Meghan E. Smith

Electrospinning of collagen nanofiber scaffolds from benign solvents.

Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro-2-propanol. Simple binary mixtures of phosphate-buffered saline and ethanol have been found to be highly effective for electrospinning. FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning. Crosslinking of the electrospun collagen scaffolds was achieved with standard methods.

The use of progenitor cell/biodegradable MMP2-PLGA polymer constructs to enhance cellular integration and retinal repopulation.

The inability of the adult mammalian retina to regenerate can be partly attributed to the expression of injury-induced inhibitory extracellular matrix (ECM) and cell adhesion molecules. In particular, photoreceptor degeneration stimulates deposition of the inhibitory ECM proteins neurocan and CD44 at the outer limits of the dystrophic retina, where they act as a barrier against cellular migration and axonal extension. We have previously shown that degradation of these molecules, via induction of MMP2, promotes host-donor integration and retinal repopulation following transplantation. Here we present a biodegradable/biocompatible polymer scaffold that has the ability to deliver MMP2, in conjunction with retinal progenitor cells, directly to the site of retinal injury in an attempt to enhance cellular integration and promote retinal repopulation. Pre-activated MMP2, loaded into a PLGA polymer, maintained its activity throughout polymer fabrication and hydrolysis. Following delivery, significant degradation of CD44 and neurocan from the outer limits of the dystrophic retina, without further disruption of retinal architecture, was observed. As a result, the number of retinal progenitor cells that migrated beyond the glial barrier into the degenerating host increased significantly. These cells took up residence in the retinal outer nuclear layer, adopted appropriate photoreceptor morphology and expressed the mature photoreceptor markers recoverin and rhodopsin. Thus, we have created a cell delivery platform that upon transplantation provides controlled release of active-MMP2 directly to the site of retinal injury, stimulating inhibitory ECM barrier removal and enhancement of stem cell integration and retinal repopulation.

Electrospinning of in situ crosslinked collagen nanofibers

A simple one-step approach to electrospin Type I collagen in the presence of the chemical crosslinking agents 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) has been developed to generate water-insoluble collagen nanofiber scaffolds without the need for post-crosslinking. SEM images indicate that fibrous surface morphology of collagen scaffolds was well retained after the in situ crosslinking process and following water treatment. The resultant collagen demonstrated a similar uniaxial tensile behavior of native tissue in mechanical testing.

Mouse retinal progenitor cell dynamics on electrospun poly (ϵ-caprolactone).

Abstract Age-related macular degeneration, retinitis pigmentosa and glaucoma are among the many retinal degenerative diseases where retinal cell death leads to irreversible vision loss and blindness. Working toward a cell-replacement-based therapy for such diseases, a number of research groups have recently evaluated the feasibility of using retinal progenitor cells (RPCs) cultured and transplanted on biodegradable polymer substrates to replace damaged retinal tissue. Appropriate polymer substrate design is essential to providing a three-dimensional environment that can facilitate cell adhesion, proliferation and post-transplantation migration into the host environment. In this study, we have designed and fabricated a novel, ultra-thin electrospun poly(ϵ-caprolactone) (PCL) scaffold with microscale fiber diameters, appropriate porosity for infiltration by RPCs, and biologically compatible mechanical characteristics. We have verified that our electrospun PCL scaffold supports robust mouse RPC proliferation, adhesion, and differentiation in vitro, as well as migration into mouse retinal explants. These promising results make PCL a strong candidate for further development as a cell transplantation substrate in retinal regenerative research.