Polycarbonate Urethane Surface Research Articles

Surface modification of polycarbonate urethane by grafting polyethylene glycol and bivalirudin drug for improving hemocompatibility

AbstractAs the clinical demand for blood‐contacting materials increases, higher requirements are placed on their physicochemical properties, durability and hemocompatibility in vivo. In this work, a multiple functionalized material was developed through a facile modification process. Herein, polycarbonate urethane (PCU) surface was co‐modified with polyethylene glycol (PEG) and bivalirudin (BVLD). PCU provides excellent physical and mechanical properties, PEG and BVLD, especially BVLD, enable the surface with outstanding anticoagulant capacity. Specifically, PCU surface was first treated with hexamethylene diisocyanate to introduce active isocyanate groups onto the surface, followed by hydroxy‐PEG grafting to improve the hydrophilicity. Finally, BVLD was immobilized on the surface via Michael addition reaction to improve antithrombotic properties. Attenuated total reflection Fourier transforms infrared spectroscopy and UV spectrophotometers were used to confirm the modified surfaces. The hydrophilicity was characterized by static water contact angle measurement, the morphology of the modified surfaces was observed by scanning electron microscopy. Blood compatibility of the modified surfaces was characterized by the hemolysis rate, platelet adhesion assay and cell culture test. The results showed that the BVLD immobilized surface has excellent anticoagulant properties, good fibrin‐bound thrombin inhibition, and good resistance against non‐specific adhesion of proteins. Hence, the co‐modification with PEG and BVLD was proved an encouraging strategy for improving hemocompatibility.

Cartilage lamina splendens inspired nanostructured coating for biomaterial lubrication

Biomaterials that are used in biological systems, such as polycarbonate urethane (PCU) knee joint implants and contact lenses, generally lack lubrication. This limits their integration with the body and impedes their function. Here, we propose a nanostructured film based on hydrophilic polysaccharide hyaluronic acid conjugated with dopamine (HADN) and zwitterionic reduced glutathione (Glu), which forms a composite coating (HADN-Glu) to enhance the lubrication between cartilage and PCU. HADN was synthesized by carbodiimide chemistry between hyaluronic acid and dopamine and deposited on PCU surface under mild oxidative conditions. Then, zwitterionic peptide-reduced glutathione was bioconjugated to HADN, forming a lubrication film. Analysis based on X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and wettability indicated that HADN and Glu had grafted successfully onto the PCU surface. Measurements of the coefficient of friction (COF), friction energy dissipation and cartilage roughness indicated that cartilage was effectively protected by the high lubrication of HADN-Glu. Both at low and high applied loads, this effect was likely due to the enhanced boundary lubrication enabled by HADN-Glu on the PCU surface. Moreover, HADN-Glu is highly biocompatible with chondrocyte cells, suggesting that this film will benefit the design of implants where lubrication is needed.

Hyperspectral chemical imaging reveals spatially varied degradation of polycarbonate urethane (PCU) biomaterials

Hyperspectral chemical imaging (HCI) is an emerging technique which combines spectroscopy with imaging. Unlike traditional point spectroscopy, which is used in the majority of polymer biomaterial degradation studies, HCI enables the acquisition of spatially localised spectra across the surface of a material in an objective manner. Here, we demonstrate that attenuated total reflectance Fourier transform infra-red (ATR-FTIR) HCI reveals spatial variation in the degradation of implantable polycarbonate urethane (PCU) biomaterials. It is also shown that HCI can detect possible defects in biomaterial formulation or specimen production; these spatially resolved images reveal regional or scattered spatial heterogeneity. Further, we demonstrate a map sampling method, which can be used in time-sensitive scenarios, allowing for the investigation of degradation across a larger component or component area. Unlike imaging, mapping does not produce a contiguous image, yet grants an insight into the spatial heterogeneity of the biomaterial across a larger area. These novel applications of HCI demonstrate its ability to assist in the detection of defective manufacturing components and lead to a deeper understanding of how a biomaterial’s chemical structure changes due to implantation. Statement of significanceThe human body is an aggressive environment for implantable devices and their biomaterial components. Polycarbonate urethane (PCU) biomaterials in particular were investigated in this study. Traditionally one or a few points on the PCU surface are analysed using ATR-FTIR spectroscopy. However the selection of acquisition points is susceptible to operator bias and critical information can be lost. This study utilises hyperspectral chemical imaging (HCI) to demonstrate that the degradation of a biomaterial varies spatially. Further, HCI revealed spatial variations of biomaterials that were not subjected to oxidative degradation leading to the possibility of HCI being used in the assessment of biomaterial formulation and/or component production.

Differential Adhesive and Bioactive Properties of the Polymeric Surface Coated with Graphene Oxide Thin Film

Surface engineering of implantable devices involving polymeric biomaterials has become an essential aspect for medical implants. A surface enhancement technique can provide an array of unique surface properties that improve its biocompatibility and functionality as an implant. Polyurethane-based implants that have found extensively acclaimed usage as an implant in biomedical applications, especially in the area of cardiovascular devices, still lack any mechanism to ward off bacterial or platelet adhesion. To bring out such a defense mechanism we are proposing a surface modification technique. Graphene oxide (GO) in very thin film form was wrapped onto the electrospun fibroporous polycarbonate urethane (PCU) membrane (GOPCU) by a simple method of electrospraying. In the present study, we have developed a simple single-step method for coating a polymeric substrate with a thin GO film and evaluated the novel antiadhesive activity of these films. SEM micrographs after coating showed the presence of very thin GO films over the PCU membrane. On the GOPCU surface, the contact angle was shifted by ∼30°, making the hydrophobic PCU surface slightly hydrophilic, while Raman spectral characterization and mapping showed the presence and distribution of GO over 75% of the membrane. A reduced platelet adhesion on the GOPCU surface was observed; meanwhile, bacterial adhesion also got reduced by 85% for Staphylococcus aureus (Gram positive, cocci) and 64% for Pseudomonas aeruginosa (Gram negative, bacilli). A cell adhesion study conducted using mammalian fibroblast cells projected its proliferation percentage in a MTT assay, with 82% cell survival on PCU and 86% on GOPCU after 24 h culture, while a study for an extended period of 72 h showed 87% of survival on PCU and 88% on GOPCU. This plethora of functionalities by a simple modification technique makes thin GO films a self-sufficient surface engineering material for future biomedical applications.

Surface Modification of Polycarbonate Urethane with Zwitterionic Polynorbornene via Thiol‐ene Click‐Reaction to Facilitate Cell Growth and Proliferation

Herein, we grafted the zwitterionic polynorbornene onto polycarbonate urethane (PCU) film surface by a convenient route of thiol‐ene click‐chemistry. The PCU film surface was first treated with hexamethylene‐1,6‐diisocynate and subsequently with two different thiol agents (l‐cysteine and β‐marcaptoethanol) in the presence of di‐n‐butyltin dilaurate (DBTDL) to immobilize sulfhydryl groups onto the surface. Here, DBTDL acted as selective catalyst for the reaction between surface‐tethered isocyanates and amine/hydroxyl groups in thiol agents over that of free thiol groups. In the next step, zwitterionic polynorbornene (poly(NSulfoZI)) having functionalizable double bonds was grafted onto these surfaces by photo‐initiated thiol‐ene click‐reaction. The modified surfaces were characterized by water contact angle and XPS analysis. Moreover, the cytocompatibility of these surfaces was investigated by model endothelial cells, EA.hy926, for 1, 3, and 7 d culture times, which showed enhanced cell adhesion and growth. Therefore, the poly(NSulfoZI) functionalized PCU surface using l‐cysteine as thiol agent could be a good candidate for tissue engineering material application.

Characterization of Coating Strategies to Generate Antithrombogenic and Endothelial Progenitor Cells Recruiting Properties on Polycarbonateurethane Surfaces

Characterization of Coating Strategies to Generate Antithrombogenic and Endothelial Progenitor Cells Recruiting Properties on Polycarbonateurethane Surfaces

Micro-structuring of polycarbonate-urethane surfaces in order to reduce platelet activation and adhesion

In the development of new hemocompatible biomaterials, surface modification appears to be a suitable method in order to reduce the thrombogenetic potential of such materials. In this study, polycarbonate-urethane (PCU) tubes with different surface microstructures to be used for aortic heart valve models were investigated with regard to the thrombogenicity. The surface structures were produced by using a centrifugal casting process for manufacturing PCU tubes with defined casting mold surfaces which are conferred to the PCU surface during the process. Tubes with different structures defined by altering groove widths were cut into films and investigated under dynamic flow conditions in contact with porcine blood. The analysis was carried out by laser scanning microscopy which allowed for counting various morphological types of platelets with regard to the grade of activation. The comparison between plain and shaped PCU samples showed that the surface topography led to a decline of the activation of the coagulation cascade and thus to the reduction of the fibrin synthesis. Comparing different types of structures revealed that smooth structures with a small groove width (d ~ 3 μm) showed less platelet activation as well as less adhesion in contrast to a distinct wave structure (d ~ 90 μm). These results prove surface modification of polymer biomaterials to be a suitable method for reducing thrombogenicity and hence give reason for further alterations and improvements.

Grafting of phosphorylcholine functional groups on polycarbonate urethane surface for resisting platelet adhesion

In order to improve the resistance of platelet adhesion on material surface, 2-methacryloyloxyethyl phosphorylcholine (MPC) was grafted onto polycarbonate urethane (PCU) surface via Michael reaction to create biomimetic structure. After introducing primary amine groups via coupling tris(2-aminoethyl)amine (TAEA) onto the polymer surface, the double bond of MPC reacted with the amino group to obtain MPC modified PCU. The modified surface was characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results verified that MPC was grafted onto PCU surface by Michael reaction method. The MPC grafted PCU surface had a low water contact angle and a high water uptake. This means that the hydrophilic PC functional groups improved the surface hydrophilicity significantly. In addition, surface morphology of MPC grafted PCU film was imaged by atomic force microscope (AFM). The results showed that the grafted surface was rougher than the blank PCU surface. In addition, platelet adhesion study was evaluated by scanning electron microscopy (SEM) observation. The PCU films after treated with platelet-rich plasma demonstrated that much fewer platelets adhered to the MPC-grafted PCU surface than to the blank PCU surface. The antithrombogenicity of the MPC-grafted PCU surface was determined by the activated partial thromboplastin time (APTT). The result suggested that the MPC modified PCU may have potential application as biomaterials in blood-contacting and some subcutaneously implanted devices.

Surface modification of polycarbonate urethane by covalent linkage of heparin with a PEG spacer

Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing, αω-diamino-poly(ethylene glycol) (APEG, M n=2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm2) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface.

Preparation and characterization of phosphorylcholine glyceraldehyde grafted polycarbonateurethane films

Phosphorylcholine glyceraldehyde (PCGA), the aldehyde derivative of L-α-glycerylphosphorylcholine (GPC), was covalently linked onto polycarbonateurethane (PCU) surface in order to introduce biomimetic structure on its surface. PCGA was grafted onto PCU surface via three coupling reactions on PCU surface using hexamethylene diisocyanate (HDI) and tris(2-aminoethyl)amine (TAEA) as spacers. X-ray photoelectron spectroscopy (XPS), fourier transform infrared (FTIR) spectroscopy and water contact angle measurements verified that PCGA had already been grafted onto PCU surfaces. In addition, surface morphology of PCGA grafted PCU film was observed using atomic force microscope (AFM), which showed that the grafted film has a pin-hole free surface which is rougher than the surface of blank PCU film. Scanning electron microscope (SEM) observation of the modified PCU films after treated with platelet-rich plasma demonstrated that much fewer platelets adhered to the surfaces of the grafted PCU films than to the surface of blank PCU film. The result suggested that these PCGA grafted polymers may have potential application as biomaterials for vascular grafts and some subcutaneously implanted devices.

Biomimetic surface modification of polycarbonateurethane film via phosphorylcholine-graft for resisting platelet adhesion

Phosphorylcholine groups were covalently introduced onto a polycarbonateurethane (PCU) surface in order to create a biomimetic structure on the polymer surfaces. After introducing primary amine groups onto the polymer surface by 1,6-hexanediamine, phosphorylcholine groups were covalently linked onto the surface by the reductive amination between the amino group and the aldehyde group of phosphorylcholine glyceraldehyde (PCGA). The results of water contact angle test, X-ray photoelectron spectroscopy (XPS), and X-ray fluorescence spectrometer (XRF) analysis of the modified films indicated that PCGA had already been covalently linked to the PCU surface. The topographies and surface roughnesses were both imaged and measured by atomic force microscopy (AFM). Scanning electron microscopy (SEM) observation of the PCU films after treatment with platelet-rich plasma demonstrated that platelets had rarely adhered to the surface of the PCGA-grafted PCU films but had mainly adhered to the surface of the blank PCU films. The platelet adhesion result indicated that the PC modified PCU films could resist platelet adhesion after grafting with PCGA, and that these PCGA-grafted PCU materials, potentially, might be applied as blood-contacting materials. Open image in new window

Grafting of a novel phosphorylcholine-containing vinyl monomer onto poly-carbonateurethane surfaces by ultraviolet radiation grafting polymerization

An original phosphorylcholine (PC) containing vinyl monomer (compound 1) was grafted onto the surface of polycarbonate urethane (PCU) films by ultraviolet (UV) initiated polymerization. The vinyl monomer was synthesized from 2-hydroxyethyl methacrylate (HEMA), hexamethylene diisocyanate (HDI) and L-α-glycerylphosphorylcholine (GPC) by two relative reactions through the coupling of the isocyanate groups in HDI with the hydroxyl groups in HEMA and GPC, respectively. The existence of phosphorylcholine groups on the surface of compound 1-grafted PCU films was verified by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. The surfaces of the grafted PCU films showed lower water contact angles than did the surfaces of non-grafted PCU films. Furthermore, the surface morphology of a grafted PCU film was observed using scanning electrical microscopy (SEM), which showed that the grafted polymer film exhibits a rough and pinhole-free surface. In addition, the blood compatibility of the compound 1-grafted PCU films was evaluated by platelet adhesion studies using the non-grafted PCU film as a reference. It was found by SEM that fewer platelets adhered to the surfaces of the grafted PCU films compared to the reference. The high PC-grafted PCU film did not show any substantial platelet attachment on its surface. These results indicated that these compound 1-grafted polymers may have potential application as biomaterials for vascular grafts and some subcutaneously implanted devices. Open image in new window

Surface Modification of Polycarbonateurethane by Grafting Phosphorylcholine Glyceraldehydes for Improving Hemocompatibility

ABSTRACTPhosphorylcholine glyceraldehyde (PCGA) was used as a phosphorylcholine (PC) group containing compound to graft onto the surface of polycarbonateurethane (PCU) film using 1,6-hexanediamine (HDA) or α,ω-diamino-poly(ethylene glycol) (APEG, Mn = 200) as a spacer, in order to introduce biomimetic structure onto the polymer surface. X-ray photoelectron spectroscopy (XPS) analysis shows that PCGA has been covalently linked to the PCU surface. Water contact angle test suggests that the surface hydrophilicity has been improved after PCGA is grafted onto the surface of PCU film. Scanning electron microscope (SEM) observation of the modified PCU films after contacting with plasma-rich plasma demonstrates that platelets rarely adhere but a large number of platelets adhere to the original PCU surface. The hemocompatibility of the PC modified PCU film has been improved obviously after grafting with PCGA with PEG spacer.

Grafting Sulfoammonium Zwitterionic Brushes onto Polycarbonateurethane Surface to Improve Hemocompatibility

Poly(3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate) (poly(DMAPS)) zwitterionic brushes were grafted onto the polycarbonateurethane (PCU) surface to improve its hydrophilicity and hemocompatibility by Ultraviolet (UV) polymerization. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle were used to characterize the chemical and physical properties of the modified PCU surface. DMAPS-grafted PCU films showed significantly high hydrophilicity owing to the high hydrophilic poly(DMAPS) zwitterionic brushes. The cytotoxicity tests revealed the sulfoammonium zwitterionic brushes modified PCU film had good cytocompatibility. In addition, the hemocompatibility of the modified PCU films was evaluated by hemolytic tests and platelet adhesion tests. The PCU films modified with zwitterionic brushes had a lower hemolytic index, showed effective resistance to platelet adhesion. Due to the fact that sulfoammonium zwitterionic brushes can improve the hemocompatibility of the PCU surface, this gives rise to its potential application as blood-contacting materials or devices.

Grafting Biomimetic Phospholipid Zwitterionic Brushes onto Polycarbonateurethane for Improving Hemocompatibility

In order to improve the hemocompatibility of polycarbonateurethane (PCU), the biomimetic phosphorylcholine (PC) group was introduced onto material surface. Brush structure having PC groups was formed by ultraviolet (UV) initiated polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) to improve the hydrophilicity and hemocompatibility of PCU surfaces. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electrical microscopy (SEM) and water contact angle were used to characterize the chemical and physical properties of the modified PCU surfaces. Compared with original PCU, the PC-grafted PCU surfaces showed significantly high hydrophilicity as indicating by low water contact angle. The hemocompatibility of the PC-grafted PCU surfaces was evaluated by platelet adhesion test. The PCU surfaces modified with phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high hemocompatibility. These PC-grafted PCU materials will have potential application as blood-contacting materials or devices due to their good mechanical and hemocompatible properties.

Shelf Life and Chemical Stability of Calcium Phosphate Coatings Applied to Poly Carbonate Urethane Substrates

Many modern orthopaedic implants are coated with calcium phosphate to improve the host tissue response to the implants. Despite numerous studies on the dissolution properties of calcium phosphate (CaP) coatings, the coating “shelf life” (i.e. the chemical stability of these coatings prior to implantation), has not been investigated adequately, particularly for CaP coatings applied to polymeric substrates. This paper examines the chemical stability of CaP coatings that were applied to a poly carbonate urethane (PCU) substrate by an aqueous, low temperature technique. Applying a CaP coating to the PCU surface is designed to enhance the fixation between the implant and adjacent vertebrae. High temperature coating techniques are unfeasible for polymeric substrates, like PCU, because the high temperature may critically degrade the substrate. The CaP coating shelf life was assessed by using FTIR-ATR and SEM to analyze changes in CaP-coated PCU discs over time. The expected in vivo chemical stability of the CaP coating was measured by immersing CaP-coated PCU discs in cell culture media under physiological conditions. ICP-OES was used to measure the calcium and phosphorus concentrations of the immersion solution.

Grafting of poly(ethylene glycol) monoacrylate onto polycarbonateurethane surfaces by ultraviolet radiation grafting polymerization to control hydrophilicity

AbstractIn this study, we used a UV radiation grafting method to modify the surface of the biomaterial polycarbonateurethane (PCU). Hydrophilic poly(ethylene glycol) monoacrylate (PEGMA; number‐average molecular weight = 526) as a macromolecular monomer was grafted onto the PCU surface by UV photopolymerization. The Fourier transform infrared and X‐ray photoelectron spectroscopy results of the graft‐modified PCU confirmed poly[poly(ethylene glycol) monoacrylate] block grafting onto the surface. We investigated the effects of the reaction temperature, macromolecular monomer concentration, UV irradiation time, and photoinitiator concentration on the grafting density (GD) in detail. Furthermore, we investigated the effects of GD under various process conditions on the water uptake and water contact angle. The modified materials had a high water uptake and low water contact angle, which indicated that the hydrophilicity of the PCU surface was improved significantly by the introduction of the hydrophilic poly(ethylene glycol) blocks on the surface. The anticoagulant properties of the material might also have been improved. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011