Surface Modifying Additives Research Articles

The role of polymer surface degradation and barium sulphate release in the pathogenesis of catheter-related infection

Susceptibility to infection and thrombosis of intravascular catheters is increased by surface irregularities, which might be prevented by coating. BaSO4 release from conventional haemodialysis catheters (CC) and modified catheters (MC) which had been coated with a surface-modifying additive (SMA) was assessed in vivo and in vitro. For the in vivo part, patients were randomized to receive a temporary CC or MC, with crossover after 1 week. After retrieval, catheters were examined using scanning electron microscopy to assess surface integrity, and an in vitro model of catheter exposure to the bloodstream was used to evaluate surface morphology and susceptibility to bacterial adhesion and proliferation. BaSO(4) moieties covered 14.7 +/- 3.7% of the surface of unused CC. After in vivo use in 16 patients, 62.7 +/- 32.9 x 10(3) holes/mm(2) were detected, indicating BaSO(4) detachment from 3.3 +/- 1.7% of the catheter surface. No defects were observed in unused CC and in MC, whether used or unused. After incubation of four catheters (two of each type) with Staphylococcus epidermidis, the two degraded CC showed an immediate and strong bacterial growth as indicated by an increase in medium impedance of 0.512%/10 min compared to -0.021%/10 min in MC (P < 0.001). Short-term exposure of CC to the bloodstream causes BaSO(4) particle release, resulting in surface irregularities predisposing to bacterial proliferation. BaSO(4) release can be prevented by SMA coating.

Antimicrobial Susceptibility of Monoculture Biofilms of a Clinical Isolate of Enterococcus faecalis

The purpose of this study was to create a monoculture biofilm of a clinical isolate of Enterococcus faecalis and to determine susceptibility against four antimicrobial irrigants. Biofilms were subjected to 1-, 3-, and 5-minute exposures to one of the following irrigants: 6% sodium hypochlorite (NaOCl), 2% chlorhexidine gluconate (CHX) or one of two new products, <6% NaOCl with surface modifiers (Chlor-XTRA) or 2% CHX with surface modifiers (CHX-Plus™) (Vista Dental Products, Racine, WI). It was hypothesized that NaOCl and CHX would be equally effective and that addition of surface modifiers would improve bactericidal activity of the respective irrigants compared to the original formulations. Results indicate that 6% NaOCl and Chlor-EXTRA™ were significantly superior against E. faecalis biolfilms compared to 2% CHX and CHX-Plus™ at all time points except five minutes.

Controlling cell-material interactions with polymer nanocomposites by use of surface modifying additives

Polymer nanocomposites (NC) are fabricated by incorporating well dispersed nanoscale particles within a polymer matrix. This study focuses on elastomeric polyurethane (PU) based nanocomposites, containing organically modified silicates (OMS), as bioactive materials. Nanocomposites incorporating chlorhexidine diacetate as an organic modifier (OM) were demonstrated to be antibacterial with a dose dependence related to both the silicate loading and the loading of OM. When the non-antibacterial OM dodecylamine was used, both cell and platelet adhesion were decreased on the nanocomposite surface. These results suggest that OM is released from the polymer and can impact on cell behaviour at the interface. Nanocomposites have potential use as bioactive materials in a range of biomedical applications.

Nonfouling biomaterials based on polyethylene oxide‐containing amphiphilic triblock copolymers as surface modifying additives: Adsorption of proteins from human plasma to copolymer/polyurethane blends

Three polyethylene oxide-polyurethane-polyethylene oxide (PEO-PU-PEO) block copolymers of variable PEO block size (MW 550, 2000, and 5000) were used to modify the surface of a conventional segmented polyurethane (PU) with the objective of inhibiting interactions with proteins. The surface-active copolymers were blended with the PU by solution methods. Protein adsorption from human plasma to the modified materials was investigated using radiolabeling and immunoblotting methods. From the radiolabeling experiments, it was found that fibrinogen adsorption from plasma to all of the modified surfaces was much lower than to the unmodified PU matrix. For blends of low copolymer content, resistance to adsorption was greatest on the copolymer 1 (PEO550)-modified materials, and increased with increasing copolymer content for all three blend types. At high copolymer content inhibition of adsorption was very strong and independent of PEO block size. The immunoblotting experiments showed that on materials of high copolymer content (20 wt %), the proteins investigated (fibrinogen, albumin, complement C3, and apolipoprotein A-I) were undetectable. At low copolymer content (< or = 5 wt %), the blends of copolymer 1, with the shortest PEO block, exhibited greater protein resistance than those of copolymers 2 and 3 (PEO blocks of MW 2000 and 5000, respectively), and resistance decreased with decreasing protein size. Evidence of complement activation was seen for the blends of low copolymer content. Adsorption of C3 and complement activation decreased with increasing content of the copolymers. It was concluded that surface density of PEO is more important than chain length for protein resistance in contact with plasma.

Gradient Elution Method for Successive Separation of Common Cations and Hydrophobic Amines using Suppressed Ion Chromatography

In mixed waste, the separation and sequential determination of alkali and alkaline earth metals mixed with hydrophobic amines represent a challenging analytical problem. The effect of a new mobile phase (amido‐sulfonic acid, ASA) on the suppressed ion chromatographic separation of alkali and alkaline earth metals and hydrophobic amines on CS12A analytical column was investigated. The addition of surface modifier to the eluent appears to provide better interfacial compatibility between the mobile and stationary phase and facilitates the rapid equilibration of analytes. Incorporation of a very low concentration of the additive may also alter the stationary phase surface by creating a fine tuning and improves the partition characteristics of the analytes. A dramatic and sufficient elution capability of amido‐sulfonic acid (ASA) for sequential separation of the analytes was reported and rational mechanisms for the separated analytes are proposed. ASA can act as an ion pairing agent resulting in the separation of a wide variety of amines. The new mobile phase (ASA) is proven to have more successful separation over methansulfonic acid (MSA), even with eluent free solvent. The proposed method shows that a profound particular effect on the separation of aliphatic diamine (Ethylenediamine) and organic amine (Cyclohexylamine) was achieved in addition to all common cations and amines using isocratic elution of 18 mM of ASA without organic eluent modifier.

Nonfouling biomaterials based on polyethylene oxide‐containing amphiphilic triblock copolymers as surface modifying additives: Synthesis and characterization of copolymers and surface properties of copolymer–polyurethane blends

AbstractThe objective of this work is to develop nonfouling biomaterials by blending polyethylene oxide (PEO)‐containing block copolymers with a polyurethane (PU) matrix; it is expected that the PEO component will migrate to the tissue‐material interface. Three amphiphilic triblock copolymers, PEO‐PU‐PEO, in which the PEO MW was 550 (copolymer 1), 2000 (copolymer 2), and 5000 (copolymer 3), respectively, were synthesized. XPS data showed that the polymer/vacuum interfaces of copolymers 2 and 3 were enriched in the PU block, whereas that of copolymer 1 was enriched in the PEO block. In contact with water, the PEO blocks for all three copolymers migrated to the surface as indicated by water contact angles. Blends of the copolymers with a segmented polyurethane were investigated. Surface enrichment of the copolymers occurred and increased over time up to a limit; the degree of enrichment was dependent on PEO block size and copolymer content. At copolymer content &lt;10%, enrichment decreased with increasing PEO block size. For the copolymer 2 and copolymer 3 blends, enrichment increased with increasing copolymer content; at 20% copolymer the surfaces consisted essentially of pure copolymer. For the copolymer 1 blends, the surface was completely covered by copolymer at content ≥ 1%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Nonfouling biomaterials based on polyethylene oxide‐containing amphiphilic triblock copolymers as surface modifying additives: Protein adsorption on PEO‐copolymer/polyurethane blends

Surface modification of a segmented polyurethane was achieved by blending with novel PEO-containing amphiphilic triblock copolymers (PEO-polyurethane-PEO). Three copolymers having different PEO MW (550, 2000, 5000) were used as surface modification additives. The protein resistance of the blend surfaces was evaluated using radiolabeling methods. On the blends of copolymers with PEO blocks of MW 2000 and 5000, fibrinogen adsorption from physiologic buffer decreased with increasing copolymer content up to 20 wt%. On the blends with PEO blocks of MW 550, resistance to adsorption for a given copolymer content was much greater. For all three blend types at 20% copolymer content, reductions in adsorption compared to the unmodified PU matrix were greater than 95%. Reductions in adsorption were similar for the 20% blends and surfaces prepared by coating the copolymers directly on the matrix, suggesting that the 20% blend surfaces were completely covered by copolymer. At low copolymer content (< or =10 wt %), fibrinogen adsorption decreased with decreasing PEO block length. This was probably due to increasing surface coverage of the copolymers with decreasing block length. It is therefore concluded that surface density of PEO is more important than PEO MW for the protein resistance of these surfaces. Lysozyme, a much smaller protein, showed adsorption trends similar to fibrinogen. The adsorption of fibrinogen and lysozyme from binary solutions to blends of the copolymer with PEO blocks of 2000 MW was investigated to probe the effects of protein size on adsorption resistance. Fibrinogen and lysozyme showed similar fractional decreases in adsorption relative to the PU matrix independent of the surface density of PEO. However lysozyme was enriched in the surface relative to the solution, that is, it was adsorbed preferentially to fibrinogen.

Nonfouling biomaterials based on polyethylene oxide‐containing amphiphilic triblock copolymers as surface modifying additives: Solid state structure of PEO‐copolymer/polyurethane blends

Three novel polyethylene oxide-containing amphiphilic triblock copolymers (PEO-PU-PEO) with PEO MWs 550, 2000, and 5000, were blended with a segmented polyurethane (PU). It was expected that the block copolymers would act as surface modifiers to produce surfaces rich in PEO. The solid state properties of the PEO-copolymer/PU blends were studied by infrared spectroscopy, differential scanning calorimetry, and tensile stress-strain measurements. Infrared analysis showed no significant hydrogen bonding between the PEO blocks of the copolymers and the PU matrix. Differential scanning calorimetry data indicated that for copolymer content up to 5 wt % the microphase structure of the blends was indistinguishable from that of the unmodified PU matrix; for copolymer content of 10% or greater, the blends showed phase separated structures. Similarly the tensile stress-strain properties of the blends were essentially the same as those of the matrix up to 5 wt % copolymer. At higher copolymer content, however, the tensile strength decreased with increasing content of the copolymers; for a given copolymer content the change in tensile properties increased with increasing PEO MW. The structures of the 20% blends were also investigated after extraction with toluene (copolymers soluble, matrix insoluble). Bulk compositional change upon extraction was determined by nuclear magnetic resonance spectroscopy. Surface compositional change was studied by X-ray photoelectron spectroscopy and water contact angles. Surface morphology was observed using scanning electron microscopy and atomic force microscopy. It was shown that the copolymers were removed from the blends by extraction and that the extent of removal increased with decreasing MW of the PEO block. After toluene extraction, the blend surfaces showed advancing water contact angle and surface elemental composition similar to those of the PU matrix. However in contrast to the relatively smooth matrix surface, the extracted blend surfaces were "decorated" with lacunae or pits. Consistent with the weight loss trends, the extent of pitting was greater for the copolymers having shorter PEO blocks, suggesting that surface enrichment of the copolymers increased with decreasing MW of the copolymers.

Estudo da produção de suspensões aquosas para serigrafia de anodos para PaCOS e introdução de modificadores de superfície

O presente trabalho tem como objetivo apresentar os resultados preliminares do desenvolvimento de suspensões cerâmicas aquosas para anodos de PaCOS. Estas suspensões foram utilizadas para a geração de eletrodos sobre eletrólitos planos de zircônia estabilizada com 8% mol de ítria (ZEI) em procedimentos compatíveis com a técnica de serigrafia, uma vez que a mesma leva a baixos custos de processamento e boas propriedades eletrocatalíticas dos componentes manufaturados dessa forma. Tais suspensões foram produzidas partindo-se de pós cerâmicos adquiridos comercialmente. Juntamente com coadjuvantes orgânicos de interesse, esse material foi processado através de moagem de alta energia, resultando em uma massa precursora da suspensão que, na fase final do procedimento, é hidratada com água destilada gerando uma pasta pronta para a deposição no eletrólito e posterior processamento cerâmico de queima e sinterização. Foi também estudada a formulação para anodo contendo, na água de intumescimento do polímero, íons precursores de óxidos com atividade eletrocatalítica (íons zircônio IV e ítrio III), visando a geração de uma estrutura auxiliar de ZEI após o processamento cerâmico, como uma maneira de otimizar a microestrutura do filme poroso formado. A utilização de dois passos de processamento, o primeiro de moagem a seco dos pós e o segundo de adição de solvente para hidratação (água), leva a uma vantagem de armazenamento, uma vez que a mistura precursora da suspensão pode ser mantida por longos períodos de tempo. A manufatura da pilha unitária para testes foi concluída pela utilização de suspensão comercial de manganita de lantânio dopada com estrôncio, utilizada como catodo. Análises da morfologia dos eletrodos fabricados, através de microscopia óptica e microscopia eletrônica de varredura, demonstraram a obtenção de estrutura porosa adequada e sua adesão ao substrato e testes de desempenho eletroquímico dos dispositivos prontos, evidenciaram uma melhora no desempenho, uma vez que houve aprimoramento do processamento com adição dos modificadores de superfície.

Effect of the surface-modifying macromolecules on the duration of the surface functionalization

Functionalization of polystyrene films by the preferential surface enrichment of surface-modifying macromolecules (SMM) to achieve a hydrophilic surface with long effective duration is described. The comb-like amphiphilic copolymers (PKG-g-PS) based on styrene-maleic anhydride copolynier (SMA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene, the preferential surface enrichment of PEG-g-PS was much evident resulting in the large increase of the surface polarity. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. Compared with the PEG-g-PS/PS and PEG/PEG-g-PS/PS blends, the surface polarity and the effective duration of surface modification both increased greatly when PEG-g-PS was used as the compatibilizer of PEG/PS blends. It was an effective solution to balance the conflict between the duration and efficiency of the surface-modifying additives.

Do Surface-Modifying Additive Circuits Reduce the Rate of Cerebral Microemboli During Cardiopulmonary Bypass?

The objective of this study was to determine if surface-modifying additive (SMA) cardiopulmonary bypass (CPB) circuits are associated with a lower rate of cerebral microemboli during CPB compared with standard circuits. In a 2 × 2 factorial design, patients undergoing coronary artery bypass graft surgery were randomized to SMA or standard CPB circuits (with and without methyl-prednisolone). Transcranial Doppler was used to detect high-intensity transient signals (HITS) in both middle cerebral arteries. HITS were counted from onset to end of CPB. Intervals of interest were as follows: period 1, from CPB onset to aortic cross-clamping; period 2, from aortic cross-clamping to immediately before de-clamping; period 3, from aortic de-clamping to before aortic side-clamping; period 4, from the application of the aortic side clamp to immediately before the release of the side clamp; period 5, from aortic side clamp release to the end of CPB. There were 14 patients in each circuit group. No significant differences were found on the partial and total counts of HITS (medians [25th, 75th percentile]) between patients exposed to standard (total count: 228 HITS [174, 280]) and SMA circuits (total count: 156 HITS [104, 356]; p = .427). The median of the sum of HITS per patient associated with perfusionist interventions was not different between both circuit groups (standard: 17 HITS [7, 80]; SMA: 43 HITS [13, 168]; p = .085). This study, with a sample size of 28 patients, indicates that it is unlikely to find any difference in the count of HITS during CPB that is greater than 117 HITS between the two CPB circuits. Moreover, our findings emphasize the relevance of minimizing additional sources of cerebral microembolization during CPB that are not directly related to the biocompatible nature of the SMA CPB circuit.

Comparison of Inflammatory Responses After Off-Pump and On-Pump Coronary Surgery Using Surface Modifying Additives Circuit

Cardiac surgery is followed by various degrees of inflammation, which have harmful consequences. Because of the central role of extracorporeal circulation (EC), off-pump coronary bypass surgery is deemed preferable. Do different modalities of EC challenge this view? Four groups of similar patients underwent coronary surgery: (group 1) on-pump, EC with closed surface modifying additives (SMA) circuit and no pump suckers (n = 20); (group 2) on-pump, EC with open SMA circuit and pump suckers (n = 20); (group 3) off-pump (beating heart) and heparin 3 mg/kg (n = 20); (group 4) off-pump (beating heart) and heparin 1 mg/kg (n = 20). Interleukins (IL)-6, IL-8, IL-10, myeloperoxidase, elastase, and terminal complex of the complement (TCC) were analyzed at various times: at induction (time I); after heparin (time II); after complete revascularization (time III); after protamine (time IV); and 24 hours later (time V). The TCC was significantly higher in groups 1 and 2 at time III. The pattern of IL-6 was the same for the four groups. No significant difference in myeloperoxydase content was noted; however, elastase was significantly higher in the two EC (on-pump) groups. Except for the complement system and elastase, on-pump surgery with SMA-coated circuits did not elicit any greater inflammatory response than off-pump surgery.

In Vivo Comparison Study of FDA-Approved Surface-Modifying Additives and Poly-2-Methoxyethylacrylate Circuit Surfaces Coatings During Cardiopulmonary Bypass

The purpose of this double-blind prospective and randomized study was to examine the effects of surface-modifying additives (SMAs) and poly-2-methoxyethylacrylate (PMEA) circuits on platelet count, platelet function (Sonoclot), postoperative chest tube drainage volume, peri- and postoperative blood product use, extubation time, and intensive care time. Terumo noncoated, Terumo-coated (PMEA), Cobe noncoated, and Cobe coated (SMA) circuits were evaluated to find the most cost-effective way to improve patient outcomes. We aimed to find if an additional charge for a coated CPB circuit would be recovered by reducing other patient costs (blood transfusions, intensive care unit time, and bring back postoperative bleeding). An initial literature review revealed the comparison of PMEA circuits vs. noncoated circuits and SMA circuits vs. noncoated circuits in both adult and porcine models. Both SMA- and PMEA-coated circuits decreased platelet consumption, platelet factor release, and the overall perioperative inflammatory response while on cardiopulmonary bypass (CPB). The question not answered in an initial search was simply, “which coated circuit is best for the patient: SMA or PMEA?” Research comparing the above coated circuits each other was not found. The study was approved by the Institutional Review Board. Thirty patients were scheduled for elective coronary artery bypass grafting and/or valvular repair or replacement surgery. These 30 patients were randomized as 10 patients to Terumo X-Coating (PMEA surface coating) (CT), 10 patients to Cobe Smart-X coating (SMA surface coating; CC), 5 patients to Terumo noncoated tubing (NCT), and 5 patients to Cobe noncoated tubing (NCC). Informed consent was obtained from each patient before surgery. The data showed no statistically significant relationship between platelet counts, platelet function (Sonoclot), postoperative chest tube drainage volume, peri- and postoperative blood products, intensive care unit time, or total hospital length of stay. Analysis revealed statistically significant clinical associations of extubation time and protamine dose with treatment group. This study provided evidence that SMA- and PMEA-coated circuits do not improve platelet consumption or decrease blood product use for patients undergoing CPB. There was statistical significance with a reduction in extubation time and total protamine requirement needed to return activated clotting time (ACT) to baseline post-CPB. Although the use of SMA and/or PMEA circuits during CPB has clinical benefit to the CPB patient, an additional charge for the specialty circuit may not be realized.

A clinical, renal and immunological assessment of Surface Modifying Additive Treated (SMART™) cardiopulmonary bypass circuits

Biocompatible cardiopulmonary bypass (CPB) circuits aim to reduce contact activation and its physiological consequences. We investigated the hypothesis that use of Surface Modifying Additive (SMA)-treated circuits (Sorin Group Ltd) compared with non-SMA circuits would be associated with preservation of blood pressure during CPB and modulation of perioperative subclinical renal function (urinary alpha-1-microglobulin (alpha-1-m)) and plasma and urinary cytokine changes. In a study of low-risk CABG patients (n=40), randomized to SMA (n=20) versus non-SMA circuits (n=20), we found better preserved blood pressure at CPB initiation in SMA patients (p <0.05), particularly in ACE-inhibited SMA patients (n =11) versus ACE-inhibited non-SMA patients (n =10) (p <0.05). Plasma anti-inflammatory IL-10, as well as urinary alpha-1-m, were elevated 48 hours postoperatively (p <0.05). SMA patients also had lower blood loss (p <0.05). SMA circuits have some clinical benefit, especially in ACE-inhibited patients.

Surface modification of poly(ether urethane urea) with modified dehydroepiandrosterone for improved in vivo biostability

In this study, a fatty acid urethane derivative of dehydroepiandrosterone (DHEA) was synthesized and evaluated as a polyurethane additive to increase long-term biostability. The modification was hypothesized to reduce the water solubility of the DHEA and physically anchor the additive in the polyurethane during implantation. Polyurethane film weight loss in water as a function of time was studied to determine the polymer retention of the modified DHEA. The polyurethane film with unmodified DHEA had significant weight loss in the first day (10%) that was previously correlated to rapid leaching of the additive. The polyurethane film with modified DHEA had significantly less weight loss at all time points indicating improved polymer retention. The effect of the modified DHEA additive on the biostability of a poly(ether urethane urea) was examined after 5 weeks of subcutaneous implantation in Sprague-Dawley rats. Optical micrographs and infrared analysis of the specimens indicated that the modified DHEA bloomed to the surface of the film forming a crystalline surface layer approximately 10-15 microns thick. After explantation, this surface layer was intact without measurable differences in surface chemistry as monitored by attenuated total reflectance-Fourier transform infrared spectroscopy. There was no evidence of degradation of the polyurethane underneath the modified DHEA surface layer as compared with the polyurethane control. We have concluded that the modified DHEA self-assembled into a protective surface coating that inhibited degradation of the polyurethane. The roughness of the modified DHEA surface layer prevented adherent cell analysis to determine if the additive retained the ability to down-regulate macrophage activity. Subsequent studies will investigate the ability of surface-modifying additives to modulate cellular respiratory bursts in addition to the formation of an impermeable barrier. This bimodal approach to improving biostability holds great promise in the field of polyurethane biomaterials.

Emerging technologies in biocompatible surface modifying additives: quest for physiologic cardiopulmonary bypass.

Modification of polymer surfaces to achieve a surface with enhanced compatibility is an important means of obtaining improved biomaterials. The molecular design of the novel technologies is carried out with attention to create a biomembrane-mimicking surface on medical devices. This review focuses on the comparison of the chemical composition of recent novel surface modifying additives and coating technologies, their biomaterial evaluation and clinical efficacy under the scope of our previous studies and current literature.

Biostability of Thoralon Left Ventricular Assist Device Blood Pumping Sacs After Long-Term Clinical Use

The purpose of this paper is to investigate the biostability of Thoralon polyurethane blood pumping sacs that have been used for up to 14 months in the Thoratec ventricular assist device (VAD) in human subjects. Thoralon is a proprietary polyetherurethaneurea (PEUU) blended with siloxane based surface modifying additive (SMA). Samples of Thoralon blood sacs that were used in Thoratec LVAD pumps for 53, 171, 336, and 434 days were taken from three distinct regions identified as high flex, medium flex, and low flex for physicochemical analysis. Explanted samples exhibited a slight but not significant increase in physical properties. The molecular weight of the blood sacs had also increased significantly in all blood sacs regardless of duration of use. SEM images did not indicate any cracking, pitting, or surface erosion; however, in a small area of the high flex region of the 336 day sac some biofilm was seen. The Attenuated Total Reflectance Fourier Transform Infra Red Spectroscopy (ATR-FTIR) analysis showed no significant reduction of surface ether content. The surface chemistry analyzed using Electron Spectroscopy for Chemical Analysis (ESCA) also indicated no significant change compared with control. These results confirm the biostability of Thoralon for long-term clinical applications in the Thoratec VAD.

The inflammatory response to cardiopulmonary bypass: a therapeutic overview.

The demographic of cardiac surgery patients continues to evolve to include older, sicker candidates, all the while maintaining an expectation of excellent outcomes. These latter results can only be achieved by the parallel advancement and re-examination of the technology of cardiopulmonary bypass (CPB); the key tool used daily by surgical teams worldwide. In this review, we will provide an overview of integrated therapeutic strategies that can be utilized to minimize the complex and myriad changes related to inflammation after CPB with the understanding that this may abrogate the detrimental end-organ and systemic effects of blood activation. Therapeutic strategies specifically related to the technology can be classified into those targeting biomaterial dependent or independent processes. The former can be addressed by the utilization of currently available biocompatible surfaces such as with heparin-coated circuits, phosphorylcholine-coated circuits ('biomembrane mimicry') and circuits composed of copolymers containing surface-modifying additives. The most important strategies related to biomaterial independent activation include the modification of techniques related to cardiotomy blood management and blood filtration. Finally, all of these strategies must be integrated and tailored with complementary pharmacologic agents such as aprotinin and steroids to optimize anti-inflammatory synergism. Only if we are armed with a comprehensive knowledge of the molecular and cellular basis for these strategies will we be able to continue to evolve our treatment in parallel with our patients to achieve these goals.

Novel human endothelial cell-engineered polyurethane biomaterials for cardiovascular biomedical applications.

A tri-block coupling-polymer composed of 4,4'-methylenediphenyl diisocyanate and poly (ethylene oxide) (PEO), abbreviated MPEO, was used as the template surface-modifying additive (SMA), based on which selected amino acids (lysine, arginine, glycin, and aspartic acid) and RGD peptide were respectively conjugated as functional endgroups of the PEO spacer-arms through sulfonyl chloride-activation routes. After the immobilization of biofunctional factors, the SMA-MPEO derivatives were noncovalently introduced onto the biomedical poly(ether urethane) (PEU) surfaces by physical blending methods. The SMA synthesis and PEU surface modification were monitored and analyzed by nuclear magnetic resonance spectroscopy, attenuated total reflection-infrared spectroscopy, and X-ray photoelectron spectroscopy. The human umbilical vein endothelial cells (HUVECs) were collected and harvested manually by collagenase digestion. The cell culture was performed respectively on the MPEO derivative-modified PEU surfaces and also on the surfaces of the commercially available polystyrene cell-culture plates (TCPS) for control. The cell adhesion rates and cell proliferation rates of the in vitro cultivated HUVEC were measured using flow cytometry. The individual cell viability rates were determined with MTT assay. The cell morphologies of the living HUVECs were investigated by optical inverted microscopy, and more detailed information was acquired from scanning electrical microscopy. The results indicated that the efficacy of SMA functional endgroups was the dominant factor for HUVEC compatibility; the proper-sized PEO spacers (M(w) 2 k) could support and mobilize the functional endgroups, optimizing the surface (interface) environment for the cell growth. As the endgroups of the SMA-MPEO derivatives and the bio-functional factors, the basic amino acids (lysine and arginine) demonstrated similar performances to that of the widely acknowledged cell growth-promoter, RGD peptide, which were superior to TCPS. Therefore, these MPEO derivative-modified PEU materials are promising to serve as novel polymeric permanent implants or interventional devices for cardiovascular biomedical applications.

Do Surface Modifying Additives (SMA) Influence Blood Loss and Thrombogenicity in Conventional Cardiopulmonary Bypass for Coronary Artery Bypass Grafting?

Cardiopulmonary bypass (CPB) leads to activation of the coagulation and fibrinolytic cascades, partially associated with foreign surface contact. Hemorrhage and the need for blood products is associated with rising cost and increased risk of infection. Treatment with surface modifying additives (SMA) has been shown to reduce thrombogenicity and improve biocompatibility. 76 elective CABG-patients were randomly assigned to surface modifying additives (group I, n = 39) or untreated circuits that were otherwise identical (group II, n = 37). Measurements of coagulation activity and fibrinolysis, platelet count and function were made. The postoperative blood loss and blood product replacement was also assessed. Thrombin formation measured by prothrombin fragments 1 + 2 (5.7±0.4 nmol/l vs. 5.6±0.4 nmol/l), fibrinolytic activity measured by plasmin-antiplasmin complex (1752.6±216.8 μg/l vs.1180.0±74.8 μg/l) and the postoperative platelet count and function did not differ significantly between the two groups. Blood loss and transfusion requirements were slightly lower in the SMA group. The treatment of extracorporeal surfaces with surface modifying additives does not appear to reduce coagulation disorders and bleeding after conventional CPB.