Prodution of non-woven materials for biotechnological applications via electrospinning

Electrospinning is a process by which a polymer solution or melt can be spun into submicron fibers by using a high potential electric field. Based on earlier research results, the average diameter of electrospun fibers ranges from 100 nm to a few microns. The advantages of the electrospinning process are its technical simplicity and its versatility. The apparatus used for electrospinning consists of a high voltage electric source with positive or negative polarity, a syringe or pipette feeding the solution by means of a syringe pump, and a conducting collector like aluminum. The collector can be made of any desired shape, like a flat plate, rotating drum, etc. This work can be divided in four parts. In the first one a review of literature is done with a special emphasis on the methods to develop an electrospinning apparatus and on possible applications. Furthermore, the apparatus set up is performed and tested by using polymer solutions widely described in the literature, such as polylactid acid (PLA), polycaprolactone (PCL) and polyethylenoxide (PEO). Different configurations of the apparatus were devised in order to obtain cylindrical and unixially aligned fiber scaffolds. In the second part, the electrospinning apparatus was used to fabricate nano/micro fibrous scaffolds of an ester of (HYAFF-11). The industrial interest in this material, which has never been electrospun before, is due to its biomedical properties combined with a slower in vivo degradation rate as compared to hyaluronic acid. The effects of solution properties and processing parameters on the structure and morphology of the electrospun HYAFF-11 membranes are thoroughly investigated to find the optimal processing conditions. The results show that the morphology of the electrospun fibers depends on the strength of the applied electric field and on the solution viscosity (i.e, concentration). The diameter of the nanofibers decreases with electrospinning voltage. It is found that higher solution concentrations favour the formation of uniform nanofibers with no bead-like defects. We have also studied cell proliferation on electrospun HYAFF-11 scaffolds in comparison with electrospun PLA and PCL scaffolds. It is found that cell proliferation on electrospun HYAFF-11 scaffolds is faster as compared to the other electrospun scaffolds. In the third part of the thesis the electrospinning process is used to fabricate polymer nanofibers containing one-dimensional arrays of sepiolite (SEP) nanoparticles. SEP is an industrially-relevant ceramic porous clay with biotechnological applications in composite materials. One of the main challenges in dispersing nanoparticles in a continuous phase is to avoid formation of aggregates. Our approach is to use electrospinning as a way of dispersing SEP at the nanoscale. A blend obtained by mixing solutions of PEO with solutions of hydroxylproylcellulose (HPC) has been successfully used as a template to arrange the SEP nanoparticles within the fibers during electrospinning and the results have been assessed by TEM. In the last part of this thesis we present how electrospun scaffolds could be use to improve a novel assay to study cell migration and chemotaxis in a direct-viewing chamber. In the chemotaxis assay presented in this work a chemoattractant concentration gradient in a collagen gel seeded with cells is generated by diffusion through a porous membrane. The diffusion process is monitored by fluorescence microscopy of FITC-labelled dextran. Cell motion under the action of the chemoattractant gradient is followed by time-lapse video microscopy. Cell tracking is performed off-line by image analysis and the results are expressed in terms of a chemotactic index. The application of electrospun membranes shows good cell proliferation and cell morphologies resembling the ones observed in the extracellular matrix, thus supporting electrospinning as a promising technique for biotechnological applications.