统基于连续基质的测量方法,细胞在致密、垂直、离散的微悬臂梁阵列顶端贴附并延展、迁移,引起微悬臂梁形变。通过对扫描电子显微镜图像处理,细胞牵引力测量精度可以达到数十nN/m。我们综述了基于微悬臂梁阵列细胞牵引力传感器测量方法,重点论述了实验原理、制作工艺和细胞实验,并讨论了微悬臂梁阵列结构倒塌机理。     

微悬臂梁阵列在细胞牵引力测量中的应用

精确测量细胞牵引力的大小及分布对细胞生物学、组织工程等研究具有重要意义.近年来,基于生物微机电系统技术制作的高深宽比聚二甲基硅氧烷 (PDMS) 微悬臂梁阵列作为细胞牵引力测量传感器受到广泛关注.不同于传统基于连续基质的测量方法,细胞在致密、垂直、离散的微悬臂梁阵列顶端贴附并延展、迁移,引起微悬臂梁形变.通过对扫描电子显微镜图像处理,细胞牵引力测量精度可以达到数十 nN/m.我们综述了基于微悬臂梁阵列细胞牵引力传感器测量方法,重点论述了实验原理、制作工艺和细胞实验,并讨论了微悬臂梁阵列结构倒塌机理.     

不同基底硬度对人肝癌细胞黏附、铺展和迁移的影响

目的研究不同基底硬度对肝癌细胞黏附、铺展和迁移行为的影响及对细胞骨架装配方式和细胞表面黏附蛋白整合素β1表达的调控,探讨基底的力学特性在肝癌细胞恶性转移过程中的作用。方法通过调节丙聚酰胺和双丙烯酰胺的比率制备不同硬度的聚丙烯酰胺基底,并在基底表面裱衬2.5μg/mL纤维连接蛋白为细胞提供黏附位点;用显微观察并记录不同硬度基底上细胞黏附、铺展和迁移的变化,并用Image J软件定量分析;分别运用免疫荧光和流式细胞仪的方法检测不同基底硬度对肝癌细胞骨架装配和细胞表面整合素β1表达的影响。结果硬基底利于肝癌细胞的黏附和铺展并缩短细胞的铺展时间。过软(1.1 kPa)或过硬(玻璃)的基底都不利于肝癌细胞的迁移,肝癌细胞在中间硬度的基底上(10.7 kPa)迁移速率最高。硬基底促进细胞骨架的装配和整合素β1表达。结论基底硬度通过调节细胞骨架装配和整合素的表达从而影响肝癌细胞的黏附、铺展和迁移。     

图像相关法测试股骨近端骨小梁压缩特性

目的改善传统方法做压缩测试的不足,更准确地反映骨小梁的压缩弹性模量,探究股骨近端骨小梁的压缩生物力学特性,为临床诊疗提供实验室依据。方法运用微材料力学测试系统,对正常国人(45～60岁)尸体股骨近端骨小梁沿主压力方向及与其垂直方向的压缩性能进行实验研究。结果测得了股骨近端骨小梁在主压力方向压缩弹性模量为(335.26±183.85)MPa,与其垂直方向的压缩弹性模量为(59.27±23.88)MPa,骨小梁在主压力方向上的生物力学性能要明显高于主张力方向;记录了载荷下的骨小梁的位移及应变分布图,负载时骨小梁的位移及应变分布是不均匀的。结论应用微材料力学测试系统测试股骨近端骨小梁压缩弹性模量以更准确地反映其力学性能的方法是可行的,股骨近端骨小梁的压缩性能具有各向异性和不均匀性。     

Component wave delineation of ECG by filtering in the Fourier domain

A complete solution to the fundamental problem of delineation of an ECG signal into its component waves by filtering the discrete Fourier transform of the signal is presented. The set of samples in a component wave is transformed into a complex sequence with a distinct frequency band. The filter characteristics are determined from the time signal itself. Multiplication of the transformed signal with a complex sinusoidal function allows the use of a bank of low-pass filters for the delineation of all component waves. Data from about 300 beats have been analysed and the results are highly satisfactory both qualitatively and quantitatively.     

Keratin‐binding ability of the N‐terminal Solo domain of Solo is critical for its function in cellular mechanotransduction

Solo (ARHGEF40) is a RhoA‐targeting guanine nucleotide exchange factor that regulates tensional force‐induced cytoskeletal reorganization. Solo binds to keratin 8/keratin 18 (K8/K18) filaments through multiple sites, but the roles of these interactions in the localization and mechanotransduction‐regulating function of Solo remain unclear. Here, we constructed two Solo mutants (L14R/L17R and L49R/L52R) with leucine‐to‐arginine replacements in the N‐terminal conserved region (which we termed the Solo domain) and analyzed their K18‐binding activities. These mutations markedly decreased the K18‐binding ability of the N‐terminal fragment (residues 1–329) of Solo but had no apparent effect on the K18‐binding ability of full‐length (FL) Solo. When expressed in cultured cells, wild‐type Solo‐FL showed a unique punctate localization near the ventral surface of cells and caused the reinforcement of actin filaments. In contrast, despite retaining the K18‐binding ability, the L14R/L17R and L49R/L52R mutants of Solo‐FL were diffusely distributed in the cytoplasm and barely induced actin cytoskeletal reinforcement. Furthermore, wild‐type Solo‐FL promoted traction force generation against extracellular matrices and tensional force‐induced stress fiber reinforcement, but its L14R/L17R and L49R/L52R mutants did not. These results suggest that the K18‐binding ability of the N‐terminal Solo domain is critical for the ventral localization of Solo and its function in regulating mechanotransduction.