Light-Activated Hydrophobic Adhesive for Shape-Memory Polymer Nerve Cuffs
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Light-Activated Hydrophobic Adhesive for Shape-Memory Polymer Nerve Cuffs Victoria Wobser1, Kejia Yang1, Romil Modi2, Wyatt Archer1, Yogi Patel3 Walter Voit1,2,4 1 Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX 75080, U.S.A. 2 Department of Bioengineering, University of Texas at Dallas 3 Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr. NW, Atlanta, GA 30332, U.S.A. 4 Department of Materials Science and Engineering, University of Texas at Dallas ABSTRACT In this study, three hydrophobic polymers are investigated as potential adhesives for a shape memory polymer nerve cuff. At room temperature, the adhesive candidate exhibited a maximum lap shear stress of 1.7251 MPa, compared to 0.87641 MPa and 2.1815 MPa for two commercially available biocompatible adhesives. INTRODUCTION Neural interfaces which allow communication between electronics and biology have been intensely studied for their potential to enable advanced forms of research, healthcare monitoring, and treatments for conditions such as paralysis[1]. Of particular interest are peripheral nerves, which act as bidirectional conduits for physiological signals. Interfacing with these nerves would provide a method of treating location-specific disorders or ailments in the body. Devices which are surgically implanted cause a chronic immune response, though a device with a substrate that has a modulus close to that of body tissue will elicit a smaller response than that of a stiff substrate such as silicon[2]. Flexible materials, however, cannot penetrate tissue and can be subject to large deformations during processing and implantation that cause the electrode to fail [3]. A shape memory polymer (SMP) substrate with a glass transition temperature slightly below body temperature allows the device to be stiff at room temperature for surgical manipulation and tissue insertion but drops in modulus when it reaches body temperature. Here, we use an SMP substrate that can be used for nerve cuffs, which wrap around a nerve[4]. Using SMPs for nerve cuffs has the aforementioned benefit of reduced immune response, but necessitates some mode of adhering the two ends of the cuff. This work sought to develop a biocompatible prepolymeric adhesive that can cure with UV light to act as a glue for the SMP cuff. Lang et al. reported a novel hydrophobic light-activated adhesive for surgical application [5]. However, the synthesis of poly(glycerol sebacate acrylate) (PGSA), one of the precursors for HLAA, suffers from poor efficiency and reproducibility[6]. We hypothesized that an equally effective glue could be synthesized more quickly, reproducibly, and at lower cost if PGSA is not required. The prepolymer that underwent mechanical testing was composed of a thiol-epoxy oligomer. Nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) were used to characterize the chemical properties of the oligomer, and lap shear testing was used to characterize the mechanical strength of the c
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