Single-Step Immobilization of Cell Adhesive Peptides on a Variety of Biomaterial Substrates via Tyrosine Oxidation with Copper Catalyst and Hydrogen Peroxide

Immobilization of biologically active peptides which were isolated from extracellular matrix proteins is a powerful strategy for the design and functionalization of biomaterial substrates. However, the method of peptide immobilization was restricted, that is, peptide is often immobilized through the reactive groups inherent in substrates with multistep reactions. Here, we report a single-step immobilization of fibronectin-derived cell adhesive peptide (Arg-Glu-Asp-Val; REDV) onto polymer materials by use of tyrosine oxidation with copper catalyst and hydrogen peroxide. REDV peptide was successfully immobilized on tissue culture polystyrene, poly­(ethylene terephthalate), poly­(vinyl chloride), expanded-poly­(tetrafluoroethylene), and poly­(l-lactic acid), resulting in enhanced adhesion of human umbilical vein endothelial cells. This method is a single-step reaction under very mild conditions and is available for the biological functionalization of various medical devices

Surface Modification of Poly(L-lactic acid) Nanofiber with Oligo(D-lactic acid) Bioactive-Peptide Conjugates for Peripheral Nerve Regeneration

In some traumatic nerve injuries, autologous nerve grafting is the first choice for bridging the gap between the severed nerve ends. However, this therapeutic strategy has some disadvantages, including permanent loss of donor function and requirement of multiple surgeries. An attractive alternative to this therapeutic technique is the use of artificial nerve conduit. Poly (L-lactic acid) (PLLA) is widely used as a substrate for artificial nerve conduit because it is readily biodegradable, but it is not inherently biologically active. In this study, we developed a PLLA nanofibrous nerve conduit, modified with a conjugate of oligo (D-lactic acid) (ODLA) and the neurite outgrowth, thereby promoting peptide AG73 (RKRLQVQLSIRT) to improve nerve regeneration. PLA/ODLA-AG73 nanofibrous conduit was fabricated by electrospinning and then transplanted at the 10 mm gap of rat sciatic nerve. After six months, electrophysiological evaluation revealed that it achieved better functional reinnervation than silicone tube (used as a reference) or unmodified PLLA nanofibrous conduit

Effects of molecular architecture of phospholipid polymers on surface modification of segmented polyurethanes

<div><p>To modify the surface properties of segmented polyurethane (SPU), effects of the molecular architecture of the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers on the performance of the SPU/MPC polymer membrane were investigated. We combined the random-type, block-type, and graft-type of the MPC polymers with a typical SPU, Tecoflex^® using double solution casting procedure. The graft-type MPC polymers composed of a poly(MPC) main chain and poly(2-ethylhexyl methacrylate (EHMA)) side chains were synthesized through the combination of two different living radical polymerization techniques to regulate the density and chain length of the side chains. The SPU membranes modified with the MPC polymers were characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results revealed that the MPC units were located on the SPU surface. Although the breaking strength of the SPU membranes modified with block-type poly(MPC-block-EHMA) and graft-type poly(MPC-graft-EHMA) was lower than that of SPU membranes modified with random-type poly(MPC-random-EHMA), their breaking strengths were adequate for manufacturing medical devices. On the other hand, better stability was observed in the MPC polymer layer on the SPU membrane after immersion in an aqueous medium, wherein the SPU membrane had been modified with the poly(MPC-<i>graft</i>-EHMA). This was because of the intermixing of the hydrophobic poly(EHMA) segments in the domain of the hard segments in the SPU membrane. After this modification, each SPU/MPC polymer membrane showed hydrophilic nature based on the MPC polymers and a dramatic suppression of protein adsorption. From these results, we concluded that the SPU membrane modified with the poly(MPC-<i>graft</i>-EHMA) was one of the promising polymeric biomaterials for making blood-contacting medical devices.</p></div

Durable modification of segmented polyurethane for elastic blood-contacting devices by graft-type 2-methacryloyloxyethyl phosphorylcholine copolymer

<div><p>We propose a novel application of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers for enhancing the performance of modified segmented polyurethane (SPU) surfaces for the development of a small-diameter vascular prosthesis. The SPU membranes were modified by random-type, block-type, and graft-type MPC polymers that were prepared using a double-solution casting procedure on stainless steel substrates. Among these MPC polymers, the graft-type poly(MPC-<i>graft</i>-2-ethylhexyl methacrylate [EHMA]), which is composed of a poly(MPC) segment as the main chain and poly(EHMA) segments as side chains, indicated a higher stability on the SPU membrane after being peeled off from the stainless steel substrate, as well as after immersion in an aqueous medium. This stability was caused by the intermiscibility in the domain of the poly(EHMA) segments and the soft segments of the SPU membrane. Each SPU/MPC polymer membrane exhibited a dramatic suppression of protein adsorption from human plasma and endothelium cell adhesion. Based on these results, the performance of SPU/poly(MPC-<i>graft</i>-EHMA) tubings 2 mm in diameter as vascular prostheses was investigated. Even after blood was passed through the tubings for 2 min, the graft-type MPC polymers effectively protected the blood-contacting surfaces from thrombus formation. In summary, SPU modified by graft-type MPC polymers has the potential for practical application in the form of a non-endothelium, small-diameter vascular prosthesis.</p></div

Gene chip/PCR-array analysis of tissue response to 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer surfaces in a mouse subcutaneous transplantation system

<div><p>To evaluate the <i>in vivo</i> foreign body reaction to bio-inert 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers, MPC polymer-coated porous substrates, with large surface area, were implanted subcutaneously in mice for 7 and 28 days, and the surrounding tissue response and cells infiltrating into the porous structure were evaluated. The MPC polymer surface induced low angiogenesis and thin encapsulation around the porous substrate, and slightly suppressed cell infiltration into the porous substrate. M1-type macrophage specific gene (CCR7) expression was suppressed by the MPC polymer surface after 7 days, resulting in the suppression of inflammatory cytokine/chemokine gene expression. However, the expression of these genes on the MPC polymer surface was higher than on the non-coated surface after 28 days. These findings suggest that MPC polymer surfaces successfully inhibit inflammatory responses during the early stage of tissue response, and seem to retard its occurrence over time.</p></div

Dynamic <I>in vitro</I> hemocompatibility of oligoproline self-assembled monolayer surfaces

The blood compatibility of self-assembled monolayers (SAMs) of oligoproline, a nonionic antifouling peptide, was investigated using the cone-and-plate assay imitating arterial blood flow conditions. End-capped oligoprolines composed of 6 and 9 proline residues (Pro6 and Pro9) and a Cys residue were synthesized for preparing SAMs (Pro-SAMs) on Au-sputtered glass. The surface of Pro-SAMs indicated hydrophilic property with a smooth topology. The adsorption of blood components and the adhesion of blood cells, including leukocytes and platelets, were strongly suppressed on Pro-SAMs. Moreover, Pro9-SAM did not trigger the activation of platelets (i.e., the conformational change of GPIIb/IIIa and P-selectin (CD62P) expression on platelets and the formation of aggregates). Our results demonstrate that Pro9-SAM completely inhibited acute thrombogenic responses and the activation of platelets under dynamic conditions