Nano-porous Poly-L-lactic acid microtube array membranes

Novel poly-L-lactic acid (PLLA) microtube array membranes (MTAMs) with a porous wall structure were prepared by electrospinning. Porogen of polyethylene glycol (PEG) was mixed with PLLA and dissolved in a dichloromethane/dimethylformamide solvent. The solution dope was delivered to the outer layer of coaxial spinneret, while the PEG/polyethylene oxide (50/50 wt. %) aqueous solution was delivered to the core layer, to form arrays of core-shell fibers through an electrospinning process. Porogen was then washed off to produce array of microtubes with a porous wall structure. The morphology and physical properties of the MTAMs were characterized by scanning electron microscopy (SEM), a texture analyzer (TA), and a thermogravimetric analysis (TGA). With porogen content of 0~50 wt.%, pores, ranging from a few tens of nanometers to a few microns, were clearly seen in SEM micrographs for the surface of PLLA/PEG0-50 MTAMs after the washing process. However, porogen was effectively washed off only from PLLA/PEG30-50 MTAMs, thus their wall structure was transformed from a dense to porous one. PLLA/PEG MTAMs remained relatively hydrophobic. Young's modulus of PLLA/PEG MTAMs decreased from 850 to 400 kPa, while the fracture work increased from 854 g · mm to a maximum value of 4478 g · mm for PLLA/PEG10. Permeation through MTAMs was conducted, and results revealed that only pores in the walls of PLLA/PEG30-50 MTAMs were well interconnected. Cumulative permeation increased with the PEG content. These results suggest that multifunctional porous PLLA MTAMs can potentially be used in medical applications, such as nerve regeneration conduits.