Functionalization And Biomedical Applications Of Electrospun Ultrafine Fibers And Electrosprayed Microspheres

In the field of tissue engineering, functionalized scaffolds have gained popularity for specific engineering applications with improved biological performance. Electrospun ultrafine fibers have been investigated as promising tissue engineering scaffolds since they can mimic the nanofibrous assembled structure of extracellular matrix (ECM). Microspheres and nanospheres produced by electrospraying are uniform-sized and monodisperse, which make it a suitable candidate for drug carrier and biological coating. In this thesis, we focused on the surface modification and functionalization of electrospun fibers and electrosprayed microspheres with different applications as drug delivery and tissue engineering system.Proteinase K was successfully loaded inside ultrafine fibers of poly(ethylene glycol)-poly(L-lactide) (PELA) by emulsion electrospinning. In vitro degradation study showed that the proteinase K-loaded PELA membranes exhibited self-accelerated biodegradability and could benefit drug controlled release and tissue regeneration. Poly(ethylene oxide) (PEO)/PELA core/shell structured ultrafine fibers, with bovine serum albumin in the core section and proteinase K in the shell section, a promising drug carrier for controlled drug release was produced by combining coaxial electrospinning and emulsion electrsospinning.A hybrid scaffod containing poly(ε-caprolactone) (PCL), gelatin and calcium phosphate which could serve as a new class of biomimetic scaffolds for bone tissue engineering was produced by surface modification. The surfaces of the PCL fibers were coated with gelatin through layer-by-layer deposition, followed by functionalization with a uniform coating of bonelike calcium phosphate by mineralization in the 10 times concentrated simulated body fluid (10SBF). It was found that the preosteoblastic MC3T3-E1 cells attached, spread, and proliferated well with a flat morphology on the mineralized scaffolds. A continuously graded, bonelike calcium phosphate coating on a nonwoven mat of electrospun PCL and poly(lactic-co-glycolic acid) (PLGA) nanofibers was achieved by adding 10SBF at a constant rate into a glass vial, which contained the electrospun mat in a titled orientation. The results of the mechanical testing showed that Young's modulus along the scaffolds increased with increasing levels of mineral. Preosteoblastic MC3T3-E1 cells were seeded onto a gelatin-coated PCL scaffold covered by a graded coating of calcium phosphate, and it was found that the cell density gradually decreased with decreasing mineral content. All the results indicated that this new class of nanofiber-based scaffolds can potentially be employed for repairing the tendon-to-bone insertion site via a tissue engineering approach. Continuous and discrete microsphere density gradients on underlying substrates were fabricated by spatially controlling collection time during electrospraying. A moveable paper mask was placed above the collector to control the collection time. Dorsal root ganglions were cultured on microsphere coatings of varying roughness. It was found that the optimal surface roughness cound promote neurite adhesion and extension.