Lee Gi-Ja, Choi Samjin, Chon Jinmann, Yoo Seungdon, Cho Ilsung, Park Hun-Kuk
Department of Biomedical Engineering, College of Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
J Nanosci Nanotechnol. 2011 Jan;11(1):773-7. doi: 10.1166/jnn.2011.3275.
The Achilles tendon consists mainly of type I collagen fibers that contain collagen fibrils. When the Achilles tendon is injured, it is inflamed. The collagenase-induced model has been widely used to study tendinitis. The major advantages of atomic force microscopy (AFM) over conventional optical and electron microscopy for bio-imaging include its non-requirement of a special coating and vacuum, and its capability to perform imaging in all environments. AFM force-distance measurements have become a fundamental tool in the fields of surface chemistry, biochemistry and materials science. Therefore, the changes in the ultrastructure and adhesion force of the collagen fibrils on the Achilles tendons of rats with Achilles tendinitis were observed using AFM. The changes in the structure of the Achilles tendons were evaluated based on the diameter and D-banding of the collagen fibrils. Collagenase-induced Achilles tendinitis was induced with the injection of 30 microl crude collagenase into 7-week-old male Sprague-Dawley rats. The animals were each sacrificed on the first, second, third, fifth and seventh day after the collagenase injection. The normal and injured Achilles tendons were fixed in 4% buffered formalin and dehydrated with increasing concentrations of ethanol. AFM was performed using the non-contact mode at the resolution of 512 x 512 pixels, with a scan speed of 0.8 line/sec. The adhesion force was measured via the force-distance curve that resulted from the interactions between the AFM tip and the collagen fibril sample using the contact mode. The diameter of the collagen fibrils in the Achilles tendons significantly decreased (p < 0.05) after the collagenase injection, and the pattern of the D-banding of the collagen fibrils was similar to that of the diameter changes. The adhesion force decreased until the fifth day after the collagenase injection, but increased on the seventh day after the collagenase injection (p < 0.0001).
跟腱主要由包含胶原原纤维的I型胶原纤维组成。当跟腱受伤时，会发生炎症。胶原酶诱导模型已被广泛用于研究肌腱炎。与传统光学显微镜和电子显微镜相比，原子力显微镜（AFM）用于生物成像的主要优点包括无需特殊涂层和真空，并且能够在所有环境中进行成像。AFM力-距离测量已成为表面化学、生物化学和材料科学领域的基本工具。因此，使用AFM观察了跟腱炎大鼠跟腱上胶原原纤维的超微结构和粘附力的变化。根据胶原原纤维的直径和D带评估跟腱结构的变化。通过向7周龄雄性Sprague-Dawley大鼠注射30微升粗胶原酶诱导胶原酶诱导的跟腱炎。在胶原酶注射后的第一天、第二天、第三天、第五天和第七天分别处死动物。将正常和受伤的跟腱固定在4%缓冲福尔马林中，并用浓度递增的乙醇脱水。使用非接触模式以512×512像素的分辨率进行AFM成像，扫描速度为0.8行/秒。通过使用接触模式下AFM探针与胶原原纤维样品之间相互作用产生的力-距离曲线测量粘附力。胶原酶注射后，跟腱中胶原原纤维的直径显著减小（p<0.05），胶原原纤维的D带模式与直径变化模式相似。粘附力在胶原酶注射后第五天之前降低，但在胶原酶注射后第七天增加（p<0.0001）。
