Synthesis and blood compatibilities of novel segmented polyurethanes grafted phospholipid analogous vinyl monomers and polyfunctional monomers

Segmented biopolyurethanes for medical applications

Polyurethanes are one of the most popular groups of biomaterials applied for medical devices. Their segmented block copolymeric character endows them a wide range of versatility in terms of tailoring their physical properties, blood and tissue compatibility. Polyester- and polyether-urethanes have been modified with hydroxypropyl cellulose aiming the change of their surface and bulk characteristics to confer them biomaterial qualities. In this respect, dynamic contact angle measurements, dynamic mechanical analyses accompanied by mechanical testing have been done. Platelet adhesion test has been carried out in vitro and the use of hydroxypropyl cellulose in the polyurethane matrix reduces the platelet adhesion and therefore recommends them as candidates for biocompatible materials.

Surface characterization of biopolyurethanes based on cellulose derivatives

Surface tension parameters and surface morphology of biopolyurethanes based on cellulose derivatives thin films, before and after HF cold plasma treatment has been investigated. Calculations are based on the geometric mean approach of Owens and Wendt, Rabel and Kälble, on the Lifshitz-van der Waals acid/base approach of van Oss and co-workers and on the theoretical methods involving quantitative structure-property relationship. For all the investigated samples the polar component contributes significantly to the total surface tensions, as due to the large electron donor interactions. HF cold plasma treatment modifies the surface energy of biopolyurethanes by changing their surface polarity and hydrophilicity. The hydrophilic/hydrophobic balance was studied by means of the free energy of hydration between the biomaterial film and water. The protein adsorption tests of fibrinogen were effected to evaluate the applicability of these biopolyurethanes as biomedical thromboresistant devices.

Synthesis, Characterization and Preliminary Investigation of Blood Compatibility of Novel Epoxy-modified Polyurethane Networks

To prepare elastomers with acceptable physical properties and good blood compatibility, polyurethane networks were synthesized via crosslinking reaction of epoxy-terminated polyurethane prepolymers (EUPs) and hexamethylene diamine. EUPs were prepared by reacting glycidol and NCO-terminated polyurethanes. All new materials were characterized by conventional spectroscopic methods and properties were evaluated and correlated to their structure. Cytotoxcicity evaluation for the films of samples based on mouse fibroblasts (L929) revealed that these elastomers posed no threat to these cells. In vitro platelet-rich plasma contact test showed reduced number of adhered platelets on the surface of the films, particularly for those with maximum crystallinity and microphase structures and high hydrophilicity. The results obtained implied the potential for the utilization of these elastomers in biomedical applications.

Construction of a biomimetic surface on microfluidic chips for biofouling resistance

A biomimetic surface has been formed on the poly(methyl methacrylate) (PMMA) microfluidic chips for biofouling resistance on the basis of a simple modification. Accordingly, an amphiphilic phospholipid copolymer of 2-methacryloyloxyethyl phosphorylcholine and n-butyl methacrylate (PMB) was developed to introduce the phosphorylcholine functional groups onto the PMMA surface via the anchoring of hydrophobic n-butyl methacrylate units. The 2-methacryloyloxyethyl phosphorylcholine segments could form hydrophilic domains, considered to be located on the surface, to provide a biocompatible surface. X-ray photoelectron spectroscopy and Fourier transform infrared spectra confirmed the success of surface functionalization. The PMB-modified microchips containing phosphorylcholine moieties exhibited more stable electroosmotic mobility compared with the untreated one. In addition to being characterized for minimized nonspecific adhesion of serum proteins and plasma platelets, the PMB-functionalized microchannels have been exemplified by electrophoresis of proteins. This one-step procedure offers an effective approach for a biomimetic surface design on microfluidic chips, which is promising in high-throughput and complex biological analysis.

Properties of phospholipid monolayer deposited on a fluorinated polyurethane

A simple procedure for surface modification of polyurethane by the Langmuir-Blodgett (LB) method using the amphiphile 1,2-distearoyl-sn-glycero-3-phosphocholine dihydrate (DSPC) was developed. The polyurethane containing the fluorinated moiety was prepared via the perfluoro-containing chain extender 2,2,3,3-tetrafluoro-1,4-butanediol. The fluorinated polyurethane (FPU) films were prepared by spin coating and dipping methods. The spin-coated FPU films exhibited hydrophobic characteristic and, thus, enhanced the transferability of DSPC. Held at constant pressure of 45 mN/m, the DSPC monolayer was transferred successfully to FPU films with a near-unity transfer ratio. The in vitro platelet adhesion assay revealed that the FPU modified with DSPC monolayer was more platelet compatible than the unmodified FPU substrates with no pseudopods and flattening of adherent platelets as well as lower platelet adhesion density. Moreover, the DSPC monolayer remained intact after platelet adhesion testing. In addition, the platelet compatibility of the unmodified FPU was affected by the film preparation methods. This might be attributed to the distinctive surface micromorphology formed. This simple DSPC deposition scheme by a LB technique would be very useful to further enhance the platelet compatibility of hydrophobic substrate and can be utilized for biomedical application in which the flow shear rate is not too high.

Various approaches to modify biomaterial surfaces for improving hemocompatibility

In this paper, the mechanism of thrombus formation on the surface of polymeric materials and the various approaches of modifying biomaterial surfaces to improve their hemocompatibility are reviewed. Moreover, the blood compatibility of the cellulose membrane grafted with O-butyrylchitosan (OBCS) by using a radiation grafting technique was studied. Surface analysis of grafted cellulose membrane was verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA), which confirmed that OBCS was successfully grafted onto the cellulose membrane surfaces. Blood compatibility of the grafted cellulose membranes was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank cellulose membranes as the control. The blood compatibility of OBCS grafted cellulose membranes is better than that of blank cellulose membranes. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving in blood-contacting applications in medical use.

Synthesis of blood compatible polyamide block copolymers

Blood compatibility of polyamides has been improved by introducing amido-amine groups in polymer backbone. Polyamide block-copolymer are synthesized by reacting amine end-capped polyamides with N,N'-methylene-bisacrylamide. Polyamide block-copolymers, thus produced found to have the ability of absorbing heparin. Heparinized polyamide block-copolymers have shown significant improvement in blood compatibility as evident from thrombus formation and hemolysis studies.

Synthesis, characterization and platelet adhesion of segmented polyurethanes grafted phospholipid analogous vinyl monomer on surface

New segmented polyurethanes (SPUs) grafted phospholipid analogous vinyl monomer, 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) on surface were synthesized. The soft segment of these polyurethanes was hydroxylated poly(isoprene) diol and the hard segments were 4,4'-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BD). SPUs were hydroxylated by potassium peroxodisulfate and MPC was grafted on the surface of hydroxylated SPUs using di-ammonium cerium (IV) nitrate (ceric ammonium nitrate, CAN) as a radical initiator. The bulk characterization of synthesized SPUs was investigated by infrared spectroscopy (IR) and gel-permeation chromatography (GPC). The existence of phospholipid analogous groups on the surface of these SPUs was revealed by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The surfaces of MPC-grafted SPUs showed decreased water contact angles compared to non-grafted SPU and the presence of phosphorylcholine groups. The blood compatibilities of the new polymers were evaluated by platelet rich plasma (PRP) contact studies and viewed by scanning electron microscopy (SEM) using BioSpan and non-grafted polyurethane as references. We found that fewer platelets adhered to the MPC-grafted surfaces and that they showed less shape variation than the references. These results suggest that these grafted polymers may have the possibility of the usage for biomaterials.