Electrospun bioresorbable nanofibrous scaffolds for tissue engineering applications

Electrospinning is a very versatile technology that enables production of nanofibrous structures with morphology and fiber diameter dimensionally comparable to that of the extracellular matrix in natural tissues. For this reason electrospun scaffolds are believed to provide a better biomimetic environment than other types of porous tissue engineering scaffolds. Electrospun scaffolds offer an ideal support for cell attachment, migration, proliferation and differentiation. Non-woven mats obtained through the common electrospinning set-up, are usually characterized by random fiber orientation. A suitable design of the experimental apparatus and careful tuning of the processing parameters yield nanofibres with desired diameter and precise alignment. Nanofiber mats with specific fiber patterning may also be fabricated. This aspect is important because it is well known that the micro/nano-architecture of the scaffold may affect cell behaviour and in particular cell differentiation. The scientific community is still divided on the controversial aspect of whether or not, cells can colonize the inner regions of an electrospun mat when in vitro growth of new tissue is pursued. Many strategies have been followed by researchers to overcome the apparent limitation of efficient cell ingrowth, that is commonly attributed to too small pore size in electrospun scaffolds.In this work bioresorbable polymer scaffolds for tissue engineering are fabricated by electrospinning technology integrated with a flexible mechatronic equipment, that allows controlled and reproducible production of scaffolds with 3-D architecture tailored to specific applications. In particular, an ‘ad hoc’ collecting device allows fabrication of variously oriented and patterned fibrous structures. Composite scaffolds can also be produced by instrument implementation with multiple spinning devices. Results of in vitro cell cultures on such scaffolds provide evidence of cell colonization and penetration. In most tissue engineering applications the scaffold supporting cell growth should be bioresorbable by the host organism. Biodegradable electrospun scaffolds are made of hydrolysable polymers and must be properly designed in order to obtain bio-resorption rates tuned to the rate of tissue regeneration. In addition to their potential in tissue reconstruction, bioabsorbable nanofibrous scaffolds may also be efficiently used as drug dispensing systems for the release of bioactive molecules, such as growth factors. Electrospinning technology is very promising for the incorporation of biomolecules into fibers, thus obtaining functionalized scaffolds. The results of this work show that growth factors can be incorporated in a fiber mat during the electrospinning process without loss of bio-activity, as demonstrated by cell response upon growth factor release in the culture medium. This result confirms the versatility of the electrospinning technique.