Electrospinning is a fabrication process that uses an electric field to control the deposition of polymer fibers onto a target substrate. This electrostatic processing strategy can be used to fabricate fibrous polymer mats composed of fiber diameters ranging from several microns down to 100 nm or less. In this study, we describe how electrospinning can be adapted to produce tissue-engineering scaffolds composed of collagen nanofibers. Optimizing conditions for calfskin type I collagen produced a matrix composed of 100 nm fibers that exhibited the 67 nm banding pattern that is characteristic of native collagen. The structural properties of electrospun collagen varied with the tissue of origin (type I from skin vs type I from placenta), the isotype (type I vs type III), and the concentration of the collagen solution used to spin the fibers. Electrospinning is a rapid and efficient process that can be used to selectively deposit polymers in a random fashion or along a predetermined and defined axis. Toward that end, our experiments demonstrate that it is possible to tailor subtle mechanical properties into a matrix by controlling fiber orientation. The inherent properties of the electrospinning process make it possible to fabricate complex, and seamless, three-dimensional shapes. Electrospun collagen promotes cell growth and the penetration of cells into the engineered matrix. The structural, material, and biological properties of electrospun collagen suggest that this material may represent a nearly ideal tissue engineering scaffold.

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The first results of electrospinning fibrinogen nanofibers for use as a tissue-engineering scaffold, wound dressing, or hemostatic bandage are reported. Structures composed of fibrinogen fibers with an average diameter of 80−700 nm were electrospun from solutions composed of human or bovine fibrinogen fraction I dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol and minimal essential medium (Earle's salts). In summary, the electrospinning process is a simple and efficient technique for the fabrication of 3D structures composed of fibrinogen fibers, as would be present in the physiologic environment.

Significant challenges must be overcome before the true benefit and economic impact of vascular tissue engineering can be fully realized. Toward that end, we have pioneered the electrospinning of micro- and nano-fibrous scaffoldings from the natural polymers collagen and elastin and applied these to development of biomimicking vascular tissue engineered constructs. The vascular wall composition and structure is highly intricate and imparts unique biomechanical properties that challenge the development of a living tissue engineered vascular replacement that can withstand the high pressure and pulsatile environment of the bloodstream. The potential of the novel scaffold presented here for the development of a viable vascular prosthetic meets these stringent requirements in that it can replicate the complex architecture of the blood vessel wall. This replication potential creates an "ideal" environment for subsequent in vitro development of a vascular replacement. The research presented herein provides preliminary data toward the development of electrospun collagen and elastin tissue engineering scaffolds for the development of a three layer vascular construct.

Fully (99+ %) hydrolyzed poly(vinyl alcohol) (PVA) was electrospun from water using Triton X-100 surfactant to lower the surface tension. The diameter of the electrospun PVA fibers ranged from 100 to 700 nm. Treatment of the PVA fiber mats with methanol for 8 h stabilized the fibers against disintegration in contact with water. In addition, the mats showed increased mechanical strength due to increased crystallinity following post-spinning treatment with methanol. We suggest that methanol treatment serves to increase the degree of crystallinity, and hence the number of physical cross-links in the electrospun PVA fibers. This may occur by removal of residual water within the fibers by the alcohol, allowing PVA-water hydrogen bonding to be replaced by intermolecular polymer hydrogen bonding resulting in additional crystallization. Potential applications of electrospun PVA include filters, precursors to graphitic fibers, and biomedical materials.

The resistivity of electrochemically synthesized polyaniline films was measured with the films submerged in electrolyte. The resistivity was found to depend on the redox state of the film, the pH of the solution and, to a lesser extent, on the type of anion present. The resistivity at a given pH is low but only inside a narrow potential window. The width of this window decreases with increasing pH and vanishes at pH 6. The walls of the potential window correlate roughly with the formal potentials of the redox processes as determined by cyclic voltammetry. It has been shown that the resistivity of polyaniline depends on its moisture content. For the wet polymer a small degree of protonation is apparently sufficient to cause a decrease in resistivity of more than 6 orders of magnitude. This behavior may be rationalized by assuming that, in the presence of water, the charge transport mechanism involves proton exchange reactions as well as intermolecular electron transport.

Poly(o-toluidine), poly(m-toluidine), and poly(o-ethylaniline) have been synthesized chemically and electrochemically. The polymers were characterized by elemental analysis, UV-vis spectroscopy, and cyclic voltammetry. Elemental analysis data suggest that the protonated polymers are derived from bases containing ca. 37-54% oxidized (imine) units. Upon treatment with 1 M HC1, conductivities of the polymers increase dramatically from ca. 10~8 S/cm to ca. 1CT1 S/cm for polytoluidines and to ca. 1CT3 S/cm for poly(oethylaniline). The conductivities, UV-vis spectra, and electrochemical reactions of the polymers are compared with those of polyaniline and are shown to be consistent with a reduction in -conjugation of the alkyl derivatives caused primarily by steric effects.