Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, Japan.
Proc Natl Acad Sci U S A. 2011 Feb 1;108(5):1777-82. doi: 10.1073/pnas.1006847108. Epub 2011 Jan 18.
When a femtosecond laser pulse (fsLP) is focused through an objective lens into a culture medium, an impulsive force (fsLP-IF) is generated that propagates from the laser focal point (O(f)) in a micron-sized space. This force can detach individual adherent cells without causing considerable cell damage. In this study, an fsLP-IF was reflected in the vibratory movement of an atomic force microscopy (AFM) cantilever. Based on the magnitude of the vibration and the geometrical relationship between O(f) and the cantilever, the fsLP-IF generated at O(f) was calculated as a unit of impulse [N-s]. This impulsive force broke adhesion molecule-mediated intercellular interactions in a manner that depended on the adhesion strength that was estimated by the cell aggregation assay. The force also broke the interactions between streptavidin-coated microspheres and a biotin-coated substrate with a measurement error of approximately 7%. These results suggest that fsLP-IF can be used to break intermolecular and intercellular interactions and estimate the adhesion strength. The fsLP-IF was used to break intercellular contacts in two biologically relevant cultures: a coculture of leukocytes seeded over on an endothelial cell monolayer, and a polarized monolayer culture of epithelial cells. The impulses needed to break leukocyte-endothelial and interepithelial interactions, which were calculated based on the geometrical relationship between O(f) and the adhesive interface, were on the order of 10(-13) and 10(-12) N-s, respectively. When the total impulse at O(f) is well-defined, fsLP-IF can be used to estimate the force required to break intercellular adhesions in a noncontact manner under biologically relevant conditions.
当飞秒激光脉冲（fsLP）通过物镜聚焦到培养基中时，会产生一个沿微米级空间从激光焦点（O(f)）传播的脉冲力（fsLP-IF）。这种力可以在不造成相当大细胞损伤的情况下分离单个贴壁细胞。在这项研究中，飞秒激光脉冲的瞬时力通过原子力显微镜（AFM）悬臂的振动运动得到反映。基于振动的幅度和 O(f)与悬臂之间的几何关系，计算出在 O(f)处产生的飞秒激光脉冲的瞬时力为脉冲[N-s]的单位。这种瞬时力以依赖于通过细胞聚集测定法估计的粘附强度的方式破坏了粘附分子介导的细胞间相互作用。该力还破坏了链霉亲和素涂覆的微球与生物素涂覆的基质之间的相互作用，测量误差约为 7%。这些结果表明，飞秒激光脉冲的瞬时力可用于破坏分子间和细胞间的相互作用，并估计粘附强度。飞秒激光脉冲的瞬时力用于打破两种生物学相关培养物中的细胞间接触：白细胞在血管内皮细胞单层上接种的共培养物，以及上皮细胞的极化单层培养物。根据 O(f)和粘附界面之间的几何关系计算出的打破白细胞-内皮和上皮间相互作用所需的脉冲数分别为 10(-13)和 10(-12)N-s。当 O(f)处的总脉冲数定义明确时，飞秒激光脉冲的瞬时力可以用于估计在生物学相关条件下以非接触方式打破细胞间粘附所需的力。
