Joseph L. Lowery

Effect of fiber diameter, pore size and seeding method on growth of human dermal fibroblasts in electrospun poly(ɛ-caprolactone) fibrous mats

Nonwoven fiber mats of poly(epsilon-caprolactone) (PCL) and PCL blended with poly(ethylene oxide) (PEO) were generated by electrospinning. Differential scanning calorimetry, scanning electron microscopy, and gravimetric measurement confirm the removal of PEO after immersion in water, as well as an increase in the PCL crystallinity. The reorganization of PCL resulted in the macroscopic alteration of the electrospun mat, decreasing the peak pore diameter up to a factor of 3 while only minimally affecting the fiber diameter. This technique was used to create electrospun PCL scaffolds with similar fiber diameters but different pore diameters to examine the effect of pore diameter on cell growth. Human Dermal Fibroblasts (HDF) were seeded into multiple samples using a perfusion seeding technique to guarantee successful cell deposition. Fluorescence analysis at 7, 14, and 21 days found that cells proliferated at a faster rate on scaffolds with peak pore diameters greater than 6 microm, as determined by mercury porosimetry. Cell conformation was also found to change as the peak pore diameter grew from 12 to 23 microm; cells began aligning along single fibers instead of attaching to multiple fibers. Knowledge of the effect of void architecture on cell proliferation and conformation could lead to the development of more effective scaffolds for tissue engineering.

Electrospun micro- and nanofiber tubes for functional nervous regeneration in sciatic nerve transections

BackgroundAlthough many nerve prostheses have been proposed in recent years, in the case of consistent loss of nervous tissue peripheral nerve injury is still a traumatic pathology that may impair patients movements by interrupting his motor-sensory pathways. In the last few decades tissue engineering has opened the door to new approaches;: however most of them make use of rigid channel guides that may cause cell loss due to the lack of physiological local stresses exerted over the nervous tissue during patients movement. Electrospinning technique makes it possible to spin microfiber and nanofiber flexible tubular scaffolds composed of a number of natural and synthetic components, showing high porosity and remarkable surface/volume ratio.ResultsIn this study we used electrospun tubes made of biodegradable polymers (a blend of PLGA/PCL) to regenerate a 10-mm nerve gap in a rat sciatic nerve in vivo. Experimental groups comprise lesioned animals (control group) and lesioned animals subjected to guide conduits implantated at the severed nerve stumps, where the tubular scaffolds are filled with saline solution. Four months after surgery, sciatic nerves failed to reconnect the two stumps of transected nerves in the control animal group. In most of the treated animals the electrospun tubes induced nervous regeneration and functional reconnection of the two severed sciatic nerve tracts. Myelination and collagen IV deposition have been detected in concurrence with regenerated fibers. No significant inflammatory response has been found. Neural tracers revealed the re-establishment of functional neuronal connections and evoked potential results showed the reinnervation of the target muscles in the majority of the treated animals.ConclusionCorroborating previous works, this study indicates that electrospun tubes, with no additional biological coating or drug loading treatment, are promising scaffolds for functional nervous regeneration. They can be knitted in meshes and various frames depending on the cytoarchitecture of the tissue to be regenerated. The versatility of this technique gives room for further scaffold improvements, like tuning the mechanical properties of the tubular structure or providing biomimetic functionalization. Moreover, these guidance conduits can be loaded with various fillers like collagen, fibrin, or self-assembling peptide gels or loaded with neurotrophic factors and seeded with cells. Electrospun scaffolds can also be synthesized in different micro-architectures to regenerate lesions in other tissues like skin and bone.

Spraying asymmetry into functional membranes layer-by-layer

As engineers strive to mimic the form and function of naturally occurring materials with synthetic alternatives, the challenges and costs of processing often limit creative innovation. Here we describe a powerful yet economical technique for developing multiple coatings of different morphologies and functions within a single textile membrane, enabling scientists to engineer the properties of a material from the nanoscopic level in commercially viable quantities. By simply varying the flow rate of charged species passing through an electrospun material during spray-assisted layer-by-layer deposition, individual fibres within the matrix can be conformally functionalized for ultrahigh-surface-area catalysis, or bridged to form a networked sublayer with complimentary properties. Exemplified here by the creation of selectively reactive gas purification membranes, the myriad applications of this technology also include self-cleaning fabrics, water purification and protein functionalization of scaffolds for tissue engineering.

Transplantation of nanostructured composite scaffolds results in the regeneration of chronically injured spinal cords

The destruction and hollowing of entire tissue segments represent an insurmountable barrier to axonal regeneration and therapeutics in chronic spinal cord injury. To circumvent this problem, we engineered neural prosthetics, by assembling electrospun nanofibers and self-assembling peptides into composite guidance channels and transplanted them into the cysts of a postcontusive, chronic spinal cord injury rat model, also providing delivery of proregenerative cytokines. Six months later conspicuous cord reconstruction was observed. The cyst was replaced by newly formed tissue comprising neural and stromal cells. Nerve fibers were interspersed between and inside the guidance channels, spanning the lesion, amidst a well-developed vascular network, basal lamina, and myelin. This was accompanied by a significant improvement in the activity of ascending and descending motor pathways and the global locomotion score. Thus by engineering nanostructured matrices into neuroprosthetics, it is possible to recreate an anatomical, structural, and histological framework, which leads to the replacement of large, hollow tissue gaps in the chronically injured spinal cord, fostering axonal regeneration and neurological recovery.