Hemocompatibility of poly(ether imide) membranes functionalized with carboxylic groups

The role of carboxylic groups in heparin-mimicking polymer-functionalized surfaces for blood compatibility: Enhanced vascular cell selectivity

Blood compatibility is an eternal topic of biomedical materials. The effect of heparin-mimicking polymers (HMPs) on blood compatibility has been well studied, especially the synergistic effect of sugar unit and sulfonate/sulfate unit. However, carboxylic groups also play an important role in HMPs. In this work, copolymers of sodium 4-vinyl-benzenesulfonate (SS) and 2-methacrylamido glucopyranose (MAG) (poly(SS-co-MAG)) and poly(acrylate acid) (PAA) were self-assembled on Au surfaces with different feed ratios. When self-assembly of poly(SS-co-MAG) alone, the optimized feed ratio of SS and MAG for vascular cell selectivity was 1:1 (PS1M1); at this ratio the Au-PS1M1 surface showed the highest human umbilical vein endothelial cells (HUVECs) density and the lowest human umbilical vein smooth muscle cells (HUVSMCs) density. When self-assembly of PAA alone (surface designated as Au-PAA), the proliferation of both HUVECs and HUVSMCs was inhibited. Compared with either PS1M1 or PAA alone, the surfaces modified with both PAA and PS1M1 at the feed ratio of 1:1 (material designated as Au-PSM/PAA-2) showed enhanced promoting effect on HUVECs as well as enhanced inhibiting effect on HUVSMCs, indicating stronger vascular cell selectivity of carboxylic groups in the presence of sugar and sulfonate units.

Heparin as a molecular spacer immobilized on microspheres to improve blood compatibility in hemoperfusion

Heparin, a highly sulfated linear polysaccharide, with anticoagulation function and blood compatibility is widely used as a biomaterials in medical application, but the most importance of heparin is its structure function as the macromolecular space arm. In this study, heparin as a spacer was covalently immobilized on the chloromethylated polystyrene microspheres (Ps) and then connected with l-phenylalanine forming the Ps-Hep-Phe structure, which was developed for endotoxin adsorption in hemoperfusion. The grafting density of heparin reach the maximum when the initial concentration of heparin solution was 5 mg/mL. The adsorbents with the heparin as a spacer showed the prolonged clotting times, low protein adsorption, and reduced the hemolysis rate, indicating that heparin-modified adsorbents have great blood compatibility. The adsorption capacity of Ps-Hep-Phe for endotoxin was 25.15 EU/g in dynamic adsorption, higher than that of Ps. Therefore, this study imply that heparin would be promising for modification of adsorbents in hemoperfusion.

Polyelectrolyte multi-layers assembly of SiCHA nanopowders and collagen type I on aminolysed PLA films to enhance cell-material interactions

This paper presents a new approach in assembling bone extracellular matrix components onto PLA films, and investigates the most favourable environment which can be created using the technique for cell-material interactions. Poly (lactic acid) (PLA) films were chemically modified by covalently binding the poly(ethylene imine) (PEI) as to prepare the substrate for immobilization of polyelectrolyte multilayers (PEMs) coating. Negatively charged polyelectrolyte consists of well-dispersed silicon-carbonated hydroxyapatite (SiCHA) nanopowders in hyaluronic acid (Hya) was deposited onto the modified PLA films followed by SiCHA in collagen type I as the positively charged polyelectrolyte. The outermost layer was finally cross-linked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrocholoride and N-hydroxysulfosuccinimide sodium salt (EDC/NHS) solutions. The physicochemical features of the coated PLA films were monitored via X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscope (AFM). The amounts of calcium and collagen deposited on the surface were qualitatively and quantitatively determined. The surface characterizations suggested that 5-BL has the optimum surface roughness and highest amounts of calcium and collagen depositions among tested films. In vitro human mesenchymal stem cells (hMSCs) cultured on the coated PLA films confirmed that the coating materials greatly improved cell attachment and survival compared to unmodified PLA films. The cell viability, cell proliferation and Alkaline Phosphatase (ALP) expression on 5-BL were found to be the most favourable of the tested films. Hence, this newly developed coating materials assembly could contribute to the improvement of the bioactivity of polymeric materials and structures aimed to bone tissue engineering applications.

In vivo biocompatibility assessment of poly (ether imide) electrospun scaffolds

Poly(ether imide) (PEI), which can be chemically functionalized with biologically active ligands, has emerged as a potential biomaterial for medical implants. Electrospun PEI scaffolds have shown advantageous properties, such as enhanced endothelial cell adherence, proliferation and low platelet adhesion in in vitro experiments. In this study, the in vivo behaviour of electrospun PEI scaffolds and PEI films was examined in a murine subcutaneous implantation model. Electrospun PEI scaffolds and films were surgically implanted subcutaneously in the dorsae of mice. The surrounding subcutaneous tissue response was examined via histopathological examination at 7 and 28 days after implantation. No serious adverse events were observed for both types of PEI implants. The presence of macrophages or foreign body giant cells in the vicinity of the implants and the formation of a fibrous capsule indicated a normal foreign body reaction towards PEI films and scaffolds. Capsule thickness and inflammatory infiltration cells significantly decreased for PEI scaffolds during days 7-28 while remaining unchanged for PEI films. The infiltration of cells into the implant was observed for PEI scaffolds 7 days after implantation and remained stable until 28 days of implantation. Additionally some, but not all, PEI scaffold implants induced the formation of functional blood vessels in the vicinity of the implants. Conclusively, this study demonstrates the in vivo biocompatibility of PEI implants, with favourable properties of electrospun PEI scaffolds regarding tissue integration and wound healing. Copyright © 2015 John Wiley & Sons, Ltd.

Direct synthesis of heparin-like poly(ether sulfone) polymer and its blood compatibility

In this study, heparin-like poly(ethersulfone) (HLPES) was synthesized by a combination of polycondensation and post-carboxylation methods, and was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography. Owing to the similar backbone structure, the synthesized HLPES could be directly blended with pristine PES at any ratios to prepare PES/HLPES membranes. After the introduction of HLPES, the microscopic structure of the modified PES membranes was changed, while the hydrophilicity was significantly enhanced. Bovine serum albumin and bovine serum fibrinogen adsorption, activated partial thromboplastin time, thromb time and platelet adhesion for the modified PES membranes were investigated. The results indicated that the blood compatibility of the PES/HLPES membranes was significantly improved compared with that of pristine PES membrane. For the PES/HLPES membranes, obvious decreases in platelet activation on PF-4 level, in complement activation on C3a and C5a levels, and in leukocytes activation on CD11b levels were observed compared with those for the pristine PES membrane. The improved blood compatibility of the PES/HLPES membrane might due to the existence of the hydrophilic groups (-SO3Na, -COONa). Furthermore, the modified PES membranes showed good cytocompatibility. Hepatocytes cultured on the PES/HLPES membranes presented improved growth in terms of SEM observation, MTT assay and confocal laser scanning microscope observation compared with those on the pristine PES membrane. These results indicate that the PES/HLPES membranes present great potential in blood-contact fields such as hemodialysis and bio-artificial liver supports.