A novel wet extrusion technique to fabricate self-assembled microfiber scaffolds for controlled drug delivery.

We have developed a novel wet extrusion process to fabricate nonwoven self-assembled microfiber scaffolds with uniform diameters less than 5 μm and without any postmanipulation. In this method, a poly(L-lactic acid) solution flows dropwise into a stirring nonsolvent bath, deforming into liquid polymer streams that self-assemble into a nonwoven microfiber scaffold. The ability to tune fiber diameter was achieved by decreasing polymer spin dope concentration and increasing the silicon oil to petroleum ether ratio of the nonsolvent spin bath. To demonstrate the drug delivery capabilities of scaffolds, heparin was encapsulated using a conventional water-in-oil (W/O) emulsion technique and a cryogenic emulsion technique developed in our laboratory. Spin dope preparation was found to significantly effect the release kinetics of self-assembled scaffolds by altering the interconnectivity of pores within the precipitating filaments. After 35 days, scaffolds prepared from W/O emulsions released up to 45% encapsulated heparin, whereas nearly 80% release of heparin was observed from cryogenic emulsion formulations. The versatility of our system, combined with the prolonged release of small molecules and the ability to control the homogeneity of self-assembling scaffolds, could be beneficial for many tissue regeneration and engineering applications.