Microengineered platforms for bone cell mechanobiology study

人工骨替代物的长期维护是骨组织工程面临的主要挑战之一。已有研究表明，机械负荷对骨组织的维持至关重要。适当的骨细胞生物力学行为对机械负荷的响应对于天然骨组织和人工骨置换的长期组织维持至关重要。大多数骨细胞居住在所谓的腔隙-管状网络（LCN）中，这对骨细胞的正常功能和对机械负荷的反应至关重要。目前，宏观生物力学测试系统已广泛用于骨细胞生物力学基础研究。然而，这种方法受到这些常规系统中细胞外环境的低生理相关性的极大限制。

One major challenge of bone tissue engineering is the long-term maintenance of the artificial bone replacement. It has been shown that mechanical loading is critical for bone tissue maintenance. Appropriate bone cell biomechanical behaviour in response to mechanical loading is essential for long-term tissue maintenance for both native bone tissue and artificial bone replacement. The majority of bone cells inhabit a so-called lacunar-canalicular network (LCN), which is critical for bone cells' normal function and response to mechanical loading. Currently, macroscale biomechanical testing systems have been widely used to study fundamental bone cell biomechanics. However, this approach is greatly limited by the low physiological relevance of the extracellular environment in these conventional systems. The overall goal of this research is to develop novel microengineered platforms to study bone cell biomechanical behaviors in physiologically relevant environments. Specifically, we aim to: • Develop a microfluidic-based artificial LCN for bone cell culture and biomechanical testing; • Develop a microscale mechano-co-culture system to allow simultaneous physiologically relevant mechanical stimulation of cells and real-time transportation of cell signaling molecules among different cell populations; and • Develop and integrate nanowire-based sensors into our microfluidic mechano-co-culture systems to allow real-time characterization of cell-to-cell communications under mechanical stimulation. First, we will design and fabricate a novel microfluidic-based artificial LCN to study fundamental bone cell biomechanics. Cell trapping in LCN will be achieved by using differential flow resistance between cell trapping channels and flow delivery channels. Physiologically-relevant oscillatory fluid flow will be generated using an on-chip pneumatically controlled system. Large arrays of single bone cells will be seeded in a uniform microscale environment with cell processes formed along patterned nanoscale channels. Second, we will develop a microfluidic multi-culture platform to allow simultaneous mechanical loading of the cells and real-time cell-cell communication within a physiologically relevant distance. The co-culture chambers in the system will be interconnected by hydrogel-filled microchannels to enable diffusive transport of soluble factors but not convective transport among chambers. Fluid flow will be delivered to the targeted culture chamber(s) without perturbing the cells located in other culture chambers. Finally, we will develop nanowire-based bone marker specific sensors and embed them in our microfluidic platforms for real-time quantification of cell-released protein concentration under mechanical loading. Batches of nanowire sensors will be constructed and analyte-specific receptors corresponding to bone markers will be conjugated to the surface of silicon nanowire transistors. The sensor signals will be accessed and converted to protein concentration in real time. In this proposed research the cutting edge microfabrication and nanofabricaton techniques are integrated with bone cell biomechanics studies. The proposed devices will allow us to conduct fundamental biomechanics research on bone cells in more physiologically relevant conditions. Knowledge gained from the studies using these proposed microengineered platforms will provide key information in bone cell mechanics and mechanobiology and bone tissue engineering design. The multi-disciplinary nature of this research will provide students training in a variety of techniques that are transferable to other research areas and industries, making them in high demand for careers in biotechnology and biomedical engineering.