33. Microfluidic Spinning of Alginate Fibers

A novel microfluidic spinning method was used to develop flat alginate fibers with grooves for cell scaffolding [12Kan] instead of using the traditional approach of microelectromechanical systems (MEMS) for topological construction of tissue engineering scaffolds. As seen in Fig. 33.1, thin flat fibers with diameters less than 10 μm were continuously fabricated by passing the alginate solution through channels containing calcium chloride. Fibers with various diameters and widths were obtained by changing the flow rate, and the fibers formed were wound continuously onto spools. SEM images of the smooth and grooved flat fibers are shown in Fig. 33.2. Figure 33.2c shows the fibers with 5 and 7 grooves obtained by changing the pattern on the sample channel. Fibers with different number of grooves on each side were also produced as seen in Fig. 33.2g. This approach of fiber formation allowed precise control of dimensions and enabled fabrication of scaffolds that could regulate cellular morphogenesis [12Kan]. The fibers developed were used to culture neuron cells, and the cell attachment, proliferation, and alignment were studied. The cells migrated to the sides of the smooth fibers and along the ridges of the grooved fibers as seen in Fig. 33.3i. As seen in the fluorescent and SEM images, cluster of cells were seen growing on the ridges of the fibers, and the cells were connected by neurites along the length of the grooves unlike the cells on the smooth fibers where the neurites formed a random network. Similar accumulation and alignment of cells in the grooves were also found for myoblast cells. The ability to guide the morphogenesis of cells and achieve topographic control over cell alignment was perceived to be crucial to reconnect muscle tissues and for other tissue engineering applications. In a similar approach, a microfluidic device was used for continuous (on the fly) production of calcium alginate fibers [07Shi]. Basically, a poly(dimethylsiloxane) (PDMS) microfluidic device embedded with a glass capillary pipet was used for fiber production. Sodium alginate solution was introduced in the sample flow, and calcium chloride solution was introduced as the sheath liquid. Sufficient time is allowed for the fibers to precipitate by changing the length of the outlet pipet. Human–mouse fibroblasts and bovine serum albumin–fluorescein isothiocyanate were loaded into the fiber during fiber production to evaluate the suitability of the fiber production method for medical applications. Cells loaded onto the fibers survived the production process and were embedded inside and had about 80 % viability after 24 h suggesting that the process could be useful to load therapeutic materials and for delivery of drugs.