RESUMO
Collective cell migration is an essential phenomenon in many naturally occurring pathophysiological processes, as well as in tissue engineering applications. Cells in tissues and organs are known to sense chemical and mechanical signals from the microenvironment and collectively respond to these signals. For the last few decades, the effects of chemical signals such as growth factors and therapeutic agents on collective cell behaviors in the context of tissue engineering have been extensively studied, whereas those of the mechanical cues have only recently been investigated. The mechanical signals can be presented to the constituent cells in different forms, including topography, substrate stiffness, and geometrical constraint. With the recent advancement in microfabrication technology, researchers have gained the ability to manipulate the geometrical constraints by creating 3D structures to mimic the tissue microenvironment. In this study, we simulate the pore curvature as presented to the cells within 3D-engineered tissue-scaffolds by developing a device that features tortuous microchannels with geometric variations. We show that both cells at the front and rear respond to the varying radii of curvature and channel amplitude by altering the collective migratory behavior, including cell velocity, morphology, and turning angle. These findings provide insights into adaptive migration modes of collective cells to better understand the underlying mechanism of cell migration for optimization of the engineered tissue-scaffold design.
RESUMO
We report an observation of rapid (exceeding 2,000 K/s) heating of polydimethylsiloxane (PDMS), one of the most popular microchannel materials, under cyclic loadings at high (~MHz) frequencies. A microheater was developed based on the finding. The heating mechanism utilized vibration damping in PDMS induced by sound waves that were generated and precisely controlled using a conventional surface acoustic wave (SAW) microfluidic system. The refraction of SAW into the PDMS microchip, called the leaky SAW, takes a form of bulk wave and rapidly heats the microchannels in a volumetric manner. The penetration depths were measured to range from 210 µm to 1290 µm, enough to cover most sizes of microchannels. The energy conversion efficiency was SAW frequency-dependent and measured to be the highest at around 30 MHz. Independent actuation of each interdigital transducer (IDT) enabled independent manipulation of SAWs, permitting spatiotemporal control of temperature on the microchip. All the advantages of this microheater facilitated a two-step continuous flow polymerase chain reaction (CFPCR) to achieve the billion-fold amplification of a 134 bp DNA amplicon in less than 3 min.
RESUMO
A major challenge in muscle tissue engineering is mimicking the ordered nanostructure of native collagen fibrils in muscles. Electrospun nanofiber constructs have been proposed as promising candidate alternatives to natural extracellular matrix. Here, we introduce a novel method to fabricate a two-dimension (2D) sheet-type and three-dimensionally integrated nanofibrous scaffolds by combining electrospinning and rapid prototyping. The aligned 2D nanofiber mats can be processed into different configurations by the CAD/CAM-based deposition of thermally extruded microstructures. We demonstrate the feasibility of these microstructures for application in muscle tissue engineering by culturing C2C12 myoblasts and then evaluating their viability and alignment. Highly aligned cellular morphologies were successfully achieved along the direction of the nanofibers in all types of scaffolds. The hybrid scaffolds provided mechanical support and served as a topographical guide at the nanoscale, exhibiting their potential to meet the requirements for practical use in tissue engineering applications.
