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

Long-Term/Bioinert Labeling of Rat Mesenchymal Stem Cells with PVA-Gd Conjugates and MRI Monitoring of the Labeled Cell Survival after Intramuscular Transplantation

Noninvasive in vivo imaging of transplanted stem cells is an effective method to clarify the mechanisms involved in stem cell transplantation therapy. We labeled rat mesenchymal stem cells (MSCs) with water-soluble magnetic resonance imaging (MRI) contrast agent poly­(vinyl alcohol)-gadolinium (PVA-Gd) in order to ascertain the fate of transplanted MSCs in vivo. PVA-Gd was retained and localized in the cytosolic compartment of MSCs for a longer period of time. The effect of PVA-Gd labeling on MSC proliferation was much less than that of the commercially available contrast agent ProHance, and the labeled MSCs were found to have osteoblastic differentiation ability. To study the MSC lifetime in vivo, MSCs were seeded and trapped in the cytocompatible three-dimensional porous scaffolds of Spongel and transplanted. The MRI signal attributed to MSCs was eliminated from the transplanted site in 14 days. Because free PVA-Gd was rapidly eliminated from the site, this signal reduction indicated MSC death in the transplantation site. The low efficiency of MSC transplantation for ischemic tissue may be due to their short lifetime, making it important to develop highly effective stem cell transplantation systems that address cell number, injection position, and cell formulation (suspension, sheet, and aggregates). Our cell survival tracking system would be a very powerful tool to this end and would be applicable in clinical cell therapies

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

Descriptions and expression levels of genes which were up-regulated in collagen and down-regulated in PMB.

<p>Numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085132#pone-0085132-g006" target="_blank">Fig. 6</a> correspond to those in the table. Plus and minus in this table indicate promotion and suppression, respectively.</p

Selected genes that were expressed differently between collagen-coated and PMB-coated and were related to tissue regeneration and inflammation.

<p>Closed circle, wound healing promotion factors; Open circle; inflammatory factors; Closed square, uncertain about tissue regeneration.</p

FTIR/ATR spectra of PMB- and collagen-coated PE films.

<p>FTIR/ATR spectra of PMB- and collagen-coated PE films.</p

Descriptions and expression levels of genes which were down-regulated in collagen and up-regulated in PMB.

<p>Numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085132#pone-0085132-g006" target="_blank">Fig. 6</a> correspond to those in the table. Plus and minus in this table indicate promotion and suppression, respectively.</p

Global analysis of host body responses to PMB-coated and collagen-coated scaffolds.

<p>All genes having valid expression levels in non-coated, collagen-coated, and PMB-coated scaffolds were plotted.</p