Jui-Hsiang Chen

Reinnervation of Muscular Targets by Nerve Regeneration through Guidance Conduits

We established histopathologic and neurophysiologic approaches to examine whether different designs of polycaprolactone-engineered nerve conduits (hollow vs. laminated) could promote nerve regeneration as autologous grafts after transection of sciatic nerves. The assessments included morphometric analysis at the level of sciatic nerve, neuromuscular junction (NMJ) and gastrocnemius muscle, and nerve conduction studies on sciatic nerves. Six months after nerve grafting, the nerve fiber density in the hollow-conduit group was similar to that in the autologous-graft group; the laminated-conduit group only achieved ∼20% of these values. The consequences of these differences were reflected in nerve growth into muscular targets; this was demonstrated by combined cholinesterase histochemistry for NMJ and immunohistochemistry for nerve fibers innervating NMJ with an axonal marker, protein gene product 9.5. Hollow conduits had similar index of NMJ innervation as autologous grafts; the values were higher than those of laminated conduits. Among the 3 groups there were same patterns of differences in the cross-sectional area of muscle fibers and amplitudes of compound muscle action potential. These results indicate that hollow conduits were as efficient as autologous grafts to facilitate nerve regeneration, and provide a multidisciplinary approach to quantitatively evaluate muscular reinnervation after nerve injury.

DEVELOPMENT OF PEG-CONTAINING BRUSH COPOLYMER: THEIR EFFECT ON RESISTANCE TO PROTEIN ADSORPTION BEHAVIORS

Polyethylene glycol (PEG) has been grafted onto surface of many medical devices to reduce or eliminate protein adsorption that often leads to infection or inflammatory responses. Besides commonly used surface activation strategies, here in this work, the novel functional brush copolymer poly (vinyl alcohol)-g-PEG-co-polyurethane (PVA-g-(PEG-co-PU)) was first synthesized, characterized, and evaluated. PVA is used here as a versatile backbone platform for grafting functional molecules. On the one hand, the PU molecules can attach to the surface of desired PU-based implants, on the other hand, the presence of densely grafted PEG at the materials–tissue interface effectively impedes nonspecific protein adsorption. These copolymers with various grafting ratio of PEG and PU were analyzed by Fourier transform infrared spectroscopy and gel permeation chromatography. The brush copolymers that were obtained were further coated on the PU surface and contact angle measurements were performed. It was found that the brush copolymers turn the surface more hydrophilic with increasing PEG grafting density. Furthermore, the effects of PEG ratio on protein adsorption-resistant behavior were investigated. Protein adsorption was found to be the lowest on the surfaces with the highest PEG grafting density on PVA backbone. The study demonstrated unique brush copolymer to work as a potentially useful coating material.