Department of Biomedical Engineering, Goergen Hall, P.O. Box 270168, University of Rochester, Rochester, New York 14627, USA.
J Acoust Soc Am. 2013 Aug;134(2):1491-502. doi: 10.1121/1.4812868.
Type I collagen is the primary fibrillar component of the extracellular matrix, and functional properties of collagen arise from variations in fiber structure. This study investigated the ability of ultrasound to control collagen microstructure during hydrogel fabrication. Under appropriate conditions, ultrasound exposure of type I collagen during polymerization altered fiber microstructure. Scanning electron microscopy and second-harmonic generation microscopy revealed decreased collagen fiber diameters in response to ultrasound compared to sham-exposed samples. Results of mechanistic investigations were consistent with a thermal mechanism for the effects of ultrasound on collagen fiber structure. To control collagen microstructure site-specifically, a high frequency, 8.3-MHz, ultrasound beam was directed within the center of a large collagen sample producing dense networks of short, thin collagen fibrils within the central core of the gel and longer, thicker fibers outside the beam area. Fibroblasts seeded onto these gels migrated rapidly into small, circularly arranged aggregates only within the beam area, and clustered fibroblasts remodeled the central, ultrasound-exposed collagen fibrils into dense sheets. These investigations demonstrate the capability of ultrasound to spatially pattern various collagen microstructures within an engineered tissue noninvasively, thus enhancing the level of complexity of extracellular matrix microenvironments and cellular functions achievable within three-dimensional engineered tissues.
I 型胶原蛋白是细胞外基质的主要纤维成分，胶原蛋白的功能特性源于纤维结构的变化。本研究探讨了超声在水凝胶制备过程中控制胶原蛋白微观结构的能力。在适当的条件下，在聚合过程中对 I 型胶原蛋白进行超声处理会改变纤维的微观结构。扫描电子显微镜和二次谐波产生显微镜显示，与未经超声处理的样品相比，超声处理后的胶原蛋白纤维直径减小。对机制研究的结果与超声对胶原蛋白纤维结构影响的热机制一致。为了在特定部位控制胶原蛋白的微观结构，将 8.3MHz 的高频超声束引导到一个大的胶原蛋白样本的中心，在凝胶的中心核心内产生密集的短而细的胶原蛋白纤维网络，而在光束区域外则形成较长而较厚的纤维。接种到这些凝胶上的成纤维细胞迅速迁移到仅在光束区域内排列成小圆形的聚集物中，并且聚集的成纤维细胞将中央的超声暴露的胶原蛋白纤维重塑成密集的薄片。这些研究表明，超声能够非侵入性地在工程组织内空间模式化各种胶原蛋白微观结构，从而提高三维工程组织内可实现的细胞外基质微环境和细胞功能的复杂程度。
